Calibration- Possibly the most important thing to read here or anywhere... - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 32 Old 01-30-2009, 05:54 PM - Thread Starter
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The title says it all, but for anyone new it does need an explanation.

Many times I see people go from one screen to another and express comments about how bad one screen is as compared to another. If the screens are both similar, then it is relevant, but if one is a white screen and the other a gray screen, a comparison this way means very little.

For starters if the screens are totally different in properties then they will perform differently. Calibration though makes a huge difference. If your projector is calibrated for a higher gain white screen then any gray screen, be it commercial or DIY will suffer by comparison. Conversely if you are calibrated to the gray screen, then the white screen suffers.

Here is a perfect demonstration of that. I have talked about this topic many times, but this illustrates it better than anything I can possibly say.

This applies to both commercial screens as well as DIY options. I think the best way to demonstrate this though is with commercial screens. That way it removes any of the hype and sometimes bias that comes with DIY.

Here we see a comparison between a Da-Lite High Power screen and a Da-Lite Silver Matte. The Silver Matte is very dark and a much lower gain screen, whereas the High Power is very white and well over double the gain.

At an initial glance, the HP totally blows away the Silver Matte as can be seen in this shot.

Let's look at this and talk about it for a minute. Nobody can deny the HP mops the floor with the much darker Silver Matte. Just look at it! How could anyone want a darker screen? The HP is bright, vibrant, and much more accurate at reproducing the projected colors.

That's a bit misleading though. This is where calibration comes in. That shot was calibrated to the HP. Any time a projector is calibrated to one particular screen of course that screen is going to look its best.

What happens though if we recalibrate? This is often overlooked and for a novice who doesn't understand this concept, they can easily be led to believe one screen is far superior than another.

Let's look at what happens after a recalibration to the darker screen.

Now the tables turn. The difference isn't nearly as dramatic as in the first comparison. Still it can be said that the HP looks better with a slightly brighter image and more vivid colors. However the Silver Matte has much better blacks and it is holding its on against the HP.

For a totally dedicated HT setup that also has total light control- and this also depends on your projector and how good the CR rating is as well as its ability to produce true blacks... a white screen rules. However more and more people are integrating projectors into family rooms and multi-purpose living rooms where light control is less than optimal or there is a desire to watch the big screen with some lights on. One scenario that comes to mind is a Super Bowl party. Nobody wants to watch the big game with all the lights out. It's a party atmosphere and completely different than a movie theater setting.

Also TV comes to mind. I personally don't use my projector for TV shows, but many people do. This is a very common environment where there is the potential for some lights to be on in the room.

A white screen will not perform as well in this type of setup- period.

There are many myths with screens, especially when it comes to DIY screens. I specifically used commercial screens here to show this isn't just a DIY dilemma, but does matter even with commercial screens. Calibration is the difference between a good image and one that blows your socks off. It also could change a person's mind between two totally different types of screens.

Always calibrate to your current screen, and always recalibrate any time you change screens. Even more important... when comparing two very different types of screens always calibrate to each screen before making a final decision. I know many people that have dedicated theaters that prefer a gray screen to a white screen. It all boils down to some basic variables- What can your projector do? In order to know this you need to do a baseline calibration to a unity gain white screen. Next is what is your viewing environment like? And last, what is your personal preference and tastes?

Do not let anyone tell you what screen is best for you and blindly accept it. Do the research and comparisons. If you are spending the time and money to build a Home Theater room or a multi-purpose room, then spend just a little extra time to do a basic calibration to see how different screens perform.

If you don't have a calibration disc like Avia or DVE then use the THX Optimizer found on all THX certified DVD. The difference really will amaze you.

