CompuServe Messages

Just for general info YIQ is the composite variation of YUV, SVHS etc. They are all encoding schemes for getting hue sarturation and luminance recorded or output. Although composite really isn't encoded per se. like YUV and SVHS where the signals are split which helps improve the output. This formula route has forced me to dig into how its affecting the image and looking back over some of the previous threads on this subject, there's a lot of inconsitency in what its actually doing. And I think I've uncovered the reason though it was rather evident to begin with. "The answer is stareing you in the face… great but what's the question?". <g> That's how it felt once I realised why there were all this contradictions. What makes it difficult to give an accurate depiction of what's going on is the NTSC color weighting system, and that being an analog signal, the effect gamma has is "cascading" as I mentioned previously. Looking at a Waveform and Vectoscope can be misleading because you can't identify the individual pixels readily. So while it may look like its desaturating the colors and the luminance is not raising above a certain point, the net effect may be quite different altogether. Which in many cases if not most it is. So sorry for the confusion on this point. Its odd that you can be looking at something and see the opposite of what you should be seeing, especially when it is counter-intuitive but there it is. In terms of 3DS the effect of gamma on the image is uniform in a logrithmic sense. Which makes sense. I started realising all this when I re-considered how I've used the formula which is after the fact. After an image has been rendered it is an easy matter to pick a pixel and run it through the formula and its dead on accurate. I think I eluded to that before but it was thinking about pre-calculating a pixel's value with gamma that confused the issue. Trying to devise a system to pre-calculate the value of a pixel or a particular color in a scene is more challenging. I don't have the exact formula that's being used, and but I'll ask if I can get it. FWIW I use QFX which has a densimometer and will give you a reading for any pixel you select. So its easy to render the image and check it against the formula. If I can nail it down I'll proceed with some kind of program to calculate it, if not, the formula does work if you use it against a rendered image which has already had gamma applied. Sorry about that but it will provide you with an accurate solution should you choose to use it. You don't really need to know what YIQ are just plug the numbers in, Y is typically luminance, I and Q are the color weighting for NTSC. Then you just compare it with the minimum and maximum allowed tolerance. Its a bit of pain but it does provide you with a totally accurate way of checking without a WFM/VS setup. P.S. I like the book idea, once I get this nailed down I'll consider persueing it. This gamma thing has been elusive and while haveing a handle on it is one thing, being able to relate how it applies in a video sense can get really messy.