At least three parameters are used to measure the size of photographs - digital image resolution (in pixels), print size (in centimeters) and print resolution (dpi - dots per inch). The user who first encountered the task of converting the image, preparing it for printing is sometimes difficult to deal with these settings, have to act at random and go to the desired result through trial and error, spending a lot of time and paper.

We give a simple example of the problem. You need to take a photo on the documents. You can go in two ways - go to the shop and take a picture there, giving 150 small rubles for 4 small photos printed on a sheet of 10 * 15 cm. The second option is to take a picture at home, prepare A4 sheet for printing, onto which so many of your photos are squeezed so that enough for several years to come. Then you go to a photo studio and print your creation on an A4 sheet for 30. It seems that the profit is ridiculous from one order, but if you need to print photos for several people at once (for example, when the whole family takes a photo for a visa before traveling to another country), then save more substantial amount. And this is just one example. Another question is how to keep the size of the photos so that they are exactly 4 * 5 cm on the print (or some other size). In order to adjust the print size to the required, you need to understand the connection centimeters, pixels  and dpi.

Pixels

A pixel is one point that the image is made up of. Also, a pixel is an image cell on a monitor or LCD TV. Take a closer look at the monitor and you will see a barely noticeable grid, one cell of this grid is the pixel. The photo you downloaded from the camera has a resolution of several megapixels, that is, for example, 6000 pixels wide and 4000 pixels high - this is 6.000 * 4.000 \u003d 24.000.000 pixels or 24 megapixels. When viewed on a monitor, the picture is automatically scaled to the resolution of the monitor (about 2 megapixels). If we try to zoom in (stretch the photo), then to some extent the picture is stretched without a visible loss of quality, but then characteristic squares appear on it. This happens when the actual resolution of the photo is less than what we want to see - the pixel size in the photo becomes larger than the pixel size in the monitor.

Centimeters

What is a "centimeter", I think, no need to explain. In our case, the size of the prints of a photograph is measured in centimeters. Usually photos are printed in size 10 * 15 cm, but sometimes larger formats are used - 20 * 30 cm (approximately corresponds to the A4 format), 30 * 45 cm (A3) and more. You probably encountered a problem - you found a beautiful photo on some site and decided to print it in large format (for example, 20 * 30 cm), but when you print it out, you notice that the print quality is not too good - the back of the objects turned out to be a bit blurry. What is most sad - this photo cannot be corrected by any processing. And all because the resolution of the photo on the site is, for example, 900 * 600 pixels. That is, 1 pixel on the print will have a size of approximately 0.33 millimeters - while it is difficult to count on “ringing” sharpness! And here another image quality parameter appears, with which you can evaluate the print quality - DPI

DPI

DPI is an abbreviation of the English phrase Dots per Inch, which is translated into Russian as dots per inch. This value just shows how many pixels of the image per one "linear" inch when printing (an inch is 2.54 cm). There is still the value of DPC (dots per centimeter), but it is used less often - whatever one may say, all these printing technologies came to us from where inches, feet, pounds, etc. are used. So, back to our example - a picture of 900 * 600 pixels, which we decided to print in a format of 30 * 20 cm. Convert centimeters to inches for convenience - we get 11.8 * 8.9 ". If we divide 900 pixels by 11.8", we get print resolution 76 DPI. This roughly corresponds to the resolution of the monitor with its "large" pixels, so the picture on the screen looks good. But to get a print of acceptable quality, you need a print resolution of at least 150 DPI, and if you want very good detail, at least 300 DPI. To provide such a resolution when printing 30 * 20 centimeters, the original digital image should have a resolution of 3540 * 2670 pixels - this is about 9 megapixels. So they found the reason why photos printed "from the Internet" look blurry and blurry. Now back to our question - how to adjust the resolution of the image so that it prints with a given size? As an example, consider preparing photographs for documents.

Creating your own photo on documents - step by step instructions

Suppose you need to take several photos 4 * 6 cm in size and place them on a 20 * 30 cm sheet. How do I do this?

1. Take the original image, open it in Photoshop. Select the menu item "image" - "image size". Before us opens a dialog box:

In the dialog that opens, we see two groups of settings - "dimension" and "print size". In the dimension group, the dimensions of the digital image in pixels are displayed. We don’t touch these settings! In the group "print size" we set the size we want in centimeters (units are selected from the drop-down lists). In our case, this is 4 * 6 cm. We also set the print resolution to 300 pixels per inch, this will ensure good print quality.

Changing the print size settings, we see that the sizes in pixels also change. It should be so! After all this, click OK. The image is resized. Now we need to copy it - use the key combination:

1. Ctrl + A (eng) - select all
2. Ctrl + C (eng) - copy to clipboard

What we copied to the clipboard will be transferred to a separate canvas, see section 2. 2. Now we need to create a new image that will correspond to a sheet of 20 * 30 cm, which we will go to print in a darkroom. Select the menu "File", "Create", a dialog box appears:

We indicate the size of the photo paper on which printing will be performed (20 by 30 cm) and set the resolution in pixels per inch to be the same as our photo - 300 DPI. Click OK.

