Creating the Illusion of 3D
Lighting a fur covered animal presents a different set of challenges than lighting a human face. There is more to hair than meets the eye. A hair shaft appears smooth and round to the eye but it actually consists of millions of tiny flat scales. It is light hitting those tiny mirror-like surfaces and reflecting back into the eye or camera which gives hair its luster and illusion of volume.
The illusion of three-dimensional shape in a photograph is created with contrasting tone. Our brains are conditioned by seeing things in overhead natural lighting to expect the higher parts of objects to be highlighted and the lower parts to be shaded or darker. So in a photograph the lighting on hair should be optimized to create crisp specular reflections on the tops of the hair shafts which reflect back into the camera. So while it is conventional wisdom of use large diffuse sources for lighting humans, for furry critters it is best to use direct light sources. Dark and light colored fur create difference challenges photographically.
Photographing Dark Furry Critters
The goals when photographing a dark animal are to show its overall shape, draw attention to the end that eats vs the one that sits, and make the fur seem real and lustrous.
A holistic strategy to meet those goals would start with the selection of the background. What is needed is a background which is lighter than the animal so the overall shape contrasts, but not so much contrast it starts to put attention away from, and overpower the darker body and head. Creating a gradient of contrast across the background so it is darker near the tail and lighter behind the head will help meet the second goal of drawing the attention over the body of the animal the head and holding it there.
Nothing beats rim lighting for creating the illusion of 3D shape of objects. Outdoors posing the animal so its back is to the direct sunlight then shooting into the shadow side with direct, non-diffused flash is a simple but effective strategy for defining 3D shape overall via the rim light, and in the fur in front via the specular reflections of the flash off the hair shafts, eyes and nose. In a studio setting using back-rim lighting will add an element of 3D realism a frontal-only strategy will lack.
Making dark fur look 3D and real requires a full tonal range with detail from the darkest shadows to just below the specular highlights on the hair shafts. For humans we use diffused lights to minimize specular reflections on skin but for a dog every light should be a direct specular reflection creating "hair" light. Simple reflectors or shiny silver umbrellas and reflectors should be the tools of choice here. They will create the specular reflections which will make the hair, exposed to keep the black parts black not gray, come alive.
The frontal light need to be positioned in a way that maximizes the reflection of the specular light off the round hair shafts back into the camera. It's the same as shooting into a mirror with a flash on camera, except that in this case the blinding reflection straight back into the lens is exactly what is needed to create specular reflections on the top if each hair facing the camera.
Using a shiny silver umbrella directly above the camera will both evenly illuminate the entire dog and eliminate any shadows which will result in dark voids if the highlighted hair is properly exposed to make it look black, and at the same time create the specular reflections which are the critical factor in making the hair look-three dimensional and shiny rather than a flat and dull.
In the same way a gradient of contrast on the background creates a clue for the eye of the viewer, a second "key" light is needed in front of to draw attention to the face and hold it there. Animals have different shaped faces than human. With a human the key light position is dictated by the need to get light into both eyes and at the same time avoid the creation of a distracting nose shadow. For an animal the goals for key light position should be pleasing lively catchlights on the eyes, nose and teeth if visible to emphasize their 3D shape.
In human portraits we try to minimize specular reflections, but on an animal they are an important component for creating the illusion of 3D shape.Modifier size on the key light is the factor which will affect the size of the catchlight reflections seen in the eyes and on the nose and other wet shiny parts of the face. If only one frontal light is available the tool of choice would be a silver umbrella aimed more towards the face than the tail by putting it on the same side as the head and large and close enough to created large attractive catchlights in the eyes. An umbrella has a characteristic brighter more direct area in the center which can be aimed at the head to achieve this objective.
Photographing White Furry Critters
Photographing white-on-white objects requires the same cause and effect strategy of creating contrast to define 3D shape of both the shape of the animal and the individual hair shafts. As with a dark animal a light one will also contain a full range of tones from black to white which must be rendered accurately using a camera which isn't capable of recording that entire range accurately in flat lighting. As with any lighting problem the solution to the technical shortcoming of the camera - its short range - is to use a foundation of even fill and an overlapping directional "key" light to create shape defining highlights.
