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Old 02-27-2015, 04:27 AM   #8
Noct Foamer
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Join Date: Sep 2008
Location: South Dakota
Posts: 571

Like everything in photography, there is a trade off when you stop down a lens. Yes, you increase the zone of focus as you tighten the aperture. I.e, more is in sharper focus in a 3D composition. OTOH, as you stop down you will start running into diffraction after f8 (f5.6 on my Nikon D800E.) Diffraction robs sharpness, and the loss increases geometrically as you stop down. This is why many lenses don't have f22, but only f16. Yes, they could make the iris so it could go really tight, like f32, but that lens is considered "diffraction limited" at f16. In other words, the manufacturer feels the sharpness suffers so much they cut it off at f16. My Sigma 50mm f1.4 ART only stops down to f16. My Nikon 70-200mm f2.8 VR will stop down to f22, and my Nikon 80-400mm AFS-G stops down to f40. I have a few large format lenses that will stop down to f128! What's the difference? Partly, it's the physical size of the "hole" (aperture), and partly it's a judgement call by the manufacturer. I generally try to keep my f-stop around f8 on my Nikon D800E, and around f22 on my 4x5. With either system, I avoid stopping down more than I need to as it can be counter productive.

Kent in SD
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