Using Photoshop Layer Masks
Photoshop layer masks are a very powerful feature in Photoshop, they let the designer hide parts of images without deleting the actual image sections (so you can delete the mask or alter the mask layer to add or remove sections of the image), here are a few tips on how to use layer masks.
Layer masks work by adding colour to the mask window, the stronger the colour strength that is added the more of the image that is masked out.
This image shows a solid fill of black, dark grey and light grey. you can see the darker the mask colour the more of the image is masked out.
Adding a Photoshop Layer Mask
Click on the layer you want the layer mask on then click on the layer mask icon to activate it (fig1). This now gives the layer two windows, the left window contains the artwork and the right window is the mask, that is coloured white by default. Now the mask is added to the layer you will need to click on either the artwork window (fig2.) or the mask window (fig3.), these windows when selected have an outline as seen below.
Layer Mask Tutorial
Here's a quick Photoshop Layer mask example. We start with adding a subtle background curve to layer below the product shot.
Create a new layer then using the Elliptical Marquee tool make a selection and invert it (Ctrl+Shift+i) then using a large soft edged brush add the colour.
I have quickly painted round the curved edge to mask out the sides using again a soft edged paintbrush. As you can see the right window shows black where the mask is applied. You can always paint white to un-mask areas or if it goes totally wrong delete the mask (click on it and drag it into the bin) and add a new one and start again.
Here I have duplicated the product layer, flipped it vertically then added a gradient fill of black fading to transparent to the masked layer, this gives it that fading out effect. I have also turned down the opacity of that layer to 30%.
You can add photoshop layer mask to Text layers and also to Folders. Adding a mask to a folder will mask all the content within that folder and can be quite handy at times for masking multiple objects quickly.