Thanks for commenting; I like having many points of view represented!

Semantics! :-)

Thanks for your reply. You raise interesting points, but I maintain that images don’t have an inherent resolution. What they do have is an inherent pixel dimension, or if you want to state it very simply, pixel count. As soon as that pixel count is applied to a measured area in physical space, it implies a resolution, but that resolution will vary based on the dimensions of the area.

In other words, you can’t take an image off of your memory card, look at it in some program, and say “this is a 182.3 DPI image,” because there are no inches involved yet. You can tell Photoshop that you wish for it to be displayed at 182.3 DPI and it will alter its rulers to demonstrate how big it will be on paper, but that is all theory; it’s all math.

You’re absolutely right that an image that measures 8×10 inches at 300 DPI, assuming your printer’s maximum resolution is 300 DPI, can’t be printed at 16×20 with full detail, but you may achieve enough detail to satisfy your needs. That’s a judgment call as far as I’m concerned; I have worked with banner printers who state 150 DPI as their absolute maximum and standing in front of it you’d never know. It depends on the application and on the artist’s needs.

Lets disregard poor photography, thus assuming an equal level of photographic data as a ratio of the number of pixels contained in the image. Yes you can upscale an image to a larger relative “resolution”, but you aren’t gaining any additional source data and are thus not increasing the actual resolution of the image.

A source image with a certain resolution can be used in certain printing applications based on the final resolution desired in the print. Economies of scale do come into play as your viewing distance increases, but when discussing home printing, the difference in viewing distance between an 8×10 and and a 16×20 is not necessarily any different. If the printer can print either of these two sizes at 300 dpi max and your source image is only 8×10×300, you aren’t going to be able to utilize the full printing resolution for the 16×20 print, producing a less defined image at the same viewing distance.

The point that I’m trying to get at is digital images do have an inherent resolution, and it relates to the source data. Just because you can scale a digital image to other resolutions doesn’t mean that the amount of data contained is not still directly related to the source resolution.

Cheers!

Resolution can be hard to understand at first, and even experienced photographers can have trouble with it. BUT NOT FOR LONG!…