Sizes of digital photographs. The relationship between pixels, centimeters and DPI

Many of us love to photograph. The variety and affordability of digital cameras make photography a popular pleasure for capturing the vivid, colorful moments of our lives. At the same time, the high quality of the obtained photos does not at all guarantee the same quality when printing digital images on standard roll photo paper. In this material I will tell you what are the sizes of photos for printing, I will give tables of available formats, and I will also give a number of examples that make it possible to clearly understand the features of different sizes of photos.

To understand what are the sizes of photographs for printing and what are their specifics, we need, first of all, to understand the basic concepts necessary to understand the process of digital printing.

Linear photo size- dimensions of the photograph in millimeters (width-height).

Photo parameters in pixels- the dimensions of your photo, expressed in the number of pixels (width-height).

Pixel- the smallest element of the image, usually a rectangular or circular point, and of a certain color. An image consists of hundreds or thousands of such pixels, which are counted both horizontally (width) and vertically (height). For example, an image size of 1181x1772 (usually corresponding to the standard 10x15 photo size) is 1181 pixels wide and 1772 pixels high.

Moreover, the more such dots-pixels in your image, the usually better it is, with better detail and rendering of objects.

Aspect ratio- the aspect ratio of the photo (for example, 1: 1, 2: 3, 3: 4, and so on). The parameter shows how much one side is shorter or longer than the other.

Bitmap (raster)- an image consisting of such pixels.

DPI- (abbreviation for "dots per inch" - dots per inch) - a parameter used to characterize the resolution of printing photos, that is, the number of dots per inch (inch is 2.54 cm). The basic printing standard is 150 dpi, the optimal one is 300 dpi. Accordingly, the higher the DPI, the higher the print quality of the existing digital photo.

Photo standard (format) Is a stereotyped aspect ratio of a photograph, which is important to adhere to in order to obtain the final image on paper.

Why it's important to consider standard photo sizes

In the vast majority of cases, your digital photographs will be printed on photo paper that has standard sizes. If the proportions of digital photographs and the selected sizes of photographic paper do not match, the photographs may come out stretched, not clear, lose the quality of the image, and have other undesirable consequences for you.

Therefore, it is important to measure the standard print sizes of your photographs against the pixel sizes of your digital photos in order to select the optimal print format.

Popular photo sizes for printing with a table of formats

The generally accepted photo standard is 10 by 15 cm. In this case, the size of a commensurate digital photo is usually slightly larger (for example, 10.2 by 15.2 cm), and the size in pixels of this photo will be 1205 by 1795 pixels.

Other formats are shown in the table below:

If you plan to work with large-format printing, then it has fairly broad requirements for a digital image:

If you know the dpi parameter and the number of pixels of your photo, then using the formula below, you can calculate the required dimensions of the sides of your photo:

In this formula:

x is the required size of one side of the photo in centimeters;
r is the resolution of the side of the photo in pixels;
d - 2.54 cm (standard inch size);
dpi - usually 300 (less often - 150).
For example, let's say the width of the image is 1772 pixels and dpi = 300.
Then 1772 * 2.54 / 300 = 15.00 cm in print width.

Popular photo formats

In addition to the classic 10 by 15 (A6 format) I have already mentioned, there are other popular photo sizes for printing. Among them, I would highlight the following:

Conclusion

This article has given the standard photo sizes for printing, popular photo formats, as well as a convenient formula for calculating the optimal sizes of the sides of a photo. I recommend sticking to the formats I listed, this guarantees the quality of the printed photos, and therefore the visual pleasure of viewing them.

Have you ever been disappointed when you print a picture from the Internet? Images looked fine on a computer screen, but printed either the size of a postage stamp or large and blurry. The culprit here is the picture resolution.

For the sake of fairness, it must be said: the permission was not invented in order to spoil our lives. The real reason for poor print quality is the very small pixel dimensions of most pictures on the Internet: usually 640x480 pixels or less, which makes them quickly and efficiently displayed on the computer screen and loaded on websites.

So what can we do to ensure that when printed, pictures from the Internet look as good as pictures from a digital camera and are of a decent size? The answer is simple: absolutely nothing. Most pictures lack pixels for high quality prints. Let's try to figure out why.

First of all, let's forget about downloading pictures from the Internet: by doing this, we are violating copyright.
Let's look at image resolution in general.

