Problem with Masking in Live Filter Layers

[Errol Egan]

I have been trying to use the inbuilt mask feature of the live filter layers but despite following (to the best of my knowledge) the procedure in the related video tutorial, I cannot get it to work. When I invert the layer the effect does disappear but when I select the paintbrush and choose white as the colour, it has no effect on the layer. The effect does not show when hovering , nor does using the paint brush lead to any change either in the image or on the icon in the mask on the live filter layer.

I have uninstalled and reinstalled Affinity Photo but it is still the same. Is there some setting I may have inadvertently changed which is stopping this working? Sorry if there is an obvious answer but I am finding this rather frustrating at present.

[stokerg]

Hi Errol Egan and Welcome to the Forums,

Which Live Adjustment Layer are you using?  Also when you've got the brush selected, make sure Protect Alpha isn't enabled on the toolbar along the top, as that could stop it from working.

 

[firstdefence]

Use Black instead of white and the layer will invert 

[Errol Egan]

6 hours ago, stokerg said:

Hi Errol Egan and Welcome to the Forums,

Which Live Adjustment Layer are you using?  Also when you've got the brush selected, make sure Protect Alpha isn't enabled on the toolbar along the top, as that could stop it from working.

 

I was using Gaussian blur but I tried other live filters and had the same problem, however having disabled Protect Alpha it now works! So thank you very much for that helpful input. Perhaps you could now help me to understand what Protect Alpha does and why I would want to use it, I had checked it just because the image seemed to look better that way to me!