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HSL adjustment Changing Luminosity also changes Saturation?


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Hi,

this is by design and works very similar to e.g. Photoshop.

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Interesing.

And actually you are not right regarding Photoshop, the Photoshop Hue/Saturation layer works in HSB mode (or HSV in Affinity). Changing the lightness in Photoshop does not affect the Saturation value. If I turn on HSV in Affinity. it does work like Photoshop (and saturation is not adjusted).

I am guessing as luminosity is a measure of how bright or dark a hue is, the HSL adjustment darkens/brightens by adjusting the L and S values.

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4 hours ago, Zero1 said:

And actually you are not right regarding Photoshop,

Yes, I checked this, too:

hsb_in_ps.png.e3735ef074cb31a0941d728567d5929a.png

 

Interesting note on the HSV, but should not 50% reduction on L still produce what is selected below and shown in the Color panel, instead of what is shown in the background and shown in Info panel: 

 hsl_in_photo.png.5dc7db86354ca7e775599b3a18fd22e8.png

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3 hours ago, Zero1 said:

And actually you are not right regarding Photoshop, the Photoshop Hue/Saturation layer works in HSB mode (or HSV in Affinity). Changing the lightness in Photoshop does not affect the Saturation value. If I turn on HSV in Affinity. it does work like Photoshop (and saturation is not adjusted).

Well, i said „similar“ and not „identical“ for the exact reason you explained after saying my answer is wrong. as i have no access to Photoshop i couldn’t test it myself.

As Affinity decided (long ago) to implement the HSL adjustment in the way it is, there is no reason to say “its a bug“, unless the results differ to older releases of Affinity, or Affinity fails to correctly render files created by Adobe. This could be an interestig test if you have PS available: just crate a test file in PS, store in a suitable format supporting layers (PDF), and inspect how Affinity renders this file. Curious to see what happens 😉

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7 hours ago, Zero1 said:

I would presume it would only affect the luminosity, but it also affects the saturation value? Any ideas why?

They are related.
Changing one affects the other.

satlight.png.0396a72f8f17ac63724c36bcc2022d61.png

Source

A similar thing happens when using blend modes. If you add a colour layer in saturation blend mode, it doesn't affect only saturation. It also affects lightness.

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18 minutes ago, Lisbon said:

They are related.
Changing one affects the other.

@Lisbon Thank you very much for your feedback! I also noticed that after some digging. . (initially i got confused it with HSB, which Photoshop uses by default)

While on the subject of blend modes... do you know why the luminosity also changes when only the Hue is adjusted in an HSL adjusment with the blend mode HUE?
(HSL adjustment -> Blend mode: Hue -> Change the hue in the HSL adjustment -> color below is shifted in hue, but also in luminosity)

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4 minutes ago, Zero1 said:

do you know why the luminosity also changes when only the Hue is adjusted in an HSL adjusment with the blend mode HUE?

I think i figured it out... Due to the fact the Hue changed, the color has changed -> different RGB values -> Cmax or Cmin can change too... -> different lightness value

 

 

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Beats me. Terminology is confusing: the components of the adjustment are in APhoto Hue, Saturity and Luminosity while the HSL components we are examining are Hue, Saturation and Lightness. In PS the adjustment controls are called Hue, Saturation and Lightness, which then shift the Hue, Saturity and Brightness values. The controls work differently unless HSV (= Hue, Saturation, Value, which seems to be then synonymous with HSB) is turned on in APhoto.

