Focusing a Canon

Started Dec 17, 2009 | Discussions thread
rolleiman
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Re: Focusing a Canon
In reply to John King, Dec 19, 2009

What I take away from all this is that the spherical aberrations that give a non flat plane of focus are hard to deal with in lens testing. If you've ever done enlargements with a cheapo enlarging lens you'll sympathize with having to sacrifice some center sharpness to keep the edges livable.

Thus a lot of lenses that appear soft in the corners aren't really so soft; they're just focussed somewhere else. If you had spherical sensors you could get by with a one element lens just as a human eyeball does. Likewise, objects in front of the lens at the same distance of plane but off to the side laterally are actually further from the lens.

Which brings up another point; digital photography eliminates the second lens with its attendant losses required for printing from a negative. No need to test those again!

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