Why Resolution Doesn’t Matter

The other day, someone complained to me that their new $1000 digital camera could only shoot images at 72 DPI, but their 3yr old, $140, Wal-Mart special took photos at 180 DPI. I think this is something that a lot of new digital photographers get confused on, so today I’m going to clear it up for those of you out there who are un-clear about on this issue.

It doesn’t matter.

First of all, when most people talk about “DPI” or “dots-per-inch” they really mean “PPI” or “pixels-per-inch” so the terminology is incorrect. DPI is a property of the printer and printer driver software and is completely independent of image size and resolution. It refers to how closely dots of ink can be placed onto the paper by the print head. Second, it still doesn’t make a difference

PPI for a digital image means nothing. Until you go to print it, it’s a useless number. It could be 1, it could be 1000. It makes no difference. What’s important is the total number of pixels, not some arbitrary PPI setting on the camera.

Look at it this way: A 1×1in image at 200 PPI is going to look just the same on-screen as a 2×2in image at 100 PPI. The two photos will be identical. They’ll have the same amount of image data, be the same quality, etc. Just take a look:

Go ahead. Save them, open them up in Photoshop and look at the image quality settings.

Shooting at a higher PPI isn’t going to give you better image quality unless the overall number of pixels (for the image as a whole, not for the image at its arbitrarily determined physical dimensions) is larger.

The only thing that different PPI ratios do for digital images is sometimes require you to type in different numbers when specifying your output settings for print.

So why do different cameras use different PPI settings? Well, everything has to be something and as with most commercial products, no two brands are completely alike. Camera manufacturers choose the settings that they do because they try to do what is most convenient for their target market. That $140 Wal-Mart special might shoot images with a physical printed size of 4×6in at 180 PPI because the target market for low-priced digital cameras is less computer-savvy. This way, if the image output settings aren’t changed, Mom’s at least going to get a decent quality 4×6in print of the kids. More expensive cameras are generally aimed at more serious photographers and experienced hobbyists who are likely going to be doing their own post-processing of digital images and adjusting these settings anyway.

SOURCE

technorati tags:photography, resolution, DPI, PPI