How Do I Use a Schneider Convertable Symmar?

[Vick Vickery]

Ole, night is probably the best time to check for focus shift...pick a street light up the way a bit, focus on it wide open, stop down and check the focus. A bright light at night is still easy to focus on as you stop down.

[Ole Tjugen]

"Street light"?

Can't see any from here.

[Bjorn Nilsson]

Vick, Ole is in Norway, not Newark. They only have electric streetlights turned on once a year, when they give out the Nobel Peace Price. Else they use lamps filled with whale grease. (Well, crude oil nowadays.)
The only possible glimmer of light is when the Polar bears show their teeth, by which I recon it's rather late, if you know what I mean.

//Björn (swedish/norwegian for "Bear")

[IanG]

He's probably in the middle of the North Sea

Ian

[mandoman7]

The removal of the front element is the correct move to get the longer focal length. The aperture settings will not be the same, and there is usually another scale written on the shutter front. My symmar 210 has the larger 370 settings written in green.

Also, the focus shift can be a problem as mentioned, which means when stopped down you'll be examining a very dark image on the ground glass that won't be snapping when you rock back and forth like the f5.6 you've grown fond of. Remember, too, that for the 370mm something like 15" of bellows is needed which some cameras don't have.

For those reasons I've never found the longer focal length useful. After a period of time I went ahead and bought a 300mm and never looked back.

JY

[Ole Tjugen]

I've checked now, and saw no discernible difference on stopping down from f:12 to f:22 with the rear cell of a 360/620mm Symmar convertible on my 24x30cm plate camera - which has the longest bellows of all my cameras. It might be that I could have spotted a slight shift if I had been watching the ground glass through a good loupe while closing the aperture, but my arms are too short to watch the ground glass and change the aperture at the same time with 76cm of bellows extension!

[Kevin Crisp]

When I test for this I stop down to f:22 and focus as best I can. There is at that stop typically a zone that seems sharpest, I find the middle of that. Then I open it up all the way and check the ground glass. Is it still the sharpest it can be for wide open? If not, try it a few more times. If you get the same result you have a little focus shift. This can be a dramatic effect with some lenses like a single element protar cell. I have a Wollensak wide angle that has a lot. I have not noticed it with the single cells of Symmars in the 180mm and 210mm convertibles.

[Len Eselson]

Having never run into focus shift caused by changing the f-stop, I would be curious if someone could explain why this happens.
Len Eselson

[jvuokko]

I did some testing against distant street lights.

Yes, the focus shift is much smaller than I remembered. Actuallu it seems to be so small that it does not have any practical meaning, as many of you have already stated
I did use 4x loupe, perhaps 8x or 10x would have shown more difference.

The bellow had to extended to the 38cm lenght to get focus at infinity (I measured only the lenght of bellow). The lens was attached to Toyo view camera.


Len, as far as I know, the focus shift is caused by aperture blades and usually it happens when there is no front element or design of front element allows it.

But that is all I know. I have found lot of discussion at the internet where common judgement is that most convertible lenses have remarkable focus shift, including symmars. But as usually, the internet facts turned out to be only rumours.

[lenser]

Daryl,

If you go to www.Cameraeccentric.com, scroll down to the Schneider Symmar catalog and click on it. It opens into the pages and gives specific data about using the lens with either element.

Good luck.

Tim