"Make everything as simple as possible, but no simpler." - Albert Einstein
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post #2 of 32 Old 01-30-2009, 07:04 PM
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I'm going out on a limb here to say that I really don't agree with you, at least on some points. I do agree that trying to compare two screens at the same time as you did here will not work. In my setup, I can switch screens and leave the settings untouched. The overall picture may be lighter or darker, but that's all. At this point, personal preference really dictates what the ideal settings should be. For instance. I have a friend that thinks my adjustments are way too bright. He's wrong by the way

I find much more variation in equipment and sources. Unlike you, I watch a lot of TV on my projector. Calibrating with Avia is a waste of time for TV because the tuner is a different piece of gear. Proper contrast and brightness on the dvd player can be a lot different than the HDTV tuner. Making adjustments by eye is my only option. Broadcasts and shows vary a great deal as well, so I end up adjusting my projector frequently trying to compensate.
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post #3 of 32 Old 01-30-2009, 07:25 PM
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wbassett,

Great demonstration of the benefits of a simple contrast & brightness calibration. I remember you telling me about the THX Optimizer that is on my Terminator II Extreme DVD. The improvement in image quality and shadow detail that I observed after performing this simple calibration to the gray screen I had at the time, was amazing. So I would like to thank you personally for encouraging me to do a calibration. That simple 5 minute task has significantly heightened my enjoyment of my projector over the past couple of years.

I would like to share an additional suggestion. Do the calibration for your darkened room viewing and for the typical ambient light conditions. Save each setup so you can recall the settings for your current viewing conditions.

I also found through a bit of experimenting that the gamma setting can make a tremendous difference also. In particular, the shadow detail was significantly improved through selecting the right gamma setting, However I do not really understand gamma settings. Maybe you could elaborate a bit on gamma settings?

Thanks for sharing!
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post #4 of 32 Old 01-30-2009, 07:58 PM
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Would you please explain how turning up the brightness and / or contrast resulted in dimmer whites on the HP. I think something is wrong with your photos. Edit... Viewing cone is causing the fall-off near the top of the screen.
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post #5 of 32 Old 01-30-2009, 08:28 PM - Thread Starter
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I don't believe I said the brightness or contrast was just turned up to result in the difference. There are many parts of calibration including pluge tests, gamma, as well as the color hues and intensities and many other adjustments. kbgl I assure you and everyone that there is nothing wrong with the photo's and they are not doctored to demonstrate the dramatic difference a caibration will make. That's exactly why this showed two commerial screens, and even from the same company. DIY was taken completely out of the equation, but... this also applies to DIY screens.

That was the entire point of this post... to demonstrate just how much of a difference proper calibration can make between screens.

As far as television and channels looking different, even TV uses th D65 standard, but yeah some programs pump things up as attention getters, commercials are particularly guilty of this. Plus there is alway going to be a difference between analog and digital channels, or even digital and HD channels. Soon though all analog channels will be gone so things should be a bit more balanced out, but as you mentioned, there still will be differences between some channels.

As Todd mentioned most projectors can store several settings. I have one for lights out and one for lights on. I'd recommend you set one for DVD and one or TV, but if you're going to tweak and adjust between channels, well like you said that's your preference but that would drive me nuts. Question... do you do the same thing with your TV or HDTV too?

I'll tell everyone a secret... well some already know this, but even at some of the brick and mortar stores they will calibrate a set they are promoting and have been guily of taking the other sets out of calibration so the one set they are trying to sell that week looks better!

"Make everything as simple as possible, but no simpler." - Albert Einstein
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post #6 of 32 Old 01-30-2009, 10:12 PM
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If those pictures are "untouched" accurate or not, why are the whites so blown out? (in the first picture)

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post #7 of 32 Old 01-31-2009, 05:47 AM
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In the first shot the HPs whites are brighter than those of the Silver matte. If you adjust the projector for the Silver Matte, The whites on the HP should still be brighter due to higher gain, but in your photo, the whites are darker.

Did you have to correct for a HUGE color push between the two screens? That's the only thing I can think of that would cause this to happen. If you reduced one of the gains enough, it could cause a large change in brightness of the whites. I would have assumed that these commercial screens would not need that much adjustment.
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post #8 of 32 Old 01-31-2009, 09:01 AM
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Are these two screenshots an accurate representation of what you actually see?