The way luminosity is connected to saturation in APhoto (HSV turned off) is pretty unintuitive, compared to way lightness is connected to saturation in PS (saturation is basically not touched when lightness is decreased, and touched when increased only when the B value is already 100%). Using the OP's example if decreasing 50% luminosity results in 50% decrease in both lightness (50% > 25%), and saturation (100% > 50%), then one might [naively] assume that [aiming at a kind of a "reverse act" and] increasing 50% luminosity of the resulting value (H=0, S=50%, L=25%) would result in increase of both saturity and lightness values, but instead, the resulting value will be S=25%, L=63% (so the current saturity value further decreased and lightness hugely increased):

hsl_in_photo_confused.png.7b86021f64db8c3d9b43c498c83d926d.png

So, nothing for common sense here. Anyway, the HSL adjustment basically works "as expected" if color values are not examined, and is probably not the tool that one would choose to use to have precise control over color values in the resulting image, once the adjustment is merged.

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2 hours ago, Lisbon said:

They are related.
Changing one affects the other.

satlight.png.0396a72f8f17ac63724c36bcc2022d61.png

Source

A similar thing happens when using blend modes. If you add a colour layer in saturation blend mode, it doesn't affect only saturation. It also affects lightness.

This could be a misinterpretation.

What is called L is either Luminosity or Lightness, and must be interpreted in the right context. There are 3 variables related, S, L, and delta. 

Using the color panel with HSL sliders, you can freely enter any combination of L and S. I assume the L from the RGB to HSL calculation has a different meaning.

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These formulas explain how exactly S and L values are being calculated when converting the given RGB value.

In theory, when we adjust any of the H/S/L values individually it shouldn't trigger other components as they are three independent vectors in these cylindrical color models.

I believe that the current behavior we're seeing with this HSL Shift Adjustment is specifically tailored for the needs of reducing possible local color saturation increase in shadows and highlights. While Color slider works just as expected.

So probably that's why saturation is being lowered automatically a little bit once you move lightness value up and down.

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6 hours ago, Zero1 said:

While on the subject of blend modes... do you know why the luminosity also changes when only the Hue is adjusted in an HSL adjusment with the blend mode HUE?
(HSL adjustment -> Blend mode: Hue -> Change the hue in the HSL adjustment -> color below is shifted in hue, but also in luminosity)

Sorry, but I don't know the answer.
Too many variables.

---###---

4 hours ago, NotMyFault said:

Using the color panel with HSL sliders, you can freely enter any combination of L and S.

4 hours ago, Alex M said:

While Color slider works just as expected.

Right.
Since there is a way of changing H/S/L independently, without affecting each other, apparently there is no reason for software developers to use an algorithm that leads to unexpected results. HSL in affinity Hue/Sat in phtotoshop.
(i suspect there must be a good reason for this)

4 hours ago, Alex M said:

I believe that the current behavior we're seeing with this HSL Shift Adjustment is specifically tailored for the needs of reducing possible local color saturation increase in shadows and highlights. While Color slider works just as expected.

Its a possibility.

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5 hours ago, NotMyFault said:

This could be a misinterpretation.

What is called L is either Luminosity or Lightness, and must be interpreted in the right context. There are 3 variables related, S, L, and delta. 

If you mean the calculation from the linked source, it is specifically referred to as "lightness," for example in the Lightness calculation.

But I have no idea how relevant this is.

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  • 4 weeks later...

HSL and HSV are different, and should behave differently as a result. 

From Wikipedia...

Quote

Meanwhile, the HSV representation models how colors appear under light. The difference between HSL and HSV is that a color with maximum lightness in HSL is pure white, but a color with maximum value/brightness in HSV is analogous to shining a white light on a colored object (e.g. shining a bright white light on a red object causes the object to still appear red, just brighter and more intense, while shining a dim light on a red object causes the object to appear darker and less bright


So, with HSL the saturation is supposed to decrease with an increase in luminosity. It also decreases with a decrease in luminosity. 

In HSV increasing the value doesn't affect the saturation as much. If Adobe Photoshop is calling something HSL and it behaves like HSV, then they are utterly incorrect in their labeling and need to learn some basic terminology before peddling their overpriced subscription software. 😒

Either way, I wish Affinity implemented the superior HCL color models based on either CIELAB or CIELUV. They are more perceptually uniform and do a better job of decomposing colors into three orthogonal components. 

