How to register film boundary on ground glass

[Tom Westbrook]

Can someone describe the best way to register the outer edges of film on the ground glass so I can quit guessing where the boundary of the film is? My Arca Swiss F-line has some corner indicators on the ground glass, but I haven't been able to tell to which holder each set of corners corresponds.

I would want to do this for various holders including Fidelity holders, Kodak Readyload and Polaroid.

[David A. Goldfarb]

You could compare the negative to the groundglass markings and figure that out. Polaroid is smaller than standard holders and is off center a bit. I'm not sure about Readyload.

[Oren Grad]

Afraid I don't have an answer for you. But whatever the proposed procedure is, be sure to take into account any "play" in the seating of the holder within the back. Vertical play is probably minimized by the rib lock, but there may be some slop in side-to-side positioning. I'd imagine that even a high-precision camera like an Arca-Swiss probably needs to leave some extra room in the back to allow for variation among film holders.

[C. D. Keth]

OK. This takes some time but it's worth it. First, tack a sheet of grid paper to the wall in a place you can leave alone for a while. Mark a center point and number the lines out from the center so that you can read them on film. Set up the camera so that the film is parallel to a wall and the grid paper fills the groundglass. Level the camera and center the grid paper's center on the groundglass. Next, shoot one polaroid, one quickload, and one sheet from a holder.

Process these (or get them processed, that is why you choose a place you can not touch for a while) and then you have a measured grid on film you can compare with your groundglass and have perfect gridlines. Note that any play in the back or the holders will throw these marks off a little bit but it's generally not far enough off to matter. Keep these pieces of film and you can mark any replacement glasses you might end up getting without having to repeat the test.

[GPS]

Put the film holder (rollfilm holder or whatever you use) on the gg as if you were taking a picture. Take out the dark slide, detach the gg assembly with the film holder from the camera and have a look at it from the lens point of view, i.e. from the other side. You should be able to see the film format through the gg and be able to mark it with reasonable precision.

[GPS]

You can also load the film holder with a white piece of paper to see it better.

[Henry Ambrose]

For sheet film holders do this:

Put a sheet of white paper in the holder in place of film, put the holder in the camera and shine a light through the ground glass. The white paper will reflect enough light back that you can mark the glass. Not precisely but well enough. I use blue painters tape cut in tiny strips on the glass. It comes off easily when I want it off.

edit: GPS, I guess great minds run together or something like that. ;)

[Dave Parker]

You can download my 4x5 templates off of my website which include a template for most roll film sizes, holders and Polaroid sizes, then print on clear transparancy film cut it to fit your camera and it will give you a good idea of where each one of the different types of holders will set on the ground glass.

http://www.satinsnowglass.com/grids.pdf

This is the product I use, sells for about $7 at Wal Mart for 10 Sheets

http://www.avery.com/us/Main?action=product.HierarchyList&node=10210787&catalogcode=WEB01

Dave Parker
Satin Snow Ground Glass

[Tom Westbrook]

Thanks, great ideas. I presume the film position won't change much by having the film side of the holders facing the ground glass.