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Discussion Starter · #1 ·
Just curious if any of you Benq 6200 or 6100 owners have discovered any more information about the Gamma Index settings in the service menu. I have been using the video mode which auto selects a gamma index of video6500K. Has anybody explored this in depth. Every time I read a projector review on the Secrets website they say the best gamma is a value of 2.5. I have also seen other sources that say that video is produced for CRT displays which have a gamma of 2.5. I notice that possible gamma index values have include a G2.5 value. Has anybody tried it or discovered which input/preset mode that it is used for? It seems that the G2.2 is used for the economic mode with composite input. When I did the gamma test on Avia with component input and video mode (gamma index = video6500k) and Color Temp at -25, the value seemed close to the 2.5 but it is kind of difficult to tell with that test. I will probably try changing to the G2.5 and try the Avia gamma test again. I am also wondering if the SMART III system would be the best way to get to the bottom of this.


Just Curious

-Angryht
 

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Angryht,


Did you notice any gamma and picture differences with component versus PC?


I remember some person got better results with an ATI VGA to Component adapter than when using a direct VGA connection to his HTPC, I assume that the projector is using different Gamma settings and also different color temp settings when using component in versus PC in.
 

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Discussion Starter · #3 ·
I have only used the PC input for trying to fix the ADC values (that was a lot of fun - wasn't it?). I believe the values were PC6500K for video, PC1100K for cinema and G2.2 for econ, but I'm not sure. I am affraid I didn't get a chance to evaluate pic quality with PC mode.
 

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Well I played with the gamma values again and found a combination that got rid of mosquito noise, and even improved detail in dark scenes.


I always use PC input in economode.

The factory default for this setup is

Gamma: Photo(G2), with PW Gamma: linear.

The new values are:

Gamma:G2.2 and PW Gamma: .7


I played Starwars Episode IV last night and remarked how much better the stars and spaceships appeared amongst a dark, mosquito-free background,


Bob
 

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Discussion Starter · #5 ·
I too have been watching the SW Triligy movies - watched VI last night - great movies!


I am surprised that you can watch econ mode. Do you change the White Peak setting down from 10 or have you changed the DLP contrast/brightness?


Did you compare Gamma Index G2.2 to G2.5?
 

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Yes, I always go in and change the White Peak to 0 each time I power-up the projector, three steps and its done under 5 seconds. Everything else is set to default (brightness/contrast: 32/32) exept for the Gamma and PW Gamma settings.


I cant really find a difference between a properly configured economode and video mode. The bulb savings along with the quiter fan noise is well worth it.


I did compare Gamma Index 2.2 and 2.5. While I liked the 2.5, I found that it crushed blacks a little too much compared to 2.2. Also I found that 2.2 worked better with PW gamma of 0.7 that got rid of mosquito noise.



On a side note: found a way to customize the color temperature functionality, I didn't like the range of warm to cool (cool was useless).

You can leave your respective 6500K color temperature to default 135,110,110 and then change the 11000K setting to say: 135,135,135 (a little less cooler but still not as extreme as the default for cool).


Now when you go into the user menu color setting, you will find that the 6500K setting sits on the extreme left end while the 11000K setting sits on the extrem right. Now you can play with a custom defined temperature control in the regular user menu without going into the service menu.
 

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I am kind of glad I amusing component for that reason alone (white peak default of 5 instead of 10). My pj is wall mounted, so switching it at every power up would be a hassle. What we really need now is to access the serial port and make that change permanent.
 

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Discussion Starter · #8 ·
Quote:
Originally posted by bob619
I did compare Gamma Index 2.2 and 2.5. While I liked the 2.5, I found that it crushed blacks a little too much compared to 2.2. Also I found that 2.2 worked better with PW gamma of 0.7 that got rid of mosquito noise.
I am not sure what 'crushed blacks' means. Is that a lack of shadow detail? I have seen that expression used before - I just am not sure I know what it means. Can you explain what it looks like?


Here is one of the articles that makes me believe that the gamma index should be set to 2.5 for films:

http://www.wordiq.com/definition/Gamma_correction


Specific quotes like: "For a CRT, [gamma] is about 2.5. By coincidence, this results in the perceptually homogeneous scale as shown in the diagram on the top of this page." and thiis: "However, such displays apply a correction onto the signal voltage in order to approximately get a standard [gamma]=2.5 behaviour. In NTSC television recording, [gamma] is 2.2."


