Possible to hit BT.1886 curve using CM Autocal and meter that reads 0 for black? - AVS Forum
Display Calibration > Possible to hit BT.1886 curve using CM Autocal and meter that reads 0 for black?
trans_lux's Avatar trans_lux 09:20 AM 08-02-2014
I'm still chasing the elusive dragon of a curve.
It's not simply to get the measurement i can see the loss of shadow detail on content that has very high native gamma-Penny Dreadful, The Strain, Game of Thrones etc. Currently I use the gamma compensation in the Lumagen and it works well. But I find I adjust and adjust continually driving my family crazy.

I've read a couple posts here and on the Spectracal forums but have not had positive results.

My little x-rite i1 Display pro reads black as 0. So BT.1886 ends up being the same as power 2.4.
Manni was kind enough to provided a black level reading using a T10 from a couple RS49/4910/x500 iris open of 0.00450 cd/m2/0.001313386 ftl.
I entered this value as black level target vs measured in Calman.
The results are not what I expected.
During the autocal process it was stuck on black as I think it was trying to achieve this level with a meter that is not capable?

Is there any other possible work around to achieve the curve with my x-rite.

Thank you in advance.

TL

sotti's Avatar sotti 09:42 AM 08-02-2014
It is trying to raise the black level to hit that target.

Your best bet is likely to create a screen offset and read from the projector. That would likely clear the whole situation up.

The other thing in the app to deal with black crush in the DDC control we call brightness factor. It brings the projector out of black faster without actually raising the black floor.
trans_lux's Avatar trans_lux 10:26 AM 08-02-2014
Quote:
Originally Posted by sotti View Post
It is trying to raise the black level to hit that target.
Your best bet is likely to create a screen offset and read from the projector. That would likely clear the whole situation up.
The other thing in the app to deal with black crush in the DDC control we call brightness factor. It brings the projector out of black faster without actually raising the black floor.
Joel
Thanks for the prompt response.
Should have clarified I'm using a Lumagen mini. I don't believe the brightness factor is available.
Update: 7:09 8/2/2014
There was very little difference between the reading off the screen for xy so I didn't end up using the screen offset.
I did have to move the meter about 7ft from the projector to get a usable black reading.
I running autocal now will report back
trans_lux's Avatar trans_lux 09:45 AM 08-05-2014
I'm getting closer

The key was using the Spectrcal C6 vs the stock X-rite.
The C6 allows you to put the diffuser on while retaining the correct table for the display type.
I also forgot how much faster it is.
The visual results are pretty spectacular.
Please note: I'm using autocal with a Lumagen Mini.


I would still like to figure out how to get a smoother transition of gamma at the bottom end if even possible with the meters I have.
I tried using a lower and high starting gamma on the projector but ended up in the same place.


sotti's Avatar sotti 11:19 AM 08-05-2014
Gamma numbers are funny I wouldn't pay them much mind regarding their smoothness.

That calibration looks fabulous, I would just sit back and enjoy the picture.
trans_lux's Avatar trans_lux 02:27 PM 08-05-2014
Joel it does produce a pretty amazing picture across lots of different content. BD always looked great but some of my favorite TV shows such as Penny Dreadful looked they used a candle for illumination or a gamma of 4 when mastering. Finally getting the bt.1886 curve it still has it's intended dark presentation but the shadow detail and differences & textures of all the dark clothing is now visible.
The key was your suggestion of facing the projector and using the C6.
Thanks again!
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