"black shading" sounds interesting, please elaborate what it is and how it is done.

Some info on black shading in Magic lantern http://www.magiclantern.fm/forum/index.php?topic=9861.0

I think it is essentially similar to black balance: http://en.m.wikipedia.org/wiki/Black_balance

http://www.red.com/learn/red-101/black-shading-calibration

https://books.google.co.uk/books?id=Hc4lPLmkESoC&pg=PA58&lpg=PA58&dq=black+shading+and+black+balance&source=bl&ots=33VMxUDWih&sig=V5Afzhor8m_cf8ud2pH1nr4axoI&hl=en&sa=X&ei=GeasVL-cJtCy7Qajx4DoCw&ved=0CEMQ6AEwCw

Also: http://en.m.wikipedia.org/wiki/Fixed-pattern_noise

http://www.automaatioseura.fi/jaostot/mvn/mvn2007/parameter.html

I think both Cmosis and Alex from Magic lantern should be able to help with this.

The black shading between each frame is indeed interesting, but it would mean the sensor can capture data without "opening" the (electronic) shutter.
What does it even mean in the context of an electronic shutter?

What can be captured in this state? Fixed noise from AD converters and electronics?

Didn't see anything like this in the cmosis sensor datasheet.

Yes, I'm not sure how it works. There are some pixels on the Cmosis chip set aside as black reference I believe but I'd need to look through the data sheet to find them.

It should, however, be possible to run a black shading/black balance operation in the usual way as Red and pretty much ever pro and prosumer camera does: you get the user to cap the lens then run an image capture sequence at various gain levels and separated RGB to produce a reference of the fixed pattern noise (I guess you average a series of frames to differentiate out fixed pattern and random noise) then save this as a reference image to subtract it from each frame (raw and non-raw - although you could, I suppose avoid this in Raw assuming you allow the reference frames to be saved for later use in post processing).

One thing worth having, since the sensor does have an in built temperature sensor, would be to have a warning come up whenever the sensor temperature changes significantly from the temperature that was present when the current black shading operation was carried out (reds do this) - as sensor temp has a big effect on FPN.

Here's the bit I was thinking about:

5.15 BLACK REFERENCE COLUMNS
When the appropriate SPI register is set, the 8 first and 8 last columns will be put to an electrical black reference. This electrical black reference can be used to correct row noise.

But there's also this:

5.16 TEST PATTERN
The CMV12000 has a built-in fixed test pattern. The pattern consists of increasing pixel values per column per channel. Per (top and bottom) channel the values of the column increase with 1. The value of the first column of a channel increases with 1 per channel. So channels 1/33 will contain 0, 1, 2 … 126, 127, channels 2/34 contain 1, 2, 3 … 127, 128, channels 32/64 contain 31, 32, 33 … 157, 158.

I'm wondering if there's any difference (caused by noise) between the test pattern read out and it's theoretical values - in which case maybe this may be used to reduce noise as well.

Although Alex at Magic Lantenr seemed to indicate that the black reference collums are too small to do much to reduce the noise: http://www.magiclantern.fm/forum/index.php?topic=11787.0

He suggested contacting Cmosis to see if they could be persuaded to increase the number of Optical Black pixel dedicated to this (from 8x8 to 200x200) - I'm not sure if any of you guys have done this.

The Test Pattern is precisely that, a pattern which is sent from the sensor _instead_ of the actual image.

It can be used to verify the sensor-FPGA connection and test the bit-error rate between sensor and FPGA.
No ADC, no conversion, no noise.

@black columns: I doubt that they are willing to change the sensor design, but feel free to try to convince them.

Best,
Herbert

I'm willing to give it a go. Who do I contact?

Response from Cmosis:

Hello Colin,

Although adding extra dark reference columns to the existing CMV12000 design is indeed not a big change, the vost involved is very high. To be able to produce sensors with such a change the masks to produce the sensors must be remade and ordered. This is very expensive so a high NRE cost will be subject to such a change (a few 100k). The cost of the sensor itself will not increase lot compared to the current CMV12000 pricing.

Regards,

Pieter Willems
Manager standard products
www.cmosis.com

I think it's probably not worth it, no? Maybe just work on better processing ;-)