After a few minutes more thought it suddenly occurred to me that maybe
ACR is prematurely rounding things down from 14 bits to 8 bits and using
8 bit values when increasing brightness. That would explain some small
values of dark gray (1-12) getting turned into 0.
Chuck Norcutt
Chuck Norcutt wrote:
> I did finally try your raw file in DPP and the difference between ACR's
> conversion and DPP's conversion is that the base image conversion in ACR
> shows many very dark areas as black (0) whereas DPP shows small but
> distinguishable dark gray values (from 1-12). Also, in the green patch
> DPP shows a red value of 1 whereas ACR shows 0.
>
> So, for whatever reason, ACR is not correctly converting very dark
> values and the color shift is due to 0 not scaling upward with the other
> non-zero values of the pixel.
>
> Sounds like a bug in ACR.
>
> Chuck Norcutt
>
>
> Chuck Norcutt wrote:
>> Simple. I don't use DPP because I don't like to use DPP. I think its
>> usage is rather primitive relative to ACR. I also don't lend much
>> credence to your test image because it's 4 stops down. I wouldn't be
>> trying to recover that. I find it curious that the black parts of the
>> image (already near 0) can be 4 stops down yet be recovered by DPP. CS4
>> is showing 0 for those parts which is what I would expect. Is DPP
>> inventing numbers? It has produced a slightly graduated scale of dark
>> grays but how did it do that? What are the values of those dark
>> grays/blacks before boosting?
>>
>> Chuck Norcutt
>>
>> C.H.Ling wrote:
>>> Why your guys don't use the free software came with your Canyon camera? CS
>>> has BIG PROBLEM in rendering at least the 5D II files, see here a test image
>>> that undered 4 stops:
>>>
>>> Converted with DPP +2 stops:
>>>
>>> http://www.accura.com.hk/temp/IMG_7217_DPP.JPG (142KB)
>>>
>>> Converted with CS4 +2 stops:
>>>
>>> http://www.accura.com.hk/temp/IMG_7217_CS4.jpg (174KB)
>>>
>>> both W/B on the "White" color. See the serious color shift in CS4 converted
>>> one, not to mention the different in exposure.
>>>
>>> Try it out yourself if you are interested, may be I have missed something:
>>>
>>> http://www.accura.com.hk/temp/IMG_7217.CR2 (6.8MB)
>>>
>>> Back to the noise issue, here are two crops from DPP, one normal
>>> exposure and the other +1 stop in DPP.
>>>
>>> http://www.accura.com.hk/temp/IMG_6442.JPG
>>>
>>> http://www.accura.com.hk/temp/IMG_6442+1.JPG
>>>
>>> There are visible noise even with the non boost one, remember this is
>>> an ISO100 image, just hard to accept!
>>>
>>> C.H.Ling
>>>
>>> ----- Original Message -----
>>> From: "Chuck Norcutt"
>>>
>>>> I must be blind. I didn't open this file before because my CS3 can't
>>>> handle 5D MkII files. However, I decided to try an ACR conversion in my
>>>> trial version of Elements which does handle it. I do see banding on the
>>>> wood paneling in the background at lower far right. But to make it
>>>> visible I have to increase fill light to 100 while also increasing
>>>> exposure by a full stop. That's something I'd never do. Are my new
>>>> eyes or monitor that bad?
>>>>
>>>> Chuck Norcutt
>>>>
>>>>
>>>> C.H.Ling wrote:
>>>>> Moose, I think you are right, it is highly possible A/D problem, I have
>>>>> checked with some low ISO images, there are large size "noise" at the
>>>>> shadow
>>>>> area even without boost up, what 14 bit A/D seems not doing better than
>>>>> the
>>>>> E-1, all are BS, even the 40D images look better.
>>>>>
>>>>> There has been a long time curious for me why some OOF background didn't
>>>>> look as smooth as they should be, it was not enough bit deep. Now there
>>>>> is
>>>>> one more thing to look for when checking out a new camera.
>>>>>
>>>>> C.H.Ling
>>>>>
>>>>>
>>>>> ----- Original Message -----
>>>>> From: "C.H.Ling"
>>>>>
>>>>>> Yes, there is similar problem even at full resolution:
>>>>>>
>>>>>> http://www.accura.com.hk/temp/IMG_6442.CR2 (23MB)
>>>>>>
>>>>>> I really have no idea how this happen as a totally dark low ISO image is
>>>>>> very clean even boost up, at the mean time high ISO image is clean
>>>>>> except
>>>>>> the shadow, just like problem with low ISO image.
>>>>>>
>>>>>> C.H.Ling
>>>>>>
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