Resolution is a value that determines the number of dots (pixels) that fit in each inch of paper when printed. Obviously, since each image has a fixed number of pixels, the more you try to fit into one inch of paper, the smaller the output image will be; the fewer pixels in one inch, the larger the image will be printed.

Resolution refers entirely to printing, but has nothing to do with displaying a picture on a monitor screen; that is why everything on the screen always looks bigger and better.

For example, consider this photo:

I can't help smiling every time I look at her. I photographed this horse, once driving through the countryside. As a rule, she always stands proudly, imperiously, her appearance is full of dignity and grace. But that day I found her in a completely ridiculous position: she bent down in a strange way, a straw was tangled in her mane, and it seemed that the horse was chewing something. Or maybe she is diligently trying to smile at me? In any case, we will take her photo as a sample.

First you need to check the size of the photo in Photoshop via the Image> Image Size menu (Ctlr + Alt + I). The dialog box that opens displays full size information:

The Image Size dialog box is divided into two parts: the top is called Pixel Dimensions, and the bottom is called Document Size. Dimension shows the width and length in pixels, and Print Size shows the actual dimensions of the picture when printed on paper.

In the Pixel Dimensions subsection it is stated: the width of our photo is 1200 pixels, the height is 800. It sounds like a lot (multiplying the values of the width and height, we get as much as 960,000 pixels in the picture!) Yes, this is really a lot for a monitor screen. A photo of this size may not fit on the screen! But, unfortunately, this does not mean that the print quality will be high. Note the subsection Print Size:

Here we will find information about the current resolution and size of the image on paper. The resolution of the photo we are examining now is 72 pixels. This means that of the 1200 pixels that make up the width of the image, 72 will be printed on every inch of paper; Of the 800 pixels that make up the height, 72 will also be printed on each inch.

The value in the Resolution box applies equally to width and height, but not to the total number of dots. In other words, for every square inch of paper, 72 pixels from our image will be printed from left to right, and 72 pixels from top to bottom. The total number of pixels in each square inch of paper is 5184 (72x72).

Let's do a little math to make sure the width and height of the image are displayed correctly in the Document Size box. We know the width of the image is 1200 pixels and the height is 800 pixels. The resolution is currently 72 pixels per inch; to find out the dimensions on paper, you need to divide the number of pixels that make up the width by 72; the height is calculated similarly.

Width (1200 pixels) divided by 72 ppi - 16.667 inches
Height (800 pixels) divided by 72 ppi - 11.111 inches

So, the size of the image on paper will be 16.667x11.111 inches.

Referring to the Document Size subsection again:

The dimensions are exactly the same! How big a photo will turn out, isn't it?

Unfortunately, not everything is so simple. This resolution is not enough to display the required sharpness and good quality when printing. Take a look at the image below: this is what a photograph would look like if printed at 72 pixels per inch.

Try to imagine the quality at 11 "x 16".

Now the points are too far apart, so there is no sharpness or detail. The quality is dull, too soft and therefore unattractive. Everything looks different on the screen: monitors are low-resolution devices. Even a photo of relatively small dimensions, for example, 640x480 pixels, looks great on them. However, printers are high-definition devices, and would require much more than 72 ppi to produce quality prints.

How high does the resolution need to be to get professional quality prints? The generally accepted value is 300 ppi; the pixels are very close to each other when printed, which makes the image appear crisp. You can even use 240 ppi, and that's enough.

Let's change the resolution of our photo: in the Resolution field, set it to 300. Note that in the Pixel Dimensions subsection, the values 1200 and 800 have been preserved.

Increasing the resolution from 72 to 300 pixels means that out of 1200 pixels wide, 300 pixels will be printed in every inch of paper, and the same amount will be printed out of 800 pixels in height. With this compression, the photo on paper will be smaller. Therefore, under Document Size, the photo is now 4 "wide by 2.667" high.

Let's do some math again:

Width (1200 pixels) divided by 300 pixels per inch - 4 inches
Height (800 pixels) divided by 300 pixels per inch - 2.667 inches

That's all right!

When printed, the photo will be much smaller than at 72 pixels, but it will be of much better quality - we will enjoy a clear and well-detailed image.

