Suter Basel Rapid Portrait lens No5 bis

[Andrzej]

Hello.
Does anyone know this lens in f4.7 version? I have bought it recently (still dont have it in hands)but all I can find in the net is about f3.75 version. Nothing about f4.7. Any info about history, focal length etc would be welcome.

[Steven Tribe]

Post #27 here.

https://www.largeformatphotography.info/forum/showthread.php?137009-Suter-serial-numbers-and-dates/page3

[Andrzej]

Thank you Mark but I did not find any info there.
This is the lens. Its bit longer than 5bis (please note the "extention" on the rear end.
The front glass is marked RP/40c (rapid portrait 40cm)
I cant find anything about this version. My lens is a Petzval
239107

[Steven Tribe]

Let’s do some simple maths!

The catalogue version of the 5 bid has a lens diameter of 81mm. The given focal length is 35cm. Using the similar data for the #5 ( lens diameter also 81mm and focal length of 28cm and has a speed of F.3.75.
If we divide 28 by 3.75 we can get very close approximation of the actual effective pupil diameter ( better than 81mm, anyway!). So the real optical aperture is 75mm!
We can can use this for the 5 bis. 35cm decided by 7.5cm gives an F value of 4.6!

The table that I (Steven, not Mark) referred to, mentions which #s are faster but doesn’t mention the slow #5 bis which is obviously a late addition to the range .

So I think your lens is the standard #5bis, with the focal length of 35cm - not 40.

[Andrzej]

Thanks and sorry Steven.
The optics (front achromatic) is marked rp/40c. It may suggest it was made or repolished for 40cm. I did not noticed big differences between images projected on gg with and without the extension.
I'm just curious , because there is no info anywhere. The barrel is clearly marked f4.7. And the barrel is made of aluminium.