Any idea what's causing these light streaks

[Bill Poole]

I am periodically getting characteristic light streaks on photos like the one below.

194561

In this instance, the streaks are most visible on the trees, particularly the left one.

The puzzle: this is one of six images from the same set exposed in a GRAFMATIC back. The other five do not show these streaks. This was the second image exposed in the back on the same day. I have had this happen several times: the same, characteristic streaks from only one image from the same Grafmatic.

The camera is a Polaroid 900 converted to 4X5 by Alpenhaus. The lens is an older 150mm Fuji 5.6 (inside lettering).

My theory to date is that this is lens flare due to poor coating or some other issue, although I do use a lens hood. The only commonality in the affected images that I can see is a source of brightness in the scene: in this instance the large white building. But I really have no idea and would welcome opinions. Should I be looking at the septums (or maybe that is "septa")?

Ah yes, the developing: All films in the same MOD 54 insert, Paterson system tank, which I have been using without issues for a while. HC100/B, although I can't see why that matters.

Thanks for any ideas.

[Doremus Scudder]

The most likely cause is that you are pulling the spring back away from the camera body when pulling or inserting the darkslide, leaving a small crack for light to get in. This is a fairly common mistake. Pinch the spring back to the camera body with your free hand when pulling/inserting the darkslide, etc.

Best,

Doremus

[Steven Ruttenberg]

I have got streaks before when I accidentally inserted the dark slide between holder and camera instead of back into the slot like it is supposed to be. That brief lifting trashed several images. Usually happens when the light has faded substantially, but I have made the mistake in broad daylight as well.

[Bill Poole]

Thanks for the ideas, Steve and Doremus. I should have clarified that the Grafmatic is solidly attached to the camera with small thumbscrews--I am not using it under the spring back. Thus the mystery. Thanks again. Bill