The Canon EOS Digital Rebel XSi/450D Companion

CHAPTER 6

SUMMING UP PROGRAM MODE

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Why Choose a Different Size?

e size of the image impacts two things: how large a print you can make and

how much you can blow up a detail in an image.

To print a large image, you want to have as many pixels as possible. While an

image-editing program can do a good job of enlarging an image, there’s no sub-

stitute for actual pixel data, and the XSi can capture a lot of pixels.

Usually, the only reason you would choose to shoot at a smaller size is if you’re

running out of space on your card or you know that you will only ever print an

image at a certain size. For example, if you’ve never printed an image larger than

4 x 6, then you might argue that you won’t ever need more than the smallest size,

because that’s more than enough data to print a 4 x 6.

Shooting at a smaller size will afford you more space, but can you be absolutely cer-

tain that you’d never want to print at a larger size? Storage is cheap now, so it’s not

unreasonable to keep full-res images, and having access to the maximum size will

ensure that you can repurpose your images for any use that you may come across.

So, if you’re really in a crunch for space, you might want to increase the level of

compression rather than reducing the image size. e XSi’s low quality compres-

sion is still very good, but if you’re planning on enlarging your images, then the

resulting JPEG artifacts ...