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Focus command - BMPCC 6k via Bluetooth

PostPosted: Tue Apr 20, 2021 9:53 pm
by joelkronk
I am developing an application to control the Focus, AutoFocus, Peak and Focus Color along with a few of the other items supplied in the API. Many of them are working very well, but I cannot seem to get Focus to work.

The developer manual references Lens Group > Focus > Command 0.0 to send an absolute focus, but the camera does not react to the command. I found another thread via the search (titled Control focus via Bluetooth from Woflgang Dippel) when searching that helped me out a little, I found out EF lenses cannot set absolute focus, but it instead uses relative focus. I am a bit of a camera n00b and need something clarified for me:

1) Can we set relative focus/What is relative focus?
2) Is there a command or response from the camera that will tell me the current mm focus distance of the camera? There is an app I got on the store that tells me the 35mm lens and its current focus distance but I cannot find that information anywhere in the API and I do not get a Lens category response back when I am adjusting the focus manually.


Re: Focus command - BMPCC 6k via Bluetooth

PostPosted: Thu Apr 22, 2021 12:05 pm
by joelkronk
So after doing some more researching, if you are using an EF lens, instead of setting the value with the buffer[7] set to 0 (assign value), update the buffer[7] to 1 (offset value) and pass in the value you wish to offset by.

One way to get around this would be to allow the user to set the offset value as they adjust the focus instead of sending an absolute focus value. Allow them to set a big or small step for focus increment/decrement. Another way would be using a control that would 'flex' send values.