Weird lines in edges of frame with Hasselblad 500 & Efke Aura IR film?

[PeteZ8]

I'm wondering what is causing these weird lines at the very edges of my frames when shooting Efke IR 820 Aura through my Hassy 500 CW? I notice these on every frame on all 4 edges. The sample frame I am showing here mostly shows it on the left and right because the top and bottom are too dark to really show it, but they are there in every frame.

Does anyone know what is causing these? My 500 is in 110% mint condition and has no brassing or paint wear on the film back that could be causing reflections, but that isn't to say that the paint itself does not reflect IR.

 

[Vaughn]

Aura has no anti-halation layer on the back to prevent light from going thru the film, bouncing off the back, and then returning to the film. So I would say that it is light reflecting off the back of the camera. When using IR film with 35mm cameras, people would get similar problems with cameras that had a textured pressure plate -- even though the pressure plate was all black (no brassing). To solve this problem, people would glue a piece of smooth black paper onto the pressure plate. (Using a removable glue, of course.)

I am not familar with Hasseys, but those lines might correspond with slight raised rails on the pressure plate?

 

[pekelnik]

I get these lines with other films as well. Sometimes they are more visible, sometimes less. Normally I would crop them out, but someone must know why this happens.

 

[PeteZ8]

Thank you for the reply Vaughn. I was thinking that lack of an AH layer, but then again unlike 35mm, 120 film has a paper backing. Is the paper not "IR proof" enough that even at the very dim levels of light inside a camera the IR can pass through and reflect?

I just looked inside my back; the Hassy pressure plate is also textured and I have never seen evidence of that in the exposure so I am thinking the lines cannot be coming from behind the film. :confused:

 

[PeteZ8]

I get these lines with virtually any film on any hasselblad back. Sometimes they are more visible, sometimes less. Normally I would crop them out, but someone must know why this happens.

Admittedly since I've had this camera I have not shot it nearly as much as I should, but I have never noticed these before shooting IR film. They are extremely noticeable with IR so perhaps I missed it in the past; or have not shot normal film in conditions that would show it. The more I look inside the back, the more I think it could be reflections of some sort from the guides on the left and right sides of the back, and the film rollers at the top and bottom, but I'm not ready to concede to that just yet. Surely someone here has to know...

 

[Vaughn]

Thank you for the reply Vaughn. I was thinking that lack of an AH layer, but then again unlike 35mm, 120 film has a paper backing. Is the paper not "IR proof" enough that even at the very dim levels of light inside a camera the IR can pass through and reflect?

I just looked inside my back; the Hassy pressure plate is also textured and I have never seen evidence of that in the exposure so I am thinking the lines cannot be coming from behind the film. :confused:

Too early in the morning -- I have not started my second cup of tea yet -- forgot about the paper backing (even though I have been developing a lot of 120 lately)!

Vaughn

 

[PeteZ8]

Perfectly understandable