 

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For those who want to visually see / inspect the HSL values at once for every pixel of an image, i create a procedural texture filter mapping the HSL values into RGB channel.

To see H, use channels panel to see only R

For S, select G channel 

For L, select B channel.

You can then modify e.g. only luminosity without affecting saturation.

 

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53 minutes ago, Aftemplate said:

IMHO. The L slider that changes the saturation is useless. Give the user at least one option to turn it off. Now, HSL is scrap. Awesome!


The lightness affecting saturation is part of how HSL works, so it's working properly. It's just a crappy model of color. The polar transformations of CIELUV and CIELAB, known as HCL or LCH (usually with ab or uv written afterwards to indicate which CIE color model is used as the basis) are far better at separating lightness and chroma (not saturation). HSV and HSL don't even separate luminosity and saturation from the hue well, and the same lightness/value for different hues corresponds to different lightness when measured with a device independent color space like CIELAB. HCLuv/ab is also independent of the particular working color space, being based on such device independent color models.

 

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7 minutes ago, ultrainfra said:


The lightness affecting saturation is part of how HSL works, so it's working properly. It's just a crappy model of color. The polar transformations of CIELUV and CIELAB, known as HCL or LCH (usually with ab or uv written afterwards to indicate which CIE color model is used as the basis) are far better at separating lightness and chroma (not saturation). HSV and HSL don't even separate luminosity and saturation from the hue well, and the same lightness/value for different hues corresponds to different lightness when measured with a device independent color space like CIELAB. HCLuv/ab is also independent of the particular working color space, being based on such device independent color models.

 

https://bottosson.github.io/posts/oklab/

https://bottosson.github.io/posts/colorpicker/

You are talking about what I am familiar. I am an expert user.

The more restricted you put on the program, the closer you program is to idiot.

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20 hours ago, Aftemplate said:

You are talking about what I am familiar. I am an expert user.

Nice work on your side. After getting oklab implanted into PS, I hope you succeed at Affinity, too.

The kind of hope like peace, curing diseases, feeding the hungry. Probably never happens.

 

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3 hours ago, NotMyFault said:

Nice work on your side. After getting oklab implanted into PS, I hope you succeed at Affinity, too.

The kind of hope like peace, curing diseases, feeding the hungry. Probably never happens.

 

You misunderstood. I'm not a coder. I don't understand software development. Like you said: Probably never happens. Our lives are short. We can't wait. Waiting for software improvements is a long time. However, if you switch to a piece of software right away, you can get something quickly. I always get the best I can have. I don't wait for developers.

The more restricted you put on the program, the closer you program is to idiot.

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On 12/30/2021 at 8:21 PM, Aftemplate said:

You are talking about what I am familiar. I am an expert user.

Ok, so that's not your blog you linked to? Which, I think is why, notmyfault thought you were a engineer, programmer, developer. If that is your blog, it states that you are a software engineer. So what is an expert user?

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1 hour ago, Ron P. said:

Ok, so that's not your blog you linked to? Which, I think is why, notmyfault thought you were a engineer, programmer, developer. If that is your blog, it states that you are a software engineer. So what is an expert user?

what is an expert user?

expert user are dismissive of answering these questions.

The more restricted you put on the program, the closer you program is to idiot.

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1 minute ago, Aftemplate said:

what is an expert user?

expert user are dismissive of answering these questions.

That makes as much sense as jumping off the top of a high-rise building to get to the ground floor.. 🤣

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5 minutes ago, Ron P. said:

That makes as much sense as jumping off the top of a high-rise building to get to the ground floor.. 🤣

Why talk about this? Meaningless things will only waste your time. And my time. It seems that you are obviously good at this.

The more restricted you put on the program, the closer you program is to idiot.

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7 hours ago, Ron P. said:

So what is an expert user?

Perhaps one definition would include someone who is an expert at using & understanding the differences in how the various color pickers work?

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