Of course, no one would print photos as large as 4x2.667 inches. How to get a high-quality 4x6 photo? We will have to turn to calculations again.

Let's say you took some pictures of a family vacation with your digital camera and want to print them so that the size of the photos is 6x4. We now know that a minimum resolution of 240 ppi (better than 300) is required to achieve professional print quality.

Let's take a look at both resolutions and decide which one to choose. At 240 ppi, the width and height will be as follows:

We multiply 240 pixels by 4 inches wide - 960 pixels (width).
We multiply 240 pixels by 6 inches in height - 1440 pixels (height).
Total number: 960х1440 - 1,382,400.

So, the dimension of the photo should be 960x1440. Nowadays most digital cameras have a resolution of 5 megapixels (megapixels or millions of pixels) or higher, so in this case it will not be a problem to print a 4x6 inch photo even with a resolution of 300pix / inch. Pixel sizes will be respectively 1200x1800 (total 2,160,000).

But what to do when photos are required not 4x6 inches, but 8x10?

240 pixels x 8 inches - 1920 pixels.
240 pixels x 10 inches - 2400 pixels.
Total: 1920x2400 - 4,608,000 pixels.

So, to print a good quality 8x10 '' photo, its pixel size must be 1920 pixels wide by 2400 high (or vice versa), and the camera must be about 4.6 million pixels.

A digital camera with a resolution of, for example, 4 megapixels will not give the required 4.6 megapixels, therefore, it will not be possible to print photos from such a camera with a size of 8x10 with a resolution of 240.

To print a photo with a size of 8x10 inches and a resolution of 300 you will need:

300 pixels times 8 inches - 2400 pixels high.
300 pixels times 10 inches - 3000 pixels wide.
The total number is 7,200,000 pixels.

This is already a really large number of points!
To print an 8x10 inch photo at 300 ppi, the photo must be 2,400 pixels wide by 3,000 pixels high (or vice versa), for a total of 7.2 million pixels. That's a lot, and the camera should have a minimum resolution of 7.2 megapixels! Keep in mind that photos sometimes need cropping. So I highly recommend getting an 8MP camera!

14.06.2016

Photos are now taken by almost everyone, and everyone has heard such a term as "resolution". But not everyone knows what exactly this word means. Resolution means the number of dots per inch.

Such points, of which the photographs are composed, are called pixels. The law here is very simple: the greater the number of these same pixels in one inch, the higher the image quality.

The resolution allows you to judge the quality of the image creation process and the detail of the picture. In modern photography, this term has a lot to do with the digital format of photographs. But it is quite possible to meet it where it is, for example, about photographic paper or photographic film.

What does high definition mean?

If we talk about high resolution, then a high degree of detail is implied. Any professional photographer knows perfectly well that resolution, that is, the number of dots per 25.4 mm (which is equal to 1 inch), is denoted by such an abbreviation as "DPI" (see the article about).

If the image resolution is 300 DPI, then we can confidently say that these photos are of good quality. Based on their experience, photographers claim that the resolution allowed for printing images should be at least 150 DPI.

When printing photographs, the most common formats are 9 by 13, 10 by 15, 13 by 18 cm, etc. For each of these formats, there are specific linear dimensions in millimeters. Taking into account the format, it is easy to calculate the optimal size of the picture in pixels, in order to ultimately get an extension of 300 or more DPI.

If we take a photograph 9 by 13 cm, then its linear dimensions will be: 89 by 127 mm. We multiply the height in millimeters by the resolution we need and divide by 25.4 mm (see above). We get: (89 * 300) / 25.4 = 1027 - this is the number of pixels in height we need to have in the original image (photo). We do the same with calculating the width (127 * 300 / 25.4 = 1500).

Based on this, we understand that when printing a 9 x 13 photo, which is more than 1027 by 1500 pixels in pixels, we will receive a high resolution photo (above 300 DPI).

But, as practice shows, often images with an expansion of 150 DPI look no worse than the same photo, but with a higher level of expansion - 300 DPI and higher. Much depends on the distance from which this image will be viewed and what exactly is depicted on it.

Interesting publications on the site

Welcome to my blog again. We are in touch with you, Timur Mustaev. It is possible that everyone had to deal with such a situation: you took pictures, the picture looked clear and high-quality on the screen.

