Upping Opacity on photos

Stroker1 · 10-19-2002, 10:05 PM

Gauss's post in the other thread has prompted me to speak up about somthing related to his topic.

I love using Edit > Fill with Mode: Behind.
101 Uses

But it doesn't always work. Like on photos when you need to bring the opacity of individual pixels in a layer up to 100% while mantaining the colour data.

Grab a photo. Grab Eraser tool, make it big and soft, and give the photo a few strokes. You know have some partial transparency in the photo.

Now, the pixels in the photo's layer have two different types of data: colour and opacity. Let's say you want to get those partially transparent pixel's opacity back up to 100% with their original colours. Well, Fill Behind just won't work because it uses a solid colour. Doh!

The fix? Simple enough.

Copy the layer
Merge down (ctrl + e)
Rinse
Repeat

The lowest % opacity pixel will basically tell you how many times to copy. Or you could just eyeball it, which is no big deal.

This trick has saved my posterior a few times.

The down side:
When a pixel reaches Opacity: 0 (Transparency: 100%), the colour information is tossed. That has Suck Factor: 115%.

The complete fix?
Use a Layer Mask! Some people don't, and dealing with it can be a pain. Hopefully you'll never have to deal with it. In case you do, the above trick should fix things (with the exception of 100% transparent pixels, which is another story all-together).

10-19-2002, 10:26 PM

Sounds all very interesting Stroker but what do exactly mean with rinse, repeat?

Stroker1 · 10-19-2002, 10:39 PM

It's a common colloquial (around here) for "do it again and again until you are done." It comes from the instructions on shampoo bottles.

In the context of the original post, keep copying and merging down until you are happy.

10-19-2002, 10:52 PM

Btw, I have another question.

Sometimes I want to create an object with highlights and shadows. I make a selection and fill it with the main color. If I want to add a shadow area in a later stage, I CTRL+click the object?s layer, create a new layer and start brushing the shadow. I create a new layer for the highlights. Now I run into a few problems when I do that. You can remember my earlier post. Well, if I CTRL+click a layer and start brushing inside that selection in a new layer, I have to deal with 2 problems;

a) Because my original object was anti-aliased, my new selection will be smaller than the original object, because of 50% grey rule. That means that I will see a light halo around the borders, especially visible when I paint dark colors on top of a bright object. If I would however select the original object including all pixels, jaggies will occur on my layer with the highlights or shadows.

b) If I would paint for example two grey strokes that intersect, I have the problem that the intersected area is darker. I run into this problem every time I want to add some extra shadow in a later stage. I try to solve that by using a very low opacity for the brush.

I just want a solution for creating an object adding highlights and shadows on separate layers and that I don't have to worry to move my brush outside the object and that the end result is anti-aliased.

Say for example that I want to create a jar with all the highlights and shadows included.

BTW, I exaggerated the examples

Stroker1 · 10-19-2002, 11:37 PM

Try clipping them. That's how I do it. Usually one set to Screen and the other set to Mulitply. Sometimes I'll try other blending modes just to see.

The above layers that are clipped will "inherit" the transparency of the base layer. No halo and no jaggies. The 50% problem in a selection is negated since the clipping runs from 0% to 100%.

That should do ya, if I'm reading your post correctly.

Oh yeah, try setting your Brush to Darken. Does wonders when you want something to be darker, but not darker to a certain point.

Blinky2004 · 10-19-2002, 11:41 PM

I've been using this method you mention for years Stroker. And it warrants being used for a LOT of things too. Good suggestion. Never thought to bring it up myself.

Gauss...
To fix your halo, just repaint that edge 1 or 2 more times. The halo will be filled in completely; and without jaggies.

To fix the darkened area of your intersected parts... just select the upper layer, and apply that selection as a layer mask to the lower layer.

10-19-2002, 11:49 PM

Woooow, some interesting info here guys, thanks a lot you both [righton]

Stroker1 · 10-19-2002, 11:53 PM

I just did some playing with painting on a selection. Man, talk about annoying.

Made a selection with Feather: 5. Filled on one Layer. Loaded it from the layer, started a new Layer, and painted away. After a few passes with the Paintbrush, I could get it to fill in decently.

Okay, then I took the Eraser and started erasing. Just to see, I loaded the transparency and tossed into an Alpha channel. No matter how much I used the Eraser tool, I could not get some of the pixels that I had painted to go away. Grrrr! Even Delete wouldn't get them all.

I'll stick with a Clipping Group. Nice and tidy for this PS'er.