3. A blank image has appeared with a transparent background. Press the key combination Ctrl + V and paste our first image on a new canvas. It will look something like this:

The image is pasted as a new layer. Move it to the upper left corner, then select the menu "Layer", "Create duplicate layer".

Another same picture will appear on the canvas, initially it "lies" on the original layer. Move it and put it next. In the same way, create as many duplicate layers as we need. After that, we perform the flattening of layers (the menu "Layer", "Perform flattening").

We save the image in JPEG format, copy it to a USB flash drive and go to the darkroom. We say to the operator the following - "print this image in 20 * 30 cm format with a resolution of 300 DPI without scaling". In this case, the small pictures will have exactly the size that we indicated for them - in our case 4 * 6 centimeters. It is advisable to have a ruler with you to check the size of the prints.

The reduction is known to designers, computer scientists, those who at least once worked with the image. Gamers with their cool special mice have also heard about this term. Now we will try to deal with this abbreviation.

Options

If you ask the Internet about DPI what it is and where it is applied, you will get several answers at once. After all, there are three decipherments of this reduction:

• Deep Packet Inspection is a provider tool that collects statistics, checks network packet filters and their contents.
• Discounted Profitability Index is an economic term that is responsible for return on investment.
• Dots per inch - from English it is translated as "dots per inch".

It is the latter option that we will consider.

Resolution

Speaking specifically about DPI, it becomes clear that it means only a unit of measurement. But why? It turns out to find out the resolution of the image and this abbreviation is applied.

Resolution in itself is an indicator that indicates the number of dots (pixels) per unit area. Most often, this indicator is applicable to digital-type images, but it is used in the work with granulation of film, photo paper, etc.

So, if you need to save the data in a graphic file with the desired scale and print it all out, then most likely DPI will come to the rescue. This value will indicate the number of dots per inch. If you have a resolution of 300 dpi, respectively, it equals 300 dots per inch.

Example

Another example is to understand how this quantity works. Suppose your picture has a resolution of 350 dpi. You need to transfer it to 10 by 10 cm paper. Translated into inches, you get 3.9 x 3.9 inches. To understand what size of the original image is needed, it is necessary to multiply 3.9 by 300. So we get 1170 x 1170 pixels. With this indicator, the picture quality will be acceptable.

Application

Now more about where and how DPI is applied. What is it, we have already figured out. A value is used to indicate resolution. We need the latter when displaying graphic data on a flat medium.

You can also find this value in the specifications for the printer. 600 to 450 dpi can be specified. So it becomes clear that the devices are endowed with a resolution that is horizontally equal to 600 points, and vertically 450 points. In this case, we take a square of 1 by 1 inch for the area.

If we talk about the printer, then often this figure is compared with PPI. These two quantities mean the same thing. Use if you need to mix inks for printing. Then 1 dpi will be equal to 1 ppi. If the device does not need to mix ink, then this formula will look different. The index N is used, which indicates the number of colors used for printing. Then dpi will be equal to ppi times that number, that is, the index N.

This calculation is the main advantage for inkjet printers. Unlike photomachines, string devices have a higher DPI value with an equal PPI value. Because they expose more points to transmit one pixel.

Other indicators

Image DPI is not the only resolution. As we already learned, there is a relationship with other similar indicators. So, in printers, a raster dot is represented by many small dots. They are called flash. The number of such flashes per inch is indicated by DPI. The number of raster dots that hide in this flash by one inch indicate PPI. Accordingly, if the ratio of the two indicators is greater, the image is better.

There is another indicator - this is LPI. The value indicates the number of lines per inch. This resolution characterizes the operation of a laser printer. The inch in this case is not represented by a dot, as before, but by a line. That is, to be more precise in the wording, then LPI is the number of lines per linear inch.

Another value is represented by the acronym SPI. It shows the number of elementary spots. The indicator is quite complex and not so often used in photo printing. But in general, it is used for printing gradients. And if the PPI indicates the end result, then the SPI is part of the process. Interestingly, in general, both indicators under equal conditions have the same value.

Gaming mice

But it turns out that this is not all DPI information. What is it, we broadly understood. For what is applied, also figured out. But they missed one thing. The fact is that the value is often found on packages with gaming mice. It is difficult to connect the information we received earlier with the parameters of the manipulator. But you can try.

The fact is that dpi in the controller is decrypted in the same way, but it has a slightly different understanding. To be precise, for a mouse it is better to decipher this indicator as dots of cursor montion per inch. That is, the number of cursor points per inch. Next to this value is cpi. It roughly means the same, and it would be logical to apply precisely this reduction. But in general, one and the second value conveys the number of steps that the manipulator goes through 1 inch.

And it is worthwhile to understand that we are talking about mouse movement, not the cursor. In this case, movement is interpreted as a step, and step as a signal. If the dpi is large, then the device moves smoothly.

Marketing?

In theory, it turns out that this indicator, which is shouted from advertising booklets and packaging, is more of a marketing ploy. The fact is that few people know, but for this very speed we must not forget about the speed of polling the port. It is known that at the moment the highest indicator is 1000 Hz. You might think that if the mouse passes 2 inches in one second, then this figure will double. In fact, it turns out that it is still impossible to cross the threshold of 1000 Hz. So then what is the advantage of this value in manipulators?

