This is a complex subject. Megapixels are a measure of quantity, not quality. An 8 megapixel camera phone isn’t the same as an 8 megapixel DSLR camera. In short, not all pixels are compared equally.
Simple formula to determine megapixels
Multiply the width (in pixels) by the height (in pixels) then divide the result by 1 million
For the sake of simplicity, we are going to assume you have a DSLR camera. I currently shoot with a Nikon D700 12.1MP camera for sports and a Nikon D810 36.3MP camera for portraits. To determine how many megapixels your camera shoots, use a program such as Lightroom or Window’s explorer to review the metadata. Look for dimensions under the Metadata panel.
The D700 shoots 4,256 by 2,832 pixels. Using our formula we multiply 4,256 by 2,832 which equals 12,052,992. Then we divide that by 1,000,000.
(4,256 x 2,832) / 1,000,000 = 12.052992 or 12.1MP
Calculate how many megapixels you need for a high quality print
( (300 x Width) x (300 x Height) ) / 1 million
300 ppi pixels per inch is recommended for high-quality prints. Determine the physical size of the print you want to make, such as 4 x 6 inches, 8 x 10 inches, etc. Now, multiply the width by 300, and the height by 300, which will give you the size in terms of pixels. Therefore, a 10 x 8 inch print would be 3,000 x 2,400 pixels equaling 7.2 million pixels. Dividing 7.2 million by 1 million will give you 7.2 megapixels, the minimum resolution you’ll want your camera to have.
( (300 x 10) x (300 x 8) ) / 1,000,000
(3,000 x 2,400) / 1,000.000
7,200,000 / 1,000,000
7.2 megapixels
Calculate the largest size the image can print at 300ppi
(Pixel Width / 300) by (Pixel Height / 300)
Dividing an image’s pixel width by 300 will give you the largest length the image can print at full resolution. Dividing an image’s pixel height by 300 will give you the largest height the image can print at full resolution. Therefore, a 6399px by 4170px image can be printed at a maximum size of 21.33 by 13.9 inches.
6399px / 300 = 21.33 inches
4170px / 300 = 13.9 inches
21.33 in by 13.9 in maximum print size
Get the optimal detail
Jeff Schewe by far is the most authoritative expert on digital printing. In fact, he has written several must have books on the subject. The Digital Print and The Digital Negative are his most current ones. I reached out to Jeff for his expert advice. He confirmed 300 is the generally accepted resolution for inkjet prints (or silver chromogentic lab prints). But he added, it gets a bit more complicated if you want to get the optimal detail.
Epson pro printers “want” 360ppi (by want, he mean that’s what the printer reports to the printing pipeline). In fact, if you have enough native resolution you can print at 720ppi if you have “Finest Detail On” in the driver. For Canon & HP printers, the numbers are 300/600.
If you print out of Lightroom, Jeff says this is easy-just click on the Print Resolution and enter 360ppi (or 720 with Finest Detail selected). The numbers would be 300 or 600 for Canon & HP. Obviously, this is more complicated when printing out of Photoshop.
If going out to a lab, the labs generally do want only 300ppi which is fine.
A solution if your Print provider demands 300ppi
If the print service you use demands you send images that are 300ppi at full size, a simple solution is using onOne’s Perfect Resize. Perfect Resize use Genuine Fractals powered algorithms for optimizing clarity and detail for different image types. It gives you the best quality enlargements for your photos, whether taken with a DSLR or your mobile device.
I would like to see an unbiased head-to-head comparison of onOne’s Perfect Resize to SourceForge’s SmillaEnlarger, the latter being Free Ware that has been around for many years. That would enable me to determine the dollar merit as well as the quality merit.
Ed why not do that yourself? You can download a trial version of onOne and make the comparison as unbiased as you like.
Thanks for the tip. Another program is DXO. I’ve used onOne for so long, I haven’t looked for another solution.
If I want the highest quality, I run it through Perfect Resize. I have never been disappointed in the results.
