-> Red color and JPG???
in [Digital Cameras]
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From: Ray Fischer on 31 Mar 2010 01:48 Paul Furman <paul-@-edgehill.net> wrote: >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. Red lead (lead tetroxide) mixed with linseed oil made a water-insoluble paint. Problematic for obvious reasons, but ignorance was bliss. -- Ray Fischer rfischer(a)sonic.net
From: Peter on 3 Apr 2010 15:32 "Mike Russell" <groupsRE(a)MOVEcurvemeister.com> wrote in message news:x18crd1j794q.dlg(a)mike.curvemeister.com... > 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 Mike, thanks for the explanation of my issues shooting red flowers. Do you have any suggestions for a cure? -- Peter
From: Mike Russell on 3 Apr 2010 15:50 On Sat, 3 Apr 2010 15:32:01 -0400, Peter wrote: > "Mike Russell" <groupsRE(a)MOVEcurvemeister.com> wrote in message > news:x18crd1j794q.dlg(a)mike.curvemeister.com... >> 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 > > > Mike, thanks for the explanation of my issues shooting red flowers. > Do you have any suggestions for a cure? One technique that deals well with this is channel mixing. The idea is to take information from the green and/or blue channels and mix it in with the red channel. If it's done right, you'll see detail in the blown out areas. Dupe the image to a new layer and set it's mode to luminance. Use curves on the blue and/or green layers to bump the contrast, and voila - detail in the blown out red areas. Apply image can be used in a similar way. The roses are starting to bloom in my neck of the woods, and I'll consider doing a video tutorial on how to do this. -- Mike Russell - http://www.curvemeister.com
From: Robert Coe on 3 Apr 2010 18:22 On Tue, 30 Mar 2010 20:36:19 -0700, Paul Furman <paul-@-edgehill.net> wrote: : 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. I jeard that it was because it's an extremely stable pigment that doesn't fade in sunlight. Bob
From: Robert Coe on 3 Apr 2010 18:31
On 31 Mar 2010 05:48:42 GMT, rfischer(a)sonic.net (Ray Fischer) wrote: : Paul Furman <paul-@-edgehill.net> wrote: : >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. : : Red lead (lead tetroxide) mixed with linseed oil made a water-insoluble : paint. Problematic for obvious reasons, but ignorance was bliss. I'm not sure that red lead and barn red are the same pigment. The former, used for painting bridges (e.g., the Golden Gate Bridge in California), looks a lot more orange than barn red (deep maroon with a definite bluish cast). Bob |