Scans overexposed top and bottom

Hi … i am using components of the Essential Film Holder with a 3D printed holder for a Lomo Digitalizer 120 film holder to scan with my Canon RP (Componar 50mm) . NLP is then used to convert the RAWs .

However, i sense overexposed areas on the top and bottom of the negatives. I cannot find a flaw on my hasselblad (light seals are serviced and ok) and the physical negatives look OK. This effect is particularly visible with darker images.

Hence i am thinking about any issues in my workflow - and was wondering if some here in that forum has an idea.
Thanks, Max

In certain circumstances people have encountered ‘shading’down the edges of the frames with the EFH, I suspect that this what might be happening here.

Thanks Harry - for the swift response. Did some digging - and you are right there is a flaw

However, my setup is quite an evolved version of the EFH - so i am wondering what causes the light decrease at the edges ? Any suggestion - cause with some smart 3D printing i could try to engineer a solution.

so when i use the Digitaliza directly on the diffusor plate - the effect doesnt occur.

You certainly do seem to have evolved the design somewhat so I guess it’s not the EFH at fault here. Tens of thousands have been sold so when it does occur it seems to be caused by an unusual combination of factors and it looks as if your design is suffering from the same problems. A blank frame of colour negative might help you to analyse the problem more easily. It’s a strange one.

looks like the distance to the diffusor is impacting the effect…when the negative is close to the diffusor the results are much better

Putting aside the EFH and just looking at your examples it would suggest to me that non-image forming light from your LED panel around your negative holder but outside of the field of view, flare in effect, is impacting your entire image and that same non-image forming light is being shaded by your holder close to the edges. When you put your holder on the diffusor there is less chance for this to happen. It’s possible that a simple card mask on the panel itself would have the same effect but you’d have to experiment with the size of the aperture and you’d need a different one for each film format.

Just conjecture on my part though.