Off-film flare?!

[Dante_Stella]

I am stumped. I am experiencing a 3mm wide circular section flare (like a rainbow; the circumference of the section is about 10mm) in the upper right hand corner of images - and just occasionally. It has a fairly sharp edge to it and looks like a 1.5 stop exposure increase. These are the parameters:

- Only happens with one lens, a symmetrical medium format wideangle
- Light source of all affected pictures is behind the camera
- It is not specific to any contrast filter
- Lens has no missing blacking or damage to the rear shroud
- There are no light seal issues with the camera
- Changing bodies does not eliminate it
- It only happens with TMY; does not happen with color film or TMX
- It seems to track the contour of the rear element/shroud

Is it possible that light is being reflected back to the lens from the film and then ghosting?

Dante

 

[Larry H-L]

Would be helpful to know the camera and lens, and see an example shot.

I have seen, on a view camera using an ultra-wide lens that places the rear element really close to the film, reflect light off the film, back to the rear element, and then back to the film as a semi-circular section of coma-like flare.

Are you using a wide lens where the rear element is close to the film /sensor?

 

[yossarian123]

Isn't that what the anti halation layer is supposed to prevent? Or are you working with a special film type [edit, just saw that you are using standard films]

 

[Dante_Stella]

Would be helpful to know the camera and lens, and see an example shot.

I have seen, on a view camera using an ultra-wide lens that places the rear element really close to the film, reflect light off the film, back to the rear element, and then back to the film as a semi-circular section of coma-like flare.

Are you using a wide lens where the rear element is close to the film /sensor?

Larry - it's a 50mm Fujinon for 6x9. I'll get a picture up, but what you describe sounds exactly like it.

Dante

 

[Dante_Stella]

Larry -

Here's the most egregious example, with a somewhat side-lit light source (but not so side-lit that it would flare other lenses).

Dante