Convertible Symmar 150/265 tested..

[Cor]

I finally did a test with my old Schneider Symmar 150 mm 5.6 lens, which is convertible to 265 mm by un-screwing the front element. I used the 265mm configuration once (on my Tech III not so handy, it uses up the full bellows at infinity), and was not impressed: it was quite soft. I have read otherwise so I wanted to do a more careful test.

It ain't conclusive in the sense that I own only one such lens (but the 150 mm is in my opinion a good performer, I am satisfied with it, granted I never tested it against the latest APO Symmar-S, but I only do B&W and use modest enlargements), and exposed only 2 sheets.

Last Sunday, under a grey sky I exposed 2 sheets of MACO (aka EFKE) PL100 at 50 ASA and souped it in ID-62, and used a Jobo310 on a roller for the first time (to many new things in one experiment, but it worked out ok).

I enlarged both negatives full frame to a sheet of 8*10 B&W paper and scanned these: (I did not apply any sharpening, which I usually do a bit)

Symmar 150mm at f22, 1/2 sec exposure



Symmar 265mm at f32, 1/2 sec exposure




And here are 2 100% crops:


Symmar 150mm at f22, 1/2 sec exposure




Symmar 150mm at f32, 1/2 sec exposure



As you can see (I hope) the test is pretty clear, at least I will not use this lens in the 265mm configuration.

Does this confirm the experience of other 150/265 Symmar lens owners?

Best,

Cor

[rdenney]

Did you refocus the lens after stopping down in the longer configuration? The aperture is in front of the lens, and there will be a focus shift as you stop down.

Of course, when converted the lens is a triplet, but it should still perform pretty well when stopped way down.

Rick "who has a 180 convertible Symmar but has not used the longer focal length for anything critical yet" Denney

[Cor]

Hi Rick,

Good point, but I guess it would have been very hard/impossible to re-focus at f32, the light wasn't that bright to start with.

Were would the plane of focus be after stopping down, behind the wall of the church, of in front of it ? The tombstones and other details in front of the wall are also soft.

At an assumed distance of 25 meters to the church wall from the camera DOF at f32 (265 mm) would be 13.25 m in front of the wall and infinity behind the wall (Bob Wheelers Vademecum), that should take care of an assumed focus shift?

Best,

Cor

[Vaughn]

Sort of -- but to keep it apples to apples, it might be better if one's comparisons have the focal plane at the wall of the building for both images. While the DoF will make the wall to be acceptably sharp if the focus is not right on the wall, it still will be not as sharp as possible...and that is what you are trying to find out.

But your results may still be the same.

[Scotty230358]

Steve Simmons, in his book using the view camera, suggested that performance does fall off when using a convertible lens at its longer focal length.

[Ole Tjugen]

Performance DOES fall off when a lens is converted, but not as much as that!

First of all, don't rely on DOF to save you when doing critical sharpness comparisons - it just doesn't work for that.

Second, when focusing the converted lens move the aperture while inspecting the GG with a good loupe. You should be able to see how the image is affected by changing aperture, and thus chose the correct way of focussing with "focus shift". It's something that cam be seen much more easily than it can be explained, but I promise you that with a little practice you will never again worry about focus shift - because you focus the correct way in the first place.

The Symmar, when converted, suffers from chromatic aberration in the outer half of the frame. So in order to make a fair comparison, use the centre of the frame, or a strong monochromatic filter.

[Floyd Waller]

I have the same experience with my Linhof select 150/265. It is sharp as a tack at 150 but goes really soft at 265, however my similar 180/315 is very sharp at both focal lengths. I am very pleased with the results at 315 except for the camera being a huge wind sail with that much extension. Both are later model black face shuttered Linhof selected Symmars. I got the 180/315 first and so impressed with it that I was sorely disappointed when I tried the 150/265 at 265. Oh well, it is still a very good 150!

[Cor]

Ole & Vaughn: I see your point.

OTOH the first image I shot in the 265mm configuration was a long street from the beginning of the street, lined with sticking out shop signs: I focused on a sign about halfway the street, even I was off due to focus shift, something in that scene should have been sharp (dis regarding camera shake), and it was not

All in all I do not think I will use that lens in 265mm, although I will check for this focus shift, just to check what happens.

Floyd: it is nice to see a conformation, although it's strange that your 180/315 does no show it, it is the same lens design. That 315mm is out of the question with my bellows though.

best,

Cor

[Vladik]

Seems to me more like a motion blur. Look at the eaves, there´s quite obvious double line, don´t you think? It wouldn´t be any wonder, if you need full extension of your camera.

[IanG]

I have the same experience with my Linhof select 150/265. It is sharp as a tack at 150 but goes really soft at 265, however my similar 180/315 is very sharp at both focal lengths. I am very pleased with the results at 315 except for the camera being a huge wind sail with that much extension. Both are later model black face shuttered Linhof selected Symmars. I got the 180/315 first and so impressed with it that I was sorely disappointed when I tried the 150/265 at 265. Oh well, it is still a very good 150!

Something sticks in my mind about the older 180mm Symmar, Ole or someone like Dan Fromm or Kerry Thalman may remember but I think the design was slightly different to all the other Symmars this may well be why it performs differently - better split.

Ian