Thanks to my niece Molly, a talented artist in her own right, for inspiring this blog post: So you have a nice little painting you've just completed, but none the photographs you took do it justice. How can you get decent photos for your website? I am certainly no expert photographer, but I will share what I do for my own website to produce decent reproductions of flat art for online display.
Photographing artwork is definitely a little tricky. If the artwork has any sheen at all, any flash or angled light can cause glare on the surface, which will distract or obscure the true nature of the picture. These days, I use a digital camera for all of my photography and tend to do a fair amount of color correction in Photoshop. But I used the same method of photography I will describe below, even in the pre-digital age when I made slides of my work.
The best conditions I've found for photographing artwork is outside on a bright but cloudy day. This gives consistent diffused light and the least amount of glare. If photographing on a sunny day, try to set your painting up at the edge of a shaded area so that enough light reaches the painting without shining directly on it. Tree shade isn't good because of the dappling. It needs to be even light, so maybe an overhang on the side of a building or something.
If you are shooting film or are otherwise not able to correct the camera angle after the fact, you'll need to make sure your canvas is as perpendicular to the camera as possible. You can either set it up on an easel or hang it on a wall on the side of a building if the overhang isn't too large. To avoid the fish-eye effect that can occur because of a wide-angle lens curve, you should set your camera up on a tripod far enough away from the painting and zoom all the way in on your painting to fill the lens as best you can with the picture. This will minimize that fish-eye distortion. (Thanks to artists David Darrow, James Abbott and others in the Daily Painters Discussion group for this and other technical tips!)
When photographing, I use my camera's manual setting so that I can set the white balance and bracket the exposures, just in case what I'm seeing in the viewfinder isn't what I get on my computer screen. Then I'll examine all of these images in Photoshop, and with the painting sitting next to me, I'll make adjustments to the chosen image in brightness, contrast, color, etc. Photoshop is great also for correcting the picture if the painting doesn't look exactly square. But Photoshop is also $$$ so if you don't already have it, you might look for a cheaper image editing software program that can do most of these basic corrections.
For the web, I will overlay my copyright info and save my images as 72 dpi JPEGs. For archiving, though, I save the image at the largest size my camera setting will allow, and save it as a TIFF. JPEGs are fine for web stuff, but not great for archiving because it is a "lossy" image format. This means that every time the JPEG is opened it looses a bit of information, even if it is a large file. For any kind of high quality reproduction (such as giclee prints), the best option is to have the painting professionally scanned or photographed at a very high resolution.