Photography Studio
Click to return to Archives
Making selections 01 to 06. By Bry Davis.
Hi
Making Selections 01.
What are selections?. A selection is a group of adjacent pixels that make
up an image and contained within a boundary selected by you or the appropriate
tool surrounded by (moving ) dotted lines or `marching ants`. Any pixels within the boundary can be edited , protecting the rest of the image, or you can go to the selection menu and invert the selection to make the rest of the image now a editable item.
Photoshop provides many selection tools from the crude to the sophisticated applications.
At the top of the tool bar is the marquee tools with a fly-out for elliptical, single row and single column pixels , the single row and single column I have never used.
Because our image is made up of millions of pixels in a grid pattern a selection that is made that `cuts across` the image such as a circle or any line that is not horizontal or vertical will show jaggies or a stair tread effect and will not be a smooth cut out, so, always leave the anti-aliased tick in place.
Prepare a new file (ctrl+n), A4 size with a white content at 300 pixels per inch (ppi).
Choose the elliptical marquee tool and drag an ellipse press shift to get a perfect circle.
Remove the tick from anti-aliased box fill the selection with black, deselect (ctrl+d) magnify greatly the edge and you will see jaggies.
Repeat the process with the tick back in to anti-aliased, examine and it will be much smoother.
Therefore always leave this ticked for 98% of selections.
Now for feather, if a selection is made with 0 feather it will appear if used in a montage as too severe and clean cut so feather to about 1 or 2 pixels.To show this feather affect, repeat your marquee, feather at 100 , fill with black and you can see the gradual fade off to white, good for vignettes but not for this, use 1to 2 pixels feather. If you forget, go to the selection menu and feather from there.
Adjusting the selection via the selection menu/modify/expand or contract. Now again fill a selection with black , leave active and choose contract as above, contract by 10 pixels,the selection will creep into the black area so you can tighten a section right up to your required edge area ,use say I or 2 pixels. You can of course do the reverse and expand the selection area.
Expand or contract should be done before choosing a feather.
The marquee tools can be made to operate by added dimensions in the boxes above and to make exactly square or circular hold down shift after clicking and starting to drag. Holding shift and alt down together will make a selection from the centre of a chosen subject.
Copying and moving selection. There are many ways to do this in photoshop.To copy an active selection to the same image you can edit menu/ copy and paste ctrl+c then ctrl+v., it will be place exactly over the selection chosen, the lines will disappear and the pasted object is on a new layer. Choose the move tool and the pasted item will have then handles around it for further editing. If you hit ctrl+j, this will by-pass the clipboard and save on ram but place the selection again on a new layer.
If you do make a large selection to the clipboard, to free up ram after pasting, hit edit/purge/clipboard and the clipboard is empty.
If you make a selection and simply use the move tool it will reveal the background below the moved selection area. Use the move tool with alt and this will allow a selection to be moved (or copied actually ) without exposing the background.
Try this, make a new file , fill with red, make a selection, fill with black and apply the move tool.
You can use the move tool to move the selection to another image, use shift at the same time and the selection will be placed in exactly the same position as the donor image.
***Don`t forget the donor and recipient images should be the same resolution size
Making selections 02 , magic wand tool.
This tool is sometimes unpredictable but very handy at times.
It works by selecting pixels at a preset value set by the user from 0
to 255.Just click on the image and all pixels at that value will be selected
either contiguous, that is touching or adjacent,or non-contiguous, that
is any pixels of that value anywhere in the image.
0 selects just that value, 255 will select all pixels in the image. The
default is 32. Try this by typing in o then deselect ctrl+d, now dial
in 255 and click again. With experience you will be able to adjust this
tolerance to meet the image.This is sometimes difficult to decide.The
tool selects shades above and below the set tolerance, say the default
at 32 is used, then it will pick 16 above and 16 below the figure so you
can see that judging the amount is very important.
A working example. A blue sky. Although you may not see this but a blue
sky will have a gradual shift in shades . Click on the blue in contiguous
mode some pixels will be selected, hold down shift and click on another
area of the sky outside the marching ants and more sky will be added..
To subtract an area . alt/shift/ click, to remove a not required portion.
Finally you will have a selection containing the sky, feather at say 2
and use anti- alias.
An intricate church steeple against a sky , the steeple being difficult
to select can be selected by selecting the sky with the wand then inverting
the selection. The steeple is now selected.
Don`t forget, feather/anti- alias/ maybe contract 1 pixel.
A tip, if you press enter while using the wand a box appears with
the wand options palette with the tolerance value highlighted,.enter a
new value and press enter.
Making selection 03, lasso, polygon and magnetic lasso.
Lasso tool. A simple tool to use but not very accurate. It `rounds
up pixels`. Hold down the mouse button and drag round the item,
but if you release the mouse too early the proggy will simply shortcut
and join the two ends with a straight line.
This tool is handy if you have a drawing tablet and pen where more precise
lines can be made.
