The LCD is both bane and boon for digital photographers. It is a wonderful tool that lets us see our images instantly, plus when used with live view, the LCD can help us focus and compose better. It can even offer sharper photos because there is no mirror bounce when you shoot with live view turned on. It is also a necessity if you want to shoot video with your DSLR.
Yet the LCD can be hard to see and difficult to use in many situations. Tilting LCD's are an improvement, but not all cameras have them.
I have had a great opportunity to work with the Marshall Electronics 5-inch accessory LCD monitor and I love it. It won't work with every camera (the camera needs an HDMI out port), but it works beautifully with my Canon EOS 7D. I am using it for both still photography and video.
I have long loved tilting LCD's ever since they first came out with Agfa and Sony cameras about 10 years ago. They make it so much easier to get low angle shots or even high angle shots and still see your subject through the lens! The Marshall Electronics V-LCD50 monitor attaches to the hot shoe of the camera and can be tilted up, down, left, right, as needed, allowing you to put your camera where you want it. There is also an accessory hood that makes it easy to see in nearly any light, though I found I often could see the LCD well if I just made a tilt adjustment.
But the big thing that I loved right away was the size. This monitor makes any camera LCD look puny and hard to read. The contrast and size of the Marshall monitor makes it very easy to check settings, to be sure of focus and to check the edges for unwanted composition spoilers. I don't care if you have aging eyes and need bifocals (like me) or are young and have great eyes, the bigger monitor truly is a pleasure to use.
The monitor will display anything that you can put on your camera's LCD (on the 7D, the camera LCD is automatically disabled), including the full range of live view displays. It also has some unique controls that can help you focus as well as set exposure. For shooting wildlife or other moving subjects with video, this larger monitor makes it much easier to see and maintain focus. (Okay, let's be honest -- shooting moving subjects with video using the standard back LCD of a digital camera is an exercise in pure frustration. It is hard to do and hard to see focus. An external monitor like this lets you actually see what is and is not in focus -- you will be a lot less frustrated.)
The downside is that this is an extra piece of gear. You do have to set it up whenever you need to use it. It is lightweight (about 8 ounces), so that helps. I would not recommend too short an HDMI cord (mine is three feet), because with a longer cord, you always have the option of separating the camera and the monitor when you need to. Another downside is that the system is powered by four AA batteries that do not have a long life when the monitor is on, so you need rechargeable batteries and extras.
I admit I am sold on this unit. It truly can make photography easier, more enjoyable, and enhance your abilities to get better photos. That is what this monitor gives you, and for a price of under $700.
Yet I also know a lot of photographers will complain about that cost even though they would spend a couple of thousand dollars or more on a camera or a lens that might not really change their photography (other than having the latest and greatest). Yet, a unit like this can be a lifesaver if you understand the great benefits of a tilting LCD but your camera doesn't have one, if your eyes are aging, or if you want to do some serious video shooting.