[IDEA] RGB filter wheel

This is just an idea.

I saw this ( https://youtu.be/x-6MYP0RxTI I did not upload this) special feature from the Wizard of OZ, it was about the restoration of the film. They said they scan the frames on 4K, 16 Bit at 50MB each frame. You can see this at 01:36 What they meant was each channel of the RGB is 16bit so it’s actually a 48-bit image.

My camera, at 4000x2750 the highest setting is RAW16 (color) and MONO16 (grey). Actually, the MONO16 pixel format could recreate a 48-bit image by using an R G B filter wheel attached to the camera and the lens. So you have for each color a 16-bit image that you can merge together as a 48-bit image. (the debayering part can be followed up at this topic: debayring point grey/FLIR)

SL1500

The 8-bit guy made a great video about this method: https://youtu.be/a-ny3geJ-nk

Is this a good idea for Kinograph V2?

And does anyone know what kind of software they were using for removing the dirt and scratches? (at 05.06)

This would work well with a monochrome sensor, if it’s used in front of a sensor that already has a color filter array then there will likely be all sorts of interference (if the filters don’t match exactly) with no gain in resolution.

Similar to the example in the Wizard of Oz you’d wind up with 3+ color records in the computer, but unlike the Wizard of Oz, they’d all be from the same piece of film, somewhat reducing their value for dust/scratch detection. You’d get a similar result from using different, discrete wavelengths of light to illuminate the film, although there is some benefit to using a full spectrum source in place of or in addition to individual color lights.

It’s hard to say what tool they’re using in the clip, but they mention the Perlmutters at WB who developed some of the custom software they used. Sadly they’re not specific and I’m betting it’s probably an internal, proprietary thing.

Good to know. And I thought so, the color filter will disturb the color’s even more.
That’s why it was just an idea.

Shooting the frame’s on a different light density can create a HDR image?

Yeah, you could create an HDR bracket from two different approaches - the first would be to vary the exposure settings in the camera/lens and keep the light constant, the second would be to use a longer exposure time and vary the intensity or duration of the lighting for each exposure.

The difficulty with the first approach is that the camera settings might have to be changed frequently, whereas the difficulty with the second approach is having both accuracy and precision in control of the lighting since even slight deviations could result in artifacts like strobing or pulsing. There are high-end scanners that use both methods, so it’s not impossible, just challenging to mitigate some of the issues.

Using a color filter wheel with a full-spectrum source and a monochrome sensor is still a very interesting idea, I think there could be some benefit depending on where in the system it’s used. I.e. if it’s between the light and the diffuser, before the film gate. I think this deserves some testing, at least from the perspective of “individual color LEDs as light source with mono sensor” VS “full-spectrum light source and color wheel with mono sensor” VS “full-spectrum light source with color sensor”.

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Hi guy’s,

This isn’t a color wheel but it’s about color so this is maybe an alternative who has only a color vision camera:

I bought myself a ColorChecker from X-rite (Classic Nano) It’s a pricy little thing around €160!!
But by this little thing an my vision camera (or any camera that you gonna use) and if @matthewepler got his light source I could create with my vision camera a LUT under that kind of environment, so that the color of the film reel is a close as it can get by the help of this ColorChecker. (RED=RED, BLUE=BLUE,…)

I did myself a little test under a not controllable environment, monitor light and a USB desk light from IKEA and I didn’t finetune after the use of ColorChecker but the color of my Yoshi comes very close to the original color:

Yoshi_UnCorrected
Yoshi_Corrected

The best solution, I think, would be if X-rite makes a 16mm ColorChecker frame and a 35mm frame. That could be easier for all of us. Attach this to an empty reel and make a single frame so we can make a LUT out of this an implement it to our projects…

Cheers!

A filter wheel tends to slow down a scan, as the scanner has to first rotate to the slot, wait for vibrations to settle, and then expose. Thus a single frame can easily take a couple of seconds.

On the upside, it makes the scanner very versatile, as one can use custom-filters according to the film stock being scanned.

Wow that scratch removal software is impressive.

Um @matthewepler I’m just testing my vision camera. This picture is just my desk with a X-rite color checker to calibrate the color space. I’m not working with film reels yet, I’m waiting for V2. :wink:

But in the meantime I can figure out how to work with my camera to get the maximum out of it.

That’s great! I’ll definitely be learning from you when I get my camera set up. I’m actually delivering it to the contractor next week so they can start setting it up and doing Computer Vision tests with it. Very excited to see what strategies will work.