DPI is an indicator that changes the speed at which the cursor moves on the display. And it does it most qualitatively in the case of high-resolution screens. It is logical that if the display is large, then the mouse should walk a distance proportional to the diagonal of the monitor. Therefore, this value is important only for players and those who work with graphics. For them, a figure of 1600 dpi is considered acceptable.

For other users who have a screen smaller than 1600x1200, 800 dpi will be enough. This value is average today. If the monitor is 1200x800, then a mouse with a resolution of 400-500 dpi will be enough.

findings

It becomes clear that DPI is a value that is more familiar to designers, those who work with graphics and printing. This resolution allows you to determine the number of dots per inch when displaying images on a flat medium. If we are talking about a mouse, then DPI in this case shows the mouse movement per inch.

If you have a question about how to configure DPI, it should not arise, because usually there is a special button on the case to adjust the resolution. In some cases, you can configure through software. If you have a normal mouse, but you want to adjust its speed, then it will be enough to go into the settings on the PC and set the slider to the desired level.

300 dpi - every photographer heard about this requirement of printers for the quality of digital photo images. But how much is it really necessary? We dealt with this with one of the leading suppliers of digital images in the Russian photo market

AA: Nikita, do you believe in the magic of numbers?

N.V .: No, I'm not superstitious. But some figures have specific occupational hazards: 32 (teeth) for the dentist, 37 (years) for the poet, 300 (dpi) for the photographer.

AA: Do you have something against 300 dpi?

NV: God forbid! Welcome, we were talking about the fundamental cosmogonic constant, like the number "pi" or the speed of light in a vacuum. And this is a figure of an arbitrarily chosen board of the Ministry of Printing of the USSR. What now can be had against 300dpi, the Mongol yoke or other pages of the history of the fatherland? It has 300dpi against me!

A.A .:?

NV: As I began to print my photos, it all started right away. One day, they are calling from the magazine "Photo Store". They report that they chose my photo for the cover of the issue. But they won’t pay money, it’s enough that the honor is offered. Okay, I say, in fact, and I have enough honor. I took to the editorial staff a photo taken by the first “democratic” Canon 30D digital SLR, 3.6 megapixels.
  After a couple of days, the call: - You that slipped us, there 180 dpi!

I object that in the year before last they printed my article with photographs in A4 format made by the same camera.

Answer: - The cover is the face of the magazine, so please 300 dpi.

I object that I printed this picture on A3 for a photo exhibition and probably it didn’t turn out so bad, because I even bought this photo.

Answer: - Perhaps it is so on your printer, but we have expensive Finnish equipment, let's get 300 dpi!

I wonder what to do. An offer comes to mind - sell expensive equipment, buy a printer, and cheaply and quality will improve! But this is a conflict, and I have already bragged about the cover for someone, it's a shame.

I say: - OK, I will send you a full-format image tomorrow.

I sit down at the computer, in the graphics editor I correct the figure of 180 dpi to the required 300 dpi. With a heavy heart, I give in a pretty heavy file, because I realize that I’m a fool for a central magazine specializing in photography, and not for the large print run of Zarechye Bread Factory.

New call from the "Photoshop". I take the phone with a trembling hand. They say: - Well, that’s a completely different matter! Well, you, Nikita, yourself do not see the difference?

Yes, I say, now I see. So that I have my hands, I say, they’re dry to send 180 dpi next time! Especially for Finnish equipment!

AA: Was it long ago?

NV: A few years ago. Yes, since then magazines are used to digital technology. A familiar photographer working for Newsweek recently shared professional tricks about how he hangs a huge DSLR with a kilogram lens on his stomach, and pretending he has not started working, he quickly shoots a hot report with a compact digital soap dish hidden in his palm .

AA: And magazines no longer require 300 dpi?

NV: Magazines no longer require. But now I work in the photo bank, and the story repeats with enviable constancy, especially in the fall, when the "calendar season" is. The client wants: format - A2, resolution - 300dpi! Gentlemen, firstly, there is no such technique to fulfill your wishes, and secondly, it is not required. And then, as in a joke about a taxi driver: Gentlemen, do you have to go or checkers? If you go, then the A2 format is possible with a technically good photo. And if the checkers, then maybe it will not be difficult for you to put in the dpi column the number "300" (or any other)?

AA: You are not mistaken that such a technique does not exist?

N.V .: Let's check together. Here is a table of modern ur.

Camera			Resolution dpi
model	matrix size, pixels	price approximately
CANON EOS 10D
CANON EOS 20D
CANON EOS 1D Mark II
NIKON D2X
CANON EOS 1Ds Mark IIs

It can be seen that no one gives 300 dpi to the A3 + format (48x32cm) unless you paint them on. At the same time, only top models are included in the table, that “soap box”, which the mentioned seasoned reporter shoots for a magazine spread, we did not even consider.

AA: But there are also digital backs for format cameras ...

N.V .: Yes. But, firstly, there are 16-22 megapixels, i.e. still do not reach A2. Secondly, can you recall someone who is filming this? Thirdly, the cost of the image corresponds to the cost of equipment - 11-19 thousand dollars only for the "back"!

AA: To listen to you - so readers may get the impression that digital backs are not worth buying! But what criterion for evaluating the suitability of a photo image do you propose in this case?

