How To Blur the Background Of a Photo On a Mac

There are many ways to blur the background of a photo. Here are two methods that use the third-party apps Pixelmator Pro and Affinity Photo, and then two methods using built-in Mac apps Preview and Keynote.
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Video Transcript: Hi, this is Gary with MacMost.com. Let me show you four different ways that you could blur the background of a photo on your Mac. 
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So a common request online no matter what type of computer or device you're using is how do you take a photo and blur the background keeping the subject in focus and the background scene blurred. Well, you can do this, of course, using many different third party apps. So I'm going to show you how to do it with two popular ones on the Mac and then two ways to do it without any extra apps at all.
So here's the photo I'm going to use as an example. First let's try to do this using the popular Pixelmator Pro app. Now the way to do this in most third party apps is to first select either a subject or the background so you could blur one and not the other. Now there are many selection tools in Pixelmator Pro. I'm going to use the Quick Selection tool right here but you can just as easily use a Free Selection, Magnetic Selection or any way that you can best select the foreground or background. So I'm going to select the foreground here. You could see as I move over the subject I could easily select it. Now I want to refine the selection so I'm going to zoom in and look for places where I can do a little bit better. So for instance here maybe I want to take something away I can hold the Option key down and remove some from there. So in this case the Shift key will Add to the selection and the Option key will Remove. It's a little hard to get it just perfect. It helps if you zoom in a lot more so you could more easily see what's there and select in finer detail. Then you've got to go through the entire border here and find areas to add or remove. Once you've got it good enough you can refine the selection even more. So if I go to Edit, Refine Selection I can see the Refine tools here. So I can expand or shrink maybe just a little bit in, maybe 3% in, add a little softness to the selection.  
Now I've got the subject selected but it's actually the background I want to blur. I'm actually going to go to Edit, and then Invert Selection. So now I've selected everything but the subject. Now I can go to Effects here, Add An Effect, I'm going to do a Gaussian blur and I can blur the background. Change the blur amounts to whatever it is I want. Then I'll Deselect here so I can see the finished version. 
Now let's try the same thing, but I'm going to do it using Affinity Photo another popular app for editing photos. So here there are selection tools as well. I could do the Flood Select tool and try to select that way. I could do the Selection Brush and try to select that way and it seems to work a little bit better in this case. Just like in Pixelmator I'm going to zoom in on areas. It doesn't show you a plus or minus in there but you can click to add more and then hold the Option key and then click to remove sections. You can keep doing that also changing the width of the selection tool and try to get it just right. Then here you could also Refine and then maybe do a little bit of feathering there to create more of a fuzzier edge. 
Now I'm going to do something a little different here. Another technique that would work in Pixelmator as well. I'm going to actually Copy this selection here and then Paste it over. So when I look at layers here you could see I've got this new one here that's just the subject and then there's the background. Let's get rid of the selection there and I'm going to choose the background here. To this I'm going to apply the effect of Gaussian Blur too and blur just the background. Actually if I go to layers here you could see if I hide that first layer everything is blurred including the subject. But now I've got the subject layered on top of itself right here so I've blurred everything and then put the subject back. You could do this in Pixelmator Pro and in most other apps like PhotoShop as well. So that's a second way to do it using an app that you can get in The Mac App Store.
But what if you just wanted to do this with the tools that come with your Mac. There's no great way to do it unfortunately. But, you could try. So let's open this up in Preview. Right. You'd think there would be a way to do this in Preview. But in fact not really. Let's go to the Markup Tools. What I'm going to do here is I'm going to go to the selection tools and I could use the Smart Lasso to try to select the subject. This will create this red dot around here and try to cutout the subject based on your outline. It actually sometimes works a little bit better with the regular tools like the Lasso tool but in this case this is as close as we're going to get. Unfortunately, you can't refine the selection in Preview. You have to do it all at once. You can't really zoom in either. So I do it here and it works okay. But not great. 
Now what I'm going to do is I'm going to Copy and then I'm going to go to the Adjustment Tools here and blur everything. Except there is no blur. So you're going to have to simulate a blur and it doesn't work very well. What I'm going to do is take the Contrast down somewhat, maybe bring the sharpness down as well. Maybe the Saturation a little bit. Take a little bit of the color out. That kind of creates a blur.  Doing it for the whole thing here so the subject is also has less contrast. But remember that we copied the subject. Now I can Paste back on top , it's centered so you're going to have to position manually right on top. Try to get it as close as you can. It kind of works especially if you shrink the image down in size and you're looking at a smaller image. Then it works a little bit better. You don't see the imperfections.
