Incremental vs all-at-once H/S adjustment

[PhotogCda]

Did a forum search and didn't find an answer. Also tried a general Google search and didn't find an answer. I may not be using the right search strings to generate the correct information.

Why would applying incremental changes to H/S via multiple adjustment layers produce a different result than applying the same total application on a single H/S layer?

E.g., Applying a Master Saturation adjustment of +10 and duping that layer 6 times (7 total H/S layers) gives a much different result than applying an adjustment of +70 on a single layer. 

Thanks

[Chuck Uebele]

Just iff the top of my head, the +70 in a single layer adjust the values just from the base layer. With 7 +10 adjustment layers, you're compounding the adjustments. You're not just changing the base layer, but all the corrections to the base layer.

[PhotogCda]

Sorry, I should have also noted that the incremental result is less dramatic than the single layer approach.

I get what you're saying and intuitively that makes sense. The end result is different; however. It doesn't appear to compound the result of each successive layer. 

Examples attached. The first is the incremental approach, the second is all-at-once.

[Chuck Uebele]

In that case, it all depends on their algorithm. The +10 is most likely a multiplier. The scale is from 0 to 100, so a +10 could be only a .1 times increase. Hard to say without actually knowing the algorithm.

[PhotogCda]

Sure. It will depend the algorithm. I just didn't know if there had been any explanation from Adobe, or one of Adobe's contracted experts, that I haven't been able to find. 

[c.pfaffenbichler]

But why would you expect the Saturation setting to operate »additively«? 

Have you done some basc testing (not on a photograph naturally but on meaningful color swatches)? 

[PhotogCda]

That would make no difference. It would generate the same result. The algorithm behind the adjustment is the same. 

Whether it operates additively, multiplicatively, or exponentially isn't the issue. The question is why incremental works differently from a single adjustment. That deals with the 'how' of the programming behind the adjustment. Whether it's on a real photo, or a colour chart is immaterial. 

[c.pfaffenbichler]

»Whether it operates additively, multiplicatively, or exponentially isn't the issue.«

Have you really thought that through? 

While the effect certainly does not differ depending on how the image was created the swatches approach makes it easier to make meaningful observations. 

Edit: This for example shows the effect of an Adjustment with Saturation 50%.