N.V .: Simple. Only. And in no way connected with either 300 or any other amount of dpi. If the image looks with this format, from a given distance is good, then it is suitable, if it is bad - no.  An image may be unsuitable for a variety of reasons besides a lack of pixels. For example, shake or lightness also delights customers a little. It is not by chance that customer photo banks ask for the type and format of use, and a larger format is not accidentally more expensive. With some experience, a cursory glance is enough to appreciate the suitability of photography. If there are doubts about the quality, the image should be stretched to the required size and print a fragment of it. If after this doubt remains, then you should pass the printed fragment to the client. If the client decides what is suitable, then it suits, if not, then it means no. The client is the highest authority, its subjective assessment is not subject to appeal.

AA: But, then a printer, or else, “Finnish equipment”!

N.V .: Well, we call for help simple common sense. The digital image is a sequence like 001011110010111010 ....

A printing device of any design does not change this sequence of zeros and ones, but only reproduces it with greater or lesser distortion. If some printing device (for example, an inexpensive printer) allows you to get a high-quality image, then this means that if someone received a low-quality image in one way or another, it is not the image that is to blame. Anyone: a drunken adjuster, counterfeit dyes, bad paper ... but not a photograph.

AA: But, polygraphists demand from the customer ...

NV: Do they require anything from Newsweek? Those involved in printing are engaged in business (printing in this case). Every normal business seeks to do the maximum amount of work for the client. But the "end consumer" is the human eye. If the eye perceives a certain small portion of the image as a point, then this is the required resolution limit. Even if it is technically possible to turn a point into a square consisting of 100 (10x10) points, then no one can appreciate the grandeur of the work done. Do you need it, does it pay?

AA: Well, let's say that you convinced me about digital photography. What can you say about the 300 dpi criterion in analog photography?

NV: But I won’t say anything. I would say, but I see no reason. No more analog photography. I recently found out from the pages of your esteemed Photonews that many foreign photobanks no longer simply accept analog photographs. The photobank I work in accepts. But we consider modern analog photos as a special case of retro photography. Accordingly, if someone wants to get a photograph of Zimny’s capture in modern quality, then I’m afraid that he will have to pay for custom-made shooting and extras.

AA: Not everyone agrees that the time for analog photography has passed.

N.V .: Not all. I respect the position “I believe, for it is absurd”. But one cannot argue with such a position by definition.

AA: Some of your statements are controversial, especially about analog photography. But here on the scales is your experience in the photobank. Let's see what objections our readers put on the other side as opposed to. I wish you success!!!

Visual acuity in humans is on average equal to 1st corner minute. Viewing a glossy magazine (or photo card) is usually carried out from a distance of 25-30cm. Then it turns out that from such a distance one can distinguish a point of order 0.073..0.87 mm.

The magic "300 dpi" means the size of the dot 25.4mm / 300 \u003d 0.085 mm. Which corresponds to the average viewing distance, more precisely 29 cm. Thus, "sculpting" smaller points or more points per unit area does not make sense - anyway, no one can distinguish them from such a distance (25-30 cm).

The angle of a "clear" vision of a person is about 40 degrees or even less. The classical theory claims that in the range of viewing angles 28-37 degrees  photographs and paintings will be perceived more naturally. It turns out that from a distance of 25-30 cm it will not be very comfortable to consider a picture of more than 20 cm on the long side. When we look at a photo A4 or more (for example, A3 - at the front of the magazine), we want to move away to look around the whole image. Thus, a comfortable distance for viewing the A2 format will be at least 82 cm (with a viewing angle of 40 degrees). And from this distance the eye cannot distinguish a point less than 0.24 mm.  It turns out that on the long side you just need about 2500 points (600mm / 0.24mm \u003d 2500).

In this way, an image of 2500 or more pixels on the long side during normal viewing will look equally good in any format.  Probably not casual, 2500 is a common minimum requirement for pictures, for which 10D with its 3072x2048 pixels per eye should be enough with accurate cropping. The race for megapixels is more of a marketing nature.

Another question is that for this any format you need to be able to print the image - prepare for printing. Here the issue of sharpening control during output plays an important role - you need to consider the output method (type of printing: printer, laser, raster, etc.).

1) firstly, megapixels are different. Yes, at least compare the same D30 and a 3-megapixel soap dish. Due to the small size of the matrix (sensor), digital prints produce a noisier and more soapy image (diffraction effects affect). Here, of course, a 6-megapixel shot with the CASIO EX-P600 will lose to the CANON 10D / 300D digital SLR.

2) Secondly, on a print of A2 format, you might want to consider some small details, that is, come closer. Then a picture of 7000 points along the long side is required.

3) "The table shows that the achievement of 300 dpi is impossible even with a format larger than A4.“In principle, such cameras already exist or will appear soon. More precisely, these are“ backs, ”for example, Phase One promised to release (or has already released) P 45 in November / December. But this is a completely different conversation. Such cameras are specific and usually should be a computer and a couple of suitcases of batteries are connected, and the price they have is another 20-30 times more than 20D.

4) And of course, one must take into account the artistic value of the image - since in most cases the photo is perceived as a work of art, like a picture. Well, and the paintings, we know from what distance should be considered (see above).