Now let me show you another way using Keynote that works pretty well but it's pretty convoluted. Let's first start off by getting the exact pixel size here. So in Preview I can go to the Information Panel here and under General it's 3088 by 2320. So in Keynote I'm going to create a new presentation. I'm going to get rid of everything on the first slide. Go to Document and I'm going to set the slide size to Custom Size and set it to exactly the size of the image. Then I'm going to shrink down so we can see it here. Then I'm going to drag and drop the image into there. Now it should snap right into place. If I go to Format, Arrange, you should see it at zero zero. Now what I want to do first is to make it blurred. So I'll select it and there's no way to blur it. You can go to image and do the same thing that you did in Preview here to kind of fake a blur. But you could also, under Style, set the Opacity down to something like 20%. Then Copy, click away and Paste. It will Paste another 20% transparent overlay. I'm going to move it over by a few pixels. Like maybe ten pixels. So Shift and Right Arrow to move it ten pixels. If I go to Arrange here you could see it's ten pixels to the right. I'm going to Paste again and move that one ten pixels to the left. Paste again ten pixels Up. Paste again ten pixels Down. So now we've got five versions of the same thing all citing different positions. So when I zoom in you could see how it's kind of blurry. So far so good. 
Now we need to put on top of this a cutout version of the subject. How to do that. There's really no good way to do it with just the image. But we have the ability to create these custom shapes. Let's zoom in here and start creating custom shapes by putting lots of points here all around the subject. You can get as detailed as you want. Take a little bit more time than what  I'm doing. Notice how here I made a mistake. It's okay. Just keep going like that. You can fix the mistakes. I'm not even going to be worried about being perfect here at the bottom.Just going to get it to be all the way around and then to finish it off you've got to click on the first point there. Now you've finished it. You can see there's a line there. I can go to Style and I could set a fill, like a color fill if I want. It's a little bit easier if it's set to No Fill. At the border maybe some color to make it really easy for me to see. Like a red like that. I can adjust any point I want. So I can fix imperfections. Not only that I can select a point and then hit the Delete key to get rid of it. So I can fix that mistake. This mistake I can fix there and I can get this all the way down even below the bottom. Like that. Then you can work on anything else you want. You can even click to add more points like that. You can curve out any point you want. You can get really detailed. So then when you're done you now have this shape here. 
Now you may think, oh let's set the Fill to an image fill. But that actually doesn't really work well. What works well is with the shape selected like that I can now drag and drop  an image into it. Then the image isn't going to fit perfectly. I have to reposition the image inside to get it just right......and done. Now I want to get rid of that line, that red line. You don't need it anymore. There I go. So now I've created this shape that's perfectly sized like the subject. I placed a copy of the image there and then I have all these other images behind it that are kind of blurry.
The results are less than perfect but mostly because I rushed. If I took a lot of time to actually work on the outline and to align everything perfectly it would look really good. Now, of course, this is a Keynote Presentation which isn't what you want. You want to Export it as an image right here and you could choose jpeg or png for even higher quality. I'm probably going to stick with jpeg and then we'll export this to the Desktop. I'm not going to bother to name it but you get a folder here and inside the folder you get this image. I can take it out of the folder and get rid of the folder. You could see here's the original image in QuickLook and then here's the version I made in Keynote.
So really if you want to do this kind of thing right you want to get an app like Affinity Photo or Pixelmator Pro to do it. Of course you can also use PhotoShop or any other image editing app. They all are going to have these basic tools in them. But if you really want to figure out a way to do it using the tools that come with your Mac you can kind of simulate this with Preview or Keynote by putting a little bit more effort into it if you don't mind the imperfect results.
Hope you found this useful. Thanks for watching.
Comments: 2 Responses to “How To Blur the Background Of a Photo On a Mac”

SimonA
3 years ago
Excellent tutorial Gary, I lost my Photoshop subscription when I lost my job so learning how to blur backgrounds in Preview and Keynote is brilliant. Thank you and keep up the great work. S
Thim Fook, Law
Much thanks for the cool tip, Gary. Much appreciated.
Comments Closed.
How To Blur the Background Of a Photo On a Mac

Comments: 2 Responses to “How To Blur the Background Of a Photo On a Mac”

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