If you have already to use a software of photography, you will have probably heard of mask (of fusion). If it is not the case, or that you never on the occasion to discover this quite useful technique, this article is yours!

What a mask?

The mask will return transparent all, or part of a copy. This tool is particularly interesting to rout an element or to carry out fakings (to amalgamate several faces for example).

One can compare it with a stencil key set, this one coming “to stick itself” to the copy which one wishes to modify.

All in all it is about a copy in level-of-gray of which the black parts will hide the image of the associated copy, while the white parts will post it. It is also possible to play with opacity, which makes it possible to obtain effects of transparencies (more or less attenuated image).

The white part of the mask leaves the intact image.	The black part of the mask hides the image.

Thanks to this technique, one can make modifications to an image as much of time than necessary without risking to damage it.

To create a mask…

General information

If no selection is active during the creation of a mask, no zone of the associated copy will be masked. It is thus necessary to paint the mask of black so that this one prevents the posting of the image.

If a selection is active, the selected zone will appear in white and will let show through the image, while the zone outside of the selection will be painted of black and will thus mask the image.

No zone of the mask is masked.	Only the selected zone appears.

With Photoshop

To create a mask, you have several possibilities:

• you click on the icon “To add a mask of fusion” in the Calques pallet;
• or you go in the Calque menu > Masque of fusion > to do everything to appear”.

Once your mask created, you it selected in double clicking on the label, and you can start to paint it using the brush or of the pencil by choosing the black like color of foreground.

To create an opposite mask, i.e. to mask the selection and not the zone which surrounds it, there exist also various possibilities:

• maybe by reversing the selection (Ctrl-Maj-I or Apple-Maj-I) before creating the mask;
• maybe by reversing the black and the white on the mask (Ctrl-I or Apple-I);
• maybe by maintaining the Alt key inserted when you to create the mask.

If you wish to make reappear part of the image, you will have to paint in white.

With Gimp

Initially, post the pallet “Copies”, while going in “Dialogue boxes > Calques” (or Ctrl-L).

Select the copy that you wish to modify and made one clicks right and to select “To add a mask of copy”.

A window opens and asks you how you wish initialized the mask. Several possibilities:

• white, if you wish to mask only some parts of the image;
• black, if you wish to mask the image in order to not post that a small surface of the copy;
• selection, if you wish to post only the selection.

There exist other options but which are less often used.

You will have included/understood it the adjustments are similar to Photoshop. If you wish to mask an image, you will use a black brush of color, on the contrary to make reappear details, you will have to paint in white…

Some examples

Here some examples which illustrates perfectly the utility of the copies of fusions.

	A flower diverted using a mask…
	A duck alligator… You will find advantages of examples on Worth 1000.
	The effect of discolouration on apple and the text in red are two effects obtained with masks.

Some references

Here some articles published on the Web:

• tutoriel of photo absolut;
• An article on the masks under Photoshop, richly illustrated;
• a tutoriel for Gimp.

In practice

The theory it is well, but a little practice does not make evil either. If you wish to know some of advantage about the masks, I invite you has to discover a tutoriel which was previously published: “how to obtain a partially colorized image”.