What are pixels and what is DPI?   September 20th, 2012

Are you afraid of the words "pixels" and "DPI" or do you not fully understand their meaning? Then a few lines below are for you.

Pixels on screen- dots on the screen that form the image.
Pixels in Raster Graphics  - The minimum color points that form the image.
Pixel Size  - width and height of the image. For example, 800x600 means that horizontally the picture has 800 points, and vertically - 600.

DPIit's short for English " dots per inch "and translates to" dots per inch ".

The number of pixels per unit of length is called resolution. The more dots per inch, the higher the resolution and thereby the better the image. The illustration below will show this difference:

What does 72 DPI or 300 DPI mean and what is the difference?

72 DPI(or 96) - files for the Internet, where one point on the screen of your monitor corresponds to one pixel of the image. Also called - screen resolution of the image. More than 72 DPI to make a picture for the Internet - it makes no sense, since the monitor will no longer display anyway.

72 dpi \u003d 28 dots per centimeter.

300 DPI necessary for high-quality printing in a printing house. The number of dots per inch is significantly increased to improve image quality. But for each type of print this value may vary. In general, if a printed product is viewed by a person at close range, then the number of dots per inch should be high. These are magazines, booklets, leaflets. For a layout to be considered at a distance the requirements below. For example, for a billboard, this value can be 56 dpi or lower.
300 dpi \u003d 118 dots per centimeter.

DPI stands for English. dots per inch  (dots per inch) is a numerical expression of the resolution of the bitmap image. Resolution determines how detailed your print will be.

So - the photo does not and cannot have any DPI! If only because she does not have a denominator of a fraction, there are not these inches themselves. While the photo lives on your computer, is viewed on the monitor, walks by e-mail, you just don’t have to talk about any dpi. The parameter only makes sense when it is printed. A photograph has only absolute resolution — the number of dots vertically and horizontally. Say, if a photograph was taken with a camera with a 6 megapixel sensor, then its absolute resolution will be 3000 x 2000 pixels. It's all!

Can such an image be printed at 300 DPI? Yes, of course. How big is the print? 25.4 cm * 16.9 cm.

If this happens in life, then I personally have never met. In any case, the sizes and proportions of your photo in the magazine will be different. When printing the same photo with different sizes, the resolution will also be different, and in any case it will not be equal to 300 dpi. Not to mention the fact that most often the typesetter frames the image in accordance with his ideas, terms of reference and the general concept. We repeat once again: as long as there is no printing, there is no and there can be no DPI.

The dpi value only makes sense when it is printed:

300 dpi  - this is technical permission requirement  illustrations in modern quality printing. The printing house makes it clear to you that printing your cover artwork is perfect, that is exactly what permission is required. Knowing the print resolution requirements and print size, you can already figure out how many vertical and horizontal dots the source image should have.

* - By the way, the figure "300" here is also very arbitrary. To dispel doubts is very simple - imagine a poster with dimensions of 1 x 1.5 meters. At the required resolution of 300 dpi by the designer, the source file should have a resolution of 11800 x 17720 pixels, i.e. approximately 210 megapixels! Even the most modern professional photographic equipment has not even come close to such a value. And the posters both hung and hang.

For a b / w newspaper, for example, 50-70 dpi is enough, for a full-color offset in a book, it takes about 120-150, and for a billboard on the street - only 6-10. Here everything determines the features of perception of the image by the observer - the larger the picture, the greater the distance a person can comfortably perceive it. The postage stamp is brought to the eyes, the magazine is held in hands, and ten meters away from Bryullov’s canvas. One thing remains unchanged - the angular limit of the resolution of the eye (about 1 arcminute). This is exactly what professionals rely on when calculating the required permit.

What permission is required in practice?  In a general sense - the more the better. If we are not dealing with outlandish areas of professional photography (aerial photography, photographic recording of scientific processes, murals), then in the vast majority of cases you can do with an absolute resolution of 6-10 megapixels. Why is de-pe-i misconception so widespread? Because people generally rarely think.

Is that simple? Yes of course. It took you and me three minutes to understand the point. Therefore, if you hear from the designer (layout designer) the phrase “give me pictures with 300 dpi” - run away from him, you are dealing with deep laziness. And laziness, sooner or later, will ruin any business.

P.S .:
What does the value specified in the file properties (72, 150, 300 dpi) mean? This is only the recommended resolution when printing photos in fully automatic mode, indicating to the printer a lazy owner. And this value can be easily changed to any positive integer. Nothing will change in the photo itself.

P.P.S .:
Do you still require "300 dpi"? They say that geisha is best taught in school by geishas: “ask for a drink - don’t be stubborn like a donkey - take a sip and put a glass on the table.” Make it 300 dpi. Or just give a link to this article.

© Dmitry Pesochinsky, 2003-2017
When reprinting, a direct link to www.nevaphoto.com is required.

Photography in St. Petersburg. +7 921 337-24-39. Photographers Service. Professional photography of corporate events, celebrations, conferences and seminars. Industrial and advertising photography, corporate photographer. Collaboration with city media, PR departments. Interior, subject, reportage, event photography. Experienced photographer, photojournalist. Professional processing and photo printing. Custom photo reports, photography for catalogs, booklets, calendars. Business portrait, photography for corporate honor boards. Virtual spherical panoramas, virtual tours. Photo services, development and compilation of a photobank.

