270mm Computar - 2 spacers?

[enochRoot]

I just picked up a 270mm Computar for insanely cheap. I'm looking for a shutter to put it into, but when unscrewing the elements I noticed that there was a spacer on each side. Based on what I have read here, they normally only came with a spacer on the rear. Any idea why mine has two? It most certainly was untampered with and came that way from the factor as it's still on the process camera lensboard.

Did I also read correctly that sometimes these spacers are left off when infinity focus is required? Is there a rule of thumb (ie: focusing distance) for when you'd want to go sans spacer?

[Lynn Jones]

They were made by Kowa as the Kowa Grafic and at their best are truly superb wide field APO lenses. The spacers were to permit altering the best focusing distances, however, I left the company 33 years ago and no longer remember all of the fine technical points. They were made as 150mm, 210mm, 240mm, 270mm, and 300mm. There was also Kowa 360 but it was made for a special purpose graphic arts camera covering only 5x7 and didn't have a great reputation as a general purpose camera. I still own 3 or 4 of these and as BJ-BBOI VP had access to the use of lots of unusual optics, they were excellent overall. BTW, I have used the 150 and 210 as single convertibles with some success (they approximately double).

Lynn

[John Schneider]

What's the thickness of the spacers? The single rear spacer on mine was 0.060" thick. Maybe you have two 0.030 spacers, and someone assumed that one went in the front and the other in the rear?

[enochRoot]

thanks for the answers! i'll dig up my calipers, measure the spacer thickness, and then report back.

[enochRoot]

ok, it would appear i was confused. the two things that i thought were spacers (more like shims) were actually retaining rings. i know this because i took one out to measure and the aperture blades proceeded to fall out onto the table. after a bit of puzzle solving, i got it back together and noticed the single spacer in the rear. thanks for the help!

now, do people leave these in when mounting in shutters, or remove them? i could have sworn i read somewhere that they were for 1:1 type focussing and the lens performed better in general use without the spacer. or would that only be at infinity focus?