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The Selection Process Mystifies Me

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The tutorial on using the selection tool shows a girl against an almost uniform background.

I am wondering whether one can isolate the baby in the picture which features a much more complex background than you have in the tutorial example.

If it isn't too much to ask, would it be possible to guide me through the steps required to effect the baby's selection?


Screen Shot 2017-08-20 at 6.42.47 PM.png

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Thanks for the reply - the video was very helpful but a bit of audio would have helped. Nevertheless, I think that I do have the hang of the selection process. So once I have the baby selected how can I copy just the selection rather than the entire picture? How can I export just the selection rather than the entire picture? Does copying the selection enable you to paste it in another application like Pages?

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I thought that I had the hang of the selection process and I suppose that technically speaking I do. But I was shocked to see how jagged the final result is. Is there any way to smooth the edges to make the result more aesthetically speaking?


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If AP's selection tool gives unsatisfactory results there are two options:


1 - Make the selection in AP another way, for example by starting with a colour channel (a photo has 10 channels: R, G, B, C, M, Y, K, L, A, B). This is more complicated than using a selection tool. You can google 'make selection from channel'. I opened your baby photo in AP and found that the B channel had the baby's head lighter than the background and the K channel had the head mostly darker. Either or both these would be a place to start.


2 - Other iOS apps have other ways to make selections. Superimpose has several tools. But the result might not be better than what AP gives you; it's a hard task for a machine when the thing you are trying to select is similar to the background. Even though it might not look similar to you; eyes are clever. There is an iOS app that helps you draw round the edge of the thing you are selecting, but I forget it's name.


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AP lets you draw a Bézier curve, but the app I'm thinking of is designed just for drawing linked Bézier curves, and so does a better job to get a selection. However, your photo has hair, so my suggestion to draw the selection isn't going to work.


i just tried your baby head in AP with the standard selection tools and got a much better result than you show. I used the smart selection brush on the face, not the background and with a couple of strokes in the middle of the face got a good selection of the whole head. I used the refine selection tool on some hair and the chin. I thought the result was pretty good, with no rough edges.


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Stanley - you must be a real artist  - my second attempt is even worse than the first. When you use the Smart Selection brush, do you fiddle around quite a bit with the Add and Subtract modes to fit the selection exactly to your subject? I find these 2 modes a bit touchy to use - the Add will sometimes shoot the outline way past the face and the Subtract will bring the outline well within the face. Very difficult, at least for me, to get the outline to coincide exactly with the subjects face (as you can see in the photo below)


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 I made one stroke of the smart selection brush on the head, shown in red below, and got this:



Which looks like this:



The forehead above looks a bit ragged, but when I zoom in I see it's done a good job, and possibly can't be improved (this is where the hair meets the forehead):


Maybe use shrink tool to get rid of the dark edge.


The image I'm using is from your first post, only about 900 px wide. You will have worked on a higher resolution image; this might explain the difference. Or maybe you got pretty much the same as this, and the problem is fixing the selection under her chin/ear.


For this, I got good results using the smart selection brush at about 5 px, being zoomed in, and using add or subtract. If I just brushed the edge of the selection it would jump the selection sideways a bit, eventually ending up where it should be. Or try 'refine selection', which you will need for the hair anyway.


Why are you doing this? That might influence what you need to do.



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I've never found a perfect selection method on any software, but do find Affinity to be pretty much as good as anything else.

My standard selection process is:

  1. Selection brush gently around edge, then fill in middle. Then zoomed in going around edges, adding and removing.
  2. Quick mask (with various softness of brush) to improve further.
  3. Refine, for things like hair and leaves of tree against sky.  Mostly with Matte and occasionals Foreground brushes.

Depending on the foreground/background contrast I may omit 2 or 3, and perhaps fiddle more with 3.

Using the right brush size and softeness can be important.


Dave Straker

Cameras: Sony A7R2, RX100V

Computers: Win10: Chillblast i9 Custom + Philips 40in 4K & Benq 23in; Surface Pro 4 i5; iPad Pro 11"

Favourite word: Aha. For me and for others.

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Thanks Stanley - very helpful instructions especially with the accompanying photos. I'll certainly give the tips you have presented a try. As to why am I doing this? It's simply a learning exercise as I am (surprise! surprise!} new to the app and wanted to work with a complex background as a learning exercise. No point in trying to use the selection tools when there is blue sky in the background. If I can get the selection process to work with this kind of background, I will be a master of the process. Then I can go on to everything else that I don't know!

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