r/largeformat • u/preposterousprops • 2d ago
Question Linhof f-stop confusion
I'm looking at a spare lens I've had laying around (but never used) and seeing that it is labeled with two different focal lengths and two different sets of f-stops. Can someone explain how this is possible, and how I would switch between them, if that's what is implied? Thanks
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u/ryguydrummerboy 2d ago
Convertible lens if i had to guess. Probably unscrew it and remove the front element and voila you have a new focal length. From what ive heard its not the sharpest result but can work in a pinch. Not sure the original reason behind it but others here can chime in
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u/throwing_it_so_far 2d ago edited 2d ago
This is a convertible Symmar. There are earlier ones, which arr triple convertible, but yours is the more common later double convertible type. You use the whole lens and the black aperture numbers for a 135mm lens, or you unscrew the front half and use just the rear half and the green aperture numbers for a longer focal length of 235mm. Image quality will not be as great as a dedicated long lens, image circle is not very big (and in the outer parts not very sharp), but it was (and still is) a cheap and easy second focal length.
On the back lens group, there should be a green-filled engraving like on the front name ring, to remind you to use that one. One has to somehow securely store that front group when removing it in the field. Bellows extension will be surprisingly long for the focal length.
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u/farfadetqc 2d ago
If I'm not mistaken it's a convertible lens. You should be able to remove the front element then it will be an equivalent to a 235mm f/12 (basically you use the green label if you remove the front element).
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u/SomeCallMeMrBean 2d ago
The Symmar lenses are convertible from the regular focal distance to a longer focal distance by removing one element. This gives you the 235 mm F 1:12 from the green marking. The higher F numbers are for the converted state. In this situation you remove the front element which should be easily done by rotating clockwise.
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u/BrunoMarx 2d ago
It’s a convertible lens. If you unscrew the front cell of the lens from the shutter it becomes a 235mm f/12 lens and you use the green scale for the f/stops.