Illustrator Tutorial - Opacity Masks Using Gradients

When we begin to create Opacity Masks by using gradients, we can 'blend' an image from 100% visible (white) fading to 100% opaque (black).

Here's our original 'sunset' image.  Using the Rectangle Tool , draw a rectangle on top of our image:


In your Gradient palette, create a black-to-white Linear gradient with the 'midpoint' (Location) at 50.

Select both your original image and the soon-to-be Opacity Mask and make sure your Transparency palette is visible.

Use the tiny black drop-down arrow and choose 'Make Opacity Mask'.

The result is on the left.

Let's spend some time to check the Transparency Panel.
After we have applied the Opacity Mask in my last image the Transparency Panel looked like the one to the right:

We have 'expanded' the panel to include the 'extras' surrounded by yellow by clicking the 'up-down' arrow shown at the top-left of the palette.
First you notice that there are two thumbnails available (ITEMS 1 & 3), one showing the photograph (ITEM 1) and one showing the mask (ITEM 3) with a lock icon in between (ITEM 2). By default the photo and the mask are locked together and what this does is - let's say you decide to move the photo, then the mask is moved together. If for some reason you want to move the photograph but you do not want to move the mask (maybe you want to show another part of the photo), then click on the lock icon (it disappears...) and reposition the photo. The mask will stay in place.

If you now click on the Mask Thumbnail (ITEM 3), then you can edit the Gradient the way you would normally do. If you pick the Gradient Tool and 'drag' across the main image...(i.e. not within the Transparency palette, but on the main image on your artboard...)

See how this change in direction is reflected in the box above?

Pay attention when you click on the Mask thumbnail because Illustrator automatically switches to Opacity Mask Mode.

Finally... what happens if you uncheck the clip checkbox? (ITEM 4)... Actually, the areas of the photograph outside the boundaries of the mask are visible after the Opacity Mask has been applied.
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