On resolution

My friend Dave asked me a question about resolution the other day:

… picked up a little Canon SD1400 IS, which we're going to take on a trip soon.  I want the best images possible, which means roughly 2 - 3 MB per image for this camera.  I'm going with 2592 X 1944 pixels, which, according to the user manual, is good to print up to 8 X 10 pixels.  It also gives me almost 10,000 images on my 16GB SD card. Does this pass the common-sense test?

It got me to thinking about the high resolutions that most modern digital cameras can achieve, and whether or not shooting at the highest resolution is really necessary.

On the one hand, a 2 megapixel camera will yield good 4x6 images and acceptable 5x7 images, and a 4 megapixel camera will give fine 8x10 images.  The above image size works out to about 5 megapixels, so in theory, it would be fine for photos up to 8x10.

 

The sensor on Dave’s camera is a 1/2.3” charged coupled device – about the size of the square on the lower right of the image above.  That’s not a lot of space to capture a good image.  If Dave saves images at the smaller resolution, he’s giving up about two thirds of that sensor. 

Dave’s points about saving space on his memory card were fine, but I had to point out some facts I felt were important:

1. Saving at the lower resolution saves space, but I don’t think it’s a case where the savings is really necessary.  10,000 photos is a huge amount; between 2006 and 2009, I averaged 12,000 photos a year. 
2. Taking photos at higher resolution means you have more data to work with.  Dave can take a full-resolution, 14-megapixel image, crop it extensively, and still come out with a usable image he can print at a decent size.  If he limits himself to the smaller resolution, he loses the ability to crop afterward and still get a nice usable image.
3. SDHC cards are cheap.  It makes more sense to purchase a separate memory card or two, simply to have a backup in case of equipment failure, than to rely on one card to hold all of your digital images – especially if you’re backing them up to your computer like you should be.

In general, I always take photos at the highest resolution I can, and shrink them later when I need to.  It goes against my instincts to discard useful data when you don’t have to.  Case in point:

The top image is a photo of me taken by another friend.  I didn’t like the result, but was able to crop it (see second image), yet still print the cropped image large enough to send to my grandmother.  My camera is 15 megapixels; if I had set it to lower resolution, an image cropped this severely would have been pixilated at best, completely unusable at worst. 

In short:  Save large, save often, and back up everything.  You can discard data after you’ve taken your shot, but you can never recover data your camera doesn’t record.