Official JVC RS20 / HD750 Calibration and CMS thread - Page 5

JeffY what software(Looks like Spectracal Calman?) and colorimeter are you using please?

Thanks.

Thanks Lawguy!

Well, first of all I got my theory right by re-reading Tom's excellent tutorial. I had used Kal's also excellent "Calibration for dummies" article (it felt at my level!) with success for learning greyscale calibration, so I initially went on with it for my first two color calibration attempts. Unfortunately, Kal doesn't really cover a full CMS and especially doesn't provide the data for the correct percentage of Y for all colors. I my first attempt, I simply ignored Y (sorry!), in my second attempt, I tried empirically to play with brightness to lower dE, and on my third attempt I started from scratch, following religiously Tom's article regarding methodology and data, and using a speadsheet to calculate the right values of Y for primaries and secondaries.

I got the greyscale close enough easily and did not spend too much time refining it, and then I started playing with the CMS.

The trick is to concentrate on green (and yellow) to start with as they are the most far off, set brightness for both to max because you'll probably need it anyway, then lower the color control to bring green within the gamut. The mistake I made in my second attempt was to lower color even more (I went from -14 to -30) and I ended up with not enough brightness to compensate, so I tried to go in the other direction and found a setting closer to Jeff's (I'm -8 and he's -5). Then play with saturation and hue to put it spot on. Don't play with brightness on these two colors (green and yellow) because for some reason it also affects saturation. That's why I went the other way, set brightness to max on these two and tried to find the least damaging value for color to bring them in reach of saturation/hue.

It's then very easy to adjust red. Blue is a bit more tricky because it needs quite a lot of subtle play with hue and saturation to get it right. I wouldn't bother with cyan until blue is adjusted (as well as green). It will stay outside the gamut but you should be able to bring it close enough. Once everything is right on the gamut on the x,y plan, adjust saturation to get Y as close as possible for all remaining primaries and secondaries (I used a spreadsheet for easy calculations). It sounds easy but it requires a lot of back and forthing!

I guess that if I could get a satisfactory result, it proves that anyone should be able to (and no doubt will get even more satisfactory results, especially with cyan)!

I forgot to say that before embarking on my 3rd attempt, I measured the THX preset again in high lamp. Gamut is about the same (not as good as what I got), but greyscale is unfortunately not better. So unless they acounted for an older lamp, the THX preset remains an ok approximation, but I wouldn't live with it because the greyscale is really bad.

Hope it helps...

Manni

Yes it's Calman, the latest pic is using Calman 3.2 which is why it looks different.

I suspect that starting with a color setting between -5 and -8 is crucial, it gives you enough room in CMS to adjust things properly. In my 2nd attempt the gamut is a bit oversaturated but that was on purpose. I'm going to have another try later with color set to -6 or -7 to see if I can keep the saturation levels as they are (maybe bring in green and Cyan a fraction) but have correct brightness levels.

You have saved me some money as I am certain I can be happy with your results and not need an outboard processor! Good work. Can you post your speadsheet or point me to it? I thought I saw it somewhere? Tom's tutorial, http://www.avsforum.com/avs-vb/showt...light=tutorial

Sure, I had posted it on my thread on AV Forums but here it is again. It's pretty basic but it does the job.

I created it to do quick calculations for the Y value of all the colors depending on white, as well as calculating the value for setting the brightness. I also used it to write down my settings as I went. It's based on Tom Huffman's tutorial.

Here is how it works:

When you set your contrast, put Y for a 100IRE window in D8
It displays Y for 10 IRE Window in A12 to set brightness

When working on the gamut, if you enter Y for white in E38, it displays Y for all the primaries and secondaries based on the percentages for REC709.

 

Calibration sheet.zip 5.119140625k . file

So it seems it is possible with some fiddling to get close to perfection calibration without an external processor. Good news.

For the guys who have successfully calibrated the RS20 with the CMS, did the brightness / lumens have to take a big hit to achieve the right calibration?

Do you have before / after lumens measurements?

I have managed to correct my green luminance issue by going with a -8 color setting. The only issue I have now is my blue luminance is a bit on the low side but better than before.

I've published all my before/after measurements in my calibration thread on AV forums here http://www.avforums.com/forums/dlp-l...attempt-5.html

EDIT: sorry I didn't see your question was specifically related to lumens. It is possible it takes a hit, as Y for white went from around 41 when I started to around 36.5 (so that's around 10%, the actual data is in the speadsheet I attached in a post earlier). But I had contrast at -8 to start with, and with an iris at -15 I still got 12 fL, so I don't think it will be an issue except for those with the biggest screens.

I will have a check on my lumens once calibrated and will report.

It's interesting you ended up with the same color setting as mine. Do you get spot on luminance (for green and yellow), or are you slightly below like I am?

Also, did you manage to get cyan spot on? I couldn't...

It's weird you have a problem with blue, as I still had some lee way to get luminance quite close. I guess (as we know) all PJs are not identical...

Also Jeff, I wanted to ask you, why don't you use a user preset for the color temp? I think you started with the 6500K (on which you can't adjust offset), then moved to a 7500K one. Is there a reason why you're not adjusting both gain and offsets in a user preset? I found adjusting both of these carefully before moving to gamma made a big difference to the greyscale you end up having to adjust.

Here is my 3rd attempt, the slight over saturation is largly on purpose. Luminance is near enough spot on apart from blue.

I have learned with my Ruby that you have to be very careful with RGB offsets, bias and gain controls. It might look great 10-100 IRE but problems below 10 IRE can really mess things up. With the Lumagen you can make changes at each level that has very little effect else where.

