View Full Version : Gamma control and High Dynamic Range

January 20, 2014, 12:57:39

does the DFK 42BUC03 CMOS camera provide some way of Gamma control to compress the dynamic range of the images? Could only find Exposure, Gain and White Balance control... Of course a gamma curve could be applied in software, but the data returned from the Camera over USB is 8-bit, so ideally I would need a Gamma setting which is directly applied in the camera.

If not, do the USB 3.0 CCD models provide such a functionality? I see that all the cameras only have an 8-bit dynamic range, even though the USB 3.0 CCD series supports Y16 format, but the A/D range is not specified.

Another nice feature would be dual exposure, i.e. expose two images directly after each other at a single trigger pulse with different timings, store them in a buffer on the camera, and then transmit them both to the host one after the other. But I suppose none of the cameras supports this, as it is a very specific feature..?

Thanks again,

Stefan Geissler
January 20, 2014, 14:51:15

the camera has only the parameters, IC Capture shows. It has no gamma, no hue, no saturation and so on.

Also the USB 3.0 version does not have this property. Maybe future drivers will implement these properties.

The A/D range is mostly 12bits

The camera has no buffer, therefore it is no possible to make a HDR capture with it.

However, the 13 Megapixel DFK AFU-L53 can do this. It has many more properties and also HDR mode. But this model has no trigger.

January 20, 2014, 16:41:54
Ok, thanks. If the A/D range is 12 bits, can you give details on what happens to this data in the camera (conversion to 8bit) and what happens in the host, when I assume that the camera sends BY8 data to the host?

Or in other words, when I get BY8 data from the camera, how "raw" is it compared to RGB24 or RGB32 in Imaging Control?

Stefan Geissler
January 21, 2014, 09:46:43
First of all, BY8 is the same as Y800, only the FourCC is different. Therefore, DirectShow automatically inserts the Debayertransform filter in the filtergraph, if BY8 is used.

Bits of the format:

These are the bits of Y16 for a camera with a 10 bit sensor:

1111111111XXXXXX - white
0000000000XXXXXX - black

For a 12 bit sensor, it looks like this:

111111111111XXXX - white
000000000000XXXX - black

(9,8,7,6,5,4,3,2 1,0,x,x,x,x,x,x) in case 10 bits
(11,10,9,8,7,6,5,4 3,2,1,0,x,x,x,x) in case 12 bits

The "x" bits should be ignored. They are open on the A/D change, so their contents is not defined.
For the 12 bit format:
Y16 and Y800 share the same upper bit from 11 to 3. This means, bit 0 of Y800 is bit 3 of Y16. If there is noise in bit 0 of Y800, then this is bit 3 of Y16. Therefore, it looks like Y16 will have much more noise, because it is bit 3, that changes changes.

If you use an 8bit sink, the lower byte of Y16 will be dropped. It makes no sense to use Y16, if you want to handle 8bit data only. You will waste bandwidth only.

For handling the Y16, please refer to http://www.imagingcontrol.com/en_US/support/documentation/dotnet/PixelformatY16.htm

If the camera runs with Y16 format, you will receive raw data. That means, you will receive 16bit Bayer data. Right now, we have no conversion to RGB48 and RGB64.

I hope, this answers your Y16 questions.

January 23, 2014, 16:02:05
Thanks Stefan! This clarifies a lot. However I find that the DFK 42BUC03 does not support Y16, although it has a 12-bit Sensor. Is there anyway of retrieving the 12-bit output from this camera? firmware update?

Thanks again!

Stefan Geissler
January 24, 2014, 09:49:59

I am very sorry, but the DFK 42BUC03 has no 16bit output at all.