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Markus Röhling
02-16-2009, 09:30 AM
Can anybody tell me where I can find the following table for my Distar lenses? I need one for 15 cm focal length.

http://www.markus-roehling.eu/wp-content/distar-01.png

This one I got together with a Distar 3/IV lens but unfortunately parts are missing.

Markus

Ian Grant
02-26-2009, 03:56 AM
You might look on this web-page (http://www.willisboyce.com/photography.htm), half way down the page there's a link to a spreadsheet that calculates DOF, but it also includes the Bellows extension factors which is what you need. Then you can calculate relative apertures etc/

Ian

Marczak
03-07-2009, 05:20 PM
Thanks Ian,

Paul

apkujeong
03-18-2009, 12:36 PM
Hope this is useful, I've attached a scan.

Markus Röhling
03-18-2009, 01:10 PM
Thank you very much! That is just what I was looking for. Saves me a lot of calculating.

Markus

Andreas
05-05-2009, 04:54 PM
Here you have it all, both Distar and Proxar. I'm pretty sure you read it like this:
Vertical column in the middle is, of course, the unaided 15cm Tessar.
f (cm) is the resulting focal length with the supplemantary lens indicated on top of each column.
V is the factor for the change in focal length (perhaps it stands for Verlängerungsfaktor?)
T is the factor for calculating new exposure time with the supplementary lens. Multiply the measured time by this factor.
Relat. Appert. is the effective apperture with supplementary lens in place, with reference to the apperture scale on the lens. Orange numbers should be avoided because of too great loss in picture sharpness. Light orange numbers are o.k. for contact prints, I guess. (That's what most users would be making with this equippement). Use white numbers for sharp pictures.

I have only made a couple of tests with Distars and Proxars at small appertures. The results were not bad. Proxar 2 enlarged from 9x12cm to about 24x30cm was quite sharp, if not stunning.

By the way: I enlarged the table a bit (to about 7x10cm) printed it and got it laminated. Very durable and handy to keep in my bag.

Markus Röhling
05-06-2009, 04:51 PM
Thank you very much for this interesting and helpful table.

Markus