Just starting to digitize my thousands of B&W 135 and medium format negatives. I have a Leica SL2 (full format) digital that I will be using and plan on getting one of the newer Sigma ART macro lenses which can do 1:1 and come in 70mm and 105mm focal lengths. Which is more appropriate as I will only be using the lens for film scanning?
shorter one will have greater DOF at the same f setting, also you can get closer to the light table. But don’t know which is sharper.
Image quality wise they are both probably really amazing, but yeah, depth of field and working distance should be a bit nicer with the 70mm. Also shorter focal lengths are theoretically slightly less prone to show vibration at equal shutter speeds, but that shouldn’t really matter if you have enough light to use fast shutter speeds.
At macro distances, dof is fairly independent of focal length. See here for details.
Longer focal lengths require a bigger rig because the camera is farther away from the negative and this means that the rig must be sturdier.
When I compare minimum focusing distances of the lenses you propose, I see that they are not that different at 1:1. The 105 still needs a bigger rig, specially for capturing the MF negatives.
The 105 has a good reputation (if we believe what is written in the internet), the new 70 has reasonable tech specs and published mtf curves. I’d probably be happy with both lenses.
Thank you for all of your replies. I think if the 70 will work with 6X6, it should be easier to work with given the additional distance the 105 would require.
The challenge in rig size is 6x9. Check this to see what size you’ll need with a 100 mm lens.