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Resolution 300 dpi - how does this compare with the size of the photo 2400x1600?

DPI is the abbreviation for Dots Per Inch and means dots per inch.

DPI \u003d 1PPI (pixels per inch).

Inch - a unit of length equal to 2.541 cm.

Pixel - “picture element” is a point (minimum part) of a digital image. Everything that you see on the monitor screen or digital camera display consists of pixels.

When talking about the resolution of a digital image or the size of a digital image, they mean the number of pixels along the length and height of the image. As a rule, the more pixels there are in an image, the larger and better quality it can be printed on a printer or displayed on a monitor.

DPI matters if you want to print an image of a certain size. Say, if you want to print a 10x10 cm image with a resolution of 300 DPI, then divide 10 cm by 2.54 (1 inch \u003d 2.54 cm) to get a 3.9 x 3.9 inch photo. Now you need to 3.9 times 300 DPI and get the size of the photo in pixels 1050 x 1050.

This is how slide scanners and digital cameras measure the input resolution - in terms of the total number of pixels that can enter the horizontal and vertical CCDs of cameras (for example, 1280x960 with AGFA ePhoto 1680) and optical systems of scanners.

The image resolution indicator is directly related to the resolution indicator of the matrix of the digital camera. 1, 2, 5 MP (megapixels) is the resolution of the matrix of a digital camera. That is, the number of minimal image elements (pixels) that it is able to capture.

The higher this resolution, the sharper, richer and simply better picture.

300 dpi, according to Russian standards, 118.11 pixels per centimeter.

There is a resolution in dpi and there is a resolution of the photo in pixels in width and height, which means we can calculate how large the photo of this is enough without losing quality.

Because you can hold out any photo (stretch to the right size) and see approximately whether the squares began to appear or be tolerant or go in the squares.

Even if the photo needs to be taken narrower or wider, you can crop the upper or side edges and not center the photo a lot and get what we wanted.

The size 2400x1600 has a standard of 96 dpi, this windows standard is known as the standard of monitors, since you have a photo, then it was taken by the camera in this resolution, because when creating photos or even in graphic editors, the standard is 96 dpi, except perhaps By default, excluding photoshop, it offers either 72 or 78 dpi which are easy to fix.

96 dpi in Russian is 37.8 pixels per centimeter.

And now we customize to centimeters, use a real dpi photo with new knowledge it is 96 dpi, which means that they will be enough in the photo:

63.50 cm wide
42.33 cm - in height.

if you hold in your hands horizontally, if vertically

42.33 cm - high
63.50 cm - wide

And you ask to print in the resolution of 300 dpi, this means this photo is enough for sizes under 300 dpi, here are some

20.32 cm wide
13.55 cm - high

At 96 dpi, approaching the eye you will see a grid and between them space
At 200 dpi nothing is visible to the eye already
At 300 dpi all the more

The resolution in pixels does not make sense to have more than dpi allows, it will simply squeeze them under the maximum resolution allowed under the printer resolution, for example, as you indicated 300 dpi. This is a huge picture, 2400x1600 is already a lot. 2400x1600 is that squares in the image would not be visible, and 300 dpi that the pixel grid would not be visible.

21,260 pixels wide. in height how many cm? Only this is a square, if it will be necessary to print on the fabric, but it is not square (the width and height are not the same), it is not known how the printer will make it of its own free will or the program will drive the picture into the printer or all of them together. measurement of the area where to print the width has already been done is 180 cm left height. Possible options if you stick a square will be either cropping or stretching (in the pictures when the faces are in breadth or upward stretched) will be if you do not suspect.

What is a resolution of 300dpi? * And how many mega should a photo need to get such a resolution?

First of all, what is dpi? dpi (pronounced dipiay) - short for English. dots per inch dpi It is used to indicate the resolution when entering or outputting information from / to a flat medium. Measured by the number of dots per inch of surface. For example, the designation 600 by 300 dpi for a printer means that its resolution is 600 dots horizontally and 300 dots vertically per 1 inch.
How high should the print resolution be so that the eye does not distinguish individual pixels and perceive the image as a quality one?
  72 ppi Standard resolution for computer monitors or prints viewed from afar (for example, posters) At close range, pixels are noticeable.
  150 ppi High enough resolution so that the eye does not notice individual pixels and perceives the picture as a whole.
  300 ppi Photographic print quality. A further increase in resolution is necessary only if the imprint is viewed through a magnifying glass.
All this and more related to the printing of digital images can be found here:
http://photo-restoration.narod.ru/page16.html

Useful tables for this:

(see http://www.olympus.com.ru/consumer/208_741.htm)

dpi - Dot Per Inch

that is - dots per inch. And how much the photo will weigh depends on the size of the photo - for example, 1024 * 768 or what size you have there

There is no unambiguous dependence of the relative resolution on the weight of the file.

It depends on what format (in centimeters or inches) we are talking about. Based on this, you can calculate how many points on each side the file should have - for output with a resolution of 300dpi.

And the weight of this file will already depend on the format in which we save it.