Then you went to the salon and printed it, and it looked completely different from the monitor screen and had a lot of digital noise. What is the problem? Today I will talk in more detail about this problem and what are the formats of photos. Let's start studying.

Basic terms for understanding the topic

Pixels - small square dots, colored with a certain light, which make up a single whole - an image.

When you look at a photograph, the eye does not notice specific raster points, since they are very small and their number can reach tens of thousands, they merge, forming one picture. Only when zoomed in will you be able to see them.

There is a peculiarity: the higher the number of raster dots, the more details are drawn and the better the photo is.

Linear dimension Is the information about the width and height of the printed image, expressed in millimeters. They can be recognized using a regular ruler. For example, the linear size of a picture with parameters 10 * 15 cm –102 * 152 mm.

Parameters in pixels Is data about the width and height of a digital image.

There is one peculiarity. Digital cameras take pictures of the same sizes: 640 * 480, 1600 * 1200, and on the monitor we see 800 * 600,1024 * 768,1280 * 1024. That is, there is a significant mismatch.

Let's look at some examples. If the picture has a size of 450 × 300 raster pixels, then the picture will be rotated under the album, that is, it will be placed horizontally. What does it depend on? The width of the image is greater than the height.

If we take the size of the picture 300 * 450, then it will be located in portrait orientation, that is, vertically. Why is this so? The width is less than the height.

Resolution is a number that connects the values in millimeters and in pixels, measured in dpi(from the English "dots per inch" - the number of dots per inch).

Experts advise setting the resolution to 300 dpi, intended for obtaining high-quality photographs. The minimum resolution is 150 dpi.

The higher the indicator, the better the photo is.

But, it is worth noting that if you take a photograph larger than the original, that is, "stretch the raster points", then the quality drops.

Resolutions may vary with different camera models. What's the secret? Photographic equipment manufacturers indicate an inaccurate number of megapixels, for example, 12 MP. In fact, it may turn out to be 12.3 or 12.5 megapixels. But the print quality will not deteriorate from this fact.

Standard sizes

What are the photo formats? Let's find out.

The most popular print size is 10 * 15 cm. It is used to form a family archive.
The next one is 15 * 20 cm or A5.
A4, 20 * 30 cm or 21 * 29.7 cm. Used to decorate walls with photographs. Since A4 is the size of office paper for printing, the printout will not be difficult, since printers are mainly designed for A4 production.
30 * 40 cm - complex format. Has two other names: A3 or A3 +. Why difficult? Because there is confusion. A3 size has parameters of 297 * 420 mm, but such photo frames cannot be found, they are not on sale. The closest photo frame to this photograph is 30 * 40 cm. Be careful when ordering. Photo frames are made with glass.

Custom sizes

Often we have to order a photo of not a standard size, but a unique one - non-standard.

13 * 18 cm. It is used extremely rarely. Printing is difficult.
40 * 50 cm or 30 * 40 cm. Pictures with these parameters will help to decorate the interior, since they are quite large. Therefore, the quality must be high.

How to calculate dimensions for high resolution

Let's take a closer look at a photo with parameters 10 * 15 cm.

The linear values of these parameters (usually indicated in special tables) are 102 * 152 mm.
Let's multiply the width of the image (102 mm) by the resolution we want to achieve, in our case it is 300 dpi.
Divide the result of the last step by the number of mm in one inch - 25.4.
We get the number of raster points of the original image in width 102 * 300 / 25.4 = 1205.

We carry out the same algorithm for the height.

152*300/25,4 = 1795.

So, we conclude that for any photograph, the value of which will be more than 1205 * 1795 raster dots, when printing on a 10 * 15 cm format, the resolution will be more than 300 units.

Sometimes it turns out that images with resolutions of 150 and 300 units look exactly the same. Why does this and what does it depend on? Depends on the genre of the picture and the distance from which it will be viewed.

Documentation

Document formats are measured in cm!

For different types of certificates - 3 * 4 cm;
For visas - 3.5 * 4.5 cm;
For passport - 3.7 * 4.7 cm;
In a personal matter - 9 * 12 cm;
Residence permit - 4 * 5 cm;
For passes - 6 * 9 cm.

