Convertible Lens/Image Circle

[Darryl Roberts]

Hi, would the image circle (500mm, according to angusparkerphoto.com): Schneider 360mm f5.6 620mm f12 Symmar Convertible Lens be the same with each element (360mm and 620mm)?

Thank you.

 

[removed account4]

Hi Darryl
Here's the lens data that Schneider used to have on their website before they changed things around a little bit

http://www.hyam.net/blog/archives/3961
it looks like the 500mm image circle is for both elements together ( 360mm ) converted to 620 it throws a much bigger image circle.
John

 

[Darryl Roberts]

Hi Darryl
Here's the lens data that Schneider used to have on their website before they changed things around a little bit

http://www.hyam.net/blog/archives/3961
it looks like the 500mm image circle is for both elements together ( 360mm ) converted to 620 it throws a much bigger image circle.
John

I greatly appreciate your reply.

 

[removed account4]

pleasure's mine, I have a 210/370 and it cast a gigantic image circle at 370. Don't forget the focus nodes are further back on these convertibles, so while it seems it would make sense
for 620 to take 620mm at infinity, its going to be a lot more than that, relating this to my experience the 370 configuration takes around 450mm at infinity so. .. the 620 will take a lot of bellows ...
have fun!
John

 

[Darryl Roberts]

pleasure's mine, I have a 210/370 and it cast a gigantic image circle at 370. Don't forget the focus nodes are further back on these convertibles, so while it seems it would make sense
for 620 to take 620mm at infinity, its going to be a lot more than that, relating this to my experience the 370 configuration takes around 450mm at infinity so. .. the 620 will take a lot of bellows ...
have fun!
John

Awesome, I have 1100mm of bellows. Thanks again.

 

[Patrick Robert James]

You'll get sharper results too if you use a colored filter when using the lens converted. Contrast can be low if you are going to shoot color. The lens isn't very well corrected with just the back half. Just some things to watch out for.

 

[Mal Paso]

pleasure's mine, I have a 210/370 and it cast a gigantic image circle at 370. Don't forget the focus nodes are further back on these convertibles, so while it seems it would make sense
for 620 to take 620mm at infinity, its going to be a lot more than that, relating this to my experience the 370 configuration takes around 450mm at infinity so. .. the 620 will take a lot of bellows ...
have fun!
John

Thank you! I always wondered why at 370, infinity focus really stretched the bellows. Softer than both elements together, it had a very nice look.

I have true telephotos now that focus shorter than focal length.

 

[Donald Qualls]

I have true telephotos now that focus shorter than focal length.

That's the definition of a telephoto -- needs less bellows than the effective focal length. Most of those from "vintage" days are a common lens -- like a Tessar type or early Plasmat -- with a matched teleconverter built into the rear group.

I always wondered why at 370, infinity focus really stretched the bellows.

Yep, I've got a 150 mm Componon that I use as a convertible, the rear group gives 265 mm but needs close to 300 mm of bellows. Works fine on my Graphic View, but might be a little stretchy on a Speed Graphic.

 

[diversey]

I have used Schneider Symmar 360/620mm convertible lens on my 12x20 camera. Both each cell covers 12x20. See a video I made below.

 

[MTGseattle]

Bumping an old thread yet again. in a convertible lens design like this where you sometimes use only a rear mounted cell/cells can one place a uv filter in the front opening to protect the innards without adverse effect?

Am I a goof? Does whichever cell is required remain on the front?

 

[ic-racer]

Not a bad idea if you have an appropriate adapter.

 

[Donald Qualls]

Does whichever cell is required remain on the front?

The way I've seen it (which may not apply to all convertible lenses) is that whichever lens group you're using goes in the rear threads of the shutter, so the aperture is in front of the glass. If you have a filter that fits the shutter threads, I don't know any reason you couldn't use it, though I'd hope it's a high quality multi-coated piece to avoid reflections from the aperture blades.

 

[MTGseattle]

I've done a bit more reading, and it seems like the vast majority end up with the required single element mounted on the rear.

 

[Donald Qualls]

This is also convenient in case you have a shutter without an aperture scale for the lens group you're using (as is the case with my 150 f/5.6 Componon) -- you can just directly measure the diameter of the aperture and calculate the f/ stop (aperture diameter divided by focal length as corrected for focus extension).