questions about converible lenses

[eddie]

hello,

i just got a new-to-me meyer plasmat.
front element is marked 15.3 cm. f4.5
single front element is marked 32 cm. f11
single rear element is marked 22cm. f8

i know that it is better to use them on the rear but for the 32 i need to put it on the front because my chamonix runs out if extension.

is there a 4th FL if i use the front on the rear and the rear on the front? it gives me a bit different FL. does it affect image quality?

i have an aperture scale that i need explained. it says "HL" and "VL" it also has a "regular" scale. the confusing part is there is a forth 4th scale that says "weitw 8cm. the last scale creates a very small aperture when compared to the rest. is that last scale the reversed elements? what does "VL" and "HL" mean? (i figure VL must be front but the scale starts at 9.5 instead of 11) please see the picture below.

thanks for the help. photos i took using this lens are in the fixer now!

eddie

[Emmanuel BIGLER]

is there a 4th FL if i use the front on the rear and the rear on the front?

No, any optical system operating in air features the same focal length when used in either direction. In order to get different focal lengths with a reversed system, you would have to operate the input (object side) and output (image side) in different transparent media e.g; input in water in direct contact with the front lens element, output in air.

However, reversing a photographic lens usually has a dramatic effect on image quality even if both focal lenghts are identical.
So in a classical convertible lens like yours, you only have access to 3 focal lengths :
- front alone
- rear alone
- both together

it gives me a bit different FL. does it affect image quality?
My guess is that all 3 combinations should be used preferably not revered i.e. front in front, rear at rear and front + rear un-reversed.

In order to have access to additional focal lengths, you would have to combine a second identical lens to get two hypothetical combinations (front + reversed front) and (read = reversed rear). This has little interest.

It should be noted that if the lens is very asymmetric like a telephoto, reversing it does not change the focale lengths but does change the numerical aperture. This effect is probably negligible with a classical convertible lenses which is only very weakly asymmetric. However if the whole (front + rear) lens is symmetyric or close to, the front element or the rear element alone are asymmetric, so if you use them reversed, the f-number mentioned by the manufacturer is no longer the actual one.

[Patrik Roseen]

I guess V = Vor (In front) and H = Hinter (behind) in German.

I could not see your picture of the lens but found this on ebay, this one only has three scales as I can see.

meyer 15.3 cm (http://cgi.ebay.es/Meyer-153mm-f4-5-22-32cm-Satz-Plasmat-set_W0QQitemZ150198313622QQihZ005QQcategoryZ101642QQcmdZViewItem)

Strangely enough I also found this lens said to be in its original shutter, where the aperture scale is different (or rather the same as what is on the lens)
meyer lens 2 (http://cgi.ebay.com/Hugo-Meyer-for-Larg-Format-Satz-Plasmat-4,5%2F15,3-cm_W0QQitemZ370022813205QQcmdZViewItem?IMSfp=TL0802141031a32902)

Weitw 8 cm might be done using a wideangle attachment?

[j.e.simmons]

I don't know the scientific reason, but my Protar focuses in a different place if the single element is in front or behind the aperture.
juan

[Dan Fromm]

John, remember that focal length = distance from rear node to film plane when the lens is focused at infinity. The cell's focal length is the same regardless of which way it is pointing (front to the front, rear to the front) but its nodes aren't equal distances from the ends of the lens and the flange to film distances aren't the same either.

[Patrik Roseen]

A long shot???
I might have found the answer to the 4th scale.

On this website is mentioned a Linhof Satzplasmat camera with a 220mm lens in shutter including also a box containing the two cells for Weitwinkel Aristostigmat 8cm.
Possibly this could screw into the same shutter?

camera with two cells Weitwinkel Aristostigmat f9/8cm (http://www.powerhousemuseum.com/collection/database/?irn=121767&img=156791)

Maybe this was how these linhof satz-plasmat cameras were sold, also including the cells of a weitw lens
one more (http://cgi.ebay.com/Meer-Hugor-Goerlitz-Silar-10x15cm-Outfit-+--Plastmat-Sa_W0QQitemZ370022813175QQcmdZViewItem?IMSfp=TL0802141041a35900)

[Ernest Purdum]

Reversing the front ands rear elements would be appropriate if, but only if, you were taking photographs at more than 1 to 1 magnification. (Subject to lens distance less than lens to film distance.)

As has been surmised, the fourth W scale was for use with wide angle (weitwinkel)cells which unfortunately are not present.

[eddie]

A long shot???
I might have found the answer to the 4th scale.

On this website is mentioned a Linhof Satzplasmat camera with a 220mm lens in shutter including also a box containing the two cells for Weitwinkel Aristostigmat 8cm.
Possibly this could screw into the same shutter?

camera with two cells Weitwinkel Aristostigmat f9/8cm (http://www.powerhousemuseum.com/collection/database/?irn=121767&img=156791)

Maybe this was how these linhof satz-plasmat cameras were sold, also including the cells of a weitw lens
one more (http://cgi.ebay.com/Meer-Hugor-Goerlitz-Silar-10x15cm-Outfit-+--Plastmat-Sa_W0QQitemZ370022813175QQcmdZViewItem?IMSfp=TL0802141041a35900)

cool! thanks for the info everyone!

i will be out shooting more tomoorrow!

eddie