Yes, we were talking about B&W conversion with red filter. I agree it is not
only noise but posterization (as mentioned in my previous email), the
question is do we see the same problem with real glass filter? Are digital
filters able to replace the traditional one in B&W processing?
C.H.Ling
----- Original Message -----
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
>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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