Mounting gels behind the lens, 4x5

[Ulophot]

In pursuit of a Wratten 47 gel for enlarging, I picked up a set including 6 other gels as well -- red, yellow, and green -- nearly all mounted in black metal frames, for $10. Made my day. Anyway, I'm inclined to keep my stack of screw-ons for my MF kit and use these for LF. Adams wrote about rear mounting to keep flare down. Since I have no matte box, it makes sense to me to mount the filters aft of the lens. My camera takes the Linhof lens board. So, two questions.

1. Do I need to make a holder for these that attaches, permanently or otherwise, to my two lenses' (210, 135) boards ?

2. If so, would you recommend keeping the filters in the frames or not?

I suppose a holder could be as simple as a little arm that clips the top corner of the gel above the lens, but then tilt could be an issue. Design thoughts or illustrations?

Thanks.

[j.e.simmons]

Fred Picker made a little U-shaped piece from spring steel. It extended a bit farther back than the rear lens element. He used a magnet to hold the filter gel in place behind the lens.

[Bob Salomon]

Fred Picker made a little U-shaped piece from spring steel. It extended a bit farther back than the rear lens element. He used a magnet to hold the filter gel in place behind the lens.

To aluminum boards and non ferrous lens barrels?

[j.e.simmons]

He glued (I think) the adapter to the back of the lensboard above the lens.

[Ulophot]

John, thanks. I'm the world's worst builder. Can you offer a drawing of the design? I can imagine something, but I'd do it wrong.

I can, however, imagine gluing vertical pieces of stiff black matte plastic or metal on either side of the lens boards' rear surfaces, acting as slots into which the other part could be easily inserted for use, so that one could be switched quickly between lens boards.

[Ulophot]

Hey, folks, I just OCR'd my PDF of the complete Zone VI newsletters and found Fred P's complete description. It in Dec. 1977. If anyone's interested, I'll transcribe it.

[j.e.simmons]

I can, however, imagine gluing vertical pieces of stiff black matte plastic or metal on either side of the lens boards' rear surfaces, acting as slots into which the other part could be easily inserted for use, so that one could be switched quickly between lens boards.

I did that using small pieces of wood. It worked just fine. Glad you found Fred’s instructions. - my drawing ability is not very good.

[Conrad . Marvin]

Gels are fragile but I never figured that I’d be using the corners so I taped them to the LB or the bellows.

[Drew Wiley]

Expect a bit of inevitable image degradation if gels are used behind the lens. This has been argued back and forth forever; but regardless of the optical theory, it's almost impossible to keep gels dirt, smudge, and crinkle free. But if ya gotta do it, there were little spring-clip devices once commercially made for that. B&H still offers the Lee metal version, which could easily be thread-adapted by epoxying on a step ring. Otherwise, improvise. It's actually easy to make a thread adapter for the front end of the lens, just like I just described. But I've bought those outright too. I never use gels for image-forming purposes unless there is no other option, or unless I'm just testing for effect prior to acquiring an equivalent real glass filter. They do need to be pampered.

[Alan9940]

I don't use gels behind the lens anymore, but back when I did, I made a simple Z thingy out of some sheet steel with a depth slightly more than the rear lens element, glued it to the back of the lens board (both wood and metal boards), then used a small magnet to hold the gel in place. As already shared, gels are a bit of a pain because they attack dust easily, scratch easily, kink easily and, yeah, can't tell ya how many times the thing blew off the back of the lens before I could get it into the camera.