One of the more common dilemmas for people is choosing the paper size for printing their photos. Everybody knows that if your digital camera does not produce enough pixels (or actually megapixels) printing its photos on a large paper size will yield poor quality and you will be able to see the actual pixels (also known as pixelation)
So how many megapixels do I really need in order to print on a specific paper size? there is no one right answer for that. The actual quality of the print depends on many factors other than the number of pixels. For example the paper quality itself the printing process that is used the lighting conditions when the photo was taken the photo itself (i.e. portraits are different than scenery) and much more.
However a rough estimation of how good a picture will be based on the number of pixels can be calculated and is actually pretty easy to do. When evaluating how good a print will be there is a measurement that is simple to use and provides a good estimation for the quality – it is called DPI (dots per inch). DPI is actually the number of pixels along one inch. To get a good print you would need a certain DPI (on both X and Y axis).
Experiments show that the following qualities are usually associated with a specific DPI number:
- DPI 100 – fair to bad
- DPI 200 – good
- DPI 300 – very good
So all we need to do now is to figure out for each paper size how many megapixels translate to those DPI numbers. To calculate this we need to simply multiply the page length by its width in inches. The result is the number of square inches on the page. Now multiply this number by the square of the DPI number and the result is the number of pixels on the page which is the number of pixels we want our source photo to have. Here are the numbers calculated for some common sizes (for 100,200 and 300 DPI respectively):
- page 4X6 0.24MP 1MP 2MP
- page 5X7 0.35MP 1.5MP 3MP
- page 8X10 0.8MP 3MP 7MP
- page 11X14 1.5MP 6MP 14MP
- page 16X20 3MP 12MP 28MP
- page 20X30 6MP 24MP 54MP
Again we would like to emphasize that these are just ballpark numbers. Factors like the ones mentioned above and also like the compression ratio used (low or high compression) and the aspect ratio difference between the paper and the camera can result in a need for more or less pixels. Our best advice is if you are not sure just try one or two photos before printing a large batch.
Ziv Haparnas is a technology veteran and writes about practical technology and science issues. This article can be reprinted and used as long as the resource box including the link is included. You can find more information about photo printing on http://www.printrates.com.
PictureCorrect Comments:
I have always wondered how many megapixels it takes to make certain sizes of prints, and I found the chart above to be very helpful. Here’s one example: If you want to make a 16X20 inch poster, you should buy a digital camera that has at least a 3 megapixel (MP) capacity.
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Well, regarding the added comment by PictureCorrect…. You can technically print a poster size photo with ANY mp capacity, but the real question is: Will it look good? No. Will it be a quality print that for example, a newly married couple, who’s wedding you were paid to photograph, be happy with? No. Its safe to go with the middle ground 12mp or above for a 16×20 in print.
I was impressed to read the accuracy of this article however. 10 years ago I was actively managing a Ritz Camera store, a company that some of you may remember. The FIRST question we asked everyone looking to purchase a digital camera was “Are you planning to print photos, and if so, what size?” Of course back then, a quality DSLR with the required 6mp needed to print an 8×10, a pro could be happy with, cost approx the same amount that a 24mp DSLR costs now. Luckily, many average consumers weren’t concerned about printing, let alone print 8×10 sized pictures. I photographed low light, live concert photos, album covers and the occasional wedding so it WAS a concern for me. Being the type that wants to get it correct the first time & being unable to afford Nikon’s premier camera then, I made a heavily researched decision to purchase Nikon’s top 6mp DSLR body (which I still own). Due to the marketing and exaggerated impression that quality is only achieved with 20+mp, those uninformed, are quick to judge a 6mp DSLR. Yet at the same time, others are (somehow) impressed & content with an older iPhone video or photo, believing it looks that good to everyone. Well, they do not.
There will always be those who expect a perfect print, and will relentlessly blame everything besides user error, when they don’t achieve that. Everything from camera and printer settings, exposure & editing (two of the things that can drastically effect end results ) to the quality of what I’ll simply call “the guts of the camera” or what some may view as the internal negative… To the things listed above as far as printer quality and settings go, will always matter when it comes to the physical end product, especially for an amateur printing at home. I could go on and on about this, obviously, but I’ll end with a huge thank you for the accuracy. In a time when experience and valid information should be crucial… When folks too easily listen to biased or uneducated opinion, I thank you.