I realize I should do some more testing (and I will in the next few weeks) but I have not had a lot of time lately. Anyway, the two references at the end of the article are the ones I have put on this forum before. I am still struggling with the gamma index options like: Video6500K, Video11000K, PC6500K, PC11000K. What do they do? I am curious to find out what default settings give you a gamma index of 2.5. I would guess that it is the s-video input and I will probably test that tonight. I am putting together a table with all inputs and gamma settings to compare.


Anyway, I appreciate everyone's participation and I hope more answers are in the near future.


-Angryht
 

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'crushed blacks' do mean lack of shadow detail.


Like the article mentions PC monitors are based on the sRGB color space, a 2.2 gamma. It is 2.2 rather than 2.5 so the white end of the curve is more linear, (it doesn't shoot out at the end like a 2.5 would). It is also easier to find an inverse without using an infinite slope at 0.


So in my scenario, using PC as input, a G2.2 is exactly right.

I also chose a 0.7 PW Gamma (Inverse Gamma) to slightly bring out the bottom dark range, while leaving the top white range alone because of the way the projector already overemphases the top white portion. The result is more detail in dark shadows while keeping control of the whites (colors in the white portion are also more saturated)


One last thing, do not take the Gamma settings as precise settings. I noticed that they are not consistent and sometimes make no sense. For Example: if you try PW Gamma 0.7 and then 0.8 and then 0.9. The blacks should theoretically get darker as you move from 0.7 to 0.9. But in the projector's case it starts to get darker from 0.7 to 0.8 but then gets inexplicably lighter from 0.8 o.9.


Your best bet is to try them out yourself and let your eyes be the judge (while using an eye based calibration tool of course).
 

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Discussion Starter · #10 ·
So I tried playing with the gamma index last night. I started with my usual movie connection (component input of the progressive scan dvd player). I changed to Cinema mode (to get the white peak to 0) then I changed the gamma index to 2.5 and went through the basics on Avia. It really looked good. Then I switched sources (composite - vcr) and switched back to component. When I checked the gamma index value, it had changed back to it's default value of video11000k - darn! Looks like that is another value that will not be saved. This was probably mentioned in the other threads about the 6100/6200. So it looks like it is back to the drawing board.


Anybody figure out how to save some of these values? I might just have to try Bob's settings and see how it looks. Because I have the pj on a shelf, it's a pain to go into the service menu everytime I power up. Oh well.
 

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Bob619:


I have a BenQ 6200 that has 2 component sources (switched through my A/V receiver). One is a high def cable box, and the other is a home theater PC. The PC is connected out from ATI Radeon card to a Key Digital transcoder (converts 15-pin VGA to Y/Pb/Pr component cables), then into DVD input on receiver, and finally output (component 'out') from receiver direct into the 6200. Thus, I DON'T use a straight 'PC' connection (I switch, with the aid of a converter/transcoder, through my receiver). The switching of component video from the cable box's component output to component input on receiver is much more straightforward.


Both sources (HTPC and HD cable box) produce what I believe are very good progressive images (either 720p in case of HD cable programs or 480p in case of progressive DVD source from the HTPC.


However, I have always thought that SHADOW DETAIL is a weakness on the 6200. I have played with video calibration discs from both Avia and DVE, and understand that black level aka 'brightness' needs to be high enough to bring out the shadow detail where required. Still, I find myself fidgeting with this setting more often than I would like, regardless of whether the source is from the HTPC or a high def cable program.


Saw this thread after searching AVS Forum a fair amount, and this thread seems closest to what I'm looking for where further fine tuning is concerned. So:


1. Can you list steps to enter the 'Service Menu' on the 6200?

2. Which settings can you recommend I alter to best bring out shadow detail? (Like you, I've found good enough settings in Economic Mode to justify leaving it there, so that's what mode I'll be in going forward).


The 6200 is a great projector for the money. I am just looking to improve upon shadow detail in particular, if at all possible. Thanks for any thoughts/ideas.
 