Other range of formats

The main thing is that the photo frame matches the photo. Therefore, manufacturers produce special paper with certain sizes:

A8 (5 * 7 cm);
A7 (7 * 10 cm);
A6 (10 * 15 cm);
A5 (15 * 21 cm);
A4 (21 * 30 cm);
A3 (30 * 42 cm).

Why choose the right paper? As a result, you do not have to look at an incomplete, cropped image, or crop out white areas that were unnecessary. Usually the photo studio provides print formats with examples.

Features of the order

If you place an order on the Internet, then the system, when sending the image, says which parameters will be more appropriate to obtain a high-quality image. If you choose the format at will, and not recommended by the program, then the administration does not take responsibility for obtaining low quality.

It would seem, why in the modern age of digital technologies printing photographs, because most of the photos are viewed in digital form. Knowledgeable people say that photography comes to life only when it is printed on paper, has a frame and hangs in the room to decorate the interior.

Remember that before printing, you need to select certain parameters that will affect the quality of the printed image.

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All the best to you, Timur Mustaev.

02.24.15 46.2K

In this article, we'll take a look at how image resolution affects print quality.

Have you ever downloaded a picture from the internet and then printed it with results that were, well, less than you'd expect? The image looked great on your computer screen, but when you printed it out, it was either printed at postage stamp size or normal size, but it looked blurry or “diced”? The reason is in the image resolution.

In fact, this is not entirely fair. It is not that the resolution of the image is specifically specified in such a way as to make you unhappy when you print a photo from the Internet. The problem is that most photos on the web are very small in pixels, typically around 640 pixels wide by 480 pixels high. Or even less.

Because the image doesn't have to be very large to look good on a computer screen. And also because small images load much faster than larger ones ( this is a completely different question, which we will not touch on in this article).

So what can we do to make photos downloaded from the Internet look like quality digital camera photos when printed? The answer is absolutely nothing. In most cases, Internet images simply do not have enough pixels to print at high quality. At least, if you don't print them in postage stamp format. Let's find out why.

First of all, let's move a little away from the topic of downloading images from the Internet, as such, and from the fact that we really shouldn't do it anyway without the permission of the copyright holder. Let's take a look at image resolution in general.
The term " image resolution"Means how many pixels your photo will fit on each inch of paper when printed.

Obviously, since your photo has a fixed number of pixels, the more pixels there are in one inch, the smaller the image will look on paper. Likewise, the fewer the pixels per inch when printed, the larger the image.

The number of pixels per inch when printed is called " image resolution". The image resolution determines the print quality of the image. It has nothing to do with how the image is displayed on the computer screen. Therefore, photos downloaded from the Internet tend to have a much higher quality on screen than when you print them.

Let's take a photo as an example:

Poor horse photo

I can't help laughing every time I see this photo of a horse, which I took while driving through the countryside. Usually this horse is a proud, powerful, dignified animal, but I seem to have caught him in a rather unsightly position. She stands at a slightly strange angle, the straw hangs from her mane, and I think I caught her chewing food.

Either that, or she's desperate to smile at me. In any case, this horse is already embarrassed that I caught her at such a moment. Let's use this image as an example.

First, let's see what Photoshop can tell us about the current size of this photo. I go to the "Image" menu at the top of the screen and select " Image size", After which a dialog box appears with the appropriate name" Image size«:

The Image Size dialog box shows us the current photo size

Dialog window " Image size"Is divided into two main parts:" Dimensions in pixels"At the top and" Document size"Directly below it.

« Dimensions in pixels"Indicate how many pixels our image contains. " Document size"Tells us how big the image will look on paper if we print it. If we look at the section " Dimensions in pixels”, We see that this photo is 1200 pixels wide and 800 pixels high. This may seem like a huge number of pixels ( 1200 by 800 = 960,000 pixels!).

And this, of course, would be the case if we were displaying an image on a computer screen. Indeed, at 1200 by 800, it might be too large to fit entirely on your monitor!

But just because it looks nice and big on screen doesn't mean it will look nice and big on print. At least not with a high degree of quality. Let's take a closer look at what the section “ Document size»:

The Document Size section tells you how large or small the photo will be when printed at a specific resolution.

Chapter " Document size"Of the" Image size»Lets us know two things: what is the current resolution of our image and how large or small the image will be if we print it based on that resolution.

