210mm f/9 Graphic Kowa - Image Circle

[Old-N-Feeble]

Greetings,

I know there are at least two varieties of the Graphic Kowa 210mm f/9 lens... 4/4 element 4/6 element versions. Does anyone know the usable image circle of one or the other? By "usable" I mean very high quality.

Thank You!!

--- Also posted on the APUG.org forum.

[Lynn Jones]

I'm unaware of a 4 element K Graphic but very aware of the 6 element which was also the f 9.0 Computar and they cover 80 degrees, your 210 should easily cover 8x10.

Lynn

[Old-N-Feeble]

Thank you, Lynn. I removed the front/rear cells and viewed the reflections and saw 4/4. However, I didn't think about how many cells may be cemented... I'm getting very forgetful these days. Is there a way to see the optical construction without having to remove the elements from the cells? I no longer trust my hands to not damage the glass.

[Zaitz]

Have you seen this old thread? May be of help...
http://www.largeformatphotography.info/forum/showthread.php?10255-The-Computar-lens-and-ULF-coverage

I think my Kowa 210mm is a fantastic lens. Seems to cover 8x10 very well and sharp. Quite a bargain I think. I can't offer much beyond that though.

[Old-N-Feeble]

Thank you, Zaitz. I did see that thread. However, I've read other threads and web pages that state a 210mm Computar doesn't always equal a 210mm Graphic Kowa and not all 210mm Graphic Kowas are the same. I'm trying to clear up my confusion which ain't easy at my age.

[Zaitz]

Yeah I've wondered that too, especially after reading that thread. I do know, so far, I haven't seen any real vignetting with my Kowa on 8x10. Someone buy me a Chamonix 12x20 and I'll test it on that :D.

[Old-N-Feeble]

Hey Zaitz... How's the corner resolution with yours? I'm embarrassed to tell you that I have yet to test mine.

[Zaitz]

I haven't run any formal tests either but I do have a few scanned photos that should tell me. I'll have to check when I get off work. I didn't see anything while processing that would make me think the corners were anything but sharp.

[Old-N-Feeble]

Thank you, Zaitz!!

[Kerry L. Thalmann]

Mine was a 6/6 construction with a usable image circle in the 380mm range. It was definitely not the same as my 210mm f9 Computar that was a 6/4 plasmat that covered about 425mm.

Kerry

[Old-N-Feeble]

Kerry,

Do you know if there's a way to determine optical construction without having to disassemble the groups?

BTW, I often visit your lens pages... great stuff there.

Mike

[Dan Fromm]

Do you know if there's a way to determine optical construction without having to disassemble the groups?

PMFJI. Counting reflections is a start. Use a point source or a single lamp. An air-glass interface makes a strong reflection, a glass-cement-glass interface makes a weak one. Weak reflections can be very hard to see.

Think about it and you'll see that Kerry's two lenses -- 6/6 sort of perhaps double Gauss and 6/4 plasmat -- are easy to tell apart.

[Old-N-Feeble]

Thanks, Dan. I checked again and could only see 4 reflections in each set of cells... all strong reflections. This time I used a small very bright LED flashlight from about 3 feet away. I tried very hard but could not see any weak reflections.

I don't know if this helps but, other than the mounts, the front and rear groups look identical and seem to have identical individual focal lengths.

[Zaitz]

Well I won't be much help with my images. They are probably not the best to tell corner sharpness, pre-sunrise dark corners... I do have one that is very sharp throughout but it was focused closer so not at infinity. I also have one from Great Sand Dunes NP but would need to re-scan it at higher resolution. Sorry for that. I have a couple getting developed but won't see those for a week unfortunately. Those might be of more help.

[Old-N-Feeble]

Thank you, Zaitz. I'm in no hurry. Please post your results as they filter in through your normal routine. :)