Q: I am an avid bird-watcher and photographer. I use a Canon 7D and have been trying to get pictures of purple martins in flight, but all I get is a silhouette of a bird against the sky. What causes this, and how can I correct it?

A: The problem is backlighting. Your camera's exposure meter looks at the whole scene, averages everything and sets the exposure. There is a lot of sky and a little bit of bird in the scene, so you get a properly exposed sky and a dark bird.

The easiest way to correct this is with the camera's exposure compensation setting. This will bump up the exposure by a preset amount above what the camera is reading. The exposure compensation function looks like a +/- sign. I'd suggest starting with +1.3. Take pictures of something small that is silhouetted against the sky, like a tree branch. Review the picture on the camera screen and zoom up on the branch to see if there is any more detail. Adjust as necessary.

Your camera has a spot meter that measures light in a very small area. This would be the most precise way to set the exposure, but it's unlikely that you could keep the spot on a moving bird. For stationary birds — say you've singled out a branch where they tend to sit — you could use the manual mode and use the spot meter to set the exposure before the birds arrive. Use the meter for test shots on the branch, checking your exposures with the screen.

APS-C sensor systems

Q: You don't write much about the Sony APS-C mirrorless system, though in the past you said that you owned one. Why do you not prefer this system over Micro Four Thirds, given the bigger sensor?

A: I sold my NEX-5 system a few years ago. While they are fine cameras and I have nothing but praise for the photo and video quality, as a complete system I found it lacking and it did not fit my needs and tastes. Micro Four Thirds has largely closed the gap in image quality with APS-C except in very low light, and there are many more cameras and lenses available for the Micro Four Thirds system.

The Sony mirrorless system to go for is the top-of-the-line A system. It features a full-frame sensor and amazing optics, and the newest models have the 5-axis image stabilization system developed by Olympus.

If you must have an APS-C sensor, I encourage you to check out Samsung. They make nice cameras, and I enjoy using them more than I did the Sony system. The lenses are excellent, and they have some intriguing new entries at the top of the market, such as the NX1 camera that can shoot 4k video, and some fast, pro-grade lenses.

Last year I wrote about the interchangeable-lens Samsung NX2000 and NX3000 cameras, which provide excellent image quality and shooting performance along with a full feature set, including Wi-Fi. I recently spent some time with the 20.3-megapixel Samsung NX30 and found it to be an excellent addition to the system. It has an SLR form factor and is very solidly made, has excellent image quality, though video quality is a bit behind the competition. It can be purchased online with lens for $606. www.samsung.com

Send questions to Don Lindich at donlindich@gmail.com. Get recommendations and read past columns at www.soundadviceblog.com.