I’m getting what looks like barrel distortion whenever I scan 6X7 120 negatives.
I’m using an A7iii with a Nikon 28-105mm f/3.5-4.5D Macro lens with an adaptor, set to about 80mm, converting with NLP.
The negative’s frame fills the Sony’s frame nearly to the edges.
I’m using the Lomography Digitiliza to keep the film flat, and placing it on top of the Skier copy box ii having removed the skier’s metal film holder.
(I removed the skier’s metal film holder, as I’ve found when trying to run 6X7 frames through it they nearly always get caught in the metal when trying to slide them through or slide off the groove. Even if I (rarely) succeed sliding them through, they’re not flat.)
I suspect the distortion is is from the lens, and if were to get a better and native lens it might fix the issue, but was hoping someone with more scanning experience would be kind enough to offer advice before I go out and buy the 90mm 2.8 which isn’t cheap.
The distortion is consistent across films I scanned.
Lightroom’s Develop module has a lens correction toolset. It allows to correct distortions and falloff both automatically and manually, at least to a certain degree. I tried the nikon lens profiles that are available and was able to fix it with these settings:
I’ve managed to improve it this way before, but wanted to confirm this is indeed lens distortion, and whether most folks scanning with adapted lenses find they need to do this. If so, that’s one more reason to get a native lens.
By the way in my version of lightroom classic (8.3.1) choosing a ‘profile’ doesn’t do anything including when changing the ‘amount’ in the distortion slider. It only changes when using the distortion slider in the ‘manual’ tab.
I’m using the current Lr Classic version 9.3. I just tried to see if the lens had a profile, pushed the sliders without bothering to go to the manual tab. Most profiles I tried did not react to sliders, but the profile for the 14-24 did.
Most zooms have both barrel and pincushion distortions depending on FL settings. Somewhere between the extremes, there is a focal length that eliminates the distortion. Macro lenses on the other hand are usually made to have low distortion, a flat field and low lateral CA and the Sony FE 90mm F2.8 Macro G OSS seems to be a top lens, also according to dxomark.com. Depending on how many negatives you want to convert, it might be worth the premium, although a Lightroom preset that corrects the barrel might do too