#apertus IRC Channel Logs

Bertl: Just did some profiling here at home to test the general RGBs... and it is entirely consistent with my estimations. (I also have a DE 1.3 here on a pretty lame ass flash shot)

okay?

let's postpone this a little ...

Bertl: Ping me when you awake Herb.

troy_s: ping

afternoon!

(wow our time zones are apart)

How goes the fight Bertl

Bertl: Rest is for the weak!

as I wrote, it looks fine to me if you are not at the lower or upper limits where clipping happens

Bertl: The upper limits? Uh that GS strip is only a couple of stops.

Bertl: As is evidenced by the error ratios.

Bertl: Those errors shouldn't be nearly that high.

i.e. the channels converge around 100-150 and they top around 2500-3000

Bertl: If that is "the best it can do" with rainbowing on the GS strips at 70% RGB, it is done.

as long as you stay in a middle ray, let's say, 500-2500 the channels look fine, linear and consistent

Bertl: This is a cinema camera. To ask shooters to stay below 70RGB is uh...

I'm not convinced yet that this sensor is the best choice, it also isn't the only one we are considering

but the actual 'range' doesn't matter that much

Bertl: Explain?

Bertl: Yes. Not surprising.

I really wonder about that red response. I mean I completely can see the double hum non narrow response of the filter.

not planning to remove anything :)

Bertl: Just going to hide the warts?

My larger concern is that the sensor cannot deliver a matrix with a smaller error than about 9, no matter how it has tried.

I know this

But that is symptomatic.

I blame the calibration process

How so?

achromatic strips with rainbow firing

because it doesn't account for the to-be-corrected effects currently plaquing the calibration attempts

Is that GS strip going to be homogenous?

So tell me why every other sensor ever profiled has never had these constraints?

which sensor have you calibrated yet?

Normally you can push white achromatic patches to 94+ RGB

You can process any DSLR with real raw data.

They all start raw Bertl. dcraw peels off the bayer

those are already pre processed

i.e. not the data acquired from the sensor

What precisely do you propose to pre-process that signal?

(asking so I can understand)

(But again, from what I see, if the raw output is symptomatic of the full latitude, you would have to very much constrict that pipe.)

Ok

maybe we can figure out how to do that in the sensor properly

then maybe (we have to check that) linearity corrections

if there is some kind of subtle non linearity

we can do that with a LUT

(per channel or one in general, we'll see)

after that, it's the 'normal' matrix ICC

i.e. the data you get from a DLSR as raw

not in the sensor, but we already do that in the FPN corrections

(was thinking it might be an interesting thing if it can twiddle the second green sensor for HDR - undergain it ex)

(Namely to drag that red way the hell down)

Bertl: Possible to scale the channel down and offset?

with a 12->16 LUT per channel you can go crazy

Ok. Well I guess will need to think on it.

so in general, I'd stay away from saturation and underexposure

mostly because one channel saturates before the other

only middle grey zone seems close

Bertl: Will be interesting to see how you work at it.

have to try a few things, but I have a number of ideas

will do

Bertl: I don't think many commercial sensors do clips as far as I have seen. Can deduce it from the highlight reconstruction etc.

Bertl: We could do a LUT.

(push the values to a threshold - not fully "corrected" but rather just enough to achieve linearity in the channels)

if 'black' is mapped to 0 and 'white' is mapped to max, how to tell if it was clipped/scaled or not?

okay, how many bit does the DSLR raw give you?

Bertl: Dumps same as what you dump.

12 bit in 16 wrappers normally

okay, so let's assume that we can use 11 of the 12bit, half the range

we still have information for interpolating brigtness across the sensels

yes

which will give us roughly one bit

Actually, I would be interested to see what happens if you only clip the red bit.

I am sure I can give you an easy "shoot until this value is xxx"

With that Bertl magic

it might help to diagnose the most surgical adjustments

for one thing, as I wrote, I want to eliminate the illumination problem from the equation

The evenness?

all of it, eveness, color temperature, etc

I think I can do perfectly fine calibration just with physics

Bertl: Non narrow filters.

first, we need a light source of known wavelength, more precisely several of them

All of the massaging is already happening.

yes, but that's exactly what we do not want

It is.

agreed, but at the sensor level, it's just physics

Yes, but that portion of physics isn't all pure physics.

You cannot generate color purely in the physics domain.

Ugh.

note: I'm not trying to calibrate the color

Sure.

like argyll and friends

If you chart how that sensor responds, you can dial it in with a decent dataset.

I mean it doesn't take Mr

Heck, you can probably see the error shooting just a grey card.

And seeing how the curves from the channels unfold (likely R then G then B)

greets intracube_

Bertl: There is _no_ disclosed gain controls on the channels at all eh?

there is gain, but not per channel

Bertl: There must be undocumented interfaces to that thing eh?

Bertl: Abd out of curiosity, has undergaining been tried?

I think there is a lot of hidden knobs and switches

*versions

and suddenly *bam* there is a test pattern :)

They might listen to you Bertl.

of course, it would be a shame to just have wasted a lot of time on figuring out sensor details, but that's life

troy_s: holding?

i was thinking if you can make a graph how values rise depending on time (should be linear)

(i did a 5.5 fhd lcd interface, and it did not worked according to datasheet, so I borrowed a competitive interface and tapped it... no surprise there - different data were used! )

not hide, just enable bits which are not documented

no, we do not know what each bit does

but logging SPI traffic won't help there, just narrow down the search space

time for bed