In the summer, I have no problem. I step out back and toss my project on the lawn. I have a beautiful, lush green backdrop and perfect light every time. In the winter, it is much more difficult. The sun rarely peeks out from behind dull gray clouds and when it does, its light is harsh. It's hard to find a good balance. Shade means you don't end up with overblown highlights, but you also loose glossy shine of long-wool fibers and silk.
I keep trying. I have a macro studio (a big box built for taking pictures), but that still needs adequate light to work well. I try my best, adjusting brightness and color carefully in editing programs to take off the harsh edge of indoor lighting. But even then, sometimes the true colors just escape you.
It also drives me nuts when people (specifically in KALs where they all bought the same yarn) start arguing about the color of their yarn when compared to what they see on their computer screen from other people. "I like yours better than mine, it's more X," they often whine. But is it? Really? Or is it just the light when the picture was taken (or the settings on your monitor) shifting the display of those colors?
Here's some recent efforts I felt like I needed to share, just to show what we're all dealing with. These four pictures are of two skeins of yarn I spun recently. They both have silk in the blend, which shows up under flash, but is lost in my daylight picture. However, the colors are closer to true in daylight. Still, none of these pictures is absolutely true to life. I wish people would think of this whenever they get the urge to debate about yarn purchased online. After all, you never know what light was used for their pictures!