Hi. Completely new to Graphics. Bought a Speed Graphic, apparently it has a Crown Graphic screen. It has a spring back. I got a fidelity film holder for it, which I had assumed were standard size, but the holder is too small for the recess under the spring back, meaning it can move around and leaks light from behind. I have tried to find out info about the correct holder to use, but to no avail so far.

Are there different standard holders for different backs, and which one should I be looking out for?

Many thanks in advance for any suggestions.

If you can pull the ground glass away from the camera to put the film holder in, then it's either a Graphic (spring back) or a Graflok back. These take standard holders.

If you have to remove the ground glass assembly to put the film holder against the camera, then it's a Graflex back and takes non standard film holders.

For the holder to be too small, I can only think of two things, It's a Graflex back, or the holder is for 3 1/4 x 4 1/4 sheet film. A standard 4x5 film holder is 4 3/4" wide on the narrow dimension.

I know there are 10x12cm film holders out there which are close but not the same image size as 4x5, and you're certainly in the right area to find these holders, but I thought the outside dimension was the same as a 4x5 film holder.

Yes they are. They superseded the one-sided metal holders that were used in Europe prior to WWII when Graflex helped put Linhof back into business after 1945. Compatibility was the goal : one back - two formats.