CurtPalme.com Home Theater Forum

[Moose]

It is my understanding that the gamma correction included in products by Moome and Beun and whoever else only offer correction on part of the curve. Why is this? Is it difficult to apply gamma correction over the entire curve? Is there any real advantage to doing so? Do scalers that offer gamma correction operate over the entire curve or are they limited only to part of it also?

[Ile]

[ecrabb]

The Moome and Beun gamma functions control only low-IRE values by design - because that's where CRTs have the least linear response. Because of CRT's low-IRE non-linear response, low IRE's (shadows) are where greyscale tracking goes to hell. As a side benefit of focusing only on the low-end, it allows us to lower G2 enough reduce black to a true black level, while using the gamma correct to boost above-black levels to the appropriate level. Without gamma correction, all low-level black shades would be "crushed" together - as in all the same level - black.

Several of the high-end scalers do allow full gamma control over the full 0-100 IRE.

SC

[perisoft]

If you use an HTPC running, say, Zoomplayer, or other software which supports ffdshow, you get full per-channel level control, so instead of just a gamma setting, you can graphically boost/cut bits of the curve - rather like the difference between a volume knob (regular gamma) a bass knob (low end gamma) and a 12-band EQ (ffdshow).

Horrible pain to set up, but the control is great.

[Moose]

[perisoft]

I don't think I'm experienced enough at this to offer a really reliable answer, but I know that in my case - where I'm working with a PJ that has some serious problems due to a toasty blue tube - it gives me the flexibility to go from a godawful image to a pretty damned good one. There's absolutely no way the PJ would throw a remotely acceptable image without a lot of software tweaks.

That said, I have a reasonable amount of experience with photoshop, image processing, and photography, so the groundwork I've already done is a huge help. Starting from zero a priori knowledge in a related field, and being uncomfortable with PCs and software setup, I tend to think it would only be worthwhile if you want to eke the last bit of performance out or if you have a projector with some nasty flaws you need to correct.

With a good PJ, little experience, and some cash to get off the rack solutions, you'll probably find that the best option.

But, like I said, I don't really know my ass from my elbow in this business yet, so take what I say with a grain of salt.