My brother was sending me SMS messages the other day asking about print quality for a 2MP picture.  I answered that for a 2MP picture, you can print 3R photos okay.  He then asked if it was okay to print a VGA quality (640×480 pixels) to a wallet sized picture, which would be approximately 2×3 inches.  To which I said yes, that would still turn out fine.

I brought this up because, relative to the number of pictures being taken, there are less and less pictures being printed.  That may be true, in relative terms, of course.  But looking at it from a different perspective, there really are a lot more pictures being printed, not just in one-hour photo developing booths or shops at the mall, but also at home on the computer with the colored printer.  And these are not just pictures taken personally with the camera, but also pictures sent via email, or posted on social-media websites.

Going back to the print sizes, there’s an almost direct relationship between the camera resolution and the size of a good print.  Or, rather, the picture resolution and the resulting print.  It’s easy to forget that the camera resolution in megapixel can be re-set to a lower resolution by the user.  This also depends on how compressed the JPEG file is (which is a related to how good the camera software  is). And it’s also much harder to realize that you can get better prints (or larger good prints) from RAW files or from TIFF pictures.

The rule of thumb I follow is relatively easy.  A 3MP picture can be printed on a 4R or up to half the size of an A4.  A 5MP can be blown-up to A4 paper size and still have good quality, but you’d be better off with an 8MP picture on A4 paper.  Again, this depends mostly on the JPEG quality.

Relating this further to JPEG quality, there are lots of algorithms for JPEG, and these yield different compression ratios.  Typically, most JPEGs have a ratio of 1:10, meaning that a JPEG of any given size is equivalent to an uncompressed bitmap (BMP or TIFF) of up to ten times the file size.  With greater compression, you would have to print to a smaller paper size to get a better quality.

However, if you have a RAW or TIFF file of the picture, you can blow that up to a larger size.  Better yet, if you have a postscript-capable printer, printing can give better results.  To do this, you have to paste the picture to a document (Word or PageMaker) or open in a photo-editing software (Adobe PhotoShop or GIMP), and print as an EPS file.  Without going into the technical details of what a PostScript printer does and what an EPS file contains, suffice to say that personally, I have had better print quality using this method.

I’ve seen pictures blown-up out of proportion to the file size and pixel resolution, and the resulting pixellation can be tolerable or not, depending on how far you are viewing it.  I sometimes think it’s such a waste to print a badly pixellated picture.