What color profile to use?

[Andrea B.]

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Experimentation and discovery are never un-messy !!

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Alaun, yes I have the Darktable manual at hand. To be clear, the goal here was not about workflow, it was rather an attempt to figure out how to get the R, G, B channels in Darktable. Something is not quite right about Darktable's channels.

 

Fandy, when you say that Linear Rec709 does not cause channel clipping, it is not clear whether you are applying Linear Rec709 as in Input Profile or as a Working Profile. Clarification, please.

[Andrea B.]

I went through my discovery posts above and added some remarks about whether the channels being shown were for the raw data or for the data "As Shot" (i.e., with white balance applied). I thought that it was not clear enough the way I initially wrote it. All new remarks are marked with "EDIT".

 

I never did ask Fandyus if he was wanting to split channels for the raw data or for the white balanced data?!

 

 

[Andrea B.]

Fandyus:   I wonder why the small blue peak at 650. One would think that since that's pure red, it would be benefitial to let the camera record it as so.

 

That is a bit strange. The red (long) line in human vision overlaps the (short) blue line. But the blue does not reach into red. So if the camera is supposed to match human color vision, this blue at 650 seems off. 

This is from Wiki.

 

MaxMax says that the Bayer filter "is not perfect".  LINK 

[Andrea B.]

Fedia - thank you for looking into the gamut clipping which I had not yet had time to investigate. Good analysis! And using the waveform instead of the histogram better showed the point.

 

Did you select the gamut clipping based a plan to output the image to an sRGB JPG? That was my initial thought - that we should set the clipping for however the photo will be displayed (sRGB or aRGB) rather than choose a working space clipping. But I wasn't completely confidant about that choice.

[Fandyus]

12 hours ago, Andrea B. said:

Fandy, when you say that Linear Rec709 does not cause channel clipping, it is not clear whether you are applying Linear Rec709 as in Input Profile or as a Working Profile. Clarification, please

input

[Fandyus]

@Andrea B.Also thank you for the MaxMax data. I actually would like to get myself a D200. It has a nice 10mp CCD sensor. I prefer CCD to CMOS  personally, when it comes to pictorial stuff. Now I also wonder if it could be better for aerochrome emulation since there is no weird secondary transmission peak in red.

[Andrea B.]

The D200 is a bit difficult to use because it has no Live View.

So for each lens and filter combo, you have to determine how much focus adjustment is needed. 

Focus without filter, add filter, adjust focus dial by amount X, make photo.

We had a nifty filter holder which flipped up & down so that the procedure was was made easier. LINK

[Andrea B.]

Guys, the big question is this:  What FREE photo software is there which can split channels properly?

Has anybody looked at GIMP? 

How about one of the command line things like Dcraw? You can run that on batches of photos if you don't mind using a command line tool in Terminal.

 

Also a repeat from above:

I never did ask Fandyus if he was wanting to split channels for the raw data or for the white balanced data? Or both?

[Andrea B.]

Downloaded GIMP, which is a Photoshop emulation. Can split channels. Shows channels in color. I'll continue playing with GIMP to see whether it can produce raw channels or only As Shot channels.

[Andrea B.]

No, Gimp is not for extracting channels even though it has a channel mixer.

Gimp has lots of Photoshop emulation tools. But it seems to be missing a sophisticated white balance tool. It seems that white can only be set by using the white pointer in the Levels tool. This is not at all my idea of white balance. 

 

I will look again later because I might have missed something!

[Andrea B.]

I note that there is currently a sale price for Raw Digger which is valid until Sept 6. I think it is the "research" version which is needed for exporting TIFFs. 

 

There is also a sale on Fast Raw Viewer. I am experimenting with that now. Fast Raw Viewer does display both raw channels and channels from the internal JPG. 

[Andrea B.]

Channels cannot be exported from Fast Raw Viewer. I wish that wasn't the case. It is much easier to run through the channels in Fast Raw Viewer.

[Yves W]

Fandyus, I have an unconverted D200, very good condition, little price and UE

[Fandyus]

Just now, Yves W said:

Fandyus, I have an unconverted D200, very good condition, little price and UE

Thanks a lot for the offer. Though now that Andrea told me it does not have live view, I'll have to reconsider. That would be a huge pain for anything non-visible indeed.

[JCDowdy]

On 8/27/2023 at 3:23 PM, Andrea B. said:

Guys, the big question is this:  What FREE photo software is there which can split channels properly?

Does ImageJ not do what you need?

[Andrea B.]

This topic has gotten away from wherever it started. 

 

Channel splitting is needed to build multispectral stacks.

For example you might channel split a UV image, an IR image and a VIS image. And then make a new image by stacking the red channel from the IR photo, the green channel from the VIS photo and the blue channel from the UV image.

 

There is an unresolved question about whether the channels used to build a multispectral stack are raw data channels or whether they are the channels split from white-balanced versions of the various images. 

 

ImageJ does split channels. I'm not sure whether they are raw data channels or channels from a white-balanced image.

 

We were trying to figure out how to do this channel splitting thing in Darktable. The raw data channels did not seem to match those produced by Raw Digger. 

 

[Yves W]

Fandyus, Ok I understand
I started with a D70 in 2009.