The High Power has a gain more than twice that of the Silver Matte (2.8 vs 1.3), yet these screenshots suggest that calibration alone will raise the white levels of the SM to match the HP. This is a physical impossibility, so I can only assume that something else is at work here. Most likely it is the digital camera compensating for overall contrast, but I'm curious what you think.

Garry
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post #9 of 32 Old 01-31-2009, 09:57 AM
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Quote:
Originally Posted by wbassett View Post

I don't believe I said the brightness or contrast was just turned up to result in the difference.

So what caused the difference then? You can't just throw up 2 images and a . Explain if you are so enlightened.

Quote:
Originally Posted by wbassett View Post

I assure you and everyone that there is nothing wrong with the photo's and they are not doctored to demonstrate the dramatic difference a caibration will make.

Are you sure about that? You've either improperly represented the photos or done a bad calibration. The whites are SOOO blown out in the first photo of the HP that there is no way the the comparison can be valid. You can't even read the numbers on top of Lightning. It looks to me as though the first photo was calibrated to the darker screen.

Quote:
Originally Posted by wbassett View Post

That was the entire point of this post... to demonstrate just how much of a difference proper calibration can make between screens.

And what exactly is your version of a proper calibration? Nearly all people in the DIY forum won't go the route of "proper" calibration. Where as Brightness and Contrast will cure about 90% of their woes.



Quote:
Originally Posted by wbassett View Post

I'll tell everyone a secret... well some already know this, but even at some of the brick and mortar stores they will calibrate a set they are promoting and have been guily of taking the other sets out of calibration so the one set they are trying to sell that week looks better!

This is a not secret. It's been know for nearly two years that BB pulls this tactic and they've been called out on it.

I would really like a clarification of those photos...

Rob

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post #10 of 32 Old 01-31-2009, 10:04 AM - Thread Starter
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Quote:
Originally Posted by Highside View Post

If those pictures are "untouched" accurate or not, why are the whites so blown out? (in the first picture)

You guys got me! I posted doctored photos and calibration is a myth!


Seriously though, they weren't altered. The sole reason for using commercial screens was to remove any 'DIY' bias from things and to try to explain and show how much difference calibration can make.

There are many variables when it comes to setting up a Home Theater system, and yes one of them is personal preference. That is the realm where a person is neither right or wrong... if they are happy, that's what matters, but often people don't understand they may have misjudged something. There is no malice in that statement, rather its a matter of a person possibly not knowing or understanding something. Many people do take a projector right out of the box and install it and don't calibrate. Some are happy, some complain that it wasn't what they expected. From my experience both are amazed after a calibration is done. The person that was happy is even happier when the image looks better than before and they thought it looked incredible originally. The person that's initially disappointed is blown away by how much difference the calibration made. I have seen this happen so many times, a person is upset at first, but once they calibrate they are totally amazed and now happy.

The other thing I was pointing out was how difficult it is to compare two distinctly different screens and make a definitive conclusion that one is better than the other. And I'll say it again, even commercial screens are subject to this. Anytime a person changes their screen with something vastly different than what they previously had, a recalibration is in order or the new screen is most likely not going to look its best and subsequently could be misjudged and said to be a horrible screen.

Honestly, in this comparison in real life and in a dedicated theater room I'd say even after seeing the Silver Matte with the projector calibrated to it most people would still pick the HP, but they still would be amazed at how much difference recalibrating made for the Silver Matte. Now change the scenario to a multi-purpose room where there are some light issues. If a person went solely on the first image where the projector is calibrated to the HP, they wouldn't even consider the Silver Matte, but if they saw it after recalibration, and then when lights start coming into play, the Silver Matte would clearly be the better screen for their overall setup, both with some lighting on and with all the lights out. Without a person seeing both screens with a projector calibrated to that screen, they could be misjudging things unintentionally.

