Saturation Mask

[hanshab]

I have several 6 TB disks a 4 TB and a 3 TB disk...  I remember when disk technology for a 8 foot high disk drive was 256 MB..... I also developed computers in the early days and have a number of patents on them  ITs come a long way.   

AS AP works in 32 bit floating point in develop it gives you a good start for any further work you do in the photo or HDR module.  I use the HDR module  a lot directly from the develop module.  You might try working in 32 bit mode in photo as most of the adjustments work in that mode.  Many folks think you dont need 32 bit and if your camera only records in 8 bit then that is true but my cameras have a very wide dynamic range  with 36 and 45 MPixels  as well as recording in 14 bit  flash  and I can recover  a lot .. You really need the dynamic range for that.  I have conversed with many photographers   on You tube working in Photoshop who insist that 16 bits is enough but watch some of the videos from James Ritson and you will see the benefits of 32 bits.  Its not for everyone,  most people will be very happy with 16 bit which is what Photo persona works in when you dont select 32 bit mode..... I have to tell you that 32 bit mode is especially useful when doing astrophotography.....

I never have to bracket a landscape photo when I work in 32 bit I have always been able to recover the darks when I expose for the lights.....  But then I have the right camera for this as well.

As far as your comment on the cost of the books.  Well, these are textbooks  and are expensive...

[hanshab]

BTW Neutral shooting only affects Jpgs not raw.....  I use the jpgs for immediate processing using snapseed but then when I get home I use Affinity Photo.    14 bit raw encoding is what is preferred for raw.;.;; if you want to talk about color then I recommend you look at these web sites . The author is a painter and photographer and he gives a very good overview of color theory.  Folks in your camera club might appreciate this.....https://www.youtube.com/user/EverydayHDR/search?query=color+theory be sure you watch both color theory 1 and 2 which are both shown on this page...  There are many others on color theory out there but I like this one as Blake is also a painter.....

[hanshab]

I keep finding things for you for your camera club:  here is a good video on why 32 bit Pro photo is the best..... today....

https://wolfcrow.com/should-you-raise-bit-depth-and-color-space-before-color-grading-part-two-raw-video/

[dmstraker]

Many thanks, @hanshab. All pointers gratefully received! I also remember 100Mb floppies, magnetic core memory, and enormous 246Mb disk 'washing machines'. Well done on patents! I got a couple in gaming machine design (in which I worked for a few years).

Very interesting that you work at 32bit level. Does your camera output to this? What camera do you use? I'm pretty happy with my A7R2, 42Mpx and 40Mb RAW image files (compressed 14 bit RAW - any opinion on using 80Mb uncompressed?).

Yes, I like f64. Blake is clear and, as a former artist, has a good creative sense and a feeling for colour. I don't know wolfcrow and will also explore (thanks). All book recommendations gratefully received. One of my favourites is Zakia's Perception and Imaging. There are a number of good books on composition but I don't have a standout favourite. One of my personal 'research' questions is 'What makes a good photo good?' I like Christopher Alexander's work in architecture in this regard.

You probably already know it, but https://www.opticallimits.com/ is helpful in determining optimal aperture range for lenses, though if you have medium format this is not covered.

[Max P]

Hi

A very interesting exchange ...

'What makes a good photo good?" 

I am  sensitive to the influence of landscape picture painting and found this interesting link  https://www.davemorrowphotography.com/color-theory-photography 

Dave, I finally saw no difference with Tony Kuyper's approach explained in his second page about saturation, a regret Photo is not compatible with his  panels
 
 

[dmstraker]

4 hours ago, Max P said:

Hi

A very interesting exchange ...

'What makes a good photo good?" 

I am  sensitive to the influence of landscape picture painting and found this interesting link  https://www.davemorrowphotography.com/color-theory-photography 

Dave, I finally saw no difference with Tony Kuyper's approach explained in his second page about saturation, a regret Photo is not compatible with his  panels
 

Thanks for the link, Max. I've been watching it.

Saturation is an interesting question. Morrow shows it as going from saturated colour down to white, yet in Affinity Photo it goes down from saturated colour to grey. In other words, RGB converge either at mid-values (128 on 8-bit schema) or top values (255 on 8-bit). This also brings up a third option of converging on black (0). In AP, saturation does go down to white when the HSV box is checked, which simply throws more confusion into the question. And if you bring up the Colour Chooser and the Saturation variant, the main square goes from white to black through the fully saturated hue, with a grey-to-saturated slider above, which effectively suggests a cube model (though with the HSL sliders, H moves x, L moves y and S changes the whole from grey to white-saturated hue-black).

Wikipedia says ' To desaturate a color of given intensity in a subtractive system (such as watercolor), one can add white, black, gray, or the hue's complement.' Indeed, black, grey and white are all desaturated when you view saturation in terms of maximum 'colour' (colour happens when R, G and B are not all equal). Wikipedia also gives an equation of saturation = chroma / luminance, which suggests that when saturation is zero, chroma = luminance, but then we have the rabbit warren of what chroma and luminance are.

My brain hurts.

 

[ch22]

I return to the original post of dmstraker. Though the recipe looks somewhat sorcery, it really builds a grey picture with R=G=B=Max-Min where Max and Min are the largest and the smallest of the original RGB components, i.e. the genuine absolute saturation in HSL models. I wrote a script which performs this computation and I obtain exactly the same results. This script can downloaded at http://www.oitregor.com/numeric/affinity_photo/divers/selection_saturations.afmacro 

Of course, this does not yield saturation in LAB sense, but in practice this should have little consequence.  I also wrote a script for chroma — SQR(a^2+b^2) — but I failed to convert it from Photoshop to AP.

