02-26-2017, 06:58 AM
Quote:The second test he shot at different distances (the lenses have different MFDs). Why does it surprise you that the Tamron at 0.9 meters gets more magnification than the Nikkor at 1.4 meters?
It is the same as the difference from the Tamron at 1.4 meters and 0.9 meters.
First of all, I want to apologize to Toni for my part in dragging the subject off topic from the original question. I couldn't help pointing out the magnification deficit, which might mean more to me than to you, but since I think you would really miss the closer option...
The second thing...Yes extension tubes are a good option if you plan on shooting a set distance. That actually might make the lens a lot more useful.
But, and remember, I don't have the Brightcolors or dave's clichés level of optical knowledge, but here is my innocent question. BC says that it's not surprising that there is more magnification at 0.9m than at 1.4 meters. And I agree, its not! By the same token I'm not surprised if bokeh is better at a closer focus distance at a given focal length. What did surprise me (I'm going to laps into feet and inches here, but if it helps 1.2m = 47.2", and 1.31m = 52.1", and the different in MFD ~= 10%
From my previous post,
<p class="">Tamron MFD 51.2 in / Mag: .13x (Sigma a little longer distance, Mag. is also .13x)
<p class="">Canon MFD 47.2 in / Mag: .21x
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<p class="">The Canon has over 50% more magnification with only 10% difference in distance.
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<p class="">To make matters worse, Canon at 1.2m has more magnification than the Tamron G2 has at 0.9m
I'm frankly confused by how at the same focal length, at the same distance, we arrive at very different magnifications. Basically, are numbers being manipulated? Is a constant aperture, really far from constant? Is the 200mm, far from 200mm in fact? I guess most defining characteristics are measured at infinity, and don't really apply very strictly at MFD. But at the very least there must be a lot of differences in these lenses, so much so that are we really talking about the same type of lens?
Canon: 0.21x is 1:4.8 @ 1.2m. G2, 1:6.1 @ 0.95m, Tamron VC 1:7.7 @ 1.31m
Those difference are big and non-linear. So...I just don't know that these can all be 70-200mm lenses. Yet, they are!