Tip of the week: Isolating your subject matter and adding a new background

Happy whippet dog with lolling tongue

If you’ve ever found yourself dissatisfied with one of your images because you weren’t completely happy with the background (perhaps it’s boring, too cluttered, or maybe you want to recycle some of your images with a different look), you’ll learn in today’s Tip of the Week how to isolate the main subject you would like to keep, and remove the background. This will leave you with your subject on an empty background and you’ll be able to insert a new image as the backdrop.

In this tutorial, we will be using Photoshop, but there is a free alternative named GIMP, which is open source software and is able to do very similar extractions or isolations, and you can find instructions available online for GIMP.

I chose one of my photos of a whippet for this example. Before we begin, however, it’s important to know that some subjects are far easier to isolate than others. You need clean, well defined edges of your subject so that it stands out from the existing background. If your subject is a brown dog, for example, and it’s standing in a muddy field, which is also brown, it’s going to be almost impossible for the software to make a good distinction between the two.

This process works best if there is a clean line around the edges of your subject, and its color is different to the background. Wispy hair in particular can be very difficult to isolate, and there are video tutorials on Youtube which tackle isolating hair, but we aren’t going to focus on hair in this example, we will keep it a little more simple.

To begin, open the image you’d like to edit in Photoshop, by going into the top menu and choosing File > Open. There are a variety of ways to make selections in Photoshop, with different tools for the job, but for our tutorial we’re going to use the Quick Selection tool which you can locate in the left menu.

Once you have this tool selected, you can change its size in the top menu if you have a large selection to make, and you may also click on the + or – buttons should you wish to add or subtract from the selection. You can also edit the hardness of the brush you use for this.

To make the selection, drag your mouse pointer around the subject you want to isolate, and as you do this you’ll notice small dashed lines appear where you make your selection. These are sometimes referred to as “marching ants” because the selection is animated. Select all of your subject, using the add or subtract as required, zoom in for finer details if you need to, and reduce the size of your brush if you need to select areas in smaller, tight areas.

Once you are satisfied with your selection, go back to the top menu and choose Select > Refine Edge.

This will bring up a new window with some settings you can adjust to fine-tune your selection.

I have checked Smart Radius, and made some adjustments with the sliders under Adjust Edge. You can play around with these settings to get the best result, and this will depend on what you are selecting. There are no specific settings you need to use, I usually just move the sliders until I am happy with the result, and you can also see the effects in real time as you move the sliders.

Finally, under Output, I choose Output to New Layer with Layer Mask, because with a mask attached to your image, you can still make further adjustments using the paint brush if you need to by painting on the mask itself to reveal or hide elements in the image. Layer masks are another feature to learn but you can simply choose Output to New Layer instead if you’re unsure how masking works, and that will give you a cut out copy of your subject matter on its own layer.

At this point, you need to decide what background you’d like to put in to replace the original.

To insert a new background, find an image of yours that you’d like to use, open it in Photoshop, choose Ctrl and A on your keyboard to select the image, and then Ctrl and C to copy it. Navigate back to the image you’re working on and paste it into the document using Ctrl and V. You will need to rearrange the layers so the background is beneath your subject, and you can simply click on the new background you pasted in and drag it downwards in the Layers palette at the bottom right of your screen.

I’ve chosen a completely different colored background and have to address some leftover color contamination between the dog’s legs...there is some green tinging from the original background.

This was easily dealt with by choosing the Sponge tool from the left menu, and making sure the Mode in the top menu is set to Desaturate, which will basically remove the color, and then lightly brushing along the edges where the green tinge is showing. In the example, half the green is removed from the lower right, and half still remains at the upper left of that section.

The new background had a pretty good depth of field, so I wanted to blur it a little to make my subject stand out more and simulate a shallow depth of field. To do this, I went to the top menu and chose Filter > Blur > Gaussian Blur at a radius setting of 50 pixels.

You can choose whatever setting you like, I recommend playing with the slider until you’re happy with the effect should you decide to blur your background.

Once you are done, you can simply flatten the image by going to the top menu and choosing Layer > Flatten Image, and then you can save it with a new file name so you don’t overwrite the original.

The final result looks like this:

Photo credits: Tamara Bauer.

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July 17, 2020


Great information, thanks for sharing it!

July 14, 2020


Nice topic

July 10, 2020


Excellent explanatory article-tutorial! The techniques for cropping in Photoshop are numerous, this one you illustrated is one of the most used, when the subject to be cropped is difficult!

July 06, 2020


This is super useful. I tried this technique last year a bit, but because I didn't do it regularly, I lost my way when trying again. Thanks!

July 05, 2020


Thank you for sharing your experience very useful tutorial

July 04, 2020


Interesting and informative article.

June 30, 2020


Very well written and good illustrations as you model the tasks.  Thanks!

June 30, 2020


Beautiful Whippet and great tutorial! William 

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