Oz Future (ozfuture) wrote in tech_nique,
Oz Future

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General Housekeeping And How To Use The Background Eraser

Hey all, another day, another technique for you all! Yes I know 2 in a month *shock horror* and pick up your chins off the floor please!

A bit of housekeeping though before I begin. To all the new people WELCOME! And to the old hands, welcome back. This community is not just for me to post hints and tips, everyone of you can and should post anything you want, if it’s a trick to take better still shots, or even how to tell Dreamweaver how to use a java script! Hell converting an jpg to a gif is good! No matter what you’re good or bad at some people may not know how to do it. So post Away!!!

Anyway I just came back from attending a 90 min talk about Photoshop CS. For those who don’t know Adobe run free Seminars every few months (well they do in Australia anyway) and you can pick up all sorts of tricks there. Sometimes its basic stuff, other times it can be how to use new the features properly. So today I’ll be passing on a few tips on how to Extract a person (dog, cat, object or mech) from a image.

First off we need our victim. Err, I mean subject, a quick search on a stock photo site came up with this

How about we move her to a place that is a bit warmer?

So we got our first composite images ready to go. Now we have a few options to mesh them together. Since the background is very much the same we could just use the magic wand tool.But that way has a drawback

Can you see what the problem is?

ok how bout now?

that’s right the magic wand tool missed the loop in the hair but also gave her a cookie cutter hairdo, we missed out on the strands of hair. It doesn’t look that good at all, does it boys and girls. So how do we get a better effect?

There are a few ways to do this but ill be looking at 2 different versions though different post The first way we will look at is the background eraser.

I know I know you have tried this one before haven’t you?

Well, if you have used the default settings then it highly probable that it hasn’t done the effect to how you like it. But trust me it is very powerful, but this technique will only work on images where most of the background is the same colour. On our 2nd one it would be painful to do it this way! The background eraser tool, is a "destructive" tool, by that I mean it actually changes the layer, so when using any tool that actively changes the layer you want to work on, unless you know what your doing, copy the layer first, you can always delete it later. (in case you cant remember how to copy a layer just drag it onto the new layer icon in the layers window).

Before we even start to work with the background eraser tool, we first need to understand the tool. Lets look at the brush itself.

now everyone have a look at the little crosshairs in the middle. That is where the tool gets the colour sample from. Also I have the actual brush a bit larger than I would like, but so you can see the crosshairs I did bump it up a bit

These are the default settings (apart from the brush size!) that are set by adobe. They are not the best default settings at all. There are 2 sections that you need to change before you can use it. First off is the limits section. Its currently set to contiguous. What dose that mean? It means this. When your bush hits something that is a different colour or has more variation than your tolerance limit is set to it will stop.

so if I’m trying to remove all the black from this picture and I have the background eraser set to contiguous it wont get the black in the middle of the white, it will only go to where the white is and no further because the change is to great and its not told to go over that limit.

so this is what you would get. Now if it’s set to discontiguous this is what you would get.

see what I mean?

Now the other thing you will need to change is the sampling. That is currently set is to Continuous, what that means is that the crosshairs will do a fresh resample every time it moves to a new area. What does this mean to you? What I did to this image was leave the background eraser brush on discontiguous but the sampling is continuous.

starts out fine, looks all good, but EEEEEEEEEK

What happened? What happened is that the automatic sampling picked up the colour of the hair we are trying to keep!!!

So anyway once you have done both of these to the tool box. This is what it should be set to.

Now you know what goes on with the defaults lets do it with the right settings! Volla!!!!

looks nice? Here have a look at a close up.

now all I have done is just dragged and dropped the layer onto the beach layer, and resized it a touch

Not bad, for a quick job if I say myself.

Ill be explaining all about the extract tool soon. So keep a eye out for that.
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