How do I program a Fotodiox/Dandelion M42-to-EF chipped adapter for focus confirmation?
Asked 1/26/2018
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2 answers
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I’m using a Fotodiox chipped M42-to-Canon EF adapter and want to use the camera’s focus-confirmation indicator with a manual-focus M42 lens. The programming instructions for the Dandelion chip are unclear.
When the instructions say to set a certain aperture value and then press the shutter release, does that mean a full press to take an exposure or a half-press?
Also, after programming focal length and maximum aperture, focus confirmation seems inaccurate and appears to back-focus. The chip’s calibration values are described as:
- 27 = default
- 13–26 = back focus values
- 28–31 and 1–12 = front focus values
If focus confirmation indicates back focus, which direction should I adjust the value?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
2
I thought it was halfway, but after a little more digging, I think it is a full exposure.
Somebody wrote up some notes here that might be of some help.
I don't know the answer to the question about the focus adjustment, but based on the way that is worded, I suspect that they wrapped a 5-bit integer in a very strange place, such that:
13 - very back focused
14 .. 25 - getting closer and closer to the center
26 - slightly back focused
27 - default
28 - slightly front focused
29, 30, 31, 0?, 1, 2, ... 12 - progressively more front focused
with 12 being the max in one direction and 13 being the max in the other direction.
Originally by user25054. Source · Licensed CC BY-SA 4.0
user25054
8y ago
0
Generated from our catalog & community — verify before relying on it.
A chipped M42-to-EF adapter does not make the lens autofocus. You still focus manually; the chip only lets the Canon body provide focus confirmation and record lens data for EXIF/manual exposure behavior.
From the community info, the programming step likely requires a full press of the shutter release (taking an exposure), not just a half-press.
For the calibration scale, the most sensible reading is:
- 27 = neutral/default
- 26 down to 13 = increasing correction in one direction
- 28, 29, 30, 31, then 1–12 = increasing correction in the opposite direction
In other words, the values appear to wrap around rather than being two simple labeled ranges. If your current setting gives back-focused confirmation, try moving away from 27 step by step toward the opposite side and test after each change. Small increments are best.
Because these chips and instructions are often inconsistent, expect some trial and error. The key point is that the chip only affects focus confirmation behavior; actual focusing remains manual.
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UniqueBot
AI8y ago
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