I think I misunderstood. I thought you were attempting a B&W conversion.
Chuck Norcutt
Chuck Norcutt wrote:
> I'm not sure I agree about noise. If I use ACR to do the B&W conversion
> of this JPEG image and set red at maximum and all other colors at
> minimum what I see at 100% is a highly pixellated image in the sky. I
> can remove the pixellation with the ACR noise control. However, after
> backing down to lower magnification what I see is posterization, not
> noise. Adding back some blue eliminates the posterization. I think
> maybe the single channel (at least as a JPEG) doesn't have the tonal
> differences to create a smooth looking image. Maybe the raw file done
> this way would be different?
>
> Chuck Norcutt
>
>
> Moose wrote:
>> On 5/25/2010 6:28 PM, C.H.Ling wrote:
>>> You are lucky, 5D II has very bad red channel noise, this one shot at
>>> ISO160
>>
>> It's been years, so I don't remember details. I read someone who
>> claimed that the intermediate ISOs on the 5D were noisier than the
>> primary ones. So I checked, and it was true of mine, as well. So, 160
>> is noisier than 200, 320 noisier than 400, and so on. Since then, I've
>> only used the one stop series starting with ISO 100.
>>
>> I have no idea whether the same might be true of the MkII, but it
>> might be worth checking.
>>
>>> , try to convert it with PS red filter. There are lots of noise and
>>> artifacts everywhere, image is totally non usable:
>>>
>>> http://www.accura.com.hk/temp/IMG_4865.JPG (4.5MB)
>>>
>>
>> I disagree, at least for this particular image. The problem is easy
>> enough to see. However, I don't like what the red filter does to the
>> mural, so wouldn't want to use it there anyway, And it doesn't do
>> anything of use to me on the rest of the buildings. If I use it
>> judiciously on sky only, it does a nice job, with only a couple of
>> areas of subtle mottling which are easily corrected. There is trouble
>> in the couple of spots where the red channel is already blown in the
>> brightest clouds, but that's an exposure/processing problem, not the
>> fault of the filter process.
>>
>> It's also possible to get the sky effect using other tools after a
>> straight B&W conversion. In the English idiom, there's more than one
>> way to skin a cat.
>>
>> I can certainly see that there would be other sorts of image where the
>> red channel problem would not be so easy to get around.
>>
>> Thanks for helping me resist the MKII. ;-)
>>
>> Moose
>>
>>> Shoot with Tamron SP 24-48.
>>>
>>> BTW, don't expect there will be any different at ISO100.
>>>
>>> C.H.Ling
>>>
>>> ----- Original Message -----
>>> From: "Moose"<olymoose@xxxxxxxxx>
>>>
>>>
>>>
>>>> Here are some samples, none of which make any difference in noise
>>>> that I
>>>> can see at full pixel.
>>>> <http://www.moosemystic.net/Gallery/tech/Process/BW/B&Wconv2.htm>
>>>>
>>>> Moose
>>>>
>>>>
>>>
>>
>
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