This tutorial shows one way of blurring a distracting background.

I want to thank Douglas Hall for allowing me to use an image of a seedling he sent me for this tutorial. Thanks, Doug! I love the seedling, but I find that the background's too much in focus for my liking and that the small grasslike brown object at about 1 o'clock behind the sepal is especially distracting.


In order to blur the background we need to isolate it from the flower. Photoshop's filters work on what's currently "selected". There are six main types of selection tools and they are the top six in the main Tools palette. We are going to be working with one of the Lasso Tools - which are the second item down on the left side. If you look carefully you'll see a small black triangle in the lower right corner of the lasso tool - this means that there are other, similar tools hiding beneath the tool that's currently shown. By default the "normal" lasso tool is shown, but to make this job easier I want to introduce you to one of the other lasso tools. Go ahead and click on the lasso tool in the palette and keep holding the mouse button down, another palette of tools will appear that should look like this:


The Lasso Tool lets you select an area by clicking and hold the mouse button down and using the mouse to select the area to be worked on. The Polygonal Lasso Tool does the same thing except only with straight lines. The tool we want to choose is the Magnetic Lasso Tool. This tool "snaps" to the nearest edge that it can "see". It's a good example of where close is good enough - you'll see. Select it to begin.

lasso at work Start at the tip of a petal, click once and start to loosely trace along the edge of the petal. You'll see that the selection area snaps to the edge and sets direction change points (the boxes) when the direction alters. You can also manually click to select a direction change point. I do that at the tips of petals and at the point where two tepals meet. This tool works on contrast between the object and the background - if the two are too close together in levels you may have to also manually click some points - on this example, where the leaf and petal meet and the shadow's close to the petal tone, I manually clicked a few times.


Continue on around the flower until the whole flower is selected - when you get back to the starting point you must complete the selection by clicking on where you started. The selected area will start to be outlined in moving white and black dots (affectionately referred to as the "marching ants"). Your selection doesn't have to be perfect either, we'll clean it up in a moment.

There's a big problem at this point, we have the flower selected and we want to blur the background. Oops!

Photoshop's designers realized that sometimes it's easier to pick what you don't want and then reverse the selection. Under the Select menu in Photoshop you should find a menu item labeled "Invert" - chose this and you'll see that the "dancing ants" are now all around the edge of the image and are surrounding the flower. You've selected the background by inverting the selection.

If you need to clean up the selection a bit, here's how. Switch your selection tool back to the "normal" Lasso Tool. Now, be careful NOT TO CLICK anywhere in the image without reading and following these instructions. If you click now, you will loose your selection! (Thankfully, you can get it back if you immediately do the Undo sequence (Control-Z on a PC, Command-Z on a Mac).

Using the Lasso Tool you can add to, and delete from, your current selection. The key here (no pun intended) is to hold down one of two keys on your keyboard while you are drawing with the lasso tool to modify your selection. To add to your selection, hold down the Shift key - you'll see a little plus sign appears by the lasso tool cursor. To delete an area from your selection, hold down the Alt key on a PC or the Option key on a Mac. A minus sign appears by the cursor. Don't be too concerned about knowing which one you are doing - if you are trying to add and the result takes away instead - do an Undo and pick the other modifier key and try again. Make corrections along the edges - adding and removing as needed. Do small sections at a time - it's easier to undo little correction mistakes and redo them than big ones. You always need to close the area being selected by returning the lasso to the starting point of each 'fix' - just try it and you'll see what I mean. When you think you have the flower isolated, continue the tutorial.

We'll do one more thing before we blur the background and that's feather the edge of the selection - this is easy, and it keeps a harsh jagged edge from appearing around our selection area. Go back to the upper Select Menu and choose "Feather..." from the menu - in the dialog that appears select a 1 pixel feather. Basically, a feathered edge is slightly blurry and looks more natural.

Now, finally we can blur the background.

We are going to use the Gaussian Blur Filter. Filters only work on the selected area, so that's why we had to spend all the time to get the background selected. Go to the Filter Menu at the top of the screen - choose Blur and then Gaussian Blur. A dialog should pop up looking something like this - you can move the picture area shown around by clicking and dragging the image in the dialog until you can find an area where you can see both flower and background. You can also enlarge or reduce the preview by clicking the plus and minus icons.

blur.01 blur 4.6

There's a small slider at the bottom of the dialog - by sliding it left and right you can preview how much blur the background has. I ended up choosing 4.6 pixels. You can click OK, see the full results and undo it and try again until you are happy.

Here's the final version:


Notice that that to me annoying piece of brown grass or leaf at 1 o'clock was "fixed" as well.

An added benefit to this technique is how it affects file sizes. The upper image is 160K, the bottom, blurred image is 92K. The more detail an image has the larger the file size, so blurring some areas can significantly reduce file sizes.

There are a number of other ways to tackle this same issue - for instance, we could select the flower, copy and paste it to a new layer. Select the green leaves and copy and paste them to another layer and select the brown leaves. Then we could blur the brown leaves more than the green leaves, leaving a bit more sense of depth - this also takes longer and is more complicated. We'll be looking at layers in a later tutorial.

This was quick and dirty, but it would look something like this...

layered blurs

Next tutorial, we'll start on one method of color correction - using the Adjustment and Variations Dialog.

Tim Fehr - Eau Claire, WI

© 2007 by Tim Fehr - all rights reserved.

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