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meltemii
September 26, 2007, 22:29:26
In an attempt to manually set the Exposure to control the shutter speed to obtain sharp images of moving objects at various lighting conditions, I have some related questions. First here is an outline of my proposed process:
- Set device parameters
- On ImageAvailable event
- Process image to obtain current Brightness
- Calculate new exposure (if exposure at max shutter increase Gain)
- Set Exposure
- Wait on next event

Questions:
1. Is there a resource that reflects which commands must be called & their sequence. Such as: LiveStop, LiveDisplay=False, LiveCaptureContinuous=True, ExposureAuto=False. Are these the right ones? And are their sequence & values correct?

2. In an earlier thread, I read that you must use the VCD properties to get & change values when ExposureAuto=True. I assume that was only the case when ExposureAuto is True, when False I can use the Exposure=xx method.

3. What is the relationship between Exposure and shutter speed?

4. Can Gain be left on auto when exposure is not?

Your help will be greatly appreciated :)

Stefan Geissler
September 27, 2007, 09:29:02
First of all, handling exposure using the VCD properties is shown here:
http://www.imagingcontrol.com/support/documentation/activex/tech_VCDProperties.htm


1. Is there a resource that reflects which commands must be called & their sequence. Such as: LiveStop, LiveDisplay=False, LiveCaptureContinuous=True, ExposureAuto=False. Are these the right ones? And are their sequence & values correct?

No. Exposure can be set as soon as a valid video capture device has been selected. It can be set while the live video runs. The only exception is that automatic for exposure must be disabled. The range of exposure can be determined using the VCD properties.


2. In an earlier thread, I read that you must use the VCD properties to get & change values when ExposureAuto=True. I assume that was only the case when ExposureAuto is True, when False I can use the Exposure=xx method.
The exposure values can not be changed, while exposure auto is true.


3. What is the relationship between Exposure and shutter speed?
Expsure = shutter speed. Only the words are different.


4. Can Gain be left on auto when exposure is not?
Yes. In the AF/BF camera models this can be done. In the F (e.g. DFK 21F04) this can not be done, exposure auto is cuppled with gain auto. You may try IC Capture to check this out.


If you set a new exposure value to the camera, then not necessarily the next incoming image is exposed with the new exposure value. I would wait up to three images, before querying the brightness of the image.

I must surrender my answer is very common. There is no sample code, that shows how to set exposure. But we can go in detail later if you want.

I hope this helps.