Black Widow - How does it calibrate?

[mechman]

If you've been following the BenQ W5000 thread in the projector forum, you may already know that I have a new projector and that I calibrated the pj as close as I am capable to D65. My goal in doing this was to show how Black Widow does with a calibrated projector. One would guess that taking a D65 calibrated projector and using it with a D65 screen, you would get a perfect D65 image.


Gamma reading from Black Widow screen



Gamma reading from the PJ



RGB reading from Black Widow



RGB reading from PJ



Gamut reading from Black Widow



Gamut reading from PJ

[mechman]

I'm awful at trying to get a pdf file converted to jpg I guess....

[Harpmaker]

mechman wrote:

I'm awful at trying to get a pdf file converted to jpg I guess....

Don't know what all the data means yet, but I can see it just fine; or at least I think I can.

[mechman]

Well, you can look at it and notice right away that it does in fact reflect a D65 image back D65. You can also notice that the gamma is darkened a tad - 2.1 to 2.2. And the last thing I noticed is that Black Widow actually dropped the DeltaE from my gamut readings to below 1.5 as opposed to below 3.

Or you could nit pick numbers and say that the "50IRE image drops the x value by .002!" But we're not the other forum!

[wbassett]

It looks to me that it is tracking pretty good, is that what you are also saying?

[mechman]

wbassett wrote:

It looks to me that it is tracking pretty good, is that what you are also saying?

Exactly! Yet more proof that you guys aren't nuts! Remember I am nuts!

[custard]

i'm still trying to understand most of that!

i tell you what though, since i have come to this forum i have been riding on a steep learning curve.

thanks guys

[mechman]

This may not be the place for it but I'll try to give you a bit of rundown on this.

Gamma

Gamma has a lot to do with your blacks and shadows. The higher your gamma the higher your brightness and also the less details in the dark areas/clips. The lower the gamma the dark clips/areas will be too bright and the overall image will be less bright. When you measure gamma you measure 10% grayscale images from 0IRE to 100IRE. The general consensus is that a gamma of 2.2 to 2.5 is preferable depending upon your tastes. Me? I like a lot of detail in the dark area so I shot for 2.2. With my projector I was able to get it 2.1. Add Black Widow to the mix and it put the gamma at 2.2. Right where I want it to be.

Gamut

Gamut is the measurement of the primary and the secondary colors. These six colors have to sit within a certain spec in order for us to achieve proper image fidelity. The DeltaE for these should be as low as you can possibly achieve with most sources saying that a DeltaE of less than 10 is what you should be shooting for. Here are the proper measurements for the 6 colors and white.

Red: x=0.640 / y=0.330
Green: x=0.300 / y=0.600
Blue: x=0.150 / y=0.060
Yellow: x=0.419 / y=0.505
Cyan: x=0.225 / y=0.329
Magenta: x=0.321 / y=0.154
White: x=0.313 / y=0.329

Keep in mind that this is the standard for HDTV (REC 709). There are different standards for NTSC and PAL. My old projector (Mitsubishi HC3000) offered no service menu and very little adjustments to try and achieve these colors. My new BenQ W5000 offers up a service and an ISF menu in which you can actually edit each of these to get the colors set properly. The key is to try and get them as close as you possibly can with the lowest possible DeltaE error. I think the best thing to look at in those charts is that the DeltaE error went from below 3 to below 1.5.


RGB levels

RGB levels are how whatever it is your measuring (your screen, your pj, your plasma, etc.) track with relation to the primaries. For our purposes we want the red, green and blue to track equally. It also shows where you device sits, color temperature wise. Black Widow tracks as the projector tracks, 6500 with equal red, green and blue. On the low end there's some wackiness which I attribute to my eye-one pro, which supposedly doesn't do that well measuring in low light. I've seen this mentioned from the calibrators at avs. Yet the folks at CalMAN thing that it should measure fine on the low end and that it's more than likely the source or the pj causing the wackiness from 0-20IRE. I'm uncertain as to what is really happening as I do not have another meter to check these values. And my feeling is to trust the folks at CalMAN - that it is either a source or pj issue, not the meter. Regardless, Black Widow tracks right at 6500 (6504 if you're picky) from 30IRE and up. Meaning that it reflects what is projected onto it accurately.

