I've noted similar issues with my Sony NEX-C3 at high ISO. at 200-400 iso
noise profiling is simply awesome in its default setting. At high ISO I get
artifacts too. I assume that I need to do my own profiling for my own
sensor at higher iso's, 3200 ISO. But being time limited, I use noise
profiling with wavelet and select hue instead of normal. It gives me the
least color artifacts. I also add some bilateral filtering on the color for
the other and non-local means filtering on lightness. The combinations
seems to give less artifacts that using multiple wavelet from my
experience.

Best,

Gert

On Mon, May 27, 2013 at 10:02 PM, johannes hanika <[email protected]> wrote:

> thanks, not sure what kind of help i would ask for at this point. i
> noticed that your flattened histogram even with a slightly improved fitting
> procedure that i just tested (will push later, doesn't really help all that
> much so far) has a 2x noise std deviation for dark regions. some other
> cameras have way worse behaviour than that for brightnesses < 0.2, but
> maybe this is enough to confuse the algorithm. i fitted a gaussian to that
> error and instructed the wavelet denoiser accordingly, but so far results
> aren't a lot better than what we had before.
>
> i could get way better results using the equalizer and manually pulling up
> the threshold for the chroma channels (start from `chroma denoise' preset
> and push it to the extreme basically).
>
> i hope to do some more tests on that tomorrow.
> j.
>
>
>
> On Tue, May 28, 2013 at 6:21 AM, Baptiste Pierrat <
> [email protected]> wrote:
>
>> I´m willing to help if you want more samples or else (I´m not a good
>> coder but I have some basic knowledge).
>>
>>
>> On Mon, May 27, 2013 at 2:50 PM, johannes hanika <[email protected]>wrote:
>>
>>> hm. if anything your sensor is cooler now and has less constant noise
>>> added on top. the data in your image matches your previous measurements
>>> very closely. i'll have to do some more digging.
>>>
>>> j.
>>>
>>>
>>> On Mon, May 27, 2013 at 1:46 PM, Baptiste Pierrat <
>>> [email protected]> wrote:
>>>
>>>> Well I did the profiling for my camera and it's currently this one that
>>>> is used in the code (git master). I took great care in doing this
>>>> correctly, I did 4 profiles and averaged the results.
>>>>
>>>> Here is the raw file from the previous example if you want to test:
>>>> https://www.dropbox.com/s/iqb04gly913vmfx/20130429_0041.ARW
>>>>
>>>> The problem for me is not only the green pixels but also the bigger
>>>> cross-shaped blue and red dots. Isn't that somehow related to the
>>>> demosaicing process?
>>>>
>>>> Thank you for helping with that.
>>>>
>>>>
>>>>
>>>>
>>>> On Mon, May 27, 2013 at 1:27 PM, johannes hanika <[email protected]>wrote:
>>>>
>>>>> hm. that looks reasonable. very surprising that those green pixels
>>>>> still stay in the color buffer. maybe the profiling doesn't match your
>>>>> particular camera model? maybe the profile was a little off for that
>>>>> particular iso value, or maybe there is some variance between individual
>>>>> sensors for sony cams?
>>>>>
>>>>> i can try and re-profile that particular raw and see if there are any
>>>>> differences to the data we have if you want.
>>>>>
>>>>> j.
>>>>>
>>>>>
>>>>> On Mon, May 27, 2013 at 12:14 PM, Baptiste Pierrat <
>>>>> [email protected]> wrote:
>>>>>
>>>>>> [image: Inline image 1]
>>>>>>
>>>>>>
>>>>>> On Mon, May 27, 2013 at 12:12 PM, johannes hanika 
>>>>>> <[email protected]>wrote:
>>>>>>
>>>>>>> what are the white balance coefficients for that image?
>>>>>>>
>>>>>>>
>>>>>>> On Mon, May 27, 2013 at 11:57 AM, Baptiste Pierrat <
>>>>>>> [email protected]> wrote:
>>>>>>>
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> I want to second this problem.
>>>>>>>>
>>>>>>>> I have a Sony Alpha 57 and have a lot of trouble with remaining
>>>>>>>> bright color dots after denoising. My usual denoising tools for 
>>>>>>>> iso>800 are
>>>>>>>> :
>>>>>>>> 1. Chroma denoise: profiled denoising with wavelets, blend with
>>>>>>>> color, then
>>>>>>>> 2. Luma denoise: profiled denoising with non-local means, blend
>>>>>>>> with lightness
>>>>>>>>
>>>>>>>> Here is an example with an iso 3200 sample:
>>>>>>>> original: http://minus.com/lU783RXDLcLH7
>>>>>>>>  chroma denoised: http://minus.com/lBe1kgj6o5aoP
>>>>>>>> chroma and luma denoised: http://minus.com/lbqRsDO5q4E617
>>>>>>>> detail after export: http://minus.com/lCLmKR1s2vh5a
>>>>>>>>
>>>>>>>> Green, red and blue larger dots remain. Also notice as chroma
>>>>>>>> denoising does not work well for green color. As suni, this problem is