We currently have a resolution of 72 ppi, which means that out of 1200 pixels, which is the size from the right to the left edge of the photo (width), there will be 72 pixels for every inch of paper. And out of the 800 pixels that make up the image size from top to bottom (height), there will also be 72 pixels for every inch of paper.

The value in the Resolution box is for width and height, not total pixels. In other words, for every square inch of paper, 72 pixels will go per inch of height and width. The total number of pixels printed in each square inch of paper would then be 72 by 72 ( 72 pixels wide by 72 pixels high). Which gives us 5184 pixels!

Let's do some simple math to make sure the width and height shown to us in the “ Document size»Is correct. We know from the section “ Size in pixels"That we have 1200 pixels from left to right and 800 pixels from top to bottom. The print resolution is currently set at 72 ppi.

To figure out how big our image will be when printed, we only need to divide the number of pixels from left to right by 72, which will give us our image width when printed. And also divide the number of pixels from top to bottom by 72, which will give us the print height. Let's do that:

1200 pixels wide divided by 72 pixels per inch = 16.667 inches wide
800 pixels divisible by 72 pixels per inch = 11.111 inches high

Based on our own simple calculations, at 72 pixels / inch (ppi for short), our image will be 16.667 inches wide and 11.111 inches high when printed. And if we look at the section " Document size" again:

Confirming Print Sizes in the Document Size Section

This is exactly what it says here! Wow, a 1200 x 800 pixel photo is big enough to print at 11 x 14 inches, we can even scale it down a bit! Wonderful!

Unfortunately no. If everything in life was so simple.

The point is, 72 pixels per inch is not enough to give us a sharp, good quality, professional-looking image when printed. Not even close. To give you an idea of what I mean, here's a rough approximation of how a photo would look on paper if we tried to print it at 72 pixels per inch.

You will need to use your imagination a little. Try to imagine it's 11 by 16 inches:

How your photo will look on paper when printed at just 72 ppi

Doesn't look very good, does it? The problem is that 72 pixels per inch provides too little image information to print a sharp, crisp photo on paper. It’s like there’s too little peanut butter on a large piece of toast. The photo now looks blurry, boring and generally unattractive.

We don't see this on a computer screen because computer monitors are usually referred to as low-resolution devices. Even a photo with relatively small pixel dimensions, such as 640x480, will look great on a computer screen.

Printers, however, are high-definition devices, and if you want your photos to print clearly and show all the small details, you need a resolution much higher than 72 pixels per inch.

So what is the maximum resolution you need for professional-quality printing? It is generally accepted that this is 300 pixels per inch. Printing an image at 300 ppi compresses the pixels enough to maintain sharpness.

In fact, 300 is usually even a little more than necessary. You can often see photos at 240 dpi without any noticeable loss in image quality. However, the professional standard is 300 ppi.

Let's take the same image, with the same 1200 pixels wide and 800 pixels high, and then change the resolution from 72 pixels per inch to 300 pixels per inch and see what happens.

Here is the dialog box " Image size"With a new resolution of 300 ppi. Note that in the section “ Size in pixels"At the top we still have 1200 pixels wide and 800 pixels high.

The only thing that has changed is our resolution - from 72 to 300:

The print resolution has been changed to 300 ppi

The fact that the resolution has increased from 72 to 300 pixels per inch means that of the 1200 pixels that our image is wide, 300 pixels are printed on one inch of paper. And out of 800 pixels in height, 300 are printed for every inch of paper in height. Naturally, with so many pixels per inch of paper, the print will be much smaller.

And of course the Document Size section now says our photo will be printed at just 4 "wide, 2.667" high:

The photo will now be printed at a much smaller size than before.

Where did these new widths and heights come from? Again, some simple math:

1200 pixels wide divided by 300 pixels per inch = 4 inches
800 pixels high divided by 300 pixels per inch = 2.667 inches

The photo will now be printed at a much smaller size than it did at 72 dpi. But what we lose in physical size, we more than make up for in image quality. At 300 ppi ( or even at 240 ppi) we will enjoy a clear, professional-quality result:

Higher print resolutions reduce the size of the photo, but the image is of much higher quality.

Of course, most people don't print their photos in non-standard formats like 4 by 2.667. So how do we make sure we get professional-quality results when printing in a more standard format like 4 by 6? Great question, and we can get the answer back to boring arithmetic.

