Protar Lenses.

[ridax]

....if single Protar lens cells should be mounted in front of or behind the iris.

I've compared the performance of the Zeiss Protar VII cells, the B&L Protar VII cells, the Wollensak Ia cells, the Turner-Reich (another Protar VII derivative) cells, as well as many other double-anastigmat cells mounted at the back a well as at the front of their barrels. Nearly all of them loose a lot in sharpness if put in front of the iris - except the convertible Sironar front that was intended for that very usage and the Dagor halves that turned out to be nearly indifferent to their position. While a Protar VII mounted behind the aperture can be stopped down at least a full stop less than a Half-Dagor to show a similar level of sharpness, the same Protar VII becomes no better than the Half-Dagor when mounted at the front. As front mounted double-anastigmat cells need far less bellows draw (working as slightly telephoto lenses actually), I enjoy the 840mm front half of my 480mm Dagor on my Calumet C-1 and the 290mm half of my 165mm Dagor on my old compact and lightweight 9x12cm folder. Normal lenses of the same focal lengths would be practically impossible to focus on those cameras except at the very infinity.

And yes all those single cells suffer from the chromatic aberration badly, and a yellow filter improves their sharpness a lot. Though myself I like the blue-sensitive film look way better....

As for the spherical aberration which is negative and thus very good for the out of focus background rendition in all those lenses well stopped down, it is of the same character but different in its amount. The complete Double-Protar VIIa (as well as the Wollensak Ia and the Tuner-Reich) has less SA and correspondingly makes less smooth background defocusing than the complete Dagor; the single Protar VII (and the Wollensak Ia and the Tuner-Reich) cells have more SA and more pleasant OOF background rendering than the complete Dagor, and the Dagor halves have still more SA and the smoothest OOF background rendering of all them. Though the difference between the 'really good' and 'still better' is probably not worth loosing sharpness - which is unavoidable with single cells instead of complete double anastigmats. For me, the complete Dagor is still the best of both worlds - if only I don't need a lens longer than my 480mm (I don't own a 600mm.... and nobody owns anything like a 840mm).

I also often prefer to put a simple negative supplementary lens on a complete Dagor to using any lens halves. Those combinations give much sharper results than any single lens cells, and are especially better in their chromatic aberration so the yellow filter is not needed.

[Jim Noel]

An interesting comparison, ridax. I assume all conclusions are based on either the negative, or final print.
Also, I expect these are made based on a single example of each lens. I currently have 2 TR's, and have owned many more through the years. Each of them has rendered a different image, some excellent, some not quite so good.
Still, a good comparison and thanks for sharing.

[ridax]

....I assume all conclusions are based on either the negative, or final print.
Also, I expect these are made based on a single example of each lens. I currently have 2 TR's, and have owned many more through the years. Each of them has rendered a different image, some excellent, some not quite so good.

There was one B&L Protar, one Wollensak Ia, one Turner-Reich (two single cells in each of them), and 4 individual Zeiss Protar VII cells (an original Satzobjektiv + one more cell). And there were well enough Dagors of the focal lengths close to those of the above Protar-type lenses.

The production quality control used to be very high at Zeiss, Goerz, Wollensak and B&L (that's widely known and also verified by myself with other type lenses by these manufacturers, produced in the same era). Besides, my observations on the sherical and chromatic aberrations (and coma and astigmatism, too) perfectly correlate with the published aberrational curves for these lenses so I don't see much of a reason to undertake any more tests with other specimens of the same glass.

Turner-Reich is most probably an exception as the Gundlach quality control is usually criticized a lot, and besides there are no published aberrational curves for the T-R that I know of. Perhaps it would be quite practical to test at least half a dozen of Turner-Reichs before making any conclusions but sorry I don't want to buy so many of them.

Most of my formal tests (as opposed to practical usage) of the lens' batch were visual (a super-fine-grain chemically etched ground glass cannibalized from an MF camera + the top of the line 7x Peak loupe), with the most critical comparisons made with an old (and thus making almost no automatic editing of the image) Canon D60 DSLR. Using LF film and paper for multiple tests with different subjects and lighting would cost quite a bit and what is much more important, would probably take at least a year instead of a couple of weeks.

[ridax]

I forgot to mention I use my 840mm Half-Dagor on 8x10" and my 290mm Half-Dagor on 9x12cm without any movements to stay within the center of their fields. I consider my 590mm to 650mm Protar-type single cells (all the above mentioned, including the T-R) to be acceptable for just a little bit of movements on 8x10" (within about 40° total) when put behind the aperture and stopped down well. If I put them on the fronts of their barrels, they become no more moveable then the 630mm half of my 360mm Dagor.

I wouldn't try using any single cells at wider angles.

[ridax]

....the difference between the 'really good' and 'still better' is probably not worth loosing sharpness - which is unavoidable with single cells instead of complete double anastigmats

A correction: the above was said about distant views with lots of fine details. I've tried virtually all my lenses on different formats from 8x10" to cropped digital for close-ups recently, and the only ones that satisfied me with their out of focus rendition were Half-Dagors. My subject consisted of tree leaves in the central part of the frame (which naturally is sharper rendered by any lens) with the background located really far, quite close to infinity. The background was a real mess with a lot of reflections in bright sunlight - not an easy task for the lens. All my Half-Dagors did their job excellently. And no other lenses could compare to them.... So now I'm keeping my 360mm Dagor that I was going to sell. I don't have much usage for the 360mm focal length but its 630mm half is just great for close-ups on my 8x10" at f/32. Shorter focal length Half-Dagors are good enough at f/22 on smaller formats. And I guess they should be fine for portraits, too - when there is enough light for the small f-stops.

[ridax]

Turner-Reich is most probably an exception as the Gundlach quality control is usually criticized a lot <...> Perhaps it would be quite practical to test at least half a dozen of Turner-Reichs before making any conclusions but sorry I don't want to buy so many of them.

Well, I've done it. No not half a dozen of complete double anastigmats but still 7 single cells (3 complete lenses + 1 more cell) came to my place to get tested a couple of months ago. And I've not seen any quality differences in those. Certainly that's no proof all the Turner-Reichs are built excellently but for me, that's well enough not to feel too suspicious about them.

More details here:
https://www.largeformatphotography.i...=1#post1623042

[Jody_S]

Well, I've done it. No not half a dozen of complete double anastigmats but still 7 single cells (3 complete lenses + 1 more cell) came to my place to get tested a couple of months ago. And I've not seen any quality differences in those. Certainly that's no proof all the Turner-Reichs are built excellently but for me, that's well enough not to feel too suspicious about them.

More details here:
https://www.largeformatphotography.i...=1#post1623042

I wonder if the hit-and-miss quality on the TRs is because nearly all suffered from balsam failure and if the lens is clear, it's most likely because someone has re-cemented it. Usually without the benefit of an optical test bench or any sort of tools to align the glasses, which is a bit of a job given that there's 5 of them.

[ridax]

I wonder if the hit-and-miss quality on the TRs is because nearly all suffered from balsam failure and if the lens is clear, it's most likely because someone has re-cemented it. Usually without the benefit of an optical test bench or any sort of tools to align the glasses, which is a bit of a job given that there's 5 of them.

Yes that's exactly my own guess. As I said in that other thread, almost all my Turner-Reich cells have balsam degradation at the edges as I preferred to buy them cheap. They seem to be never recemented since their manufacture and have no centering problems at all.... Strangely enough, it looks like cheaper means more secure in the Turner-Reich case . :)