>>>>>>>> partially solved by using the color smoothing option in demosaic but 
>>>>>>>> the
>>>>>>>> image is slightly blurred.
>>>>>>>>
>>>>>>>> Thanks!
>>>>>>>>
>>>>>>>>
>>>>>>>> On Mon, May 27, 2013 at 11:25 AM, johannes hanika <
>>>>>>>> [email protected]> wrote:
>>>>>>>>
>>>>>>>>> you left in all the luma noise in your lightroom comparison image.
>>>>>>>>> to do that in darktable, use `color' blend mode in the profiled 
>>>>>>>>> denoising
>>>>>>>>> module. you may want to use the wavelet method, it is usually a 
>>>>>>>>> little more
>>>>>>>>> effective against color noise.
>>>>>>>>>
>>>>>>>>> j.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Mon, May 27, 2013 at 11:21 AM, suni <[email protected]> wrote:
>>>>>>>>>
>>>>>>>>>> Hi all,
>>>>>>>>>>
>>>>>>>>>> I'm fighting the high ISO noise of my A550 camera, but I still
>>>>>>>>>> cannot achieve the reasonable output. Even the new profiled denoise 
>>>>>>>>>> filter
>>>>>>>>>> doesn't help much.
>>>>>>>>>>
>>>>>>>>>> Below is the example of the ISO12800 image. I do not take images
>>>>>>>>>> on such high ISO but it makes this problem more visible for this 
>>>>>>>>>> purpose.
>>>>>>>>>> This behaviour may be observed even at ISO1600 and higher. The RAW 
>>>>>>>>>> image
>>>>>>>>>> below is totally unaltered RAW for comparison opened side by side in 
>>>>>>>>>> dt and
>>>>>>>>>> in Lt. Only the base curve is applied at dt side because otherwise 
>>>>>>>>>> the
>>>>>>>>>> image looks very ugly and not comparable to the Lt from the visual 
>>>>>>>>>> point of
>>>>>>>>>> view.
>>>>>>>>>>
>>>>>>>>>> Link to unaltered RAW image:
>>>>>>>>>> https://dl.dropboxusercontent.com/u/9454436/sony_noise/raw_not_altered.jpg
>>>>>>>>>>
>>>>>>>>>> As you can see the image looks almost the same in both tools.
>>>>>>>>>> Just note the bright red dots. The Lt shows less of them especially 
>>>>>>>>>> on the
>>>>>>>>>> right side of the paper Christmas tree. These red dots cannot be 
>>>>>>>>>> removed by
>>>>>>>>>> any of the dt denoising filters unless the image becomes almost 
>>>>>>>>>> blurred.
>>>>>>>>>>
>>>>>>>>>> Now see the next image below. This shows what can be achieved in
>>>>>>>>>> dt and in Lt. While only activating the luma and chroma denoise 
>>>>>>>>>> sliders in
>>>>>>>>>> Lt produces the acceptable and (to me) pretty usable output where 
>>>>>>>>>> only some
>>>>>>>>>> luma noise remains, with dt I cannot achieve similar output by no 
>>>>>>>>>> means.
>>>>>>>>>> The most strange finding is that no one from all the denoising 
>>>>>>>>>> filters
>>>>>>>>>> available in dt can remove these bright red dots unless it is pushed 
>>>>>>>>>> to not
>>>>>>>>>> acceptable high strength producing the blurred image. The only 
>>>>>>>>>> strategy I
>>>>>>>>>> found to be somehow working here is as follows:
>>>>>>>>>> 1) turn off the sharpen filter
>>>>>>>>>> 2) apply the hot pixel filter at its maximum strength
>>>>>>>>>> 3) set the color smoothing of the demosaic filter to maximum
>>>>>>>>>>
>>>>>>>>>> These three steps do remove the bright red dots. But the image
>>>>>>>>>> still suffers of the high chroma noise. The only possible way to get 
>>>>>>>>>> rid of
>>>>>>>>>> it while maintaining the image sharpness at the level comparable to 
>>>>>>>>>> the Lt
>>>>>>>>>> I found is the profiled denoise set to less than default strength. 
>>>>>>>>>> But as
>>>>>>>>>> you can see there still remain far more chroma noise than in the Lt 
>>>>>>>>>> case.
>>>>>>>>>>
>>>>>>>>>> Link to altered RAW image:
>>>>>>>>>> https://dl.dropboxusercontent.com/u/9454436/sony_noise/raw_altered.jpg
>>>>>>>>>>
>>>>>>>>>> Because I've got to that point I didn't know what to do more,
>>>>>>>>>> I profiled my camera. But even though my profile seems to me to be a 
>>>>>>>>>> bit
>>>>>>>>>> better than the one packed with dt, it produces no visible 
>>>>>>>>>> difference here.
>>>>>>>>>>
>>>>>>>>>> I would like to ask all of you experienced in fighting the high
>>>>>>>>>> ISO noise for your experiences and recommendations. It would be 
>>>>>>>>>> great to
>>>>>>>>>> get to know that the problem is in between the chair and the 
>>>>>>>>>> keyboard, not
>>>>>>>>>> in the excellent dt tool!:-)
>>>>>>>>>>
>>>>>>>>>> If someone is interested, the original RAW image can be found
>>>>>>>>>> here:
>>>>>>>>>> https://dl.dropboxusercontent.com/u/9454436/sony_noise/DSC09533.ARW
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Thank you in advance for any reply!
>>>>>>>>>>
>>>>>>>>>> Suni
>>>>>>>>>>
>>>>>>>>>>
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