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Selecting a circle; I must be missing something

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I have a photo that includes several round balls.  I want to select one of the balls, which is mostly round and I would like to use the 'Elliptical Marquee Tool' not the Selection Brush because I can 'see' the edges I want better than the Selection Brush.  But I just don't get how to use the Elliptical selection tool.  If I start a new selection at say point X, Y, the larger the selection, the more the 'top left' corner moves off of X,Y to a new position, X+a, Y+b.  My selection ends up not aligning perfectly the ball.  How do I micro adjust the selection to get the proper alignment?  I don't have the 'balls' shot handy but assume this light is a ball and I want to very carefully select a round object.  I don't understand why I can't start the circle at the top left edge or how to properly refine it later



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The 'Elliptical Marquee Tool' is sometimes hard to size and position adequately, though you can also move it in small pixel steps via the cursor keys. To refine it go to the top bar and press the "refine" button which gives you a panel with some adjustment sliders for finer grade setup.

However another often better way to setup/get a good visable round elleptical selection is, to use the shape tool and draw and adjust first a fitting shape covering/over the round areas. This gives you a layer with an elliptical shape from which you can make a selection with the menu entry "Selections -> Select from Layer". The result will be too a elleptical selection, which here goes conform to the setup elliptical shape. You can then delete the shape and keep the selection for any further processing.

☛ Affinity Designer 1.6.1 ◆ Affinity Photo 1.6.7 ◆ OSX El Capitan

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You can transform the elliptical selection marquee as if it were a pixel layer if you switch to Quick Mask mode (press Q) and activate the Move Tool (press V). Press Q again to exit QM mode.


Alternatively, use the Ellipse Tool (the vector shape tool, not the Elliptical Marquee Tool), draw and align an ellipse and then make a pixel selection from the ellipse:

  1. draw a vector Ellipse with 100% opaque fill colour and no stroke, and with layer opacity of about 20% so you can see through it to the underlying image
  2. fine tune the size and position of the Ellipse
  3. cmd-click (ctrl-click on Windows) the Ellipse's thumbnail to get a pixel selection marquee of the same shape
  4. hide or delete the vector Ellipse


Or use a fully opaque vector ellipse as a vector mask on the image, or clip-nest the image inside it.


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