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TFT and EVF Viewfinders

What you see is what you get...almost

It's a bright sunny day and you're trying to take photos with your new digital camera.

It may be hard for you to see the image on your LCD screen due to reflection and glare. To address this problem, some cameras now come equipped with a TFT (Thin Film Transistor) or EVF (Electronic Viewfinder) — a tiny LCD screen inside the viewfinder.

No more problems seeing what you're going to photograph, right? Well, not exactly.

Optical, Electronic and Pentaprism Viewfinders

Before we get too deep into a discussion about electronic viewfinders, it's important to understand the distinction between an optical viewfinder, an electronic viewfinder and the viewfinder on a digital SLR (typically called a pentaprism).

Optical Viewfinders

These are the most common viewfinders on compact digital cameras. An optical viewfinder is a little window in the camera body that sits above (and sometimes to the side) of the lens.

When you look through the viewfinder, you see an approximation of what the lens sees (and the photo that you're about to take). Since the optical viewfinder is offset from the lens, the lens covers a different area than the viewfinder.

Many optical viewfinders also have tunnel vision, and don't show you the entire scene the lens will capture. Don't be surprised if the image you see in the viewfinder is not what you see when you look at the photo later.

Electronic Viewfinders

Electronic viewfinders do show you the same view that the lens sees. In fact, what you see when you look through an electronic viewfinder is identical to what you see on the camera's LCD screen.

The same image projected onto the LCD is also projected onto a tiny LCD within the viewfinder.

If it shows the same thing as the LCD, what's the purpose? On a bright day when you can't see the LCD, you can use the electronic viewfinder instead to compose your photo. Since the viewfinder is shaded, it is easier to see the image you are going to photograph.

Some cameras make you turn the electronic viewfinder on and off. You have to switch between the LCD or the viewfinder. Other cameras are smart enough to know that you are looking in the viewfinder, and they activate it automatically.

Pentaprisms

All digital SLR cameras (with the exception of the few that use electronic viewfinders) have a pentaprism inside the camera.

A pentaprism reflects light so that when you look through the viewfinder you see exactly what the lens sees. If the scene is out of focus, the image in the viewfinder is out of focus.

A viewfinder with a pentaprism is probably the easiest way to get accurate photographs. The image that you see is exactly what the lens sees, and you can see every minute adjustments to focus that you make.

Electronics vs. The Human Eye

When you look through an optical viewfinder or a SLR viewfinder, your eye is seeing the scene laid out before you. Eyes are remarkably versatile: they can perceive shifts in color, an enormous range from light to dark, and subtle changes in focus.

Electronic viewfinders are like looking at the world through a television set. Colors are not as accurate and images are not as sharp. If you move the camera quickly, you will see image trails as the viewfinder tries to keep up.

Great improvements have been made in the resolution of EVFs, but they cannot match the human eye. If you are familiar with film SLR cameras, I would recommend you avoid digital cameras with electronic viewfinders. This is especially true if you like manual focus, since it's almost impossible to tell if your subject is in focus when you look through an EVF.

The Basic Rule of Thumb

An electronic viewfinder can help on a very bright day or in conditions where you cannot clearly see your camera's LCD. The viewfinder creates enough shade to help you see your subject.

An EVF is a video display, and cannot match what you can see with your eyes.

If you find a camera with great features and a EVF, don't think of this as a deterrent. But also don't go out of your way to get a camera with an EVF, unless you really think you're going to use it. More often than not, you will find yourself using the LCD.

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