Thanks, it makes sense. Although I don't think I can check that with my i1LT given its limited precision at 10 IRE and below (that's also why I didn't bother trying to measure my contrast ratio)... The CMS of the 750 does offer a point at 5 IRE though so correction is possible if you have a colorimeter precise enough at that level. Are you using both a Spyder3 and an i1 Pro?

Doing an optical comparison at the low light levels can work very well if your higher light levels are accurate. The darkest grays should have a look of charcoal if things are setup well. With a front projector and a diffuser on your sensor you can also measure at near 0 luminance. Unfortunately, these JVC projectors are some of the most challenging products to measure accurately. The error with my i1 Pro is 5 dE u*v* at D65 for example.

The gray scale adjustments in the JVC interact with higher light levels much more than a Lumagen, but you should be able to come close to the Lumagen with the controls in the JVC. These units can track very well.

Moved.

Second impression: too bright. I closed the iris all the way down. Still plently bright on my 106" High Power screen.
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Lawguy:
Thanks for the feedback and encouraging words on this unit. Followup please- how far did you have the lens from your Hi-Power screen, and is that screen 106" diagonal or width? When you said "plenty bright," do you mean "ideal", "barely OK", or actually "TOO bright" for your taste? I wonder how many ftL you are getting w/ the iris down to...what?...-15, I believe? This unit with my planned Hi-Power 100" diag./87" wide purchase continues to concern me. Thanks for reply.

Lawguy:
Thanks for the feedback and encouraging words on this unit. Followup please- how far did you have the lens from your Hi-Power screen, and is that screen 106" diagonal or width? When you said "plenty bright," do you mean "ideal", "barely OK", or actually "TOO bright" for your taste? I wonder how many ftL you are getting w/ the iris down to...what?...-15, I believe? This unit with my planned Hi-Power 100" diag./87" wide purchase continues to concern me. Thanks for reply.[/quote]

It is 106" diagonal. I would have preferred more Iris stops, ie darker! Lamp aging should take care of it.

Thanks, I'll give it a try...

Lawguy:
Thanks for the feedback and encouraging words on this unit. Followup please- how far did you have the lens from your Hi-Power screen, and is that screen 106" diagonal or width? When you said "plenty bright," do you mean "ideal", "barely OK", or actually "TOO bright" for your taste? I wonder how many ftL you are getting w/ the iris down to...what?...-15, I believe? This unit with my planned Hi-Power 100" diag./87" wide purchase continues to concern me. Thanks for reply.[/quote]

Mine is putting out about 170 lumens at the minimum iris setting with low lamp power and a 10 ft throw to a 84" screen.

I spoke to a person that works for JVC Canada yesterday (he comes to my store regularly) about the THX mode & how many people here are finding it not perfect and he responded that it will be in about 200+ hours, JVC with THX deliberately did this to allow for a run in period fwiw. So we shall see how the THX mode is after a couple hundred hours.

Many of the errors I find in THX mode will not be corrected with time.

That sounds like pretty much what I would like. If you get some time it would be great to see the adjustments you made to achieve that (including the RGB offsets in the 6500 adjustment menu and whether you manually adjusted the gamma to get there).

One thing I've found with the first test pattern on the AVS Blu-ray disc and a PS3 is that I can't get the bar for 17 to show up without the bar for 16 showing up with the THX mode and HDMI on enhanced (or whatever it is called) to get below black and above reference white. With a user setting I could get 16 to be black and 17 to come on by setting each RGB value to -1 in the 6500 menu and then setting Brightness to -6 (at least that is what I recall from late night calibrating). Although that was with a slightly adjusted 2.5 gamma.

Thanks,
Darin

I have it in high lamp mode to maximize contrast.

If you mean contrast ratio, high lamp only maximizes on/off CR if it means you can use a lower iris setting for the same lumens. If you are already at -15 on the iris then the high lamp doesn't do anything for your CR (unless you have lights on or some small factors like color balance or the way the light source spot is in the lamp, where either high or low could be better).

--Darin

Okay. I sent you a PM followup. BTW, I guess the high lamp mode/better contrast discussion has flowed through here, but that just never made sense to me (brighter = + contrast).

It isn't that brighter equals more CR. It is that a tighter iris means more CR (with a proper iris implementation). And with more light going from the lamp you can close the iris tighter for the same lumens out the lens, meaning more CR. But if you can't close the iris any further, it doesn't mean more CR in general.

I should add that the above is for CR from the projector. If you have lights on in the room then brighter helps fight that light and provide more CR off the screen. And a darker screen from a gray layer can help fight reflections off the walls, so high lamp with a darker screen may provide more ANSI CR in the images than low lamp with lighter screen, all else being equal (like not using screns with different directionality effects, which can also help ANSI CR retention to viewers in high gain viewing positions).

--Darin

IIRC, all other things being equal, Ekkehart's measurments showed slightly better on/off CR in high lamp mode than in normal lamp mode.

And if one is using 75% colors rather than 100% colors for testpatterns - this is also a very dangerous practice. It can force the color brightness into clipping at 75% - in attempting to eliminate neon colors for more realistic ones - one increases neon highlites making them cartoony! When using this method be sure to check a colorscales pattern (DisplayMate has one) to make sure you can see all the RGBCMY steps!

Green is clipped a bit but I'm not going to loose any sleep over it.

Here are my setting from the last attempt.

Contrast 2
Brightness 1
Color -8
Tint 0
Color Temp 7500 offset red 1, offset green 1, offset Blue -1 (Grey scale finished on Lumagen)
Gamma Custom1 (2.3, unchanged)
Sharpness 0
Lens Aperture -15
Lamp normal

CMS (Hue, Saturation, Brightness)
Red -4,-10, 29
Yellow -4, -24, 11
Green -4, -30, 5
Cyan, 9,-30, 25
Blue 3,-3,30
Magenta 1,-11,28