CurtPalme.com Home Theater Forum

skippyar · Joined: 22 May 2009 Posts: 108 Location: Bristol, UK

Now satisfied my CRT's colours are as best balanced by eye that I can achieve using test cards and my LCD TV for comparsion (I know I shouldn't) my final question...

Accepting CRTs / LCDs are two completely different technologies and *NOT* intending to fashion my CRT on an "LCD image", imagine if you will an display consisting horizontally of 1/3 sky, 1/3 sea and 1/3 greenland.

Obviously my LCD TV has the capabilities to display this image with exceptional clarity with each pixel's colour defined respectively.

On my CRT I can obviously differentiate every colour element of the same image, however, as the sky and the sea make up 2/3s blue of the image this causes the entire image to 'lead blue', so the greenland appears to have a blue tint**.

I used to think this was a Drive fault of the Gun, but then imagine a display consisting horizontally of 2/3 red brick building 1/3 grey road with a black car parked and in this scenario the 'red leads' and it can be seen in the black of the car and the grey of the road.

So now it would appear both Blue and Red are leading but obviously can't be. (But as the above mentions the more dominating presence of a colour tints the entire image).

From memory if I recall correctly it is perfectly normal and acceptable of Red or Blue to tint/lead on a CRT and also a CRT's whites are conditioned by preset colour temperature settings; 5200K, 5600k, 9300K...

With respect of each device to their own:

My CRT whites and colours are characterised by a more daylight 5200K*, if I attempt to control the bias/cut off of my CRT's RGB to suppress/attenuate red or blue to balance and compensate for a more "brilliant" White Balance it simply doesn't work. Its almost as though regardless of the RGB individual parameters the entire scaling collectively is within a "bracketed" spectrum. IE: "You can't have that particular black or that particular white"

(I'm assuming this is due to the limitations then of the CRT's greyscale.) If I remember rightly my black (really a dark grey) is dictated by the "blackness" of the tube phosphur.

*Is this because I am going against the probable factory defaults of 5200k trying to make the CRT doing something its not intended to do (and I don't mean looking like an "LCD image"; or

Should I be looking elsewhere, perhaps are the Red / Blue Drive Control? I ask this before venturing into making any further adjustments that are otherwise pointless.

I think where I'm perhaps confusing myself is 1) comparing against an LCD in the first place and 2) I'm sure my LCD tv is auto balancing whites /colours anyway as ALL video signals via CRT are fashioned by 5200k as expected but ALL the same video signals via LCD vary (independant of) (IE: TV channels)

NB: The above is scrutinising extreme purity of an otherwise perfectly acceptable viewing image on my CRT.
** My tint control doesn't do nothing, never has done?!

Yes there is 15 years age gap of technology and component wear between devices, however, I still believe a better image could be achieved.

This question really pertains to the dominance of a colour presence affecting the overall image.

Cheers!

Q: What do you get when you cross an elephant and a rhino?
A: Eleph-ino

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

Generally, the bias/cutoff adjustments are for black and the darkest grays. Do this first. Use the drive adjsutments for color balancing.

Scott

skippyar · Joined: 22 May 2009 Posts: 108 Location: Bristol, UK

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

I know nothing about Barcos so I can't help you there. But there is *clearly* something very wrong with your setup.

When you say "red 'leads' into the car" &etc -- do you mean the red streaks left-to-right from the brick area into the car area? If so, that sounds like what is usually called "bleeding." In other projectors I'm familiar with, it is usually caused by overdriving the video circuitry, either by feeding the projector a signal that is "too hot" (peak-to-peak voltage is too large) or possibly by cranking the drive too high.

Your "blue leading" sounds like something different. When you have blue in the top 2/3 of the image, the entire image gets a blue tint!? I've never seen that behavior.

BTW 5200K is the wrong color temp if you want your colors to look correct. Video signals are calibrated against a standard of 6500K. The signal assumes your "white" is 6500K, and it offsets all other colors from that central standard. By setting it to 5200K you shift your "white" towards red, which means all other colors shift towards red as well. However it sounds like you're eyeballing this whole setup, so I suspect you've just chosen a 5200K setting in your projector and have tweaked from there? If so there is no way of knowing what your white balance really is. The 5200K setting is just a preset and it is not guaranteed to be precisely 5200K -- especially after you have tweaked with the color controls. You really need a colorimeter of some type if you expect to get the colors right.

Finally, your "black is really dark gray" comment indicates your brightness / bias / cutoff is set too high. Usually projectors have a "brightness" setting on the remote, and a "bias" or "cutoff" setting in the internal adjustments. Both do roughly the same thing. The important thing to understand is that the "brightness" control is very badly named! "Brightness" controls how DARK your image can get, and "Contrast" controls how BRIGHT it can get. So use the Brightness or Bias to get a full-black screen to look black, then use Contrast to control how bright a full-white image gets.

