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Hi
I'm working on a little timelapse remote control program for canon cameras (with the Canon EDSDK).
to adjust to the light situation dynamically I need to know the exposure value, i.e. the values from the metering.

does anyone know how to get those values or know if it's even possible to get them?
I'd greatly appreciate some help.

Kind Regards
Johannes

PS: I'd rather don't use Auto/AV/TV-Mode because it causes heavy flickering.
Posted 23-Jul-13 13:08pm
Comments
The_Inventor 25-Jul-13 5:23am
   
Maybe go to the Cannon website, and download the drivers needed to access the camera via USB?
Johannes Bildstein 25-Jul-13 5:53am
   
that's not the problem, I have the driver and SDK and can handle the camera so far. I just need to know if/how I can get those values.
The_Inventor 31-Jul-13 1:48am
   
Then use what is in the SDK, to query the camera, that is if you have access to the Digital Information Structure, that which drives or interfaces with the electronics aspects of the camera itself.
Johannes Bildstein 31-Jul-13 12:57pm
   
well yes... and my question was: how do I do that/is that possible?
I need some command/method/specific topic; fancy wording does not help me here
The_Inventor 1-Aug-13 0:41am
   
In mechanical cameras, the light that exposed the film, was adjusted by two things that I can remember. F-Stop and Shutter Speed. Just set up a method in your program that looks at the cameras F-Stop, this is the camera's iris opening, like your eye's pupil, and is a digital light meter output, if you can control it then you can take instantaneous readings, put them into an array or list then process them in real time, and cause the 'brightness control to do its job. Todays modern digital cameras do this kind of thing automatically. You just have be able to strobe your loop to take the data.
Johannes Bildstein 1-Aug-13 7:19am
   
I know all of this stuff and you forgot ISO. Of course I can let the camera decide the values but that's not what I want. as I mentioned in the question, Auto/Tv/Av Mode causes flickering. I need to know the metering do decide on earlier settings if the new settings should be different or not. the camera doesn't take earlier settings into account and that's bad for timelapse -> need to use manual mode
The_Inventor 1-Aug-13 22:09pm
   
Then you need to increase the frame rate from lets say 20FPS to 30FPS, this will take of the flickering, but will increase the file size, unless you decrease color-depth or the size of the image, like from 1024x768 to something lower like 800x600, or if your camera is good enough, other aspect ratios resulting in fewer pixels.

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