Yes it is a good representation of what was seen, but agreed that cameras do come into play too, but I can't stress it enough that I didn't post this to try and 'trick' anyone. The sole message was to calibrate to the screen before making any decisions, and if two very difference screens are trying to be compared side by side, make sure to calibrate to each screen so you can truly see the good and bad of both. To only calibrate to one screen and then say the other is inferior or 'bad' is only seeing half, and that happens a lot.

Prof if you really look, you'll see the white levels still aren't the same, but neither are the black levels. This wasn't a trick, I assure you, there's nothing to be gained by trickery and this isn't even about DIY, it's trying to get people to think about how much calibration really does matter. Calibration really is important when it comes to comparing screens, we just saw it with commercial screens, and the same goes with DIY. That's it, that's all I'm trying to say. To just take some time to recalibrate before making a snap decision, whether it's with a commercial screen or DIY.

Each screen has its pros and cons, and I won't say either screen is the best or worse, however they both excel in certain settings. Again, the sole purpose was to show how much difference calibration can make and how sometimes people make judgements without recalibrating to the other screen and seeing it perform at its best.

If I confused anyone or anyone feels I am being dishonest and trying to mislead people, I sincerely apologize.

"Make everything as simple as possible, but no simpler." - Albert Einstein
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post #11 of 32 Old 01-31-2009, 10:09 AM
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I think you made the point quite well.

Yes, calibration is important...every user should be calibrated.

Need electronics repair? A great place to start looking for a shop in your area: http://www.tvrepairpros.com/
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post #12 of 32 Old 01-31-2009, 12:07 PM
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While I understand the questions regarding the photographs wbassett presented, I don't really want to wade into that debate.

I think the key point wbassett was trying to make is that calibration is essential to realizing the best results from a particular screen type. Most notably when you go from a white screen to a gray screen, it is essential that you calibrate the projector for the new gray surface.

I have heard many people say they don't like gray screens because the whites are gray looking. At one time I might have agreed with that. That was before I tried calibrating my projector (just contrast & brightness in my case) for the screen surface I was using. The resulting difference in perceived white levels was nothing short of amazing.

If anything I often marvel at how white the whites look on my N8 screen. That goes for both the current Black Widow screen and the previous N8 tinted Behr ULTRA 4850 painted screen.

Unfortunately I suspect the effort on wbassett's part, to simply encourage everyone to perform at least a rudimentary calibration when they try a screen surface other than a matte white, will be lost in the debate over the quality or correctness of the photographs he used to try to demonstrate the point.
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post #13 of 32 Old 01-31-2009, 01:10 PM
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The effort will only be lost if readers allow themselves to be distracted as such and attend to these matters rather than what is clearly the point of his post.

Yes, calibration is important...every user should be calibrated.

Need electronics repair? A great place to start looking for a shop in your area: http://www.tvrepairpros.com/
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post #14 of 32 Old 01-31-2009, 04:40 PM
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Quote:
Originally Posted by wbassett View Post

If I confused anyone or anyone feels I am being dishonest and trying to mislead people, I sincerely apologize.

I'm not saying that you are trying to mislead anyone, and I don't mean to be critical of your post. Hey, at least we've got something to discuss. I would agree that the lower gain screen can be adjusted to look just as good, but with both screens in the same photo, the difference in gain should be very apparent.

The higher gain screen should have brighter whites than the lower gain screen at ANY light level. A 10% or 20% white field ( dark gray ) should be brighter on the higher gain screen, just like an 80% or 100% ( white ) should be. Changing the projector calibration will not change that. The higher gain screen will be some percentage brighter than the low gain screen at all light levels.


I just thought of something. The high gain screen is likely very directional. The top of the screen looks darker than it should, but this could be due to the angles involved. Take that same photo again with the camera up high, and I bet it will look a lot different!

