Naively, it seems you're doubling the focal length, so what's marked as f/8 is now f/16; two stops?
+1Hmm. I thought that afocal adapters mounted in front of a lens don't change the f/ number.
Hmm. I thought that afocal adapters mounted in front of a lens don't change the f/ number.
Patric, although I lived in Germany for a year and played in my town's orchestra, I never learned German. Well, enough musical German to follow our conductor.
Please translate and summarize.
I have some Agfa Verlängerungslinsen, which fit my 9x12 Standard (I have hardly usedthe camera, and never the lenses). They are described on page 19 of this (German - sorry) catalogue reproduced at Pacific Rim Camera:
https://www.pacificrimcamera.com/rl/02375/02375.pdf (PDF, about 59MB)
Google translates that page as
The Agfa extension lenses are manufactured in 2 types, type A for 1.3x focal length extension, type B for 1.5x. The image magnification corresponds to the focal length extension. For better depth of field, it is recommended to stop down slightly, especially for landscapes, while for portraits where pin sharpness is not a priority, you can work without stopping down. The aperture numbers of the lens are no longer decisive. The exposure is extended by 7 times for type A, and by 2 times for type B.
Agfa extension lens type A ........ RM.4.95
Agfa extension lens type B .........RM.4.95
An extension of 1.3x hardly seems worth bothering with.
This thingy is presumably, like the Zeiss Distars, Proxars, and ordinary closeup lenses, a simple lens, in this case it should be a concave, diverging lens. It's not afocal - an afocal lens has no net power, like the cheapo screw-in front mount converters you can get for video cameras, or the close-up and tele attachments sold for 1960s TLRs and rangefinders. That's why those don't require exposure compensation, but this one does, at least in theory.
When focused at infinity. Good idea, I'll do that later this week when I have access to my tripod and light meter. And take test shots to see how it behaves.Hi JPD,
what about an empirical approach:
Take a handheld meter and measure how much light gets to the image plane with the lens attached and without it.
Best
Jens
... one more literature based guess: (nearly) 2 Stops.
Windisch (Die neue Photo-Schule, 1943, p. 176) gives:
Extended focal lengh..............Exposure
1.5x......................2x
1.75x....................3x
2.0x......................4x
Greetings
Jens
Right. I'll go by that, but also do the light meter test. I have that book by Windisch somewhere. Is it the one that came in three parts? Maybe that depends on the edition.
Hej,Hej again,
no, my edition is just a single book, 255 pages.
No references/advertisements to other parts inside of the book.
Maybe there have been extended editions after war?
Jens
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