All About Digital Photos

What Print Shops Really Mean by DPI

Okay - your print shop/graphics designer/magazine has asked for a digital photo at 300 DPI. What do they really mean by this?

What they are really asking for is a photo that will print at a certain paper dimension in inches at 300 pixels per inch (PPI). If you remember from the Myth of DPI, the term DPI is a holdover from when this setting in a digital photo would set the paper output quality (resolution) of a printed image (number of printer dots per inch). This is no longer the case, but people still confuse DPI with PPI.

Back to our print shop - if they are looking for a digital photo to print at 10 inches by 8 inches, at 300 PPI, then they are really looking for a digital image with a resolution of 3000 pixels by 2400 pixels (regardless of the DPI setting of that image).

What Print Shops Really Need

The concept that 300 PPI = photographic quality is also a holdover from the quality of printing equipment a decade ago. Present day printers will output a good quality digital photo, with "photographic quality" at 200 PPI - so the requirements for a 10 inch by 8 inch paper photo become a good quality digital image with pixel dimensions of 2000 pixels by 1600 pixels.

A good quality digital photo is one:

taken with a good quality digital camera (good optics and digital sensor)
a photo that has not been enlarged either in post-processing or by in-camera digital zoom (never (ever) use digital zoom).
a photo that has been properly shot (good lighting, no blur)
a photo shot within the camera's ideal ISO range (usually a low ISO such as ISO 100)
a photo that has been stored in either a lossless format (i.e. TIF) or a very low compressed JPEG (highest camera JPEG quality setting).

Such a photo will reproduce on paper at photographic quality (assuming current printing technology) at 200 PPI.

A Note to Print Shops and Graphics Designers

I keep getting emails from poor folk who say that their print shop or graphics designer keep asking for digital phots at ___DPI (usually 300 DPI). Please STOP DOING THIS to your poor clients - ask for what you really need, ____ pixels in your prefered format (i.e. low compressed JPG or a TIF). If your need is for a digital photo that can be printed at high quality at a width of 6 inches, and you think that 300 ppi is what is required to do this (based on your equipment), then you need a digital photo that is 1800 pixels in width (regardless of its DPI setting since it's a meaningless figure). So, ask for a digital photo that is at least 1800 pixels in width. Tell your client not to resize the photo. If the photo is less 1800 pixels, ask them to send it along anyway (so that you can test it) and that if it is larger than 1800 pixels it's also okay (don't have them resize a larger photo down to your "at least" pixel figure). If you are running older equipment/software that needs a particular DPI setting, then set it in the photo after you have received it.

Also, please don't ask for a digital image of ____Kb in file size (I've had print shops do this). This is even more meaningless than the DPI figure since the file size depends not only on the format (JPEG, TIF) but the compression used with that format. If you are in a long term relationship with the client, educate the client to take photos at the highest quality setting their digital camera allows (and then ask for a copy of the original photo) or if they are scanning (where DPI does count in converting paper inches to digital pixels), specify the resulting pixel dimensions that you want.

If everyone simply worked with pixels we'd have a happier (and much less confused) digital photo world.