Does one really need sharp zoom lenses? ...

Started Feb 26, 2012 | Discussions thread
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BertIverson
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Does one really need sharp zoom lenses? ...
Feb 26, 2012

Hopefully, we can have a friendly discussion of the following assertions:

Do most of us amateur shooters really need expensive sharp zoom lenses? (better than the kit lenses) Let me say up front that I am not talking about many other lens characteristics such as focus speed and large apertures. Bokeh, color, flare, distortion, vignetting can all be addressed in post processing.

Assume one does not print larger than 8x10 and views shots on a monitor or HDTV. For his type of viewing, 2-3 MP is sufficient. With 12MP or more, this type of viewing causes 4 pixels to be merged into one. So, as long as one "fills the frame" when shooting, lens sharpness at the single pixel level is irrelevant. If a lens offers 600 LW/PH (DPR MTF-50 numbers), that implies about 1200 pixel vertical resolution. 1200 pixel vertical is a reasonable quality monitor and more than HDTV. Most lenses in DPR reviews exceed this 600 LW/PH except maybe the extreme corners. All one's zoom lenses except one's telephoto can fill the frame. (I guess one's primes need to be sharp unless one can "feet zoom") Only one's telephoto lens may not be able to fill the frame at its long end. But even one's telephoto, at the extreme long end, needs to be sharp only in the center region so that cropping leaves one with 1200 pixels vertically. This center 1/4 region needs to be sharp at the single pixel level . Obviously, those who print very large from single frames will need excellent lenses (and high pixel count sensors).
I look forward to your comments and corrections.
Bert

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