Here's an example of what I'm talking about, but side to side instead of up and down. I have seen the same sort of thing vertically as well. With a very high gain screen, I imagine the narrow viewing cone will make this more apparent. I'm convinced this is the reason the whites near the top of the screen on the HP are not as bright as I was saying they should they should appear.



If you take a photo of a 80% white field and compare the brightness variation top to bottom, I think you will see what I'm talking about. There will be more variation on the HP than the other screen. (If you would like, I can take a screenshot that will show the effect. )
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post #15 of 32 Old 01-31-2009, 04:54 PM
 
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Being mainly a lurker here and at your other home, I've seen those pictures before! And your point is well taken and sound. I think what folks here are lost on is the fact that one material is retro-reflective and the other being angular reflective.

This may be better served in the calibration forum or the regular screen forum than here in diy.
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post #16 of 32 Old 01-31-2009, 05:05 PM
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Quote:
Originally Posted by jib-jab View Post

Being mainly a lurker here and at your other home, I've seen those pictures before! And your point is well taken and sound. I think what folks here are lost on is the fact that one material is retro-reflective and the other being angular reflective.

This may be better served in the calibration forum or the regular screen forum than here in diy.

I agree that the issues introduced by the retro-reflective High Power material are probably at the core of the concerns regarding the photos. I think the effort to avoid controversy by using some DIY screens has actually lead to controversy. I suspect if simple flat white and matte gray OTS screen paint panels had been used the demonstration photos may have been more effective.

While this topic is no doubt relevant to the Calibration forum it has particular relevance here in the DIY Screen forum too. The quest of gray or white is central to most people exploring the possibilities of a painted DIY screen. To properly evaluate the performance of a gray screen it is essential to calibrate the projector's contrast & brightness for the gray screen surface. So I personally think this was a n excellent place to start a thread who's intent was to encourage people to calibrate their projectors when they try a new screen. Otherwise any evaluation of that screen is not valid.

It is unfortunate that this basic message may have been lost in the fray over the choice of demonstration materials and the exposure of the photographs.
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post #17 of 32 Old 01-31-2009, 05:15 PM
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Quote:
Originally Posted by tiddler View Post

I agree that the issues introduced by the retro-reflective High Power material are probably at the core of the concerns regarding the photos. I think the effort to avoid controversy by using some DIY screens has actually lead to controversy. I suspect if simple flat white and matte gray OTS screen paint panels had been used the demonstration photos may have been more effective.

While this topic is no doubt relevant to the Calibration forum it has particular relevance here in the DIY Screen forum too. The quest of gray or white is central to most people exploring the possibilities of a painted DIY screen. To properly evaluate the performance of a gray screen it is essential to calibrate the projector's contrast & brightness for the gray screen surface. So I personally think this was a n excellent place to start a thread who's intent was to encourage people to calibrate their projectors when they try a new screen. Otherwise any evaluation of that screen is not valid.

It is unfortunate that this basic message may have been lost in the fray over the choice of demonstration materials and the exposure of the photographs.


If it makes people think, it's a good thing! If we all agreed about everything, this would be a very dull place.
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post #18 of 32 Old 01-31-2009, 06:11 PM
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Quote:
Originally Posted by wbassett View Post

You guys got me! I posted doctored photos and calibration is a myth!

I never said your photos were doctored. What I said id that if your photos are untouched and (reasonably) accurate in what we see on the monitor, then you have improperly calibrated or improperly represented the HP material.

Ask anyone over in the Calibration forum to comment on your first photo. They will parallel what I just stated. I have been using calibration software for over 2 years now and I may not know all the specifics and math behind the logic, but I do know that based on that first picture on my monitor, the projector IS NOT calibrated to the HP screen. If it was then you should have re-exposed the photo to represent what we SHOULD BE seeing. My monitor is calibrated too.

Based on the basic logic that the gamut of adjustments will go up when recalibrating to a gray screen, the second photo should have been even brighter that the first picture and looked even worse.

