Hello Folks, I have a Symmar 150 / 265mm lens that does not appear to conform to the expected specifications.

With both lens elements attached the lens will focus on infinity at 150mm from the film plane. With the front element removed it reaches infinity at around 187mm from the film plane and with just the rear element removed it goes way beyond 265mm - too far to be measured on my 'Baby' Color monorail which would just cope with that extension.

Have any of you guys had any similar experiences with this lens and I would appreciate any help on resolving (sorry!) this issue.

Regards,

Clive

-- Clive Kenyon (clivekenyon@hotmail.com), March 06, 2002

Answers

The bellows draw always seemed to be a bit much with the conversion lens. To my recollection also, alot less sharp than the primary lens. I have since bought the lens that I need to cover...

-- Scott Walton (walton@ll.mit.edu), March 06, 2002.

It's a long time since I used a convertible Symmar, but that sounds about right to me. The rear component alone acts as a telephoto lens, and the back focus is shorter than its focal-length.
Schneider don't recommend using the front component on its own, BTW.
The image quality of the converted lens is only just acceptable anyway, and the convertible facility is really only for use in an emergency. (Though what kind of emergency would crop up that suddenly required a short tele lens and a 5x4 camera, I find difficult to imagine. Maybe if your portrait sitter turned up with a very infectious disease, or turned out to be so ugly you couldn't possibly look at them too close. I dunno.)

-- Pete Andrews (p.l.andrews@bham.ac.uk), March 06, 2002.

Clive,

I also own a Symmar 150/265mm convertible. The operation you describe is consistent with my own. As a symmar design, the lens was designed so that the front and rear elements balance each other. Once you remove an element the nodal point of the lens moves as it is no longer being balanced by the other half of the design. This is also why it is softer when "converted" as the lens is no longer able to correct certain abberations and will be considerably softer at the edges.

-- Dominique Labrosse (d_labrosse@hotmail.com), March 06, 2002.

Thanks Folks, Looks like I need a long prime lens - 240mm should do it.

Clive

-- Clive Kenyon (clivekenyon@hotmail.com), March 09, 2002.