[mechman]

A couple other things to look at are Luminance values. The luminance tells you how 'bright' a color is. It also gives you the information you need to set proper white and black levels.

White Level or Contrast

Most folks who 'calibrate' using one of the various calibration dvds can do this using the Pluge pattern. You adjust the contrast up and down until you get the pattern to look proper. If it's too high then the patterns start to bulge or bleed over into the other patterns. If it's too low then the just below 100IRE pattern blends with the 100IRE pattern.

The best way to do it though is with a light meter or a within the software calibration itself. If you look at the graphs above for Black Widow, you'll see that the Y value for the 100IRE window is 50.4195. That translates to just under 15fL. So my contrast is set just fine.

Black Level or Brightness

If you have the tools to do a calibration, however, it's simple to set contrast without doing it by eye. The Y (luminance) value for 10IRE should be .63% of the Y value for 100IRE. Mine calculates out to .31764285. And my measured reading at 10IRE is .3192. Easily close enough!

[mechman]

Luminance isn't just limited to the grayscales either. The primaries and the secondaries should be set to their proper luminance as well.

White - 1.00
Red - .213
Green - .715
Blue - .072
Cyan - .787
Magenta - .285
Yellow - .928

What that means is that red is 21.3% of white, green is 71.5% of white, and so forth. What's important to keep in mind here is that if you use a 75% red image to get your red measurement, than the Y value should be 21.3% of a 75% white image.

Here's how Black Widow did (the calculated readings are in parentheses)

White = 27.3462
Red = 5.8986 (5.8247406)
Green = 19.7989 (19.552533)
Blue = 1.7133 (1.9689264)
Cyan = 21.3738 (21.5214594)
Magenta = 7.0978 (7.793667)
Yellow = 24.7010 (25.3772736)

As you can see the only ones I really need to brighten up, if I cared to would be magenta and yellow. But since my DeltaE for all of these is below 1.5 and Kal in his GREYSCALE & COLOUR CALIBRATION FOR DUMMIES says to shoot for less than 10, I'm not going to worry about it.

Hopefully this helps a bit. I know that every time I have to calibrate I have to reread some of this stuff. I'm hoping that typing some of this out will help me remember it in the future. Well that and all the repetition I'm going to get with all of the commercial samples.

[custard]

quite abit to digest there. i really would like to calibrate my projector with the equipment you have.

i can feel myself wanting to acquire an eye-one pro.
whats holding me back is that a new one is gonna cost me more than my projector

[mechman]

I'd think 'munki' first. I beleive those are supported by CalMAN. And if that's out of the realm go with the eye-one display2. They're colorimeters which will do just as well as the eye-one pro and not break the bank. There's also the Chroma 5 colorimeter which is also available at SpectraCal.

The cheapest way though would be to buy a Display2 and run it with HCFR.

[mechman]

That would the Colormunki Create by the way. There is a difference. The Colormunki Photo has uv filters.

[custard]

on the subject of colorimeters and their method of measuring.
i always thought that the use of color filters would limit the accuracy of the colorimeter over a spectrophotometer.

i reallly need to to carry out some calibration on my projector as i have noticed that some of the gray bars on test patterns i use have a slight hue to them.

i may just pick up an eye-one display for now.

[Harpmaker]

For doing this type of calibration all that is needed is R, G and B sensors (Tristimulus values).

Here is the link for HCFR http://www.homecinema-fr.com/colorimetre/index_en.php

[mechman]

Yep you could build one as well. Smokey Joe built one and used it for awhile before giving it up for his eye-one pro.

Hey! They have a new version out. I was running 2.01. I'm gonna have to check it out. I've also been doing more reading in CalMAN. Turns out I can do much better charts than what I have been using.