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post #19 of 32 Old 01-31-2009, 06:46 PM
 
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While I cannot speak for wbassett, I do know for a fact that those are not his pictures. And I also know that when one performs a calibration, one performs the calibration with respect to the material you're calibrating - ie the HP is calibrated retro-reflective and the other angular reflective. The high gain of the HP disappears when one uses it angular reflective. While the other material, which also has a positive gain, seems to 'shine' angular reflective.

As for what appears to be blooming of the whites in the first image, it is more than likely camera error and really has no relevance whatsoever to the discussion wbassett is trying to encourage. lcaillo caught on right away and I tried to help a bit but I guess I was a bit obtuse. I apologize for that. The images have very little to do with the post/thread.

And I again think this may be better served elsewhere. That has become readily apparent.
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post #20 of 32 Old 01-31-2009, 07:11 PM
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For those who may have been interested in what wbassett had to say about gamma:

Quote:
Originally Posted by wbassett View Post

Gamma affects middle tones; it has no effect on black or white. If gamma is set too high, middle tones appear too dark. Conversely, if it's set too low, middle tones appear too light.

Depending on the device, the gamma may have a significant effect on the way colors are perceived too.

Gamma is the control of gray scale light values.

This can be very confusing I know. Think of midtones though, or shadow detail. Gamma correction has a big influence over them and that can have a dramatic impact on the overall brightness and contrast as well as how we perceive it. Gamma also controls color midtones too.

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post #21 of 32 Old 02-06-2009, 11:31 AM
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Unless the second picture is a double exposure, this is an impossibility. Prof55 is right on the mark here.

There is NOTHING you can do to the projector that will change the physical limitations of a screen. The High Power will always be twice as bright as the 1.3 gain screen.

Maybe the title of this thread should be modified....substituting "least" for "most"
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post #22 of 32 Old 02-07-2009, 12:01 AM - Thread Starter
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I'm not quite sure I would be so absolute as to say "NOTHING".

Calibration will make a huge difference as well as proper room setting and projector setup.

Although I respect your opinion, I personally never deal with absolutes or statements that leave no room for alternatives. I do believe I never said the HP was a bad screen, and in fact even said most would probably still opt for it in certain situations, but the fact is proper calibration and setup will make a world of difference.

I think the message was lost here. This wasn't a debate over which screen is better. Both are very good screens when used in the right setting. The point is and was that a person can easily misjudge a screen because they did not see it with the projector recalibrated and setup to that screen. Many people are misled this way, and no I am not saying intentionally misled, but sometimes that does happen.

I will stick to my guns and say it is impossible to compare two very different screens at the same time and gleen anything other than they are different. In fact I'll say neither screen really can look or perform its best because it is virtually impossible to calibrate to two screens at once. If you try that then both screens are not showing their best performance. The only way is to calibrate and setup to each screen seperately and then try to compare them. Still even at that I maintain it is impossible to compare screens this way.

The point was that people may not always recalibrate or adjust their setups so they could possibly throw out a screen option when in reality it just might be the screen they are looking for.

If the current debate is that calibration and setup does not make a difference, then I totally disagree with that as will any professional out there that does installations and professional calibrations.

With that I'll stand my ground and I still say this is a very important topic that many people either over look or don't fully understand... and yes I stand by the title of the thread as well. Calibration and setup is probably the most singularly important item a person can do that makes a dramatic difference.

And again I will restate as well as put my reputation on the line an say those photos were not altered or doctored in any way.

"Make everything as simple as possible, but no simpler." - Albert Einstein
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post #23 of 32 Old 02-07-2009, 06:26 AM
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Originally Posted by wbassett View Post

I'm not quite sure I would be so absolute as to say "NOTHING".

Calibration will make a huge difference as well as proper room setting and projector setup.

Although I respect your opinion, I personally never deal with absolutes or statements that leave no room for alternatives. I do believe I never said the HP was a bad screen, and in fact even said most would probably still opt for it in certain situations, but the fact is proper calibration and setup will make a world of difference.