300dpi - myths and reality. How much do you really need?

Frequently asked questions on this topic: less or more dpi? The more - the better the quality of the photo? And how does this relate to the size of the photo itself?
More and more often there is a misconception about the "quality" of images and the required 300dpi.

First, let's define what dpi is ... Dpi Is a parameter that indicates the resolution of the image per inch when printing it. And then the attentive reader will think about it. Yes, yes, when printing. And until you print the image, but just look at the monitor, process it in Photoshop - dpi does not matter at all. It does not affect either the quality or the size you will print the photo (10 * 15 or A4) and generally does not affect anything. The only important parameter while you have a photo in digital form is the size in pixels. And that’s it! This is a harsh reality.

Let's look in order:

1. What if less or more than 300?
Yes, you can any number. While you are not printing, there is no difference, at least 1dpi, at least 1000dpi.

2. But what about the quality? After all, at 300 everything will be fine, as everywhere they write on the Internet, and in general this is widely heard. So, if the value is less, then the quality is worse?
As I wrote above, the quality is in no way connected with the dpi parameter. Point. Deal with it.

3. Well, what if I am going to print a photo? Then this parameter is already important and here the more - the better?
Not really. This parameter indicates how many dots (read: pixels) will be printed per inch of image. In this case, the dpi value can be set to any. For example, there is a photo sized 4000 * 6000 pixels. At 300dpi, it can be printed with a size of 34 cm * 51 cm (rounded tenths). But you can also print with a different dpi value. At 150dpi, it will be 67.7 cm * 101.6 cm.

4. And then what is the value?
It already depends on where the print is going. If in a glossy magazine, then 300dpi is quite suitable. For a home in a family album - 100-300dpi (approximately). And for a huge billboard, generally 20-70dpi is enough.
But I repeat once again - the size in pixels is more important when it comes to quality! Imagine that you have 2 photos on your computer: One with a size of 600 * 800 pixels with 600dpi. And the second is 2000 * 3000 pixels with 70dpi. Which of them can be printed more and better? It would seem that the first, he has as much as 600dpi - cool, then him! But no, the physical size in pixels is larger in the second file, despite the miserable 70dpi. The dpi parameter itself, while it is in a digital file, does not mean anything. When printing these two files, you can already select the desired dpi value. We will average it to an adequate value of 250 (you could take any number here) and get the physical print of the first file 6.1 cm * 8.1 cm, and the second 20.3 cm * 30.5 cm. As you can see, whose size is the pixels are larger - the physical size of the print is larger.

5. Where did 300dpi come from, and why is it required almost everywhere?
I don’t know where exactly the 300 number came from, but with this value, the printing house or photolab guarantees excellent print quality (considering that the size in pixels corresponds to that). In fact, this is an average figure, which may vary depending on your printing tasks.

In this photo, 2 photos are open in Photoshop. The photo on the left is 900dpi. The photo on the right is 1 dpi. As you can see, physically they look exactly the same.

If you suddenly come across a person who calls himself a professional and requires some ridiculous 300 dpi from you, without realizing what they mean - this is an ignoramus who is not worth working with. A person cannot be a professional if he needs some parameters in which he himself does not understand anything. It is better to refuse the services of such a person. Be it a retoucher, photographer, illustrator or anyone else.

And now some lyrics. For a long time I was going to write this article, but I put it off. And recently, more and more often I explain to people that dpi in the digital form of photography means nothing. Boiling up.

From real cases:
1 - The customer writes to me. Initially, there was a scan of the photo. And the output is needed, I quote: “The quality is about 600dpi, that is, a digital photo, not an edited scan .. ".
2 - In one public of retouchers, a conversation arose about how much dpi should be set during retouching ... And here is a quote from one retoucher: “They somehow wanted to force me to redo it because it was 240.”
3 - We need a photo shoot, 10 photos at the output with 300dpi.

I hope you also appreciated the absurdity of these cases. and this is only in the last week.

sergbrezhnev.livejournal.com

Resolution 300 dpi is how much

I continue the rubric “Frequently Asked Questions | ( FAQ) ". Traditionally, the questions themselves can be asked in the comments or sent by mail:

So, today's question, which I am asked regularly, as soon as it comes to saving processed photos to disk:

#16   What should be the resolution of the photograph?

It's about mysterious dpi, about which customers often mention in and out of place in the technical requirements for photographs. But not everywhere else you will find this - more often in the program interfaces comes across ppi  and no dpi. And customers write and write everything “Send us a photograph of at least 300dpi!»   What is all this and why is it for photographers?

In short, this is the location density:

dpi (dot per inch) - dpi

ppi (pixels per inch) - pixels per inch
And, most interestingly, all these things have nothing to do with digital raster photography until you are going to print it! That is, if you do not print your pictures (and now there are more such photographers than those who print), then you don’t have to bother with these parameters at all, you won’t need them.

But, just in case, in the resolution window you can set the value to 300. In Lr, for example, this can be done when exporting images, here:

For everyone else, there is a detailed answer. \u003d :)

Detailed answer:

A digital photo in a computer has only one size characteristic - the number of pixels vertically and horizontally (or their product, now calculated in megapixels). Here is this card, for example:

It has a size of 900 x 600 pixels (or 540,000 pixels, which is equal to 0.54 megapixels). The original frame from which this small copy was made was 3600 x 2400 pixels (or 8.64 megapixels) in size. And these values \u200b\u200bin pixels are the only parameter responsible for the size of photographs in digital form.

