Toyo back on 4X5 Graphic modification

I just completed installation of a Toyo 4X5 revolving back using the adapter plate now being sold from China on the big auction site. There was a thread on this subject recently but I feel some of the information was not quite accurate, so I will share my experience. First, this is not a project you want to attempt without some small machine tool experience, and no instructions are provided by the plate maker. Second, decide if you really want this mod after I describe the functionality.

The addition of the revolving back with the adapter plate adds about 3/8" of extension and will affect your ability to focus some very short lenses to infinity. The plate is designed to also fit the revolving back Graflex SLRS which have a square bellows. However, when fitted to a Graphic, which has a rectangular bellows, part of the 4X5 image would be lost if the back were turned vertical. A 6x9 roll film back may be used vertically with no problem.

The 90mm, 75mm and 65mm lenses all focus to infinity if mounted on the inner tracks with the bed dropped. No movement is possible with any of these lenses. A 47mm, which used to reach infinity on the old Graphic back cannot do so now with the Toyo mod. Most of my lenses for Toyo are mounted in Graphic lens boards and the idea of being able to to use Toyo back components on a hand-holdable, RF-coupled Crown or Speed Graphic is appealing. If a Toyo non-revolving back was used it might only add about 1/8" of extension.

You need to drill and tap the Toyo back for 4 4-40 screws (not supplied) Attachment 192238which hold it to the plate. Attachment 192239 Attachment 192240

Quote:

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Originally Posted by Neal Chaves

The 90mm, 75mm and 65mm lenses all focus to infinity if mounted on the inner tracks with the bed dropped. No movement is possible with any of these lenses. A 47mm, which used to reach infinity on the old Graphic back cannot do so now with the Toyo mod.

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Thanks, Neal.

To expand a little on what Neal wrote, his camera is a 4x5 Crown Graphic. Speed Graphics have significantly longer minimum extensions. See https://1drv.ms/x/s!AggQfcczvHGN2SQA6nudVURbcUFI before going ahead with this modification.

Hi,

I purchased one of these exact adapters about a year ago and have just now found a rotating back that I was willing to purchase. So I'm going to be doing this modification soon myself.

Did you run into any issues when drilling through the back plate on the rotating Toyo? Are there any mechanisms I should be aware of at the corners of the plate that you could offer insight on before I drill?

Thanks so much for any information!
-Adam

Three corners are quite easy to drill and tap for. The fourth corner has the lock mechanism for the revolving back and the screw has to be spaced so as not to interfere. I'm not sure exactly where I put it, cannot see from the outside and I'm not going to take the plate off to find out. On the three corners I can see I had drilled all the way through. There is no provision on these plates for the peep finder for the open frame finder, something I miss.