Crazy speculation: lens aperture

Started Oct 19, 2011 | Discussions thread
iljai
Contributing MemberPosts: 562
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Re: Crazy speculation: lens aperture
In reply to Kreitmann, Oct 19, 2011

Kreitmann wrote:

Not crazy at all.

Once I made a comparison between the 50mm 1.8 and the Tamron 17-50mm 2.8. At 50mm f/2.8 the Canon had a tighter framing and it was significantly brighter than the zoom lens. This was not only due to vignetting, the center of the image was darker too, in the same light, M mode, same settings. The Tamron looked more like 45mm f/3.2.

Darker/lighter - that's transparency or t-stops. All that glass works like weak nd filter.

And shortening of FL (framing) could happens when focusing on closer subjects - it's called breathing. It's done to make shorter both lens and minimal focusing distance.

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