Compositing might be something as simple as adding a texture overlay, or adding some birds or a cloud to add interest to a bland blue sky, or making, say, a triptych. Or you might want to make a complex image in which multiple images are combined to create a more conceptual image.
Below, this composite by WCC member Rosie Hughes creates a far more memorable image than either of the two images separately. On the right, compositing has allowed muratsuyur to tell a powerful story.
When you start to make composites you will almost certainly need to use transformations to rescale and reshape the component images so they match. If you make these transformations on a plain raster layer and shrink the layer, pixels will be lost. If you later decide to enlarge it, it will possibly become jaggy or pixelated. If you convert the layer to a smart object, the original pixels will be retained so transforms are lossless.
Lighting and colour balance
Your composite images won’t look convincing if the lighting on the compiled images does not match. If the images look like the light is coming from different directions, you can sometimes dodge and burn to shift the apparent illumination to the other side. Try to avoid situations where parts are taken in bright sunshine with sharp shadows, compiled with images taken on overcast days with flat soft lighting.
Colour balance is another thing to check: images taken during golden hour with a golden glow together with, say, a bluish midday shot, or a shot under green trees, or perhaps the model was standing next to a red brick wall and has a reddish cast from the reflected light. Try to use the colour balance tools to achieve similar colour balance. Check the colour temperature settings (raw images), Colour balance and Hue Saturation adjustments. You can also adjust colour balance finely using the Curves (and even the Levels) controls, by adjusting the Red, Green and Blue channels independently.
Photoshop has an interesting tool to help with this. Try the menu Image >> Adjust >> Match Color. In the resulting dialog you can set a source image, and there are sliders for Luminance and Color Intensity and a Neutralise checkbox, all of which control how the matching operates. Give it a try, next time you are compositing, if you have images with different colour balances.
When you make a composite, creating realistic shadows is vital. Whilst we don’t usually consciously pay much attention to shadows, they provide context and objects without shadows, or with shadows that are not realistic can really jar in an image.
Go out on a sunny day and look at some shadows. The direction of the shadow is determined by the direction of the light. With a point light source (the sun is near enough to a point), shadows will look sharp. With diffuse light sources, shadows will be soft and diffuse. And shadows are sharper if they are closer to the shadowed object, and fuzzier away from the object. If the light source is close to the object, the shadow will expand noticeably as it extends away from the object. If there are multiple light sources, the shadow will be a combination of the shadow and light from each light source, and can get very complex. Fortunately for the sake of image composites, you don’t need to get photon perfect shadows, just good enough to look ok to the viewer.
Consider the examples of shadows below. The first image was taken with a diffuse light (softbox). Note the shadow is soft and diffuse. It is darker close to the marker and fades off quickly with distance along the back wall. In the middle panel I have removed the softbox leaving the naked light, a small light source. The shadow is much sharper. Note the difference in dimension of the shadow on the floor (narrow) vs the back wall (wide) because of the angle between the direction of the light and the plane of the wall. The third panel has the same lighting as the middle panel, but I have placed a coloured card to the right. Note how the light reflected from the card gives a colour cast to the adjacent areas and tints the shadow in particular, where the only light comes from reflected light.
Some Other Resources
- This is an excellent introduction to using Photoshop’s 3D tools to make shadows. It’s a little involved, and needs reasonably powerful hardware, but can produce good results. https://photoshoptrainingchannel.com/make-realistic-shadows-photoshop/