-> Red color and JPG???
in [Digital Cameras]
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From: Martin Brown on 29 Mar 2010 03:47 Robert Coe wrote: > On 26 Mar 2010 09:58:24 GMT, Chris Malcolm <cam(a)holyrood.ed.ac.uk> wrote: > : Steve JORDI <stevejordiI_REALLY_HATE_SPAMMERS(a)hotmail.com> wrote: > : > Hi, > : > I tried to find an explanation on the web but without success. > : > : > Does anybody know why the red color looks so ugly when a digital > : > picture is saved as JPG? > : > It looks like it's the only dominant color that gets very pixelated > : > and grainy. > : > The cause of this artefact? > : > : Because bright red pigments are more easily come by than other > : colours, and evolution has tuned plant fruits and flowers and animal > : eyes to prefer it and to be most sensitive to small difference in red > : quality. ... > > Actually, there are some plant flowers whose dominant color is ultraviolet; > and bees, which care more about finding and differentiating flowers than > humans do, have learned to see it. They co-evolved. Insect eyes can see further into the ultra violet than most mammals so plants make pigments that are strong in that waveband. The plants want to attract insects. That we find them pretty is a by product. UV electric fly zappers exploit this insect feature too. There is a significantly higher proportion of scattered UV shortly after sunset with a clear blue sky and some things can be seen to fluoresce in the early evening under the right conditions. Regards, Martin Brown
From: Ray Fischer on 30 Mar 2010 01:36 Steve JORDI <stevejordiI_REALLY_HATE_SPAMMERS(a)hotmail.com> wrote: >Hi, >I tried to find an explanation on the web but without success. > >Does anybody know why the red color looks so ugly when a digital >picture is saved as JPG? >It looks like it's the only dominant color that gets very pixelated >and grainy. >The cause of this artefact? Most indoor lighting is very red. -- Ray Fischer rfischer(a)sonic.net
From: Mike Russell on 30 Mar 2010 03:43 Steve JORDI <stevejordiI_REALLY_HATE_SPAMMERS(a)hotmail.com> wrote: >Hi, >I tried to find an explanation on the web but without success. > >Does anybody know why the red color looks so ugly when a digital >picture is saved as JPG? This is not always the case. Usually the blue channel is the weakest of the three - more noise and less shadow detail. >It looks like it's the only dominant color that gets very pixelated >and grainy. >The cause of this artefact? It's hard to answer this without seeing an image that demonstrates what you are saying. There could be several reasons for a poor quality red channel: 1) lighting - skylight is strong in blue, weakest in red, and could cause noise and jpeg artifacting, which matches some of what you are describing 2) exposure - saturated red objects, roses being an example, often blow out the red channel, resulting in orange or yellow areas with little detail 3) aliasing - an object with fine lines or edges, that contrast with a saturated red background, will tend to cause jaggies. This is equally true for the blue channel, and less so for the green channel because it has twice the number of pixels. These are all stabs in the dark, though, without an actual image to look at. All the best, -- Mike Russell - http://www.curvemeister.com
From: Paul Furman on 30 Mar 2010 23:36 Laurence Payne wrote: > On 26 Mar 2010 09:58:24 GMT, Chris Malcolm <cam(a)holyrood.ed.ac.uk> > wrote: > >> Because bright red pigments are more easily come by than other >> colours, > > Historically, wasn't blue the original pigment generally available? I always heard barns were painted red because that's the cheapest paint. -- Paul Furman www.edgehill.net www.baynatives.com all google groups messages filtered due to spam
From: Paul Furman on 30 Mar 2010 23:38
Martin Brown wrote: > Robert Coe wrote: >> Chris Malcolm wrote: >> : Steve JORDI wrote: >> : > Hi, >> : > I tried to find an explanation on the web but without success. >> : : > Does anybody know why the red color looks so ugly when a digital >> : > picture is saved as JPG? >> : > It looks like it's the only dominant color that gets very pixelated >> : > and grainy. >> : > The cause of this artefact? >> : : Because bright red pigments are more easily come by than other >> : colours, and evolution has tuned plant fruits and flowers and animal >> : eyes to prefer it and to be most sensitive to small difference in red >> : quality. ... >> >> Actually, there are some plant flowers whose dominant color is >> ultraviolet; >> and bees, which care more about finding and differentiating flowers than >> humans do, have learned to see it. > > They co-evolved. Insect eyes can see further into the ultra violet than > most mammals so plants make pigments that are strong in that waveband. > The plants want to attract insects. That we find them pretty is a by > product. We aren't so different from insects. Flowers are 'designed' to make us all swoon. > UV electric fly zappers exploit this insect feature too. > > There is a significantly higher proportion of scattered UV shortly after > sunset with a clear blue sky and some things can be seen to fluoresce in > the early evening under the right conditions. -- Paul Furman www.edgehill.net www.baynatives.com all google groups messages filtered due to spam |