Camera-back/film-holder interface lightproofing

I would like to make a pinhole camera that uses 4x5 filmholders. Not ever having seen the inside of a large format camera, I'm not sure how to make the film-holder/camera-back interface light tight.

<p>

Presumably the film-holder should be pressed tightly up against the back of the camera. Is this pressure normally achieved by means of leaf springs?

<p>

Presumably the user slides the film-holder into and out of the back of the camera at right angles to the axis of the lens, rather than moving it along the axis towards the lens.

<p>

What methods are commonly used to prevent light from leaking around the four sides of the film-holder and fogging the film? Particularly from the top, where most ambient light will be coming from, and which must be open to allow access to the dark slide.

<p>

Any advice that you can offer would be very welcome. Thank you.

That's somewhat difficult to explain in words, but become clear

when you see a spring back. I suggest that you visit a local store,

maybe buy a holder from them (since you'll need them anyway) then

ask them to try it on one of the cameras they stock, preferably a

wooden one.

I already have some used Fidelity film holders. Unfortunately, there doesn't seem to be a supplier of LF cameras anywhere near where I am in the UK, which is why I posted the message :-)

<p>

LF seems to be a lot more popular among "amateurs" in the US - here in the UK their use seems to be limited to professionals. Maybe I'm wrong ...

<p>

Meanwhile, someone has suggested using draught/draft excluder strip. I still need to devise a way of pressing the film-holder against the strip.

If you can't look at an actual camera back, see if you can find an illustration of one in a book. The way the leaf springs provide the necessary pressure is difficult to explain, but will be quite apparent when you see it.

<p>

Most of the cameras that I've seen do not use weatherstripping or any similar soft material to provide a light trap; they rely instead on pressure and a smooth mating surface. My guess is that a soft material could cause problems in focussing accuracy for a regular camera, since the exact position of the film would depend on the degree of compression of the material. However, this shouldn't be a problem for a pinhole, which has virtually infinite depth of focus.