I was thinking about this - one of the problems with current cameras is the relatively long delay after the full shutter press to the actual shutter activation. To close the gap I wonder if we could put a hook in wait_until_remote_button_is_released to wait for the motion detector instead of the remote trigger?
Updated patch and test script.
Run the script and see if the AF flash is captured. Adjust the 'AF on delay' and 'AF on time' to measure when the image is being captured after the MD detect. If you see the AF light in the image then you know the image capture was between 'AF on delay' and 'AF on delay + AF on time' milliseconds after the MD triggered.On my G1X 'AF on time' of 1 (10ms) does not work so 20ms (value = 2) may be the lowest you can reliably capture the AF led in the image.It helps to have a dark background in the image so the AF led is easily 'seen' by the camera for triggering (and review). Also make sure the shutter speed is not too slow - it should probably be < 1/100th second.
Quote from: philmoz on 08 / February / 2013, 21:23:46Run the script and see if the AF flash is captured. Adjust the 'AF on delay' and 'AF on time' to measure when the image is being captured after the MD detect. If you see the AF light in the image then you know the image capture was between 'AF on delay' and 'AF on delay + AF on time' milliseconds after the MD triggered.On my G1X 'AF on time' of 1 (10ms) does not work so 20ms (value = 2) may be the lowest you can reliably capture the AF led in the image.It helps to have a dark background in the image so the AF led is easily 'seen' by the camera for triggering (and review). Also make sure the shutter speed is not too slow - it should probably be < 1/100th second.Finally got back to this - sorry for the delay.With my A1200, I set Tv=0.01seconds and ISO to 4000. Using an iterative approach, the lowest usable value I can get for AF on delay (x10ms) is 3 and AF on time (x10ms) is 5. Going any lower than that means the AF image does not appear in the picture.But what does this tell me? Do I add the 30mSec to the 50 mSec I get with shooting turned off for an average response time of 80mSec ?
One thing to try would be use a long shutter speed (e.g. 1/3 sec) in a dark room, set 'AF on delay' to 15 (150ms) so you know the shutter will be open, and then play with the 'AF on time' value to see what the shortest duration is for turning on the LED that is still captured.
You can then go back to a fast shutter speed and play with the 'AF on delay' value to try and narrow down the capture time window. You can use a faster shutter speed than 0.01 seconds - it doesn't matter if the rest of the image is underexposed, the AF led should be bright enough to show.
Quote from: philmoz on 10 / February / 2013, 16:45:00One thing to try would be use a long shutter speed (e.g. 1/3 sec) in a dark room, set 'AF on delay' to 15 (150ms) so you know the shutter will be open, and then play with the 'AF on time' value to see what the shortest duration is for turning on the LED that is still captured.Tried that - was able to get the 'AF on time' value down to 1.QuoteYou can then go back to a fast shutter speed and play with the 'AF on delay' value to try and narrow down the capture time window. You can use a faster shutter speed than 0.01 seconds - it doesn't matter if the rest of the image is underexposed, the AF led should be bright enough to show.Looks like I wasn't patient enough with my previous test. I now capture the AF flash with "AF on delay" set to either 10 or 11 (only) and the "AF on time" set at 1.Meaning my fastest capture time will be about 150mSec for the A1200 ?
I noticed the code is using camera_set_led. On some cameras, this uses firmware LED drive functions, which may have additional latency or unpredictability compared to just poking the MMIO. I believe canon LED control goes through the LEDDrive task, so there might be context switches etc involved. On a540, set_led pokes the MMIOs.
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