Turner Reich Triple Convertible

[lenser]

Thanks to everyone who has answered with their good ideas about the top hat board question.

I've tried looking at the ground glass image with the 36" element in back and in front of the shutter and I don't see an appreciable difference in magnification or sharpness. This brings up the question of why is there a difference and what is that difference in performance between having the lens behind as is recommended and having it in front which does allow for a much shorter top hat board?

The few references I have found on line and in Adams "Camera and Lens" simply mention to put the cells behind the shutter, but don't give actual data on why.

Again, thanks to everyone for helping on these questions.

Tim

[Walter Calahan]

I've never bothered to ask, so perhaps I'm just dumb. So good for you for asking. I just follow the lemmings by putting the elements to the rear of the shutter on my Cooke XVa. Good luck.

[ljsegil]

I've used the front element of the Cooke XVa in front of the shutter to enable focusing the lens on my 5x7 and gotten good results, although I think better image sharpness requires more stopping down than when the element is mounted behind the shutter, when it gives perfectly sharp images wide open (albeit on my 8x10 which has longer bellows than the 5x7 and can focus in that configuration).
LJS

[lenser]

Anyone else have any information on this? I appreciate anything anyone can tell me about the various configurations.

Thanks.

Tim

[EdWorkman]

You can [probably] find something at cameraeccentric [to support any point].
In my wanderings over the web I have noted that the recommendations by lensmakers flipped and flopped with time and company. And I'm pretty sure I read one catalog from some era that said it didn't matter. Later one said put the element in front so as to protect the aperature/shutter blades. And I could probly find another that said it will only work if you put the element BEHIND the iris. I have extreme doubt that anything substantive changed in the design of convertible lenses to make differences. The only concensus is that the single elements work best if stopped down. I did recently find some notes I made in the 80s about my Protar. IIRC , knowing not "better" I put the element in front and noted that the focus shift on stopping down was roughly 3/8 inch- IIRC it was the 24 in element of a B&L VIIa 18/24/11+. In any case in front makes some sense for extension considerations. In back, if one wants to use the rear element, is easy. If you can't see any difference, any that might exist isn't.

[lenser]

Thanks, Ed. I'm kind of in a Catch 22 here, hence the appreciation for any information.

I want to use this with my 8x10, but need to be sure of how to configure due to the difference in length of the needed top hat style board. But, I can't run sharpness tests first due to not having the boards made. But I can't make the boards until I know the needed length.

You get the idea. I may try to cobble together a temporary rear extension frame and shoot a few images at both positions to see if there is an appreciable change in either magnification or sharpness.

Thanks again.