Camera Labs

Hello,

Just a couple questions on Aperture lingo.

stoping down would mean eg changing from f4 to f8?

wide open would mean e.g. on a 50mm 1.4 setting to f1.4?

Do all lenses have a sweet spot Ap wise? From reading lens reviews here and in other places I've come to realize the expensive lenses keep a fairly consistent quality through all Ap ranges but in good lighting conditions I see many lens x vs lens y sharpness tests people test at f11 a lot. Just coincidence or is f11 a "sweet" spot under good light?


Thx for any answers!

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Canon 60D
EF-S 15 - 85 IS USM
EF 70 - 300 IS
EF 50 1.4
EF 100 - 400L

The general rule of thumb seems to be that lenses perform best two stops down from their max aperture. Obviously each lens is different and more expensive lenses are engineered to better tolerances.

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Canon EOS 400D, EF-S 18-55mm, EF 24-105mm f/4L IS USM, EF 50mm f/1.8 MK I, EF-S 10-22mm, EF 70-200mm f/4L IS USM, EF 28mm f/1.8, EF 85mm f/1.8
Canon 430EX II, Manfrotto 055CXPRO3, Arca Swiss P0
Panasonic GF3, Panasonic 20mm f/1.7, Olympus 45mm f/1.8

MY FLICKR!

2 stops down from a maximum on a 50 mm 1.4 would be 1.8 or 3.6?

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Canon 60D
EF-S 15 - 85 IS USM
EF 70 - 300 IS
EF 50 1.4
EF 100 - 400L

f/1.8 is 2/3 stops down from f/1.4. Each stop down halves the aperture area, that is divides the f-number by sqrt(2) which is about 1.4.
That means 2 stops down from f/1.4 is f/2.8

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Canon DSLRs: 5D Mark III, 7D
Canon lenses: 17-40/4L, 24-105/4L, 24/1.4L II, 50/1.4, 85/1.8, 100/2.8L Macro, 70-200/2.8L IS, 100-400L
Other stuff: Canon Extender 1.4x II, Canon 580 EX II, Canon 430EX II, Velbon Sherpa 600R
Apple: MacBook Pro 15", iMac 27", iPad III, iPhone 4S, Apple TV

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