And go read Kal's superlative calibration guide to understand all this stuff MUCH better!

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

skippyar · Joined: 22 May 2009 Posts: 108 Location: Bristol, UK

skippyar · Joined: 22 May 2009 Posts: 108 Location: Bristol, UK

skippyar · Joined: 22 May 2009 Posts: 108 Location: Bristol, UK

Apologisies for seeming to be asking technical colour temperature questions without having the correct equipment too. I know it sounds stupid not having the tools for the job; what do I expect!! Rolling Eyes

I might try and take a photo when the lounge is dark enough to demostrate an example of the red/blue presence.

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

jcmccorm · Joined: 15 Jan 2008 Posts: 21

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Yes. Those tinted blacks are a clear indication of calibration error. Read Kal's guide and you will understand the issues much better. You should set the Brightness to a proper black level (so black screens LOOK black), then adjust the bias/cutoff at about 30IRE to get the color temp right at low levels (while alternating with adjusting the Drive at 70-80 IRE to get the color temp right at high levels), then re-tweak the Brightness.

(Now why changing the Brightness changes the hue, I'm not sure. Unless that's a characteristic of Barcos, which I doubt, it sounds like something faulty in the circuitry. Changing the Brightness shouldn't cause dramatic visible shifts in hue.)

Dave is absolutely right (of course!! Laughing

) that CRTs can't display a full-white screen with the same color/intensity as a full-white window. It just takes too much current. Outside of Ice Age, though, full-white images are fairly rare so it's not generally a big problem.

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Yes, and tell me, how often do you watch Happy Feet? Nevermind, maybe your daughter loves it. Smile

Outside of the Ice Age franchise most people aren't likely to watch many all-white scenes, at least more than once.

skippyar · Joined: 22 May 2009 Posts: 108 Location: Bristol, UK

All absolutely excellent and valued advice gents. Thanks for the understanding too.

When I purchased this Barco in favour of a DLP I knowing didn't have the technical knowledge of financial backing for such a specialised field. (probably why it always feels like I'm tip toeing through a minefield worried that one wrong adjust could kill everything.)

I figured I'd give it a home and try my best to apply my readings of Eugene Trundles - "Newnes Guide To TV & Video Technology" 1988 and "Television & Video Engineer's Pocket Book" 1987.

Seen here: http://www.flickr.com/photos/skippyxp/3887700764/

As it would appear the relationship between my Cutoff/bias and brightness adjustments are not harmonised correctly thus becoming visably apparent in conflict at low/high ends of the brightness scales.

I am incline then to suggest that perhaps this is also why red/blue exhibits more presence in certain senarios of intensity.

Basically to concluded, unless I invest in professional equipment it'll never be 100%.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Remember that the "professional equipment" can be as little as £100 or less. E.g. Spyder 2's sell on eBay for $50 or less. Spyder2's are not at all ideal but they're better than eyeballing it. Several Eye-One Display 2's have sold for $150 recently -- should be under £100 shipped. A Display LT sold for $95 with free shipping.

Combine that colorimeter with the free Colorimetre HCFR software and you've got a great calibration tool. Not professional-grade, but certainly good enough for your needs. And you could use it on your LCD TV too -- it's unlikely it has the right color balance either, though its failings are probably not as noticeable as the Barco's.

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

skippyar · Joined: 22 May 2009 Posts: 108 Location: Bristol, UK

Ok folks here are a couple of photos to try and help explain this query I have.

http://www.flickr.com/photos/skippyxp/

Simple click on each image to enlarge, thanks!

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

I assume the left screen is the Barco's projection, and the right screen is the LCD. What is the small screen in the middle?? You talk about it being flooded with green, and showing the "green leading" you mentioned, but that's not your projector! What IS it?

In any event, the Barco looks bloody awful. But you didn't need me to tell you that. Smile

You might check with some of the Brits on the board -- or better, on one of the UK HT forums -- to see if there's a CRT enthusiast near you who can help out. It's mighty difficult to diagnose this issue remotely.

skippyar · Joined: 22 May 2009 Posts: 108 Location: Bristol, UK

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

OK. On several of those pictures, you point out the "green leading" problem in the little TV. That indicates the "green leading" is NOT a problem with your Barco at all, but is somehow present in the signal you're feeding to the TV -- and possibly to one or both of the other displays. I don't know what the signal source is, nor how you're splitting it to the three displays, nor why the LCD doesn't show the green. But the fact that a second display (the TV) shows these color problems indicates that you have problems outside the Barco. You need to get your signal source straightened out and make sure you're delivering a good signal to the Barco before you can attempt to get the Barco to display it properly!