Still, IMHO gamma correction shouldn't be about the look, but the -weight-. I mean, the goal behind proper gamma correction is that black text on white has the same weight as white text on black. I don't know how your monitors are calibrated, but on the ones I have here, this (1.4) looks like more or less equal weighting https://docs.google.com/file/d/0B6Cr7wjQ2EPudk1uV01NWjRjc2c/edit?usp=sharing while this (2.2) doesn't at all https://docs.google.com/file/d/0B6Cr7wjQ2EPuZWpMYWl4T2ZobzQ/edit?usp=sharing It could be that all of my monitors have a 1.4 gamma, but really, I never saw it looking wrong on any monitor, & there must be a reason Windows defaults to 1.4. I strongly suspect that the 2.2 standard gamma is either a myth or an old truth that doesn't apply anymore.
As for color fringing, reducing it is the role of the filter, and this one only goes horizontally, I don't think that color fringing should be a factor when picking gamma correction.If there's too much color fringing, you can still enlarge the blur filter, it's always a tradeoff between sharpness & color fringing. On Thu, Nov 7, 2013 at 7:02 PM, Dave Arnold <darn...@adobe.com> wrote: > You are correct that gamma 2.2 is a better approximation to sRGB. I agree > with using that gamma for large area regions. But there are two reasons why > I prefer gamma 1.8 for text. > > The first is something I call "effective gamma". We first encountered this > back in the era of CRT displays. Unlike image data, text is mostly edges. > The area covered by stems is on the order of a pixel wide. If you look at > text as a video signal, it is very high frequency—often close to the limit > of the display device. Rather than seeing a vertical stem as a perfect > square wave, the video electronics tend to round it off and reduce its > amplitude slightly. Both of these effects move the active signal closer to > the middle of the gamma curve, where the curve is flatter. This has the > effect of reducing the gamma at high frequencies. Everything in the signal > path contributes to this. Even video cables could make a significant > difference in the appearance of text. I know less about the electronics in > an LCD but, empirically, the effect seems to still be present. > > The second reason is that not all text rendering systems are able to > provide the stem darkening technology to compensate for the loss of > contrast at small sizes. This is particularly challenging, given the way > that TrueType hints work. For example, both Windows XP and Android chose > gamma 1.4 as a default for text blending. It's not as accurate as a higher > gamma, but it doesn't lose as much contrast as gamma 2.2. So, designing for > gamma 1.8 rather than 2.2 will work better if the system gamma turns out to > be 1.4. > > Both of these arguments pertain mostly to grayscale antialiasing. For > subpixel rendering, I agree that you will see more color fringing at 1.4. > Some people are more sensitive to this than others. I know several people > who never could get used to ClearType on Windows XP. > > -Dave > > > On 11/6/2013 11:47 AM, Antti Lankila wrote: > >> Dave Arnold <darn...@adobe.com> kirjoitti 6.11.2013 kello 20.43: >> >> Hi Antti, >>> I've attached an image comparing darkened gamma 1.8 to darkened gamma >>> 2.2. The differences between 1.8 and 2.2 are much more subtle than those >>> between 1.0 and 1.8. >>> >> Yeah, there’s admittedly not much difference. I was just curious because >> in theory gamma 2.2 is more correct when it comes to approximating the >> behavior of the sRGB color space. If the rendering was based on subpixels, >> there might be perceptibly more color fringing at small sizes. >> >> — >> Antti >> > > > _______________________________________________ > Freetype-devel mailing list > Freetype-devel@nongnu.org > https://lists.nongnu.org/mailman/listinfo/freetype-devel >
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