I think the message was lost here. This wasn't a debate over which screen is better. Both are very good screens when used in the right setting. The point is and was that a person can easily misjudge a screen because they did not see it with the projector recalibrated and setup to that screen. Many people are misled this way, and no I am not saying intentionally misled, but sometimes that does happen.

I will stick to my guns and say it is impossible to compare two very different screens at the same time and gleen anything other than they are different. In fact I'll say neither screen really can look or perform its best because it is virtually impossible to calibrate to two screens at once. If you try that then both screens are not showing their best performance. The only way is to calibrate and setup to each screen seperately and then try to compare them. Still even at that I maintain it is impossible to compare screens this way.

The point was that people may not always recalibrate or adjust their setups so they could possibly throw out a screen option when in reality it just might be the screen they are looking for.

If the current debate is that calibration and setup does not make a difference, then I totally disagree with that as will any professional out there that does installations and professional calibrations.

With that I'll stand my ground and I still say this is a very important topic that many people either over look or don't fully understand... and yes I stand by the title of the thread as well. Calibration and setup is probably the most singularly important item a person can do that makes a dramatic difference.

And again I will restate as well as put my reputation on the line an say those photos were not altered or doctored in any way.

The photos are very misleading, and reportedly, were not taken by you.

Maybe you could start a new thread, and post some new pictures where you have complete knowledge and control of all variables, and then we can see how critical the calibration is, or is not. Discussing your first set here is a waste of time.
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post #24 of 32 Old 02-07-2009, 06:51 AM
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I think a better explanation of the pictures is in order here (projector/camera angles, etc), as well as a description of what specific parameters were changed in the calibrations. I'm sure this would go a long way towards clearing up the confusion.

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post #25 of 32 Old 02-07-2009, 07:25 AM
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kbgl : "Did you have to correct for a HUGE color push between the two screens? That's the only thing I can think of that would cause this to happen. If you reduced one of the gains enough, it could cause a large change in brightness of the whites. I would have assumed that these commercial screens would not need that much adjustment"

From what I have read I would not assume commercial screens do not have a big color push. There was a post I read on AVS or AVForum that had a spread sheet with commercial screen rgb values. I remember being suprised at the figures. Just had a search and can not find the post now, if anyone who read it also remembers where it was please post a link.

Also I believe digital cameras are incaplable of taking a picture showing the whole dynamic range of a projector. You either make black level look better than in real life and lose shadow detail, or crushing whites. The camera white balance will also adjust the colors of the image. I assume the camera exposure was set so white level was not crushed. This means black level was exagerated. Since max white level in the photo is dictated by the camera, could the brighter but off white projector image appear darker in the photo due to being off white?
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post #26 of 32 Old 02-07-2009, 10:54 AM
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It really is a shame that everyone seems to have gotten hung up on the photos. I agree they may not have been the best demonstration of wbassett's point that calibration can make a huge difference. I also think that whoever did take the photos had good intentions when they tried to compare High Power to Silver Matte.

So can we not agree to disregard the unfortunate use of these particular photographs and get back to the spirit of this thread.

To that end I would like to point out that the current project I am working on is the construction of a white / gray reversible, tab-tension, roll-able DIY screen. It will be approximately a month before it is constructed, painted, and fully cured. At that time I will be calibrating my HD72 to work with the white side with all lights off and the gray side with some ambient light present.

The point is that I will have an opportunity to photograph these two sides, white & gray, with and without proper calibration. I'm not sure what those photographs will capture or reveal but I am willing to try.

In the meantime maybe wbassett should remove the current photos in the opening post along with any reference to them. Naturally everyone else should remove their posts dealing with the photographs since those posts and comments are to some degree off topic.

There is an extremely important point being lost here. One that I did not really take seriously until I tried calibrating my own projector. I really don't think anyone who has posted to this thread really means to make it sound like calibrating is not important but that is the subliminal message that is coming through. By casting doubt on the quality of the photos in the opening post you are also casting doubt on the benefits of calibrating the projector. I ask you all, is that really your intention?

