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.)
ColSebastianMoran
( IRL Richard Karash )
Here's similar test shot with the 70 f/2.8 Sigma Macro ART, no flare in corners.
ColSebastianMoran
( IRL Richard Karash )
Here's an example of the flare I'm talking about. Camera scan of a color negative, using a good enlarging lens 80 f/4 Componon-S. After inversion in NLP, the flare becomes a dark streak.
Any reactions to my theory that this is coming from the first sprocket hole on the next frame?
Any reactions to my theory that this is coming from the first sprocket hole on the next frame?
Ronald M
Mentor
Cover the hole with negative carrier.
ColSebastianMoran
( IRL Richard Karash )
Yup. It surprised me that the holes along side the image area cause no problem, but the four off the corners outside the image circle can cause problems.