Adjusting modules: directly vs. blending/opacity

Both reading and watching tutorials, I’ve seen two methods to fine tune some modules using either 1) the adjustment sliders directly or 2) by applying a uniform blend and adjusting opacity. This, of course, when you need to reduce default settings when turning on the module.

A good example of this I’ve seen is with the dehaze module, which is always too strong when turning the module on. Some will reduce the strength slider, others will reduce opacity.

Both processes give me good results, but my question is whether or not there are any technical advantages or any technical considerations to be aware of before choosing between adjusting a module effect directly or through using a uniform blend opacity adjustment?

It depends on what strength means. dehaze doesn’t apply the correction uniformly, so uniform opacity control is not the same thing.

Sometimes I use the lowpass filter with a softlight blend mode to increase contrast in certain areas.
With one slider I increase the distance between dark and bright areas. After I find the bright value I find the impact in the image too string. Then I reduce the opacity oft thr module.
In this case the opacity controls the strength oft the whole module while the other spiders controls parameters oft certain details within the module.

@Afre described it well. To see difference, do a simple test:

On the dehaze module pull the slider “Strength” on the left down to -0.80 and see what the image looks like. Then move it back to its original value and then move the “opacity” slider on the left to the value 10% and you will see the difference.

I’m somehow missing it. If I reduce dehaze strength in half from the default strength setting of 50 down to 25, and then compare that result to one where the default of 50 is maintained but the opacity lowered to 50%, they look the same to me.

You must reduce the strength more than half to see the difference. Try the very low values I described above.

As for practicality, in your example the differences are indeed not very big and both options have similar results.

Thanks Boris. I did follow your numbers and there is a difference. What I was questioning is whether there is a difference if the proportion reduction from strength results in the same effect on the image if the same proportion from opacity is used. For example, if I reduce default strength down to 10% of its default (so moved to 0.05) or I keep at the default and move the opacity down to 10%, is there any difference I should be aware of - because they look the same to me but I’m not sure if there is any technical difference or potential effects of either method I should be aware of.

By the way, a big thanks for your videos, they are very helpful!

Ok. We take preferably a specific example to clarify what is the difference and what can happen::

In this picture I want to define the texture of the clouds better with the help of the Dehaze module. I have moved the slider of the strength up to the value 0.18:

Now, I would like to have more texture, but if I increase the strength value (to 0.60. which I like), I also getting the halo in darker and brighter areas:

But now, with the help of the opacity slider, I can make the opacity of the effect so low that the halo almost disappears and I still “keep” enough texture, a bit more than with the lower strength value alone:

Disadvantage is of course that it can actually happen - depending on which modules come later in the pipeline - that the halo appears again, or it comes to other unwanted effects.

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Ah, got it, thanks for the examples.