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Forum: Pentax Lens Articles
10-27-2016, 03:12 PM
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Weird. I have a total reciprocity failure when I use this system on my K5 iiS. Have tried it on two different lenses (Pentax M-100 macro and Voigtlander Ultron 40 SLii). Green button stop down works at large apertures, and progressively underexposes as I close down the aperture. For example, with the camera setup at the same target, in M, fixed ISO, etc etc. I get:
f2: 125
f2.8: 60
f4: 30 .... so far so good....
f5.6: 20
f8: 15 .... What...
f11: 13 .....the....
f16: 13 ...heck.....
f22: 13 ....????... (correct exposure should be 1.3" here, as checked in Av mode)
Needless to say, the latter apertures are way underexposed. Same story with the M-100mm macro. Also, the switching the DOFP lever trick mentioned in the article does not meter for me (I have it set to optical preview). I used it on the Voigtlander merely to test, as it works as an A lens in fact. And I have checked from the front that the aperture blades are stopping down correctly.
I'm stumped. Any ideas?
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