It is very important to have good clear, close-up photographs to work from when creating a portrait of your pet. The quality of the photos will determine the ultimate quality of your portrait. If your photos are blurry or your pet is very tiny in the picture, I will have to guess to fill in the details, and your portrait may not look as much like your pet as you'd like. If possible, take some pictures of your pet with a portrait in mind.
I speak from experience when I say a great deal of patience is the key to getting great photos of your pet. Take your time and make it fun for both of you, and you'll be sure to end up with some great pictures. Here are some tips to help you get great pet photos:
The best lighting is natural lighting. Take your pictures outdoors or near a window in a room that gets a lot of natural sunlight, usually on the south side of your house (be sure to keep your back to the window). The best kind of day for taking photographs outdoors is a bright overcast day, where the cloud cover is not so thick as to obscure all the light, but the harsh shadows are reduced.
Avoid taking photographs in direct sunlight. This can change the appearance of the colors of your pet's fur, and can cast dark shadows on the face and body. It is especially difficult to discern details of a black or otherwise dark pet who is standing in the full sun. If the sun is out, take your pictures in the shade with your back to the sunlight.
No matter where you choose to take your photographs, don't use the flash. The flash will distort your pet's colors, will likely cast strange shadows, and will almost certainly cause red eye.
The absolute best position for taking pictures of your pet is to get the camera down on their level. Don't stand above your pet and snap photos looking down at them; rather, sit or lie down on the ground, at their level. Full-body shots in particular will not look right when taken from above. If you do not want to lie down on the ground, you can elevate your pet so that you will be on their level when you are sitting or kneeling. Try putting them on a chair or bed, or even a table (recommended for very small pets only). I have had good success placing my cats on a simple wooden stool.
Fill up the entire frame with your pet's face or body. Get as close to them as necessary so that their face or body takes up as much of your viewfinder as possible, while still remaining in focus. Also keep in mind that the details of your pet will show up best against a plain background, such as a flat wooden fence, the side of the house, or a plain wall. If possible, avoid busy backgrounds such as the garden, a patterened bedspread or sofa, or a cluttered room.
Expression of Your Pet
The best expression is usually when your pet is alert but relaxed, with ears up and forward and attention focused just off to one side of the camera (not directly sideways, but at a slight angle). To help get your pet's attention, it's best to have some toys or treats handy. Noise makers work especially well to get an alert expression.
Pets often will not sit still for photographs. For this reason, it is often best and easiest on you and your pet to have somebody helping you to take the picutres. Your assistant can be solely responsible for getting and keeping your pet's attention with toys and treats while you focus on capturing the best photographs.
Finally, here are a few photographs that I have taken of my own pets that would be ideal to use for pet portraits. I hope these will help to give you a better idea of what you should be shooting for. You can click on any of the pictures for a larger view.