CurtPalme.com Home Theater Forum

[AVphile]

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I think I goofed on my earlier Gamut measurements. The tool (CalMan 3.7) is expecting 75% color bars but I was using 100%. Of course the Video Essentials Blu-ray doesn't have 75% so I dusted off the HD-DVD and re-measured (see attached). Looks better now but I will try removing the green filter next time.

Thanks

PS - I hope this doesn't matter for comparing gamut but these measurements are after trying to re-build the greyscale from scratch (again). I've been wrestling with this to get the green under control and I've maxed out the CUTs & MIDs on this set! I know what needs to be achieved but I've run out of adjustment range.

[garyfritz]

75% vs 100% shouldn't make any difference. That doesn't change the fundamental color of the phosphor/filter.

But your measurements do look different. Very strange.

My 8500 has 180DMB22's vs. your Barco's 180DVB22's, but I strongly suspect they use the same phosphors. And yet your measurements look pretty different from mine. E.g. your blue is well inside the SMPTE standard, and mine was outside. I suspect it's a difference in the colorimeters, and yours is probably better. My Minolta TV2150 is an ooold box and it have drifted over time.

With your current measurements, your red is almost spot on. The green doesn't look as extreme. Would be interesting to measure it without the filters, to see how it compares to my no-filter measurements.

[AVphile]

I removed the green filter. Turns out I couldn't get grey because the green filter was too dark. Now I can get grey easily but the greens are rather weak. Full report attached.

PS - I have the Sony 07MFP2 tubes.

[garyfritz]

Hm, Sony tubes, eh? I don't know if they use the same phosphors.

But without the filter, your green looks about like mine did. That causes the yellowish greens and messes up skintones &etc.

What filter are you using? Are you using a filtered lens, or a DIY experiment with something like the gels I used in my original post? Maybe you can get a lighter green that will work better. You can see I tested a "light" and "medium" green in my original post.

[AVphile]

It's just a green sheet of plastic film (acetate?) that Curt threw in when I bought the new PJ. He says it is dark green. I'll check out the local pro lighting store for something lighter. I'm so glad that I have a half-decent picture now I've finally been able to watch movies, and I must say the color is not as nice as the old PJ. I see a lens upgrade in my future

[garyfritz]

I didn't test the dark green, but the med green and light green were big improvements over the unfiltered lens. See if the lighting shop has the 4430 and 4460 Calcolor gels.

The gels are a great way to test it and see if it's worth changing. (Some people don't seem to notice the lifeless colors you get without color filtering.) They're not ideal. They tend to blur the image slightly, since they were never intended to be used in the optical path. And they're not the ideal color for CRT filtering. They're cheap and easy to test, but for best results you have to bite the bullet with filtered lenses and, I assume, adapters.

[AVphile]

The local shop has unbranded gels. I was able to choose what I thought was a "medium green" just by looking at them. It's a lot lighter than the one I was using before, but not the lightest green they had, which turns out to be just right! Attached are the measurements.

Side Note: Although it wasn't easy I was able to get a half-decent greyscale with this one, unlike the dark green. However the result is a very high gamma (virtually no curve left to it) and there is still a red glow at low (< 20) IRE. So there is work yet to be done.

[garyfritz]

Looks pretty good! I think that should work. Good luck with the grayscale...

[AVphile]

Yeah, so far so good. I thought I would post back with some more info about the green gel that I bought locally.

They are made by Cinemills and the dealer said they use the same numbering system as Lee, but they are designed for higher temperature movie set lighting or something. I got #121.

There is a Lee / Roscoe cross reference table here, in case anyone finds it useful:

http://www.truecolorgel.com/1%20TRUEcolor%20GEL%20to%20Rosco%20&%20Lee%202011%20.pdf

[AVphile]

As discussed in the Joustmods forum, I now have the real deal HD-145 lenses. Thought I would post an updated CIE gamut

[garyfritz]

That looks pretty good! I'm surprised your readings are all inside the CIE gamut triangle, though. My measurements showed the blue being outside the blue corner without correction, and similar for the corrected red. But maybe my colorimeter wasn't exactly calibrated.

[benareeno]

gary,

you need to use your colorimeter with another more accurate one...then you will know how much of an offset you can account for. At which point, your meter should be just as accurate as anything else out there.

Which gels are best? the ones from the original post or something more recent? My brother has an rp crt and he wants to see what the filters might do.

Ben

[benareeno]

AVphile, have you defocused your blue? It might help add a touch of saturation...and it will definitely improve the linearity of your greyscale.

[AVphile]

No, I haven't defocused the blue yet, because I thought it was beyond help. Would you do that using the electronic focus controls or the optics? Can I defocus while measuring grey and see it change in real time?

Thanks

[benareeno]

electronic focus...i would measure the linearity of the greyscale, then defocus and redo greyscale, then measure again...etc.etc.

[AVphile]

So Anthem has finally released new firmware for my AVM-50v that allows control of the VXP chip's RGB gamma curves. Rather than defocus the blue, I was able to painfully (the interface is horrid) do the full greyscale and this time with a proper gamma curve

As I said earlier, with my Barco controls maxxed out to get the greyscale as close as possible, the gamma curve was a disaster (average about 1.5!). This is the correction I have applied in the VXP and the resulting measurements.

I must say everything looks amazing now, but I do wonder what's next... Would a Color Management System (CMS) make a profound improvement still?

[AVphile]

These pics sum up the Before & After. The before shows the CIE gamut with HD145 filtered lenses - that has not changed. I suppose a full CMS would make the gamut even more accurate, but would I notice?

[garyfritz]

I'm surprised you can get a grayscale like that without defocusing the blue. See this post and this post for an explanation of why you need to defocus.

You must be driving your blue really hard at higher IREs (which will probably shorten the blue's life), or you're running the R/G fairly low. But as you can see in the second link above, some people do prefer the hyper-sharp blue. Unless you have eagle eyes you won't notice it, but if you're really particular, you may prefer the tradeoff to get the sharp blues.

[AVphile]

Even with the Red and Green being filtered by the lenses now, as you said in your first post?

I am curious about getting a Radiance as the next step. There is a lot of talk about CMS on the JVC threads but not so much with CRT projectors. I wonder if that's the nature of digital compared to CRT...

[garyfritz]

R/G filters cut out some light. Most people will boost their Contrast to compensate, but you could run them at lower levels if you're satisfied with the resulting light levels. If the R/G are really dim, then you might be able to keep the blue in the more-linear response range. But if you drive the R/G where most people do, then your blue starts to top out and just doesn't have enough brightness to keep up. If you have a VP with sufficient controls, you could drive the blue really hard in the higher IREs to get a linear response. (The guy in one of the threads I linked to did that. He has eagle eyes and couldn't stand any blurriness in the blue.)

Or you could just defocus so the blue doesn't max out. Most people see blue fairly blurry anyway.