Thursday, February 02, 2012

Scallop's Novel Color Filters Improve Low-Light Imaging

Scallop Imaging, a division of Tenebraex, presents "Gemini Technology: Color imaging under all lighting conditions, including extreme low light". The company says "we have developed a new system of producing color video imagery in low light that offers an order of magnitude better low light performance compared to standard RGB sensors.

Instead of the standard RGB three-filter set, our Gemini system uses unique high transmission color filters to produce a full color image from two channels under all lighting conditions, including extreme low light

Scallop says that from its research over the years in human color vision it has developed a system that human observer perceives at full color despite only 2 colors are being used.

Not much more info is given. A 112MB video file from 1.2MP monochrome CMOS sensor (3.75 µm pixel) equipped with Gemini color filters compares to the color version of the same image sensor.

A video frame recorded at 0.18 lux (equivalent to 3/4 moon), 15 fps taken with
a color 1.2 megapixel image sensor.
Capture from video - same image as above post-processed to add brightness
A Gemini prototype video frame taken with the same exposure and frame rate
as above, with monochrome 1.2 Mpixel image sensors equipped with Gemini
color filters.
0.06 Lux (equivalent to crescent moon), 15fps Capture from Gemini video
Magnified image shows there are only two color channels.
Thanks to EC for the link!

Update: Added another snapshot of Gemini technology demo from the video - the picture below was created out of one monochrome and one filtered channel:


  1. The website has a .pdf download, which while not too much more informative, mentions they are working on an even more sensitive filter scheme with 1 color filter and 1 panchromatic color filter. Is this even possible without horrible noise artifacts?

  2. Well, as I already mentioned to the company a few days ago, it is hard to explain the improvement shown on the basis of color filters. Worst case, CFA v. monochrome should yield a 1.7-ish improvement in SNR, and they still use filters so SNR improvement should be less (esp. considering CCM effect). I suspect the conventional color image is just poorly tuned for the imaging conditions.

  3. @ "even more sensitive filter scheme with 1 color filter and 1 panchromatic color filter."

    I've updated the post with a screen capture from the video showing this version of image.

  4. Frankly, I find this sort of announcement more annoying than anything considering that Edwin Land did 2-filter color work sixty years ago. If these companies want to be treated seriously, they need to discuss the science.

  5. Is Tenebreax, the parent company, did an add-on to transformer a classic green night vision goggle into a color one ???

    -yang ni

  6. Yes. I didn't realize this but the guys running Tenebraex and making these color devices worked at Polaroid and are using the Retinex function to produce color perception. So it is not like Land, it actually is Land.

  7. Just curious, can anyone point me to the reference you are talking about by Edwin Land?

  8. Scientifc Anerican, May 1959 and December 1977

    Other references at the end of this article -

    More here -

  9. @Dave, thanks a lot for the references.


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