ColSebastianMoran
( IRL Richard Karash )
Camera scanning with a nice Skier film holder that exposes sprocket holes. This holder has an opening about 32mm x 72mm to permit wide 35mm negatives.
I find a visible flare in the corners with otherwise good-as-1x lenses (including 80 f/4 Componon-S, 75 f/4 APO Rodagon-D 1x, and some other enlarging lenses). I have traced this flare to the first sprocket hole in the adjacent frame. There is no apparent flare or loss of contrast from the sprocket holes for the subject image. I have seen the same thing with the excellent Negative Supply MK-1 which partially exposes sprocket holes depending on the exact position of the film.
The flare is a bright streak at the corner of the negative image, becomes a darker streak after conversion to positive.
To test, I do a strenuous test by placing a piece of developed, exposed film in the holder. I push through enough light for normal exposure of that darkened film. This is a stress test because it's more light through the sprocket holes.
There is no such flare with:
- the current 70 f/2.8 Sigma Macro ART lens at 1x; I suspect no flare with most modern macros
- with any lens I've tried at 0.67x for camera scan to an APS body
My theory:
- Sprocket holes at the subject image are within the image circle of the lens. The flare issue is for light from outside the image circle.
- Designers of enlarging and copy lenses don't have to worry about light from outside the image circle; designers of macro lenses do attend to flare.
Looking for reactions to this theory.
Flare at 1x with the 75 f/4 APO Rodagon-D 1x (Crop of upper left portion of image area; note bright flare streak at corner, and note no flare from the sprocket holes across the top. To R is tape and a stick-on label from the lab.)
I find a visible flare in the corners with otherwise good-as-1x lenses (including 80 f/4 Componon-S, 75 f/4 APO Rodagon-D 1x, and some other enlarging lenses). I have traced this flare to the first sprocket hole in the adjacent frame. There is no apparent flare or loss of contrast from the sprocket holes for the subject image. I have seen the same thing with the excellent Negative Supply MK-1 which partially exposes sprocket holes depending on the exact position of the film.
The flare is a bright streak at the corner of the negative image, becomes a darker streak after conversion to positive.
To test, I do a strenuous test by placing a piece of developed, exposed film in the holder. I push through enough light for normal exposure of that darkened film. This is a stress test because it's more light through the sprocket holes.
There is no such flare with:
- the current 70 f/2.8 Sigma Macro ART lens at 1x; I suspect no flare with most modern macros
- with any lens I've tried at 0.67x for camera scan to an APS body
My theory:
- Sprocket holes at the subject image are within the image circle of the lens. The flare issue is for light from outside the image circle.
- Designers of enlarging and copy lenses don't have to worry about light from outside the image circle; designers of macro lenses do attend to flare.
Looking for reactions to this theory.
Flare at 1x with the 75 f/4 APO Rodagon-D 1x (Crop of upper left portion of image area; note bright flare streak at corner, and note no flare from the sprocket holes across the top. To R is tape and a stick-on label from the lab.)
