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james_screech
March 6, 2014, 11:44:13
What happens if I set my camera to 30FPS but have an exposure time of 1/20sec? :confused:

Will I get some duplicate frames or will the camera / IC Capture just write 20 frame per second to the AVI but label it as being 30FPS for playback?

James

Stefan Geissler
March 6, 2014, 16:49:48
Hi James,

20 frames will be written. But they playback will be 30fps . No double frames

merlin66
March 11, 2014, 09:53:48
james,
I sometimes have to use 1/11sec exposures for faint Ha proms...the entered exposure takes precedence over the selected frame rate.
Playback will be at the frame rate selected.....

james_screech
March 12, 2014, 09:16:40
It would appear that with exposures over 1/30sec there are some issues. At 1/13sec I would expect 1300 frames in 100sec (30fps) however I get less then 800! This is writing to a RAM disk so that is not a limiting factor (I can write 30FPS when exposure is 1/30sec).

James

Stefan Geissler
March 12, 2014, 12:22:02
James,

please let me know your camera model and its serial number.

james_screech
March 12, 2014, 18:29:02
The camera is a DFK31AU03.AS and it's serial number is 46310176

merlin66
March 12, 2014, 21:02:41
James,
an exposure of 1/13sec, would only give 4.6 images per sec....over 100sec I'd expect to see around 450 frames/images????

james_screech
March 13, 2014, 09:17:21
James,
an exposure of 1/13sec, would only give 4.6 images per sec....over 100sec I'd expect to see around 450 frames/images????

At 1/30 second I get 30 exposures per second.
If each exposure is 1/13 second then you should get 13 per second which is 1300 over 100 seconds.

James

Stefan Geissler
March 13, 2014, 13:54:58
Hello,

The DFK 31AU03.AS works a little bit different. If the exposure time does not fit into the frame rates time interval, the frame have is halved, until the lowed 3.75fps are reached. Therefore, at 1/13 second exposure time at 30fps settings, I would expect 7.5 frames per second as result. If you receive 4.6 frames per second, then I think, there are some frame drops too. In case you use an Intel CPU, you can try the Processor Idle State Manager, which sometimes helps avoiding frame drops. (http://www.theimagingsource.com/en_US/support/downloads/)

james_screech
March 13, 2014, 14:34:16
. If you receive 4.6 frames per second, then I think, there are some frame drops too.

I never said I was getting 4.6 frames per second. I said I had less then 800 frames in 100 seconds, so 7.5 fps would be about right.

So the DMK31 captures frames at:
3.75 fps if the exposure is greater than 1/7.5
7.5 fps if the exposure is greater than 1/15 and less than or equal 1/7.5
15 fps if the exposure is greater then 1/30 and less than or equal 1/15
30 fps if the exposure is less than or equal to 1/30

That would explain why in my recent experiments I have been not been getting as many frames as I was expecting in a given time.

Why does the DFK31 work different from your other cameras? Is there any chance that you will fix this in a software / firmware update?

James

Stefan Geissler
March 13, 2014, 15:40:24
James,

more or less, this is correct. However, it is a little bit more complicate, therefore, you will not receive the exact 15 fps. at 30fps with long exposure time.

The camera works different, because the hardware is completely different compared to the newer USB 3.0 cameras. We also will not change this for the DxK 21,31,41 and 51 series.

mdarius
July 9, 2014, 10:29:52
Its shouldnt be the same 30 fps and 30 expousure time ?

Stefan Geissler
July 9, 2014, 15:19:13
Its shouldnt be the same 30 fps and 30 expousure time ?
Not necessarily.