The image above was created using 17 different pictures, shooting on a Nikon D3 the continuous high speed shooting mode was cranked right up to it's maximum of 11 frames per second.and the focus was also set to continuous servo mode.
Once the images were taken and downloaded onto the computer, they were renamed and file info applied. Then all 18 were opened into Photoshop, the last landing picture was used as the template image. Then using the Marquee tool to select the skier and a bit of surrounding area and copied it onto the background template. This was done for all additional 16 skiers that were added. The template was then cropped to the images size above.
The opacity of the additional layers were dropped to around 75% briefly so each layer could be individually aligned into it's correct position on the template layer. Each layer then had a layer mask applied to it, then using the the brush tool on the layer mask to paint out the surrounding landscape so each skier blends into the template layer.
A few of the layer required a mid tones adjustment in levels before the layer mask was painted out. Once all the layer had been done a psd copy was saved with all the layers and masks for any adjustments you may wish to make later. A section of background was also used from one layer to remove the shadow of a ski lift chair(this was also done using the layer mask method as used on the skiers).Once all the layers had been flatten, any spots on the background were cleaned up. The levels were adjusted and the contrast boosted, a slight vignette was applied using the Dodge tool on the mid tones with a soft edge brush.
Finally if you wanted to you could turn the whole thing black and white using the Black and white tool or hit Alt+Shift+Ctrl+B.