Polygon tool. This will make selections with straight lines. Click on
the start point of your required selection, release, move to the next
point and click and so on, keep clicking until you reach the start point,
hover over this point until the cursor changes then click, you will have
a selection.
If you meet a curved section hold down the alt key and the tool will change
to the lasso.
Tip if you are using the lasso tool, using alt will change it to the polygon
tool.
Magnetic lasso. Good tool used with high contrast images which have high
contrast edges of the required selection. Click on the edge required ,
let go the mouse and drag around the area reqd this will create a line
with anchor points. Anchor points fix the selection line to the edges.If
you want to delete an inaccurate point press the backspace key to delete
.To complete the selection hover over the start point and click. to make
a straight line hold down alt and click the next reqd point.
Options. Lasso width
determines how close to the `edge` you have to drag the cursor for it
to `see` this edge.
High no. Good contrast images.
Low no. For intricate low contrast images.
Tolerance. 1 to 40
Frequency
0% to 100%
Tells the tool where to attach the anchor points.
High. For intricate, rough edges.
Low For smoother edges.
Edge Contrast.
1% to 100 %
Good contrast use a high setting for a smoother selection.
Low contrast use a lower value.
Don`t forget... Feather/ anti-alias and contract selection.
Colour Range 04 ( found under the selection menu.
Now we are getting the big guns out.
This tool allows you to select areas of colour in the image that are not
continuous .
You can also adjust the tolerance setting and check real time the effect
in the preview box,. ( change the preview to greyscale in the dialog box
) before applying.
I would suggest that you firstly practice with a new A4 sheet , white,
then make several selections with the marquee tool and fill with different
colours.
Select the eyedropper tool from the box., click on an area that you want
to select. The eyedropper acts like the magic wand tool .
The preview lets you see your first selection area in black and white.,
white the selected area, black, not .Grey areas are blurred edges like
a great deal of feather.
However at the top of the box is a fuzziness slider from 1 to 200 to adjust
the tolerance.
High no. More shades.
Low no Less shades.
By moving the slider you will see the selection change.
If you want to add to the selection , press shift with the eyedropper
or alt with the dropper to delete areas.
Some versions of the proggy have plus and minus eyedroppers icons.
When you are happy with your selection press enter and your chosen area/areas
will convert to a selection.
This is very handy if you want to change the hue of say flowers that are
spread around the image.
Replace colour
This tool is not really a selection tool but as the name suggests you
can replace rapidly any hue with another.
Found under the image menu/ adjustments/ replace colour.
Click on this a box will pop up, use the eyedropper click on the image
say flower petals, then use the sliders to adjust the hue/ saturations
and lightness. You can also add and delete.
This tool is handy but not as sophisticated as the colour range tool.
Don`t forget., feather/anti-alias and contract.
Making selections 05. Pen tools.
Pen tools
This is the `big bertha` of selection tools which on the surface looks
very daunting indeed but is the very best tool for precise selections.
But needs some practice.
It is too difficult to put into words how to use this without graphic
drawings but I would suggest that you look in the help files.
If you are serious on making convincing montages buy a book and learn
the basics and practice, practice.
The pen tool does not make a selection first of all but a path that can
be used in many ways as you get used to your proggy and want to do more
image work.
You basically drag the tool around the chosen part of the image with straight
lines , curves, sharp corners and any shape.
It produces anchor points that can be edited, moved, deleted, added etc.,
When you reach the start point and hover and click you get a line, not
marching ants. This is a mathmatical line but forget a said that.
Right click inside the lines and choose ,make selection, choose a feather
1 or 2.
This path is on its own layer but not in the layers palette but in the
paths palette.
It worked by dragging handles, by clicking on the end of the handle and
then pressing ctrl, dragging the line like a rubberband to fit the shape
of your chosen selection.
Paths can be saved for future work with the image file.
Well so can selections.
Paths can be exported to other vector graphic progs ,like illustrator
so that text can be accurately wrapped around or stroked along the path
and then imported back in to your image proggy.
But at this stage get used to just making simple paths using the new A4
file, white foreground , making shapes like marquee and elliptical and
filling with a colour then delecting.
Then use the pen tool around these easier shapes.
It took me some time to get my head round this tool but it is
the best.
Making selections 06,Transforming ( final part ).
Transforming selections.
Now that we can make decent selections, these can be transformed into
many shapes.
You can transform just the marching ants or all of the pixels within the
selection.
If you hit ctrl+j together the contents (pixels ) will be placed on a
new layer.
Activate this layer by clicking on it in the layers palette and choose
the move tool.
Now go to the edit menu and choose transform, a bounding box appears with
small boxes that can be dragged to a lot of shapes.
If you just want to increase the size choose scale and with shift key
down drag on the corner of the bounding box.This selection then can be
scaled up or down to suit.
Other options are,
rotate
skew
distort
perspective
flip horizontal/vertical
numeric
rotate 180/90cw/90ccw degrees
When finished hit enter.