 

 

[hanshab]

I cannot open your file.. But just going by your text whenever R=G=B, the color is a shade of grey.  But if you say Max=Min,  is this supposed to be irregardless of if its blue green or red?  Ie Max (R,G,B)  = Min(R,G,B)   it always will involve the lightness as that is always part of RGB so you are setting the lightness to some single value over all colours in RGB.   but I can't be sure as your file does not open... Thanks

[ch22]

My file is a macro record ; you must import it in the AP macro ou library panel

[Ganna]

Is your file for PC or for Mac? When I click on your link, this is what I get: Don't know what to do with it, sorry

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[Alfred]

6 hours ago, ch22 said:

My file is a macro record ; you must import it in the AP macro ou library panel

No, not the Library panel: that’s for collections of macros (*.macros, with an ‘s’). For a single macro in a *.macro file, you need to use the Macro panel.

13 minutes ago, Ganna said:

Is your file for PC or for Mac? When I click on your link, this is what I get: Don't know what to do with it, sorry

{snip}

All Affinity files can be used on either PC or Mac.

You should be downloading it, not opening it in your browser. Try right-clicking on the link and choosing ‘Save link as...’ or ‘Save target as...’ (or similar, depending on the particular browser you’re using).

[Ganna]

Thanks a lot. I'm learning every day  :-)

[ch22]

Alfred : thanks

dmstraker : finally the sorcery can be easily explained, provided that HSV model is really the cylindrical HSL model used in Photoshop Adobe color requester. In this model, if the RGB components are sorted in decreasing order as (Max, Mid, Min) — think of these components as reduced quantities varying from 0 to 1— the HSL components can be then written as

H =(Max-Mid)/(Max-Min)    ;    S = Max -Min   ;    L = Max   

where H  actually is the decimal part of a reduced hue varying from 0 to 6, with an integer part depending on which colors correspond to Max and Min components. This formulas can be inverted as

Max = L   ;  Min = L-S   ;  Mid = L-TS

Now, following the dmstracker process :

(i) putting S to 0 in the first HSL adjustment makes the three components replaced by L (the largest component)

(ii) switching to the Difference blending mode replaces the (Max,Mid,Min) trio with (0,S,TS). Since T<1, the largest component is now S  (there is also a hue jump but it does not matter) 

(iii) opening the 2nd HSL adjustment and putting the Saturation slider to 0 makes the three components all equal to the largest component, i.e. S : we thus obtain the wanted mapping of the initial picture saturation.

Unfortunately, I am not sure this Photoshop model really is the HSV Affinity model, since when one moves the Luminosity slider the above RGB components do not change in agreement with the above formulas... But maybe that's another story! 

 

[ch22]

Sorry,  my reference to the Photoshop model was somewhat irrelevant... and it does not matter. The key point is, whatever the actual model used in the AP colorimetric model,  that putting saturation to 0 in the HSL adjustment makes the (Max, Mid, Min) trio replaced with (Max, Max, Max). This can be checked in a practical way by monitoring what happens to RGB components of a color sample in the Infos panel. Then, switching to the difference blending mode makes the original trio replaced with (0, Max-Min, Max-Mid). Since the largest component is now Max-Min,  the second HSL adjustment puts the three components to Max-Min.

[ch22]

Another method for obtaining the saturation mask or the equivalent saturation selection, which requires no HSV capacity :

(1) open an HSL adjustment,  put saturation to -100 and put  the blending mode to "difference"

(2) open a level or curve adjustment so as to get a x2 gain (for instance, with levels, put the white glider at 50%). This amplifying step will allow to get a full saturation mask, i.e. with white or black corresponding to fully saturated colors  or gray tones. At this stage, the (max, med, min)  triplet for color components is replaced with (max-min, xxx, max-min) where xxx is lower than max-min

(3) in order to retain only the difference (max-min), open the channel panel and successively  (i) right-click the red line for " load in the pixel selection", (ii) and (iii) right-click the green and the blue lines for "add to the pixel selection"  —this is equivalent to choosing the highest of the three RGB components.

We then have the wanted saturation selection. 

 

[amyhimesama1598]

On 10/30/2018 at 4:28 PM, dmstraker said:

I've been tinkering with the idea of saturation masks for a while and I've just found a very simple way to create one. It is based on the principle that we want all tones to go black, including whites and greys, leaving fully saturated colours white and partially saturated colours in shades of grey.

The steps are as follows:

1. Duplicate layer.
2. HSL layer, check HSV, slide Saturation fully left, Blend Mode: Difference. (removes tones - blacks, whites and greys all go black).
3. Another HSL layer, check HSV, slide Saturation fully left (turns saturated colours white).
4. Layer/Merge Visible and Layer/Rasterise to Mask, then use mask as you like (or use the pixel layer otherwise).

Here's a video tutorial I've just uploaded to my InAffinity YouTube channel:

 

 

If you are using the @fotoloco version, the third step from the bottom should be HSL, not HSV, then the two HSLs above should be HSV

[dmstraker]

On 11/11/2019 at 9:39 PM, amyhimesama1598 said:

If you are using the @fotoloco version, the third step from the bottom should be HSL, not HSV, then the two HSLs above should be HSV

Thanks, though a little academic at the moment as Affinity, in their wisdom, decided to remove the HSV checkbox from the HSL dialogue in 1.7. I've moaned and they said they'll restore it at some time...