{ "numMessagesInTopic": 5, "nextInTime": 351, "senderId": "1AuGcpnYDQPgUO87u7zHUNpCMCZhVM4qkb5xjtUnKtKcmyoTPwf6c6JdpePHlIBCnaMPtAeksR-AyKfX7Cuhb8qKFUU4Uuf_napG", "systemMessage": false, "subject": "Re: Colour correction query", "from": ""yeangchng" <yeang_chng@...>", "authorName": "yeangchng", "msgSnippet": "Fluppeteer, This is one of the cases that you might want to do an archive search. I asked a similar question a while back, and Steve (from IBM) kindly provided", "msgId": 350, "profile": "yeangchng", "topicId": 348, "spamInfo": { "reason": "0", "isSpam": false }, "replyTo": "LIST", "userId": 39184597, "messageBody": "
--- In IBM_T2X_LCD@yahoogroups.com, "fluppeteer" <yahoo@f...> wrote:
\n> Excuse me if this is obvious/has been covered before...
\n>
\n> I was just chatting to a friend about colour calibration, and
\n> recalled that the T221 has some internal facility for this. Out of
\n> interest, since this kind of thing has always confused me a bit,
\ncan
\n> anyone tell me whether the *output* of this internal colour
\nmapping
\n> is just 8-bit, or whether it tweaks the TFT response/does
\nsomething
\n> else internal at greater precision?
\n>
\n> I'm just wondering how/where best to do the colour conversion
\n(other
\n> than in floating point, with the original image, of course). With
\na
\n> non-linear calibration, I could see that the monitor could either
\n> map back to the same 256 colours per channel, or tweak things so
\n> that the 256 colours are all still distinct (or mapped to more
\nthan
\n> 256 level accuracy).
\n>
\n> If, for example, I'm running a 10-bit (A2R10G10B10) desktop, I can
\n> tweak the colour curves in a graphics driver before the DVI output
\n> happens, giving me colour correction, 256 colours per channel
\n> (assuming the correction isn't too extreme), but with an uneven
\n> spacing between levels according to the monitor's response. If I
\n> drive an uncorrected linear image at the monitor, then if it
\n> internally maps to the same 256 colour levels the situation will
\nbe
\n> even worse (<256 distinct colour levels), whereas if the response
\nis
\n> analogue (or at least, has >256 possible values) then all the
\nlevels
\n> can be represented, and more evenly spaced.
\n>
\n> Simply put: the T221 can display 16777216 distinct colours. If you
\n> turn on the colour correction (and make it non-1:1), does it
\n*still*
\n> display 16777216 *different* colours, or does it display a subset
\nof
\n> them?
\n>
\n> [As an aside, I've been having half a look into driving dual
\nT221s,
\n> and it occurred to me that if both are turned through 90 degrees,
\n> you get a 5:4 aspect ratio as used by a number of old UK
\ncomputers;
\n> hence such a set up can display BBC Micro "mode 1" (320x256) with
\n15
\n> pixels per input pixel in each direction. I love the maths of
\nthese
\n> things. :-) ]
\n>
\n> --
\n> Fluppeteer