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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