SURF
19-Nov-2012, 05:50
Hi! Playing with USAF resolution target on a modified scanner I have realised that original scanner masks (200um) are TOO thick for scanning at 5000 dpi real optical. It comes critical in a case of 35mm curly films.
When USAF target is upped by the mask for those masks 200um the focus and resolution drops dramatically - from 5000 dpi to 3000 dpi or less. Using micrometer and some luck made me find the best thin substitute for the mask. Well... it's a black thin plactic black garbage bag. [It's fantastic :)] Only 20 microns thick and this has no influence on a focus (double checked).
I want to add, that the scanner at first looked excellent for scanning curly films with the standard mask - it has two heavy glasses and it works fine when there is no mask between (only film). As long as the mask is inserted you have to double check the focus even if the film is placed emulsion down on the bottom glass. In a case of curly film the standard mask (100 or 200um) gives the freedom for films trip and that removes peak scanner resolution. The scanner has fixed focus, but nothing changes in a case of automatic or manual focus (on different scanners) - still there will be a difference between the center and the edge.
Best luck
Al
When USAF target is upped by the mask for those masks 200um the focus and resolution drops dramatically - from 5000 dpi to 3000 dpi or less. Using micrometer and some luck made me find the best thin substitute for the mask. Well... it's a black thin plactic black garbage bag. [It's fantastic :)] Only 20 microns thick and this has no influence on a focus (double checked).
I want to add, that the scanner at first looked excellent for scanning curly films with the standard mask - it has two heavy glasses and it works fine when there is no mask between (only film). As long as the mask is inserted you have to double check the focus even if the film is placed emulsion down on the bottom glass. In a case of curly film the standard mask (100 or 200um) gives the freedom for films trip and that removes peak scanner resolution. The scanner has fixed focus, but nothing changes in a case of automatic or manual focus (on different scanners) - still there will be a difference between the center and the edge.
Best luck
Al