    
Glenn
Tinkerer
Username: Glenn
Post Number: 895
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 03, 2011 - 07:07 am: | 
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it is well known that we are all a very helpful bunch on here, but sometimes I get a little pissed off when it appears that some people think that some of us have nothing better to do than stare at a computer screen all day!
Typing 'Dogmar Lens' into Google produces pages of information/discussions on Goerz lenses in under 5 seconds and is in such detail as to answer all likely present day questions.
By all means ask for clarification on points that are not clear, but please do a little basic research first. I do not want this to appear rude or unfriendly - many will not agree with my sentiments - but this 'I can't be bothered myself, some other poor sod can do the legwork' seems to be creeping insidiously into all types of 'hobby' forum these days.
The quote below from the Photo.net Large Format Forum gives belt and braces on this 1914 four element optic and will allow you to garner further technical details on the optical formulation.
Dogmar A new dialyt series was announced in Photography 26/05/1914, working at f4.5 in the shorter foci. Since it was very late prewar, most examples will be postwar. Adverts. stressed it was a very highly corrected lens, but the major sales feature was that it was separable, the front cell giving 2x focus, and the rear one 1.5x focus. It was said to be free from ghosting, and the f4.5 was initially made in up to wholeplate size, the longer sizes being in f5.5. It covers 55deg or 54deg at full aperture, and 60deg at smaller apertures. It was suggested to use 21cm for 13x18cm plate. The f5.5 covered a slightly larger angle (54-60deg) and a slower version at f6.3 covered a bit more again (60-65deg). However it was not primarily sold for its angle of cover, and the slower version was short lived, being replaced by the Tenastigmats, etc. The designer was W. Zschokke, and it was covered under Patent 258,494 and sold from 1914. It is sharper than Celor, and shows better edge detail than the Q15 type designs. [Zschokke then left Goerz after the association as Zeiss Ikon, and designed rather similar lenses for Kern, possible perhaps due to the take over by Zeiss Ikon and the absence of this lens type in the Zeiss lists.] Dogmar f4.5 60, 75mm for 2.375x2in, 90mm for 2.75x2.375in, 100mm for 2.5x3.5in, 125mm for 4.25x3.25in, 125mm for 4.25x3.25in, 135mm for 4.25x3.25in, 150mm for 4.75x3.5in, 165mm for 5x4in, 180mm for 6x4in, 195mm for 6.5x4.75in, 210mm for 7x5in, 240, 270, 300mm. Use 165mm for 5x4., 14in for 10x8. (Goe005,009. Q26 type). Separable, 3 focus. It covers 55deg and there is no suggestion of improved cover when closed down. The other foci of the single cells were not detailed in adverts. (eg B.J.A. 1925, p739 |
