Mirage Recorder

[Djee Smit]

Hey Take, it's looking more promising every day. Maybe a bit too early to ask, but do you have any ideas on how the camera as a total package is going to look like? Not in an esthetical way, more in a practical sense. Somehing like the SI-2k (mini)?

[Take Vos]

Hello Djee,

Yes, I am pretty sure how it will look.

The camera head will be:
- The pike 210 C fiber
- A gate in front of the sensor for 2.40:1 filming
- An alluminum block that will be the:
tripod mount
lens rods mount
the trigger and temperature controller casing
a mount for the exposure rotary switch and mode switch.
a mount for the screen
a mount for the battery
and will also function as a cool block.
- Temperature Controller
- Peltier element
- Battery for 4-8 hours running time
- Trigger controller for a stable 24fps

The camera head will only be connected to the computer by a fiber cable, which can be rather long.

The computer:
- MacBook Pro
- Firewire 800 fiber hub
- eSATA controller in the PCI Express Card slot
- single SATA disk to record on
- VGA->composite converter
- video transmitter
- A sort of a docking station to put all the extra equipment in.
- USB high quality audio interface.

The edit computer could attach to the recording computer using ethernet and its own SATA disk, so it could make backups of the data and start editing on-set.

The monitor:
- LCD monitor
- Battery mount
- Battery for 4-8 hours of operation
- video receiver

Of course things can change, I am not sure yet about the monitor solution.

[Djee Smit]

sounds good, good luck with it. When do you think it's ready for use?

[Take Vos]

Djee,

I will probably start using it with my friends in a month or two. In principle it seems that the recording application, calibration application and QuickTime component are functioning pretty good.
So I could already start with filming and increase the quality of the calibration application and QuickTime component as I get more experience with it.

But I would love to first electrically separating the camera from the computer before starting filming. And a tripod mount and screen would also be nice.

Creating a package that someone will be able to buy is a whole other can-'o-worms. I would love to assemble a package which includes everything (excluding the computer) even with a nice carrying case.

[Take Vos]

So, I was quite annoyed by the maze pattern, so I build a new debayer algorithm that interpolates horizontally, vertically and crosswise.
The crosswise interpolation is used when there is no edge in the neighbourhood. This means that noise now shows as noise, not as a decoration of a greek restaurant.

Of course after this I found that the noise was actually fixed pattern noise caused by my own fixed-pattern-elimination-algorithm, ironic I guess.
Somehow the green pixels in the red line are brighter than the green pixels on the blue lines. I seem to have fix this bug, somehow.

The system now works in 12 bit linear, instead of 12 bit non linear.
Although the A/D converter is 14 bit, the sensor is only 12 bit. It makes processing much easier though.

Cheers,
Take

[Take Vos]

Hi,

Here is a new image, I am not entirely happy with the calibration in the almost black, like on the black/white pillows on the right.

Also it seems my debayer algorithm can't handle blacker than black (negative values), so I will need to find out how to solve that.

http://www.vosgames.nl/images/Mirage...alibrated2.png

Cheers,
Take

[John Papadopoulos]

I think you should leave resolution aside and compare with a commercial ccd camcorder. Try to reduce the resolution and see if the image has any punch or realism in comparison. The outputs reminds me of a CMOS sensor. The lighting looks normal but there is lack of saturation and the blacks have a very unnatural character. If you try to push the shadows you will not get the natural grain like pattern of a ccd outputing uncompressed video. If you add saturation in post you will add more problems. If this happens at 0dB of gain how will a pushed 12dB image handle the processing? The loss of power in blue and green spectrum of an incadescent shot will quickly make it look very noisy. Generally, it is a good idea to check all algorithms at high gain with some ccd noise present. It's easier to fix the problems there.

[Take Vos]

Hello John,

I can not test my algorithms at high gain, I will need to do all the calibrations again.

The lack of saturation is normal, there has not been any color conversion to rec/itu 709 space done, so the RGB is still in camera color space.

I explained that the fixed pattern noise in the dark areas is still apparent, which with some tweaking I hope will be gone. This is what you mean by unnatural, that is the fixed pattern noise of the sensor.
It also seems because the fixed pattern noise here has actual zero values that it doesn't look good when increasing the contrast in the dark areas.

If you look at the black patch of the ColorChecker, it does hold up well after pushing the contrast.

Below I include the same image that has been pushed a bit by Final Cut Pro. The original bayer image was first rendered by Final Cut Pro and rendered into the 16 bit float intermediate format. Then the 3-Way Color Corrector filter was used on this intermediate, added some saturation, pushed the mids (increases contrast in the blacks) and white balanced.

http://www.vosgames.nl/images/Mirage...ed2_pushed.png

Cheers,
Take

[John Papadopoulos]

You have a bug which creates a positive offset in the Red channel.

[Take Vos]

Hi John,

How did you notice that, I did notice there is some mathematical/physical seepage of red into the green channels on the red/green line?

I think I found more prove of the bug, my calibration program should operate almost as good with or without a black field. However when I don't add a black field it goes completely wonkers. I hate it, I've been looking at this bug for a couple of days now.

Cheers,
Take

[John Papadopoulos]

I just looked at the frame! There is a red cast all over the frame.

If you correct it, dip the noise to black and change gamma to something approaching video gamma, it will look like this:

http://img265.imageshack.us/img265/9...hed1coplo0.jpg

[John Papadopoulos]

Btw, did you get the color correction coefficients from the manufacturer preset of calculated them youself?

[Take Vos]

Hello John,

I do have the color conversion matrix from the manufacturer, but I rather calculate them myself. But I first need my other algorithms to function correctly.

The red cast is strange, but I've got all sorts of strange things happening now, it almost seems like something is overwriting the calibration values. The red cast could be caused by wrong calibration values as well.

Cheers,
Take

[Paul Curtis]

Take,

Great work, i assume all the later images are via the Pike 210? This uses the KAI2093 CCD sensor at 1920x1080?

Are you able to get the full un bayered data from this over firewire? (at 30/32fps)? I didn't think there would be enough bandwidth over firewire for this. (or is this the reason for 2.40?)

Do you have any problems with getting lenses to cover the sensor (14.2mm x 7.9mm). The circle needed for that is bigger than 16mm and a little bigger than S16. Most c mount and older style cine lenses would vignette on that size.

cheers
paul

[Take Vos]

Hello Paul,

Bandwidth is the reason for the 2.40 ratio, but I actually transfer at 2.00 ratio to get some black bars. It is firewire 800 at 12 bits and my framerate is only 24 fps. Also I get bayered data, debayering is done in the QuickTime codec.

I have a lens designed for 1" sensors, and it doesn't show vignetting.

All my images are from the Pike 210, although earlier images where screenshots which had lower resolution. The newer images are exported from Final Cut Pro.