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need help with black levels - dlp front projector


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23 replies to this topic

#1 of 24 Oupei

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Posted July 24 2004 - 10:10 AM

hey guys,

I'm having some trouble with black levels with my new home theater and I'm not sure who's the culprit. First, here's the gear:

InFocus 5700
DIY 106in. screen with BO fabric
DIY component and composite cables (50ft)
S-Video Cables from wholesalecables.com
Sony DVD/VHS combo player
my receiver is in the shop so the dvd player is connected directly to the projector.

there's a pic at www.prism.gatech.edu/~gtg890r/theater1.JPG

In dark scenes some things are pretty difficult to see, enough to watching a movie laboring enough to ruin the experience. i was suspecting that the walls weren't dark enough, but then I noticed that even for black bars, it was not truly black (as in no light emitted from projector). So i was wondering if maybe I should be messing with some of the settings on the projector or the dvd player. I haven't touched any of the video settings on the projector yet so they're all at factory presets. For the dvd player, there's a setting called "black level" that raises the contrast, but only works in interlaced mode (which I am using anyways cuz the 5700 has the faroudja thing). Does anyone know exactly what that does? I tried it and it does make things appear more clearly though the contrast does appear exaggerated at some areas. Or maybe i'm just not used to it yet?

bottom line: should i repaint my walls?

#2 of 24 ChrisWiggles

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Posted July 24 2004 - 10:45 AM

First, no digital projector can hit black yet, so this is normal. Second, a black room will not improve on/off contrast, but will improve your ANSI contrast (essentially keeping the bright parts from washing out darker parts of the image). Thirdly, you really need to calibrate your projector, the best way to set black levels with a DLP is to look at the dithering as you set it with black.

#3 of 24 Max Leung

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Posted July 24 2004 - 11:37 AM

I suggest buying a calibration disc like Avia Guide to Home Theater or Digital Video Essentials.

The Infocus 5700 is a bright projector, so black levels are not the best. However, it sounds like you're having trouble with shadow detail. Try one of the discs above, and see if you can get your brightness settings on the projector (try to avoid making picture adjustments using the DVD controls) in line.

To tell if you have the best possible black on your projector, do as Chris suggests: Turn down the brightness on the projector (using a black image from one of the discs above) until you see no DLP dithering. That is as black as the projector will get.

If it is still too black, you could try placing a neutral density filter in front of the projector's lens. Although, on a 106" screen, it shouldn't really be necessary I think.

EDIT: oops meant to say black levels are NOT the best
Mahatma Gandhi, as you know, walked barefoot most of the time, which produced an impressive set of calluses on his feet. He also ate very little, which made him rather frail and with his odd diet, he suffered from bad breath. This made him...a super-callused fragile mystic hexed by halitosis.

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#4 of 24 Scott Dautel

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Posted July 24 2004 - 11:42 AM

I had a similar complaint with my X1 initially. Discovered that running through the video settings with THX Optimizer made amazing improvements. In fact, regarding shadow detail, the THX Optimizer results were better than I got from VE. You'll find THX Optimizer on numerous 2003/2004 DVD releases (Findng Nemo comes to mind) ... just do a search

BTW ... I'm also using a DIY screen w/ blackout cloth (for now).
Scott

#5 of 24 Oupei

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Posted July 24 2004 - 12:03 PM

hmm...

calibration - 3
wall color - 0 (maybe half a vote from chris?)

ok, i guess it's time to go tweak with the picture settings. I looked up dithering in the glossary but it was only defined in the context of audio, I assume it is low-level noise in the video signal that would only show up in dark areas? is this what is washing out my picture? THX Optimizer that comes with a DVD such as Finding Nemo sounds very good to my wallet, I think I'll go look for one of those...

edit: did a search as suggested. looks like the THX Optimizers aren't regarded with very high esteem. I guess I'll go with DVE then. Does this thing have sound tests on it too?

#6 of 24 Max Leung

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Posted July 24 2004 - 02:15 PM

DVE has sound tests too.

When we say dither, we meant DLP dithering, where in dark scenes you can see individual mirrors turn off and on when you move a little closer to the screen. DLP dithering is very apparent when looking at grayscale patterns found on the calibration discs, particularly on the low IRE (dimmer) gray bars.
Mahatma Gandhi, as you know, walked barefoot most of the time, which produced an impressive set of calluses on his feet. He also ate very little, which made him rather frail and with his odd diet, he suffered from bad breath. This made him...a super-callused fragile mystic hexed by halitosis.

Gamesh....

#7 of 24 Stephen Dodds

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Posted July 24 2004 - 04:19 PM

You definately need to calibrate. Virtually all projectors are way off straight from the box.

By all mains use AVIA or Video Essentials, or even the THX Optimode, but there is an even simpler way to do a quick black level calibration.

Firstly stick a letterboxed movie on. Then go into the menu of the projector and select the Brightness control. This is the one that adjusts blacks. Turn it all the way up. You should notice that the area around the letterboxed movie is a brighter gray than the rest of the screen.

Now turn the brightness control down until these brighter areas are as dark as the rest of the picture. Stop there.

That should be reasonably close to correct black levels.

The Contrast control adjusts white levels, and you should tweak this so that the are just below the level where you can still see details in them.

Cheers

Steve

#8 of 24 Oupei

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Posted July 24 2004 - 04:26 PM

is this the right dvd: deepdiscountdvd.com/dvd.cfm?itemID=VMG010712 ? It says it's fullscreen 1.33... or is their info wrong?

Stephen: I'm a little confused here, which area is which now? One of them I assume is the black bar. What's the other area?

