Resolution…

Today, we are going to hit on a topic of interest to every photographer…resolution. Before we get started, a quick defenition. The American Heritiage Dictionary defines resolution as The fineness of detail that can be distinguished in an image, as on a video display terminal.

The number that most people associate with resolution is ppi, or, pixels per inch. What this is is the number of pixels (dots) in each linear inch of  printed photograph (not digital file). I know this will sound strange to most people, but, digital photo files have no inherent resolution. The resolution of a file comes from trying to squeeze a certain number of pixels onto a certain size print. A digital file contains a fixed number of pixels. This generally determines how large you can print the photo, and hence, the resolution.

When you print a photo, you resolve the photo at a certain number of pixels per inch. Do not confuse this with dpi (dots per inch), which is a measure of printer resolution. I think this is where a lot of people get hung up at on this subject. Also, the larger you print the photo, the less pixels per inch you need because the viewer is not going to be right on top of the photo, so the loss of detail will not be as big of a deal.

 Anyways, here is a quick method to roughly determine how large you can print a given photograph. Most people seem to agree that anywhere between 200 and 300 pixels per inch nets you the highest quality photo with detail noticable by the human eye. So, if you have a digital file that has pixel dimensions of 1200×1500, you could print a pretty well detailed 4×6 in photo. (1200 pixels divided by 300 pixels per in). Remember, this is just for MAXIMUM detail. you could print a 8×10 in photo and would get a ppi of 150. The photo would probably appear a bit blocky or fuzzy.

In a nutshell, divide your pixel dimensions by your inteded output resoultion to get your maximum print size. You can get your print dimensions from the EXIF data embedded in your file. In Windows, right click the photo, go down to properties, click on it, then click on summary. Ignore the horizontal and vertical resolution, that only has to do with on screen resolution.

If you have any questions, comments or concerns, as always, feel free to email me.

Dave

This entry was posted on 12. March 2009 at 17:48 and is filed under Photographic Techniques. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response or trackback from your own site.