Hello. been watching a lens on ebay - EWA Dallmeyer 4 1/4 inch f6.5.
It claims its about 83mm focal length with an angle of 100-110 degrees coverage. It also claims it cover 4x5. Comes in a Compur 1 shutter, witch is what I'm really interested in. But I'm curious about the lens and the claims made for it!
Any info?
It's a 3 1/4" lens, not 4 1/4". The 83mm is correct.
The angle of coverage seems reasonable. That means it should cover about 3x focal length, or (in this case) 249mm, in other words 5x7" with movements!
Front-mounting wide angle lenses tends to lose some coverage. But it will certainly cover 4x5", although 5x7" might not quite work with front-mounting.
What was the auction?
Surely if it was a anastigmat like a Protar or a aplanat then it'd be a f16 max aperture at best?
Neil, I found it easily.
I noticed the aperture scale starts at f:11, so the "F:6.5" is probably a wide open setting for focussing only. It's not that uncommon in these little old WA lenses.
My apologies, I found the auction. F6.5, wow that's fast! What type is it?
I would guess it's a double Gauss, which would fit with the f:11 as max. usable aperture. That makes the 110 degrees a little over-optimistic, and 100 degrees quite possible (at f:32 or smaller).
Hello, thanks Ole, thanks Neil. I'll be keeping my eye on that lens. Not sure if i'll bid though. Trying to keep those impulses in check...!
KK
According to a Dallmeyer catalogue, the f6.5 aperture is indeed for focusing only, f11 being the maximum taking aperture.
Regarding coverage, the catalogue states "At small apertures the angle in some cases exceeds 100 degrees" - not a very precise statement.
These lenses were still being offered in Dallmeyer's last years, so some would be factory coated.
Hello Ernest. the description of the lens says that the maximum aperture is for focusing and that it should be used stopped down two or more times.
It also says its coated so it must be a late lens.
KK
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