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Slide holding for Scanning - Ohnar and Other Options

Started May 21, 2021 | Questions thread
OP Halina3000 Junior Member • Posts: 32
Re: blade test... and bleed, ghosting, halo or whatever it is called

Cheers. I will have another try next time I have everything set up. I will us an actual razor blade and make sure it is in focus. I don't think there is much mileage in analysing the etch image further because the metal edges will be less than perfect and my focus was off because the metal fret has very little rigidity.

Having read a little more about MTF I'm not sure that it's addressing the same issue. If I understand it correctly, it is looking for the boundary where the contrast is wrong by 50%. My haloes are probably a good deal less than 50% but they are visible and I'd love to reduce them. Can that software use a different contrast value?

In terms of sharpness I think that I'm already near the limits of what most of my sldes can deliver - not the film, just the limitations of my cameras and my ability to use them at the time the photos were taken.

My best guess is that the halo is a variation of ghosting flare but that is just my guess. Most discussions about flare concentrate on the effect of the Sun or other concentrated light sources rather than a diffused backlight.

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