Partial Scan

[Bob_McBob]

This isn't exactly an astronomy question, but since this is the only hardware forum, I thought it would be best to post here.

I am interested in purchasing a monochrome Firewire camera for a video extensometer system. This involves capturing a video of the material while it is being tested, then processing the video to track two markers and produce measurements for strain and other data. Both the Sony XCD-X710 and XCD-SX910 are suggested as cameras suitable for this purpose. I noticed The Imaging Source sell similar cameras with their own brand name that use the same sensors, and I was wondering if anyone could clarify the differences and answer a few questions.

I am mainly interested in the horizontal resolution of the camera (it will be turned vertically), so the "partial scan" feature the Sony cameras have is of particular interest. The 15fps max framerate of the 1280x960 cameras is not really ideal, but as I said, the horizontal resolution of the sensor is most important. The manual of the XCD-SX910 says the framerate increases as you lower the vertical resolution -- around 25fps at 1280x480.

I'd like to know whether I'm interpreting the partial scan feature correctly. Is there an increase in framerate, and can the supplied software take advantage of this? I'd also like to know whether the Imaging Source cameras have a similar partial scan feature, since they are half the price of the Sonys.

[Stefan Geissler]

Hi Bob,

I am very sorry, but the DMK 41AF02 and the DMK 31AF03 cameras do not support partial scan. Thus the frame rate can not be increased.

Yes, you interpret the partial scan property correctly.

[Bob_McBob]

Thanks, that is very helpful. Does the IC Capture software support the partial scan feature? I noticed in a PDF about the Sony cameras that partial scan produces odd frame rates like 25.1fps (for example). Does the software keep track of the exact frame rate, and is there any way to make it go at whole frame intervals (e.g. 25fps instead of 25.1fps)? I ask because it's important that I know exactly how long a video is in real time so I can merge the tracking data with data from the testing machine.

[Stefan Geissler]

Hi Bob,

We tested this with a special camera that needed a special interface. But we did not test this with the SONY driver, thus I would think, it is not supported by IC Capture.

[Bob_McBob]

Is it necessary to write your own software to take advantage of the partial scan features on the Sony cameras, then?

I don't have a lot of experience with this type of camera. Would your own cameras and software be suitable for the sort of thing I want to do? What I really need is to take a video at a definite frame rate so it correlates with real time and can be synced up with the other data. Dropped frames, skewed frame rates, etc. would obviously introduce error.

[Stefan Geissler]

Is it necessary to write your own software to take advantage of the partial scan features on the Sony cameras, then?
Good question. I do not know.
I don't have a lot of experience with this type of camera. Would your own cameras and software be suitable for the sort of thing I want to do? What I really need is to take a video at a definite frame rate so it correlates with real time and can be synced up with the other data. Dropped frames, skewed frame rates, etc. would obviously introduce error.
Edit/Delete Message
Our cameras are not suitable for you, because the video format can not reduce to 320*240 through hardware. This could be done software using a frame filter, that resizes the incoming image.
The other problem is the frame rate. If the frame rate is set to 15 fps, then you would also need to handly only every third image.

[Bob_McBob]

Our cameras are not suitable for you, because the video format can not reduce to 320*240 through hardware. This could be done software using a frame filter, that resizes the incoming image.
The other problem is the frame rate. If the frame rate is set to 15 fps, then you would also need to handly only every third image.

Sorry, I'm not sure exactly what you mean. Is it not possible to record at 15fps at the full resolution? Partial scan aside, I just need to be able to record at high resolution at a definite framerate so I can merge the two sets of data and not have to worry about dropped frames, weird frame rates, etc. Is that possible with your cameras or any other Firewire camera?

[Stefan Geissler]

Oh, sorry, I misunderstood.

You can capture AVI files with full resolution and a frame rate of 3.75, 7.5, 15, 30 and 60 frames per second. (60 fps only with VGA).
The program "IC Capture", that comes for free with our cameras, provides the complete functionality for AVI capture.