Why does DPR care about per-pixel sharpness?

Started Nov 9, 2008 | Discussions thread
brendansimons
New MemberPosts: 14
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Also because it affects your choice of lenses
In reply to SLove, Nov 17, 2008

Lets say you always frame your shots perfectly, and always print 8 x 10s (or reduce to 2 megapixel web images, or something else, pick a standard). The 50d will probably look a little better than the 40d in this case.

Now say you instead choose a 1ds instead of the 50d. To get the same shot, you choose a lens with 50% more magnification. The 6 year old camera has much sharper per pixel image quality, and since you are putting (roughly) the same number of pixels on your perfectly framed image, this picture has a much better image sharpness as well.

This is particularly troublesome with point-and-shoot cameras. Everyone wants to sell cameras with an "35mm equivalent focal range" of 28-300. However no-one wants a bigger lens, so every increase in megapixels comes with a corresponding decrease in sensor size to maintain the same focal range. This counter intuitively yields a worse per pixel AND per image sharpness for every increase in megapixels. SLR users are at least aware (I hope) of their crop ratio, and how it affects image quality.

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