In all the experimenting I have done, and that includes comparing many similar shades of gray and many grays to whites etc, the most improvement I ever saw was the difference between the image produced by my HD72 on an N8 flat gray with the projector still using factory settings, and the image produced on the same flat N8 gray after I did a contrast & brightness calibration using the THX Optimiser and then tried the 4 different presets for gamma.

So to anyone reading this thread, please don't let the rhetoric regarding the demonstration photos convinced you that calibration is overrated. Especially if you have chosen to try a gray screen with some ambient light present. Don't allow yourself to become one of the unfortunate people that think gray screens produce gray looking whites and crushed black levels. They don't but a bad calibration does.
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post #27 of 32 Old 02-08-2009, 06:24 AM
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Quote:
Originally Posted by tiddler View Post


There is an extremely important point being lost here. One that I did not really take seriously until I tried calibrating my own projector. I really don't think anyone who has posted to this thread really means to make it sound like calibrating is not important but that is the subliminal message that is coming through. By casting doubt on the quality of the photos in the opening post you are also casting doubt on the benefits of calibrating the projector. I ask you all, is that really your intention?

Try this Tiddler, and tell us your results. (Anyone else for that matter.)

Last night, I calibrated using Avias white and black bars on my current screen to adjust contrast and brightness. (This is the one with the two bars that stay in motion side to side while you make adjustments.) I then hung a much darker gray screen test panel over my screen to see how much the settings would need to be changed.

No change was required!

None, nada, zip. The "correct" setting was the same!

(Note. It's my understanding that this test pattern is used to determine the maximum contrast without clipping the whites. It is considered permissible to reduce contrast from this maximum level to suit personal preference. I think the same can be said for the brightness setting, and crushing the blacks.)

It is my feeling, and I know you all will disagree, that calibration is for the projector. (At least in a room with dark walls like mine.) There is the possibility that screen generated ambient light could affect the brightness setting by a little. Reducing contrast for personal preference could change the amount of screen generated ambient light, much like using a gray screen can. This could explain the result of my experiment, because the bright white portion of the test pattern was not muted by a darker gray. The results could be diffrerent if the test panel had actually been a full screen. I think in my room that it wouldn't matter since the walls are so dark.

OK.. Flame suit is on!
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post #28 of 32 Old 02-08-2009, 07:41 AM
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To do a proper contrast & brightness calibration there are usually two different images. One will have some very dark areas that you will adjust the brightness until they disappear. The other image is usually a group of white blocks. You adjust the contrast until all the blocks blend together. Then you reduce the contrast until all the white blocks are clearly distinguishable. If you have done a good job of it and the selected gamma is a good match then you should be able to see all the steps in a gray scale image.

When I was putting together comparison slides and test images I made one image that combines all three calibration elements into one image.



This sort of adjustment utility is available in the THX Optimizer found of some DVDs like Terminator II, Cars, and Finding Nemo.
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post #29 of 32 Old 02-08-2009, 08:41 AM
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Originally Posted by tiddler View Post

To do a proper contrast & brightness calibration there are usually two different images. One will have some very dark areas that you will adjust the brightness until they disappear. The other image is usually a group of white blocks. You adjust the contrast until all the blocks blend together. Then you reduce the contrast until all the white blocks are clearly distinguishable. If you have done a good job of it and the selected gamma is a good match then you should be able to see all the steps in a gray scale image.

When I was putting together comparison slides and test images I made one image that combines all three calibration elements into one image.



This sort of adjustment utility is available in the THX Optimizer found of some DVDs like Terminator II, Cars, and Finding Nemo.

So hang some test panels in front of that image and tell me I'm wrong!
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post #30 of 32 Old 02-08-2009, 09:20 AM
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So hang some test panels in front of that image and tell me I'm wrong!

I am currently building a white / gray reversible screen. When it is done I will try to do some experimenting with calibration. That will be a month from now though.
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