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From: Peter on 4 Apr 2010 13:00
"Savageduck" <savageduck1@{REMOVESPAM}me.com> wrote in message
news:2010040321133822503-savageduck1(a)REMOVESPAMmecom...
> On 2010-04-03 20:39:36 -0700, "Peter" <peternew(a)nospamoptonline.net> said:
>
>> "Savageduck" <savageduck1@{REMOVESPAM}me.com> wrote in message
>> news:2010040319293137709-savageduck1(a)REMOVESPAMmecom...
>>> On 2010-04-03 18:06:19 -0700, "Peter" <peternew(a)nospamoptonline.net>
>>> said:
>>>
>>>> "Mike Russell" <groupsRE(a)MOVEcurvemeister.com> wrote in message
>>>> news:dwng21qp3i5x$.dlg(a)mike.curvemeister.com...
>>>>> 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.
>>>>
>>>>
>>>> I am looking forward to it. Meanwhile, I am playing with your
>>>> suggestion using levels, since I am not very comfortable using curves.
>>>> Yes, I understand you can get a lot more control with curves and I will
>>>> try it.
>>>> BTW, I should have mentioned I do all my shooting in raw
>>>
>>> Peter,
>>> If you are doing all your shooting in RAW, you should be able to make
>>> the adjustments in ACR or whatever RAW converter you are using.
>>> I am making the assumption you are dong more than White Balance
>>> adjustments with ACR or your RAW converter.
>>>
>>> Just to check, here is ACR "White Balance" adjust panel;
>>> http://homepage.mac.com/lco/filechute/ACR-WB-01.jpg
>>>
>>> Then "Camera Profile" panel;
>>> http://homepage.mac.com/lco/filechute/ACR-Camera%20Profile-01.jpg
>>>
>>> and "Hue, Saturation & Luminosity" (HSL) panel;
>>> http://homepage.mac.com/lco/filechute/ACR-HSL-01.jpg
>>>
>>> Those alone should give you what you need to make the adjustments to
>>> those reds.
>>>
>>> There are all the other adjustment available in ACR, so give them a try.
>>>
>>
>>
>> I try to do as much as I can in ACR, except sharpening. My red problem is
>> only with flowers. The problem with ACR is that it shifts all colors.
>> Also, when I view the flower in the camera LCD it looks washed out even
>> though the histogram shows proper exposure.
>>
>> Also,
>
> In ACR have you tried the "targeted Adjustment Tool" from the toolbar in
> conjunction with the HSL panel.
> Select that tool, open HSL, pick H, S, or L click in the ajustment value
> window. place the tool on the flower needing adjustment, and click & drag
> to left or right to adjust the target.
>


thanks, I still have a lot to learn

--
Peter

From: Martin Brown on 6 Apr 2010 03:51
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?

It would be a lot easier if you posted an example of the sort of
problems you are encountering. Psychic remote viewing and guessing is
not effective at judging photographs. A sample image would be invaluable
here - preferably in PNG format showing the detail problem that you
refer to.

The smaller number of red photosites in a Bayer sensor means that
resolution is degraded in the absence of any strong luminance contrast.
But it should work OK for fine black detail on a red ground provided
that you stick to raw an use a reputable converter. It is one example
where the Foveon tricolour sensor would be beneficial.

The JPEG images out of a normal digicam are already chroma subsampled
2x1 and no current mainstream decoders reproduce that faithfully where
high saturation red or blue colours are combined with black detail.

Regards,
Martin Brown
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