Gaussian blur question....

[Krusty]

Say you're working with something trying to get an effect, so you apply a guassian blur. Say you set it to 2.0. Then say you do it again and you like that end result. Now you want to apply this same effect to other layers. Can you simply blur them to 4.0, or do you have to do the double stage of blurring every time?

I use it when screwing around for camo effects, wear, tear, etc. It's come up recently and I was wondering if I could double the value and halve the steps, or what?

[potsNpans]

I thought blur numbers were in relation to pixel diffusion. So 4 might get you there sooner than 2 repeated, but I'm using paint.net free software. So effects might vary on retail graphics program.

[Stoney]

Krusty, I always apply the effect and evaluate the result, then ctrl-z.  I'll do this a couple of times until I find what I want, and then apply the affect at whatever level I liked. 

Short answer is "I don't know" but typically the effects don't stack like that.  However, the perceptible difference between (2) successive 2.0 g blurs and (1) 4.0 may not be perceptible.

[Larry]

It really depends on how you want it to look. You could do that but you wont get the same effect. Here's an example. Top one is two layers 0,0,0RGB at 2.0 each. The bottom is a single layer 0,0,0 RGB at 4.0. As you can see they are very different.

[Krusty]

I don't necessarily mean 2 layers on top of each other, I meant apply 2.0 to one layer, and then apply it again after it had already been blurred. Although, you have given me a good way of testing it that I hadn't thought of, just use a couple of layers and test it out.

EDIT: After a bit of testing, simply skipping to 4.0 pixels of blur is significantly more than applying 2.0 pixels twice consecutively. It must be geometric increase, or something.