View Full Version : 210mm f/9 Graphic Kowa - Image Circle
Old-N-Feeble
23-Feb-2012, 13:09
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
23-Feb-2012, 14:48
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
23-Feb-2012, 15:02
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.
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
23-Feb-2012, 16:52
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.
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
23-Feb-2012, 17:11
Hey Zaitz... How's the corner resolution with yours? I'm embarrassed to tell you that I have yet to test mine.
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
23-Feb-2012, 19:04
Thank you, Zaitz!!
Kerry L. Thalmann
23-Feb-2012, 23:16
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
24-Feb-2012, 08:12
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
24-Feb-2012, 09:19
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
24-Feb-2012, 10:09
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.
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
24-Feb-2012, 15:54
Thank you, Zaitz. I'm in no hurry. Please post your results as they filter in through your normal routine. :)
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