Is the image quality of say a Symmar 180 convertible compromised by being a convertible?
Is the image quality of say a Symmar 180 convertible compromised by being a convertible?
Mark- I have a Symmar 240/480 and I think the 480 side is not as good as the 240. It stands to reason, if you think about it, that the image is sharper with all the lens elements involved in the image formation. It does help, tho, to use a #15 yellow or even an orange filter when using the 480 length. That makes it pretty usable. But to answer your question; in a word, yes.
Looks just as good as the coupe!
Mark: As a fan of convertible lenses of all vintages, I have to admit that the answer is, in virtually every case including the 180 Symmar, yes. The footnote is that while using half the lens may inevitably deliver somewhat less performance, the difference can be undectable in common print sizes and the converted image can be plenty sharp to be useful enough for what you need. Don't let the theoretically inevitable image degradation dissuade you from trying it and seeing if it is good enough for your purposes. It may well be. Unlike so many others who say this, I have not found it necessary to use a filter to obtain usable results with a converted lens. My short reviews on convertibles when converted, assuming in all cases the lens is stopped down to f:22 or smaller: Protars? Probably decent to excellent, depends on the sample. Symmars? Depends on the sample and the focal length. I thought the 180/315 was quite decent when I had one, the sharpness of my sample (late production in Copal shutter) was incredible edge to edge with 5X7 film when used at the 180 length. I also used the front element alone with my 180/315, it does provide an intermediate length with a different angle of view, and it was decent that way too. I know this is contrary to Schneider's instructions, but it worked quite well. I was less impressed with the longer focal length Symmars. Turner-Reich? Sorry, I can't live with the quality of the ones I tried if converted. (x3) Intact they are usable but kind of flat. Gundlach Periograph? Haven't made up my mind yet, I'm trying one of those.
If I understand Mark's question correctly, he wants to know about the quality of the complete lens. If so, the answere is that Schneider was able to obtain some improvement by departing from the strict symmetry of the converible lens. Schneider claimed reduction of field curvature and of chromatic aberration. The improvement was not due entirely to going to a near symmetrical design. Schneider used new glass types and computer ray-tracing techniques in creating the Symmar-S.
This does not at all mean that the earlier lens design is unusable. Many excellent photos have been and are still being taken with convertible Symmars. In general, when a new lens design is introduced one should be able to expect an improvement over the type it replaces. No doubt the Apo-Symmar-L (which uses still newer glasses) will eventually be replaced. When it happens, those who make their living by producing mural size enlargements will have to consider whether the cost of the new type must be spent. The rest of us may find earlier products still adequate for our use.
From what I've heard, the reason the Symmar-S was not convertible was that they could then drop the compromises necessary to make the Symmar usable as a convertible. A single cell can never be as good as a complete lens, and will be a lot poorer unless these compromises are made.
Still, I think the Symmar (non-S) is still a good lens, and more than adequate for 99% of all my uses. As a single-cell converted it is less impressive, but at least it gets the shot.
I'll be selling my Symmar 150mm soon, since I have a 150mm APO-Lanthar which I use instead. I also have a 210 Xenar which covers the need for the longer focal length. I'm not at all dissatisfied with the 150mm Symmar, it's just that I don't need 5 lenses in the 135 to 150mm range...
Yes, but not by much, and in real use, if you usually shoot around f:22 anyway, it might not really matter at all. I have a 135/235 and 210/340 Symmar, and they are both quite good lenses with both cells, and a little soft converted, but even converted, they'll sharpen up as you stop down.
I have one of the older Symmar 150s and find it to be quite sharp on 4x5 on an 11x14 print (haven't printed larger yet) with FP4+. I have not tried it with one element alone.
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