Problems can arise when you want to print a photo. Different printing machines and printers, depending on their device and the purpose of the print result, allow you to make images with different pixel sizes. That is, you can print pixels large and then on one inch (about 2.5 cm) they fit a little:

And you can play pixels a little smaller and then they already fit one inch more:

And you can make them tiny and then on the same linear inch there will already be a lot of them:

As a result, if you take and print the same image with a different pixel density per inch ( ppi), then it will have a different size on paper:

It is believed that when more than 300 pixels fit on one linear inch, the human eye is no longer able to separate them, and this gives a high-quality, “smooth” print, without noticeable pixelation. The vast majority of glossy magazines use exactly this (or so) print density and you can see the result yourself by buying a “glossy” printing in any kiosk.

In fact, now the density of 300 ppi is considered a kind of unwritten standard, which most publishers will focus on. Although nowhere, as far as I know, this figure in official standards does not appear. Well, let me correct, if I'm wrong.

At the same time, if we are talking about printing, for example, outdoor advertising posters (billboards) of large size (3 x 6 meters, for example), then there is no such need to make the microscopic pixels and print them tightly to each other - anyway, the audience will be on the poster look from a fair distance, not like a magazine. Therefore, very often when printing materials for such billboards, a resolution of about 50 ppi is used (there are 50 pixels of an image on one inch of a printed poster).

Ideally, you should yourself know what print density you will need and accordingly prepare your photos. If we talk about Ps, then there it can be done in the menu item Image -\u003e Image Size:

At the top of this palette, we can see the size of the photo in pixels (3600 x 2400):

And at the bottom - the size in centimeters (127 x 85 cm) at a density of 72 pixels per inch.

These 72 pixels per inch now, in general, look like a kind of spherical horse in a vacuum, because this is a purely rare indicator, which is now traditionally assigned to all digital images by default. And it has no real embodiment, because someone is now looking at the image on the monitor with a diagonal of 15 ″ and a resolution of 1024 x 768 pixels and he will have an image density of one, but someone can look at 25 ″ from 2560 x 1600 and his density will be different. But it’s so traditionally accepted that such a figure is assigned to digital photos - 72 ppi. “The answer to the main question of life, the universe and all that is 42!”

By the way, Apple engineers knowingly described the advantages of screens on iPhone4 in such detail when they first appeared on the market. With a diagonal of 3.5 inches, the image size is 960 x 640 pixels, which gives a resolution of 326 ppi. Which, as you know, is quite comparable with the quality of a good printing printing industry. And in the future, I'm sure the number of devices with high ppi will grow steadily.

If you uncheck this checkmark:

Then you can see how the image size changes depending on the ppi density (and with a constant image size in pixels - 3600 x 2400). At a density of 5 ppi (each pixel will be printed with a square of 5 x 5 mm), the image size will be 1829 x 1219 cm:

With a “journal” density of 300 ppi, the size will be already 30 x 20 cm (almost A4 format, that is, a cover, for example):

At 600 ppi, the photograph will take on 15 x 10 paper (“photograph, 10 by 15 with a naive signature.”):

And at 10,000 ppi, the size of this photo will be less than one centimeter on its larger side:

It is clear that printing with a resolution of 10.000 ppi in general does not make sense, especially when you consider that the threshold at which pixels are visible is considered to be 300 ppi.

If you still want to certainly display a picture with a resolution of 300 ppi, but on a larger medium, then you will need to turn on the checkboxes again and change the image size in centimeters:

At the same time, note that the image size in pixels will also grow. This is inevitable, because you want to keep the print density high and want a larger size, which means there will be more pixels in the image. Ps will add the missing pixels, calculating them from neighboring ones. Image quality may be noticeably affected.

Well, then what is it dpithat customers like to write about in terms of image quality? This is the print density of the dots by the output device. And this parameter is purely technical, it can tell the specialist how many dots it can print, for example, a particular printer on one inch of the image.

Strictly speaking, dpi  not always equal ppi. After all, one pixel of the image must be transmitted by several points of the printing device:

Here we can see that each square (pixel of a digital image) is displayed using several circles of different diameters. Due to their different sizes, it turns out to make a different color density, and, as a result, to get full-color images with halftones on print. But the printing machine does not know how to make dots of different sizes, it can only create spots of a certain diameter embedded in the design. Therefore, the circles we see actually consist of many small dots:

The density of these dots per inch is the parameter that is denoted as dpi. And if you count, then ppi  this example is, say, equal to 25, then dpi  will be many times more.

But in modern practice, it so happened that in the quality requirements, photographers very often put an equal sign between ppi  and dpi. And come as a result of requirements like “The final image should be 6 x 3 meters at 50 dpi”that in translation into the language of digital images means that the picture should be 11811 x 5905 pixels in size. As well as requirements, like “The picture should be no more than 3600 x 2400 at 300 dpi”, which, as you now understand, does not even look like "butter oil", but like "square butter." \u003d :)