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Discussion Starter · #12 ·
back2boston,


Here is a post that discusses the way to get into the service menu:

http://www.avsforum.com/avs-vb/showt...10#post3968410


This post lists the different menus:

http://www.avsforum.com/avs-vb/showt...54#post3993754


Be very careful, especially the part of the menu that has the sunrays (ADC brightness, ADC contrast......). In fact you should not even go into that part of the menu even if it is grayed out. I would suggest a lot of reading in "First Impressions" thread as well as this thread, in which a bunch of us had screwed up the ADC values but we fixed them:

http://www.avsforum.com/avs-vb/showt...88#post4362088


I guess the biggest thing is to be cautious.


That written, I have been very happy with using the economic mode because of the quieter fan and extended bulb life. The problem with the econ mode is that the whites shimmer and it can be distracting. I also have the 6200 but not connected to a PC (just component through the vga input). I have struggled with getting black levels correct but this is what I did in the service menu. I left the 'white peak' at the default (5 for component input - I think it is 10 for PC input) because any changes to that are not saved after the machine is powered off. Some don't mind changing that every time they power up (it honestly does not take very long) but I'm kind of lazy. I reduced the DLP Contrast from 32 to 24 and there is no shimmer in the whites and I don't have to go into service menu every time. My contrast is set to 19 (user menu) and brightness is set to -1. I think one of the reasons that I like the economic mode is that the gamma index is G2.2. I think (haven't bought a colorimeter and confirmed) that the light response is closer to ideal. Actually, I would like to buy SMART III and check but it's not in the budget yet.


Anyway, I hope this helps you out but be careful and do some more searches. This is just about the best source for information that I have come across.


-Angry
 

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back2boston,


It's a good idea to use a transcoder ( VGA to Y/Pb/Pr component ) as it forces the 6100 to use the component settings.


Using just a direct VGA connection forces the 6100 to use PC mode settings:

10 White level, G2 (photo) gamma, and uses the PC6500 color settings. These settings are only good for PC presentations.


Y/Pb/Pr (Component) is tailored for Cinema viewing:

4 White level, G2.2 gamma, PW Gamma is linear (but you could experiment with other values such as 0.7 or 0.8 to bring out more details in the blacks without crushing whites).
 

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Hey guys,

You all know better than to have a party and not invite me!!! Hey, I've enjoyed the reading. Lately, I've been a bit lazy about getting into the service menu to make changes before serious dvd and hd viewing, but you've all just inspired me to start doing that again. My whites have been shimmering, and I know that I can improve that. Keep me in the loop.
 

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Discussion Starter · #16 ·
Good to hear from you, Jedi. You're right, this stuff is "pure gold, Jerry" (Sorry, obscure Seinfeld reference). Bob is tough to keep up with but it is usually worth it.


-Angry
 

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Ok, I got back into my service menu for some Voom hd viewing last night, and I made the changes that Bob and Angry suggested. I must say that I have really been missing out on better image quality, as things looked FANTASTIC with the changes. I'm only watching component through the vga adapter. I did think blacks were blacker with the dlp contrast set to 24, but my overall image seemed a bit too dark. I'll bump it up a little. Bottom line...serious viewing needs the service menu tweaks that won't stay in the pj's memory at power down or source switches. Yes, it was great to see clean whites again that weren't shimmering.


Oh, I can't remember if I mentioned this in another thread or not, but I pulled my component video switcher out of the system, and I'm watching each source directly through the vga adapter, and the image quality is killer!! My switcher was definitely taking away quite a bit of signal, I guess. If you are using one, you might want to check out what the picture looks like going direct like me. Yes it's a pain to unplug the component connectors, but I have as many as 3 adapters right now(I've got 6 or 7 hd/ component sources). If I buy a couple more, then all I'll have to do is line up the vga connectors, label them, and just do quick switches at the pj end. My pj just sits on a counter behind my head...easy access.
 

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jedi35,


When you change the gamma settings you do have to recalibrate.

So when change these two gamma settings:

1. Gamma:G2.2

2. PW Gamma: .7 (this guy will bring out the bottom range while reducing the top)


The image will appear darker, but after calibration (usually have to increase brightness, you could also increase contrast to give it more punch ) you will notice that the details in the blacks should be better without crushing the whites.
 

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Happy Thanksgiving!!


Yes, Bob, you are right. Once I get the brightness and contrast back to where I want it, I can just quickly make the service menu changes each time I boot up without having to make other adjustments.
 
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