Cirkut lens swap?

[mferrarini]

I have a #10 Cirkut in working order except for the lens (and me). The original T-R Triple Convertible was ruined due to balsam separation, although it might be salvaged, at what cost I wouldn't know. I happen to have another T-R Triple, an identical focal length combination (10.5,18,24) but a more recent vintage, with slightly larger maximum apertures. I've read that no two lenses are actually identical and that I would need to have the exact focal point of the new lens measured in order to determine the proper gears for each focal length. I find this difficult to comprehend. According to the focusing scales on the camera, each gear appears to have considerable latitude over a range of distances, a range that in my mind anyway, would exceed any variations between different lenses of the same focal length. (Whew - I hope that I've expressed this clearly). Anyway - can I use the new lens, and, if I've got this wrong, can someone explain this to me?

 

[jamie young]

There is some variation, and you would want to test the lense with the gear to see if it's sharp, especially with the older lenses. Remember you need to line the arrow up with the mark, not focus off the mark. You get the best images with the lense set at the exact gear setting, and use depth of field to get the rest of the image sharp. Kodak would fit each lense to the camera, so if you can find someone to re cement the lense it might be worth it. I've fit other lenses to various cirkuts, and it's certainly possible, be you have to test.
Jamie

 

[mferrarini]

There is some variation, and you would want to test the lense with the gear to see if it's sharp, especially with the older lenses. Remember you need to line the arrow up with the mark, not focus off the mark. You get the best images with the lense set at the exact gear setting, and use depth of field to get the rest of the image sharp. Kodak would fit each lense to the camera, so if you can find someone to re cement the lense it might be worth it. I've fit other lenses to various cirkuts, and it's certainly possible, be you have to test.
Jamie

Thanks for the reply. Using depth of field to sharpen the image certainly makes sense. I'm trying to do a close reading of the operating manual and to execute MANY dry runs before exposing film. My interpretation of the focusing instructions were to use the 100' mark as a starting point and then rack the lens as required to fine tune the focus. The manual does allow for the possibility of the pointer ending up between the marks, in which case it specifies to "use the next rearward gear". This would indicate to me that there is some manoeuvring room between marks. But then this may only be a compromise resulting in less than optimal sharpness.

 

[panoramic]

Give it a try....

You might as well try your new lens with the gears you already have. You might get lucky. Just remember the old scale will not be exactly right. Use some old 220 film and see what you get.

It is more critical with longer focal length lenses to have the right gear because the gears are smaller in number.

I have taken old TR lenses apart and re-cemented them, but it is a bit of a challenge. The lens needs to be put in a lathe and have some metal removed as the cells have a lip that was rolled down to hold them in place. One slip up and the lens is toast.

But if you get lucky and get the glass out, you can re-cement them fairly easy. With TR lenses all the elements are cemented, no air spaces. This might not be the best way, but before I take them apart, I scratch a fine line on the side of the cell so the elements will exactly line up to the way they were exactly. Since they were ground together after cementing the centering should be OK too. And what the hell, nothing ventured nothing gained. TR lenses are easy enough to find, but not worth the expense of having them professionally done unless it is an odd focal length.

On another note, I have a TR that is separating and I keep shooting with it. I kinda like the slight softness for group shots. I think it got screwed up when I shipped it to Barrow Alaska for a job once. The change in temperature and air pressure must have done a number on it in baggage. Not necessarily from the fight itself, but the freezing temperature between the plane and the terminal and then warming again.

Ron in cold Alaska (actually it is 38 degrees ABOVE zero and raining)