Shooting 46mm films on MF Cameras

[mtjade2007]

I made some special reels for loading 46 mm films to shoot on any MF cameras that can use 220 films. I have cold stored quite a few 100 ft and 200 ft long rolls of 46mm Kodak 400NC and 400VC in my freezer. Those films are now long expired of course. I figured a way to use them on my Pentax 67-ii. I hope it will yield 7x4.5 panorama shots for me without using and cropping my 220 films. I will need to cut in a darkroom the right length of my 46 mm film out the 100/200 rolls and use leader and trailer paper from 220 films that is trimmed to 46mm wide, Then I can use it just like using a 220 film except it is only 46mm wide. Here are the special reels I converted from 120.220 reels:

 

[wiltw]

So how would the film edges rest, held flat against the rails of the opening by the pressure plate?!

No rails for the smaller opening, film not flat.

 

[ic-racer]

If you measure how high the film edges curl, you can calculate your aperture and focus shift needed to get it in focus.

For example if it is 2mm you could focus shift 1 mm and use f16.

https://www.largeformatphotography.info/fstop.html

 

[mtjade2007]

So how would the film edges rest, held flat against the rails of the opening by the pressure plate?!

Good question. Take my Pentax 67-ii as an example, there are two metal rods one on each end of the 6x7 frame. The 46mm film will be pressured against these two rods but without the support of the upper and lower rails. I checked the flatness of the film by setting the shutter to B then fired the shutter without lens and looked into the camera at the film. It eas flat enough to y eyes. I can imagine there maybe flatness issue still but I can crop out 1 to 2 mm from the top and bottom of the image. Panorama image is what I will get any way. There won't be flatness issues if I regard it as 7x4.

 

[mtjade2007]

If you measure how high the film edges curl, you can calculate your aperture and focus shift needed to get it in focus.

For example if it is 2mm you could focus shift 1 mm and use f16.

https://www.largeformatphotography.info/fstop.html

It will be the upper and lower edges of the film that may be subject to the flatness issue. What I saw in my camera is it is quite flat so no way it could be 2 mm off. It's probably not even 1 mm.

 

[mtjade2007]

I noticed that unprocessed roll films, 35 mm or 120/220, are quite flat across the height of the frame. But once processed the film curls a bit. I have a cut piece of unprocessed 46 mm film. It lays totally flat on my table.

 

[Donald Qualls]

So, we'll call this new film format 227?

 

[gone]

That's interesting knowing that the film out of the roll is flat, it's only after developing that it curls on the top and bottom. I I knew that, but forgot it because I'm so used to seeing the developed film hanging in the bathroom.

 

[wiltw]

Unprocessed film may be relatively flat, but that did not disuade some manufacturers from developing film backs that had special emphasis on holding film absolutely flat on the pressure plate, both ceramic plates and vaccuum plates! Some were outfitted as standard (Contax RTSIII), others were accessory backs made for specific cameras (Hasselblad, Pentax67)