| Tramm Hudson |
July 17th, 2009 06:36 AM |
Quote:
Originally Posted by Tramm Hudson
(Post 1171889)
I've posted a short video showing an upcoming Magic Lantern feature: software focus pulls. This is a demonstration of how smooth the software control can be with a very fine step size. It is doing 30 steps/sec in the video with a stepsize of 1 and speed of 1.
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Now that my camera's batteries are recharged, I've done some more analysis and found that there are not separate stepsize and speed controls; instead it is a signed 16-bit value for the number of counts. Positive is a longer focus distance, negative is a shorter focus distance.
Here is a better video showing a range of speeds: Magic Lantern - software rack focus speeds
These were generated by selecting the different speeds from the Magic Lantern menu and hitting "Test rack focus". If I had thought about it, I would have written a short program to loop over the desired speeds and reset the focus to 0.85 m after each one. That way the video wouldn't have any edits at all and would demonstrate something approaching scriptability (in C).
The slow speeds work fairly well (although there is still an occasional hiccup), but since the AF motor seems to only run at full speed when commanded with PROP_LV_FOCUS, it is hard do a smooth, fast focus pull. The really fast pulls even over-shoot the desired 2.9 m distance. I'm hoping that there is another command that allows a selectable focus speed.
When focusing with the "focus by wire" 85 mm f/1.2 L, does it seem to have multiple smooth speeds or does the lens always jump to the new focus distance? If anyone has one that I can use for non-destructive testing near Charleston, or if you just aren't happy with it and want to trade it for my 85 mm f/1.8, you know how to reach me. |
