What do ya' think ?

[gene m]

This irisless 150 f4 Rodagon is sharpest at f8. Would it be possible

to place some sort of orifice between the lens sections to stop the

lens down to f8 ? Installing a real iris would cost in the area of

$500 (S.K. Grimes.)

 

Any other suggestions ?

 

<img

src="http://ebay2.ipixmedia.com/abc/M28/_EBAY_050eee4755ccd3afd7d5ebf

0e25c1a63/i-5_B_L.JPG">

[tracy_storer1]

You could have them cut a slot and make a set of waterhouse stops....that

would probably cut the price in half.

[alex_hawley]

How about placing the aperature over the front element? I've seen "pinhole" aperatures that were done this way.

[michael_briggs2]

Did Rodenstock reject the solution that I previously suggested (http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=0053bk)? Custom work is normally more expensive than mass production -- since the normal enlarging lens version of this lens is still in production, you might be able to get Rodenstock to install the lens cells in the standard enlarging lens barrel with iris. If this isn't possible, a Waterhouse stop would work -- but for best performance you need to know where to place it.

[kott]

Just using this lens for macro at a scale of reproduction of 1:1 would change the effective apeture to f8. This may not be the answer you are looking for but it is free!

[jim_galli4]

Seperate the groups. Front group. Rear group. Try the threads in different shutters. Copal 0 and 1. Schnieder was always real good about making threads and spacings so that it is easy to mount your groups in shutter instead of barrel. Rodenstock didn't consider this very important but it's worth a try. If you find it will go into a size 0 or 1 shutter, I've got a pile of Schneider barrels in that size, and can send you one. If it's obvious it isn't standard size 1 or 0 threads, have Bob Salomon quote you a price for a correct factory barrel with aperture.

[michael_briggs2]

I don't know whether the lens is sharpest at f8 -- of the two apertures for which Rodenstock shows MTF curves, f8 is better than f4. It may be sharpest at f8 because the brochure lists the "working aperture from" as "8".

 

The point is that the sharpness improves as the lens is stopped down -- using it at 1:1 won't change this.

 

I measured the threads on the rear cell of one: 36 X 0.75 mm. These are the threads of a #1 shutter so Jim's idea might work. I don't know about the front threads because disassembly wasn't obvious.

 

The best plan is probably to talk to the Rodenstock distributer in your country.