White dogs also need light sources which create specular reflections, but shadows are also needed to contrast with the highlights and create the illusion of three dimensional shape. Backlight to define the shape of the animal is still needed but the frontal lighting should be directional, as with a human portrait, rather than on the camera axis as with dark dogs. In a human portrait directional light without a frontal fill component would create harsh distracting shadows, but with a white dog that is exactly the kind of contrast necessary to reveal the texture in the layers of white-on-white fur. Selecting the Right Background
I approach "lighting" holistically and think in terms of overall effectiveness of the photo and the goals and strategies needed to achieve it. The goal for photographing a dog has two parts: 1) See the overall shape of the dog against the background, and; 2) having defined the overall dog lead the viewer to the face area and hold it there.
The best strategy for attracting the attention of the viewer is to create strong contrast between what you want them to see. The trick, to the extent there is one, is creating the right balance of contrast between the background and the dog so the viewer sees the overall dog but is not overpowered so much that they can't see the detail in the dog.
For example, put a jet black Lab first on three different backgrounds: 1) pure white, 2) bright red, 3) med. gray.
White will create great shape defining contrast but "blind" the viewer with that contrast to the point they will not see the shadow detail. Much like the glare of on-coming headlights at night or walking from a dark room into the bright sunshine outside.
Red would work the same way. The viewer would see the shape of the dog, but not able to focus on the detail in the dog or detect subtle eye leading differences in tone. Medium gray would create sufficient contrast that the shape of the dog would be clearly defined, but the darker tone wouldn't overpower the shadows. The viewer would be able to see and follow visual clues such as the feathering of the frontal light so the face is a bit brighter than the tail end or perhaps that a grid was used on the background to make the spot behind the head a bit brighter. The best way to describe the overall goal would be to create a moderate "external" contrast of dog tone/ color to background tone/color, which will define the dog against the background but still allow the viewer to see the "internal" contrast on the dog's body between the face, which would contrast with the background tone slightly more than the back end.
For neutral tone black / white / spotted pooches neutral backgrounds would be the most effective because they would be least distracting. That's not to say color couldn't be used effectively, but you'd need to step back and consider whether the "external" contrast is overpowering the "internal" tonal variation on the dog. For colored dogs you could either stick with the same color pallatte and just alter the value (tone), or go for a contrasting color of similar tonal value. For example a light Golden Lab would be presented well on either a med. earth tone or light blue background. For a darker more reddish Retriever the same earth-tone background would work, but you'd want to light in in a way that made it a bit darker and less overpower. If a colored background was desired a light-med pastel green would provide good color contrast with the overall dog without overpowering it.
See a pattern here? If you go with a similarly colored background you'll need to control the contrast of dog to background with the amount of light on the background to create TONAL contrast, but with good external / internal balance. If you want a colorful background the COLOR alone will provide the needed external contrast but you will need to take care to pick color that contrasts harmoniously with the dog's overall color (it is opposite on the color wheel) and isn't so bright it overpowers the viewer's ability to follow the tonal clues of the "internal" contrast on the dog's body to differentiate head from tail. Don't let the background contrast trump the tonal variation on the body of the dog.
If one were shooting at a dog show with a huge variety of dogs and a limited amount of set-up time the simplest approach would seem to be a plain or mottled gray background illuminated with a variety of color gels as need to either match or contrast with colored dogs. Look at the dog's color and tone, swap gels, and then adjust power on the background based on the color and tone of the dog. The acid test is whether a viewer says "Wow, nice background" or "Wow, great looking dog" when looking at the photo. When you are the one who took the photo its sometimes difficult to be objective about how effective the presentation of the subject is because you will immediately see the face and tune out everything else. Try this test:
Take your photo, apply a 10px gaussian blur to the entire image, then stand across the room and look at it. If the most dominant tonal area isn't where the dog's head is, whatever is the most dominant tonal area will pull attention away from the head and face. When your eye gravitates naturally by tonal contrast alone to the face area you'll have a more effective overall balance in the photo -- if your goal is for the face to attract and hold the most attention.
There is a simple post processing over-sharpening trick which will add sparkle to a dog's coat:
Holistic Concepts for Lighting