After hunting for hours for a definitive answer about pixel size and prints, I finally found this fantastic blog post. Thank you so much for laying it out in clear, easy to understand detail!
thank you!
Incredibly helpful article, one question it leads me to if I’m understanding correctly is billboards and other large prints require resizing, so what is the common method they use? Software similar to onOne? Something else? Thanks!
Billboards are usually printed in strips, then pieced together. Yes, software like onOne does a great job at re-sampling an image. Also keep in mind, images that large are usually seen from a distance.
Thank you for the response.
I think these Digital Backs goes upto 80MP, and quite useful for such high quality huge images.
The one you recommended “onOne’s Perfect Resize” will be useful in my case I think i.e a 22MP image can be enlarged using this software and printed as huge banner images. Correct me if I am wrong.
I am taking pics in Canon 5D mkIII, and the size obtained for one of my recent pic is
5760 × 3840
Which comes to 22 mega pixel
Is that means it can be printed @300ppi to the maximum size of (w)19.2inch x(h)12,8inch?
In that case how do they print big banners of several feet of width and hight for advertisements? Are they not printed with full resolution?
Billboards for example are printed in strips then pieced together plus they are meant to be seen from a distance so they can afford to print at a lower resolution. Special enlargement prints are usually shot with digital backs at a much higher resolution.
Such a helpful article! Thanks for sharing these tips for printing!
for BW the 7.2 would be right, but you might want to multiply the
( (300 x 10) x (300 x 8) ) / 1,000,000
(3,000 x 2,400) / 1,000.000
7,200,000 / 1,000,000
7.2 megapixels
by 3 for a color image which is 3 BW channels to make the color 21mb color file. pixel diminsions and actual file size can get confusing for people
I would like to see an unbiased head-to-head comparison of onOne’s Perfect Resize to SourceForge’s SmillaEnlarger, the latter being Free Ware that has been around for many years. That would enable me to determine the dollar merit as well as the quality merit.
Thanks for the tip. Another program is DXO. I’ve used onOne for so long, I haven’t looked for another solution.
Ed why not do that yourself? You can download a trial version of onOne and make the comparison as unbiased as you like.
After hunting for hours for a definitive answer about pixel size and prints, I finally found this fantastic blog post. Thank you so much for laying it out in clear, easy to understand detail!
thank you!
Incredibly helpful article, one question it leads me to if I’m understanding correctly is billboards and other large prints require resizing, so what is the common method they use? Software similar to onOne? Something else? Thanks!
Billboards are usually printed in strips, then pieced together. Yes, software like onOne does a great job at re-sampling an image. Also keep in mind, images that large are usually seen from a distance.
Thank you for the response.
I think these Digital Backs goes upto 80MP, and quite useful for such high quality huge images.
The one you recommended “onOne’s Perfect Resize” will be useful in my case I think i.e a 22MP image can be enlarged using this software and printed as huge banner images. Correct me if I am wrong.
If I want the highest quality, I run it through Perfect Resize. I have never been disappointed in the results.
Such a helpful article! Thanks for sharing these tips for printing!
for BW the 7.2 would be right, but you might want to multiply the
( (300 x 10) x (300 x 8) ) / 1,000,000
(3,000 x 2,400) / 1,000.000
7,200,000 / 1,000,000
7.2 megapixels
by 3 for a color image which is 3 BW channels to make the color 21mb color file. pixel diminsions and actual file size can get confusing for people
I am taking pics in Canon 5D mkIII, and the size obtained for one of my recent pic is
5760 × 3840
Which comes to 22 mega pixel
Is that means it can be printed @300ppi to the maximum size of (w)19.2inch x(h)12,8inch?
In that case how do they print big banners of several feet of width and hight for advertisements? Are they not printed with full resolution?
Billboards for example are printed in strips then pieced together plus they are meant to be seen from a distance so they can afford to print at a lower resolution. Special enlargement prints are usually shot with digital backs at a much higher resolution.