Sigma 30mm 2.8 vs Canon FD 50mm 1.4, Lowlight Test

Started Apr 26, 2012 | Discussions thread
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In reply to bryanbrun, Apr 26, 2012

What if you are shooting a large back object with a white background. The wider lens would let in more light...depending on the metering?

bryanbrun wrote:

MadsR wrote:

hhcs wrote:

The sigma has a faster shutter speed because the focal length is wider than the canon. The wider focal length of the sigma captures more light in the room (and less isolation) as you can see from your pics. If you used another lens with a similar focal length to the canon, such as the oly 45mm, the shutter speeds of the canon and oly will be similar.

That is not how it works... At f2.8 they let the same light in. The closer view of the 50mm let to a different exposure (it could be an error, the light levels are slightly different)

I agree with you, the light at 2.8 should be identical. However, I was so confused by this that I verified the behavior from a number of different locations and angles. The Sigma effectively acted identically to the Canon FD, allowing the same shutter speed, only when the Canon was stopped down to F2.0.

I have a number of other FD lenses that I can use to verify this behavior.

Perhaps it was due to the angle of the overhead light, and the longer barrel of the Canon FD? The light at that angle could not penetrate through the long Canon FD 1.4 barrel?

It doesn't really mean two cents to me theoretically: the practical implications are more important. Basically when shooting indoors at night, the Sigma behaves just as good as a Canon FD at F2.0.

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