#9 of 24 Stephen Dodds

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Posted July 25 2004 - 10:23 AM

That's the DVD, or you can use the THX Optomode section that comes on many THX approved discs.

I'm a bit confused by the last part of your response. I'll be more specific. I forgot you had a 16:9 projector.

If you have Lord of the Rings or any other 2.35 aspect ratio movie, stick in your DVD player and start playing it. Find I section of the movie that is mostly black and then pause the picture. In LOTR the opening titles will work.

Now turn the brightness up full. You should notice that the area of the picture becomes an obvious grey, with darker sections above and below where no light from the proector is falling. Now reduce the brightness until the area of the picture is as dark as these sections above and below. That is as black as the combination of your proector, screen and room can show.

Cheers

Steve

#10 of 24 Oupei

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Posted July 25 2004 - 01:54 PM

so turn the brightness down from maximum level until the black images in the movie look the same as the black bars. ok, I think I got it. I'll go try it tomorrow.

And I'm gonna go buy that DVD then, hope it comes in this week Posted Image

thanks everybody.

#11 of 24 Neil Joseph

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Posted July 26 2004 - 03:33 AM

3 things....

1- a silver or gray screen will help increase the black level

2- painting at least the front wall flat black

3- re-calibration of the projector using VE or AVIA
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#12 of 24 Ron-P

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Posted July 26 2004 - 04:12 AM

From my experience, the largest improvement came from the gray screen. I had the white BO screen and then painted it with a custom mix gray from Lowes. Improvement in blacks was substantial.

First, I'd get or paint yourself a gray screen. Then, calibrate with AVIA. If your still not happy, paint at least your screen wall flat black.
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#13 of 24 frank g.

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Posted July 27 2004 - 03:47 AM

I have found that the infocus projectors are so bright that a neutral density filter and some careful calibration is required. My first experience with this projector has been a treat to say the least. Everything is great about it but a demo at a local store showed me it,s strengths and weaknesses. An over abundance of light output made even the letter box bars seem dark grey at best. The salesman put on the filter and with some carefull calibration with an avia disc, it came to life. This is coming from a person who has demoed alot of projectors over the last few months. I find that exterior wall treatments will help dramaticaly with the wow. factor and also any excess light reflections washing out the picture. This will make your blacks seem weak. But if everything else is good but just your blacks are bad then dark areas around your screen will do almost nothing for this condition you are experiencing.

#14 of 24 Jack Gilvey

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Posted July 27 2004 - 05:50 AM

The brightness of something like the 4805 allows you to use a grey screen to get deeper blacks while still having adequate brightness. Brightness is a good thing...
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#15 of 24 ChrisWiggles

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Posted July 27 2004 - 06:01 AM

The brightness does not allow for "improved" absolute blacks, however what it provides is flexibility, usually. Iris control can improve on/off contrast in lower modes, but what really bright projectors give you is options. If you want to go huge, you can, and if you want to go really bright for sports and ambient light, you can. But what you can also do, is get a *really* low gain screen to get back to the black levels that a dimmer projector would give you, and the low-gain screen will then reduce the impact of room reflections thus improving your ANSI contrast. Too bright a picture, IMO will resolve and highlight source and projector artifacts more, so it demands not only a better projector, but also better sources.

#16 of 24 Oupei

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Posted July 27 2004 - 10:02 AM

hmmm... It seems like you guys are talking about absolute colors and stuff. For now, I'm looking just for higher contrast in the darker scenes so that I can make out more details and see what's going on. at this point, it doesn't matter if blacks show up as greys as long as blacks can be differentiated from dark greys.

I've turned up the brightness a few notches and turned down the contrast a little to compensate for the whites and it has already improved a lot. Already, there's a lot more detail in dark scenes. When DVE comes in I'll make some more minor adjustments but I think it is already pretty close to as good as it will get. I'm am hitting a brick wall with what I think is the DLP dithering that you're referring to. If I turn up the brightness any more, there will be noticeable specks that flicker on and off all over the dark scenes kinda like static, even on a paused picture. and although it's not noticeable without walking up to the screen, it's something I would prefer not to have, so I'm probably not gonna get any more out of the brightness settings.

The dark scenes still don't look as clear as on CRT TVs, so I would still like a little more improvement. I'm planning on painting the walls darker after final exams and then I guess we'll go from there.

#17 of 24 ChrisWiggles

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Posted July 27 2004 - 10:33 AM

Ah, I see what you mean. You are interested in improving shadow detail. Darker colors will improve your ANSI contrast (which is how well your setup, projector plus room, maintains blacks when there are bright parts of the picture up Bright parts of the picture will spill onto other parts of the screen, both from within the optics of the projector and from reflections from the room back onto the screen, which will wash out shadow detail in dark parts of the picture.)

#18 of 24 Neil Joseph

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Posted July 27 2004 - 01:33 PM

Using VE or AVIA will have you check for "blacker than black" and adjust the contrast (and other settings) to the optimal place which would help you see the shadow detail better.
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#19 of 24 Max Leung

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Posted July 28 2004 - 06:03 AM

Hmm, I don't recall AVIA having "blacker than black" bars, but it will still help. Posted Image
Mahatma Gandhi, as you know, walked barefoot most of the time, which produced an impressive set of calluses on his feet. He also ate very little, which made him rather frail and with his odd diet, he suffered from bad breath. This made him...a super-callused fragile mystic hexed by halitosis.

Gamesh....

#20 of 24 ChrisWiggles

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Posted July 28 2004 - 09:00 AM

Max is right, consumer Avia is limited to 16-235. There is no BTB or WTW material on that disc. DVE, however, does contain BTB and WTW in it's patterns, and can be used to test whether your system is clipping this information. I use both discs in conjunction to test things.