Graflex.org

Ronin · Joined: 07 May 2004 Posts: 16 Location: Tuscany, Italy

Hi,

I'd like to have one of those convertible lenses made by Schneider, like the Symmar 240-420, for use on my Graflex Super Speed Graphic. Question is: does the bellows extend enough to focus correctly at 420mm?

Les · Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI

The Super Graphic has an approximate bellows draw of 12" so a 240mm lens of normal design will work within reason, although you won't be able to focus very close with it.

A 420mm lens is 16.5 inches and won't come close to focusing at infinity. Further, a convertible lens uses more bellows draw than normal when the cell is in the rear so unless you mount this with a 6" extension tube, it won't work.

Ronin · Joined: 07 May 2004 Posts: 16 Location: Tuscany, Italy

I've heard somewhere that if the rear element is removed instead of the front one, it can be focused without too much extension... Is this true? If yes, would it still work as a 420mm without the rear element? Or has a different focal?

thanks,

Fulvio

Les · Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI

Yes, putting the single cell infront will not so much a shorter bellows draw, but the right amount. The focal length on a lens is measured from the rear node of the lens to the film plane. In most cases the rear node fall fairly close to where the lensboard is.

With half the lens, the rear node is shifted in front of the board so that 420mm is measured not from the film plane to the board, but to somewhere in front, probably about 10mm.

By putting the cell in front, you move the rear node behind the lensboard, so now it focuses infinity at 410mm instead of 430mm, but a Speed Graphic can only stretch to 300mm. So it still won't fit.

Siu Fai · Joined: 25 Sep 2003 Posts: 15

I use the 150mm Symmar and with the front cell removed I can't get focus even at infinity on the Super Speed. It is do-able on the regular Speed Graphic.

So with a 240 symmar, forgetaboutit.

troublemaker · Joined: 24 Nov 2003 Posts: 715 Location: So Cal

I use the Symmar 135 / 235, and while the 135mm is of reasonable quality, but not as good as either of my older 135 Optars, the longer conversion is pretty bad as far as sharpness goes, and as noted above, requires the max bellows draw and will still only get in to about six feet. A nice portrait lens? I haven't found this to be a very good lens for the Graphic, but it is the one that works both ways.
Regards,
Stephen