Creating Realisitic Composite Images in Adobe Photoshop 3.0



Photographing the Subject

The illustrations seen in magazine articles about compositing images in Photoshop and other image processing applications often use royalty-free photographs commonly found on clip-photo CD-ROMs as the source images for the composite. This is fine for the purposes of demonstrating the technique, but the results usually leave something to be desired when it comes to producing a genuinely convincing single image that looks like a simple undoctored photograph.

In advertising photography, subjects are often photographed in the studio, to be dropped on to a separate background image. In the dark ages of publishing, pre-DTP, this operation had to be done at the printing stage by non-design-friendly technicians in white coats. Even now, in the brave new world of desktop image-editing, some dire examples of image-compositing are foisted on the innocent readership of catalogues and consumer magazines. The main reason for this, leaving aside the limited awareness of what constitutes a visually-pleasing picture to the average printer, is that no consideration was ever given to the inter-reaction of the subject and background images. Now that those individuals best qualified to judge what looks convincing in a photograph, i.e. photographers, have belatedly got around to equipping themselves with Macs and a copy of Photoshop, the world of image-compositing is indeed a sunnier, more beautiful place to be.

As may now be obvious, I am an advertising photographer using Photoshop to composite images which previously either had to be shot in highly elaborate, time-consuming, and expensive studio sets, or hauled around the countryside in vans carrying unfeasibly large amounts of cameras, lights, tripods, models etc., while outlandishly-dressed "Art Directors" from Ad Agencies hopefully scanned the horizon for the perfect location. Needless to say, on arrival at the perfect location, the previously cloudless sky of azure blue would immediately produce torrents of rain unseen in this country since the last location shoot. Mountain bikes are particularly fraught with grief in this respect. By definition, the locations are on the top of mountains, where weather conditions, even abroad, are less than ideal, and the sheer logistical problems of transport and equipment begin to resemble a Hollywood epic about Hannibal crossing the Alps. Anyway, that's all changed now that I can shoot the bikes in the comfort and warmth of the studio, and then, by the magic of Photoshop, place the bike anywhere my "Art Director"s heart desires, without ever leaving the comfort and warmth.

The first step is to construct a realistic foreground set for the bike to sit on. People ("Art Directors") often assume that the subject must be shot on a completely featureless background, but this is seldom the case. The final image will be far more convincing if the foreground area is real, with the composited background appearing behind it. In this case, following a wallet-lightening visit to the garden centre for two tons of rocks and boulders, a stony outcrop was built to support the bike. Judicious planting of alpine-type heathers helped with the illusion. A plain blue background paper was suspended behind the set, to give a solid colour to key on in Photoshop. Blue was chosen to suggest the sky reflecting in the bright metallic parts, to help the bike merge with the background image. The set was then lit with a single large light-source from high up, to simulate direct sunlight, and soft ambient light to fill in the shadows.


Mountain bike in studio set
The set was photographed on to 5x4 Ektachrome transparency film, and after processing, scanned on to Kodak PhotoCD. The bike image was opened in Photoshop at 300dpi and a file size of 18Mb. The first stage is to correct the colour balance of the image using the Image-Adjust-Levels control. By using the eyedroppers and clicking on appropriate black shadow, bright highlight, and neutral grey areas, any colour cast created by the PhotoCD scanning is removed, and the overall contrast is improved. It also helps to apply the Unsharp Mask filter, but only after any other corrections have been made, as artefacts can be created in the image which will be exaggerated by subsequent processing.

Having corrected and sharpened the image, the bike can now be cut out of the image. Using the Magic Wand tool, the blue background colour can be selected, followed by the Select-Similar command to add non-contiguous areas of the same colour. To tidy the selection, and ensure crisp edges, save the selection to a new channel, using the Save Selection command in the Select menu. Open the channel and deselect the selection. With the Magic Wand tolerance set at 1, click in the black area outside the white image mask. Return to the RGB channel - the new selection will be automatically loaded. Now invert the selection using Select-Inverse, and the bike will be selected. From the Edit menu, copy the image to the clipboard.


Background landscape
The background image was opened in Photoshop at the same size and resolution as the bike, and given the same colour and contrast corrrections. The image was then flipped through the vertical axis so that the direction of the lighting matched that of the bike shot. The background was slightly retouched by cloning trees over some heavy shadow areas, and a Gaussian blur with a radius of 2 pixels was applied. The bike image was then pasted on to the background and nudged into position so that the handlebars and saddle broke through the horizon. The smudge and blur tools were used to soften the transition between the real foreground set, and the background. The final 15.4 Mb file was copied to a 44Mb SyQuest cartridge, and a Matchprint was produced to show the client.