tv picture question [Archive] - Audio & Video Forums


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01-19-2007, 11:35 AM
Haven't been around for a long time, haven't been getting anything new for a while.

Anyway, I've had a toshiba RPTV for a year and a half or so, and have set up the picture with AVIA, but I'm having a problem with the picture. I also had to turn down the red shift a little because otherwise, the edges of the screen would glow red on very dark scenes. The picture is very good now except for one problem. WHen I'm watching movies or tv shows that are dark, it seems like the tv doesn't do dark colors. It goes from light to black, with not enough in between. I've messed around with the settings a little, but can't seem to fix the problem. I can make it brighter, but then the brights are too bright, and it doesn't really help the issue of missing the dark colors. Anybody have any advise? What settings in the picture menue should I be adjusting to improve this?

01-19-2007, 12:34 PM
Gamma is the function that controls the rate at which the grayscale goes from dark to bright. It is available in the user menu of relatively few TVs--for good reason; you need the proper instruments to work with it. Sometimes a TV (or DVD player) will have a gamma control that is labeled with a few general options for users to try. I doubt that yours is one of them. A trip to the service menu is typically unavoidable. However, it's hard to tell from what you say whether gamma correction would do the trick. The red along the edges may be a relic of the color decoder, the infamous "red push"--a deliberate strategy by manufacturers either to create a vivid impression or to balance a blue push (intended to enhance brightness) that would otherwise make skin tones wildly inaccurate. Correction requires service-menu codes, but should not be undertaken carelessly. Messing with the service color controls can screw things up royally. Alternatively, if you have a CRT, the convergence may be skewed.

01-19-2007, 01:41 PM
thanks for the input. Well, I have been into the service menu before, and when I did that last time, and I did all the research and all that stuff. That's how I had to corrected the red. I sort of remember having the same problem before going into the menu, but the red shift was my main concern at the time so maybe I need to move the red back? Is it possible that I am stuck with one or the other set up correctly? I may have to look into the gamma as well. Is there any thing that might help without having to go into the service menu?

01-19-2007, 02:32 PM
From what you said, gamma seems to be the problem. Excessively high brightness and contrast can totally eliminate the dark end of the scale, but they can't create a gap between a deep black and bright white. But I don't understand how gamma could have gone awry so quickly, or did it? It's unlikely that the red decoding per se is related to gamma in the service menu, but who knows what happened? Did you touch another setting? Do you have Toshiba's service manual, or did you get your settings from the web? You might want to see how the gamma is coded and what the default values are. With many TVs, you have to choose which of two values are more important, since they may diverge with certain other settings--say, black level or grayscale accuracy being affected by the intensity of the backlighting in an LCD. It gets to be a slippery slope when you start changing parameters on the instigation of web forums without knowing exactly what you're doing.

01-19-2007, 02:59 PM
To start with, it's a CRT RPTV, sorry, should have mentioned it in the beginning. When I changed the value of the red shift, I just turned it down a few from where it was. I guess I could figure out what the gamma is and try moving that a few notches in either direction and see what happens. Will it just be one setting in the menu, or will there be multiple things to adjust, because that might just be more that I bargined for.

01-19-2007, 06:43 PM
Different gamma values might be 2.0, 2.2, 2.6, etc. I don't know how Toshiba codes them. If you can recognize a setting with a number like these that you can change, you might try 2.2. But don't proceed until you get a sense of what to expect in the service menu from the forum that you used for the red push. If you're at 2.2, or something fairly similar, something else may be wrong with your set, since 2.2 should give you a fairly smooth gradation, not an abrupt break.