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 p.1 #16 · 100 mm macro GM vs Sigma 105 mm macro | |
hasenbein wrote:
ALL the macros have heavy focus breathing!
Right. All lenses have breathing due to magnification and pupil factor variation.
The following relationship holds for the angle of view (AoV):
where x is the diagonal of the sensor (43 mm for 24x36, 28 mm for APS-C, etc.) F is the actual focal length, R is the reproduction ratio (aka magnification) and P the "pupillary magnification factor" or just "pupil factor", i.e., the ratio of diameters between the exit and entrance pupils of a lens.
If we look at 90/2.8 Macro Sony data from https://www.photonstophotos.net, we get:
@ infinity F = 92.6 mm, R = 0, P = 0.60, AoV = 26.5°
@ 1.0 m F = 85.8 mm, R = 1:9.3, P = 0.53, AoV = 23.6°
@ 34 cm F = 65.2, R = 1:2, P = 0.3, AoV = 14.3°
@ 28 cm F = 45.9 mm, R = 1:1, AoV = 5.88°
If look at (my) Nikkor Z 105/2.8 MC data, we get (from same source):
@ infinity F = 102.9 mm, R = 0, P = 0.65, AoV = 24.05°
@ 1.1 m F = 95 mm, R = 1:9.6, P = 0.59, AoV = 21.8°
@ 38 cm F = 70.5 mm, R= 1:2, P = 0.38, AoV = 14.9°
@ 29 cm F = 49.3 mm, R = 1:1, P = 0.23, AoV = 9°
These data clearly show that the AoV of both lenses decreases from infinity to shorter focusing distances, even if the actual focal length decreases too. This is due to the effect of both magnification AND pupil factor, according to the above formula. Please note that the effect is present even at "normal" distances (e.g., @ around 1 m focus distance and 1:10 magnification).
Cine lenses, whose breathing must be negligible, have to compensate both the actual focal length and the pupil factor as magnification increases from R = 0 (at infinity) to R values > 0 (at focus distances < infinity) in order to keep the AoV as constant as possible. For example, in the case of the Arri Zeiss Master Prime T1.3 100 mm, the AoV changes from 17.8° at infinity to 17.6° at the minimum focus distance (R = 1:8.77). Differently from most, if not all, lenses for our (DSLR & MIL) cameras, the Arri Zeiss doesn't show breathing.
hasenbein wrote:
If anything, the breathing of the Sigma is stronger.
Do you have data or pictures validating this conclusion?
Stefan Official wrote:
But for macro photography, working distance is an extremely important factor.
I agree. To get larger WDs, an APS-C body is preferable: we get the same framing at longer distance. I guess this is the reason why we don't see longer macro lenses (I mean, with focal length in the 150-200 mm range) manufactured by Canon, Nikon or Sony. We can buy a A6700 or EOS R7 (or crop a high-res 45-60 Mpix file) to get a similar result with a common (and lighter) 90-105 macro lens.
Stefan Official wrote:
Sony only lists the minimum focusing distance in their specs – and that’s measured from the sensor plane, not from the front element.
It's easy to estimate the WD for IF lenses: we have to substract the length of the lens barrel and the bayonet-to-sensor distance to the focusing distance.
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. 95% of my macro lens use is for underwater photography of small critters. With the 90mm lens' 1.0x magnification, you can still manage to take the occasional photo of larger critters. That's an important aspect, since there's no changing lenses while diving. I'm wondering whether the higher 1.4x magnification will get in the way of that, limiting the lens to truly small critters, and limiting the ability to take capture the occasional larger critter swimming by. Very recently, I even went and got a used MC-11 adapter to try out my old Canon 60mm Macro lens on my A1, as something with a wider applicability than the 90mm for UW photography, though I haven't had a chance to take that combo out diving yet. I expect there will maybe be some vignetting, but that should be fixable in post.