Let's say you took photos from your recent family vacation with a digital camera and you want to print some of them on a 4 x 6 printer. Now we know that in order to achieve professional quality pictures, we must set the resolution images at a minimum of 240 ppi. Although the official standard is 300 ppi.

Let's look at both of these resolutions to see how large camera images need to be in order to print them in good quality 4x6. First, let's look at 240 pixels per inch.

To figure out how large in pixels our images need to be in order for them to be printed in 4x6 in professional quality, we just need to multiply 240 by 4 in width and then 240 by 6 in height ( or vice versa, depending on whether your photos are in landscape or portrait orientation).

Let's do that:

240 pixels per inch x 4 inches wide = 960 pixels
240 pixels per inch x 6 inches high = 1440 pixels

Based on these calculations, we can see that in order to print a digital photo in 4x6 format with a resolution of 240 ppi, while maintaining excellent quality, the photo size in pixels must be at least 960x1440. We see also, how many pixels the photo should contain as a whole, 960 times 1440 gives us 1,382,400 pixels.

Let's round this up to 1,400,000 pixels. This may sound like a lot, but it really is. 1.4 million is the minimum number of pixels required to print a 4 x 6 photograph at the minimum resolution of 240 ppi for normal quality.

The good news is that most digital cameras on the market today are 5MP (“ mega pixels "or" million pixels") and higher. So you won't have a problem with good quality 4 x 6 prints, even at 300 ppi.

Of course, we haven't figured out exactly how many pixels we need to have to print a professional quality 4x6 photo at 300 ppi. So let's do it. We will use the same simple formula as described above.

We'll multiply 300 by 4 and then 300 by 6 to get the pixel dimensions we need:

300 pixels per inch x 4 inches wide = 1200 pixels
300 pixels per inch x 6 inches high = 1800 pixels

Let's do another quick calculation to find out how many pixels we need in total:

1200 pixels wide times 1800 pixels high = 2160000

So, in order to print 4 x 6 photos in good quality using the professional standard of 300 ppi for resolution, our photo must be 1200 pixels wide by 1800 pixels high (or vice versa). This means that we should have a total of 2,160,000 pixels. Again, this shouldn't be a problem for most digital cameras on the market that have 5MP or more.

But what if you have a photo that you adore and think it deserves to be printed in 8x10 instead of 4x6? How large does the image need to be to look normal when printed in 8x10 format? The answer to this question is as easy to give as before.

All you have to do is multiply the pixels per inch by the width in inches, and then do the same for the height.

Let's use 240 ppi first:

240 pixels per inch x 8 inches wide = 1920 pixels
240 pixels per inch x 10 inches high = 2400 pixels

Total pixels = 1920 pixels wide x 2400 pixels high = 4,608,000 pixels.

Based on the results of the calculations, we can see that in order to print a photo in good quality in an 8 by 10 format, the image must be 1920 pixels wide and 2400 pixels high (or vice versa). A total of about 4.6 million pixels.

We are now starting to approach the frontier of the technical capabilities of digital cameras. A 4-megapixel digital camera will no longer be enough for us to be able to print an image in 8 x 10 format with a resolution of 240 pixels per inch. The loss of about 600,000 pixels is not too significant. You will still be able to print an image in 8x10 format, but most likely you will not get professional quality anymore.

Let's do the same calculations for 8x10 at 300 ppi:

300 pixels per inch x 8 inches wide = 2400 pixels
300 pixels per inch x 10 inches high = 3000 pixels

Total pixels = 2,400 pixels wide x 3,000 pixels high = 7,200,000 pixels

We are now truly moving beyond the limitations of some digital cameras. In order to be able to print a photo in 8 x 10 format with a resolution of 300 pixels per inch, our photo must be 2,400 pixels wide by 3,000 pixels high (or vice versa), for a total of 7.2 million pixels! Now that's actually a lot!

This means that you must have at least a 7.2 megapixel digital camera. In this case, you will be able to print your photos in 8x10 format, and still be able to get professional quality images. Of course, do not forget that most photos require at least some cropping, which means you lose a few more pixels.

If you are confident that you will be printing a lot of 8x10 photos, investing in a quality 8MP or higher camera is highly recommended.

That's all in general!

This publication is a translation of the article " Image Resolution And Print Quality"Prepared by the friendly project team

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