chris_ma wrote: ↑
Sun Jan 09, 2022 6:36 am
lothman wrote: ↑
Sun Jan 09, 2022 4:13 am
I also can‘t imagine there‘s much difference, maybe lou was talking about the corners (but the sigma 70 shows some fall off in the MTF curves as well).
I tested the Sigma Art 70 in 2020
It beat all the lenses in the test at 1x other than the PN105A. IQ was better than the APO-Lanthar 110 and 125 (my APO-Lanthar 125 is very sharp) at 1x. The MacroVaron came in 3rd beating the Sigma Art 70 in the corners slightly but the Sigma was better than the SK lens in the center by quite a margin.
Sigma Art 70 is upper right corner in the photo.
I would manly use it for repros and copy stand animation work, so in the 40x30cm to 15x10cm range, and for that a fully manual lens could have some advantages too since it‘s easy to adapt to different camera systems and a manual aperture will eliminate any risk of flickering on animation films.
Actually that‘s an interesting question for stacking too:
Has anybody ever had problems with slight exposure fluctuations on long stacks due to the jumping aperture, or ever worried about wearing out the lens diagram motor?
Electronic is a little bit better with this, but either mechanical or electronic, it can be an issue. One way to stop it? Set the aperture, disconnect the lens to the point where it loses electronic contact so the lens stops down. This locks the iris stopped down. Time lapse photographers do this to save themselves all the correction work in post. (mechanical iris lenses need to have the level locked down). This trick also works when reversing lenses also, set, remove the lens, it should lock to the f/stop when you remove the lens with the camera power on (at least on the cameras I've tried, your mileage may vary). I just thought about it, I've only used this on vertical stands, this trick might not be safe on a horizontal setup now that I think about it.