Choosing Long Glass

The image above is from one of my favorite bird photographers, Wayne Bennett. He is gong to be one of six instructors at the Moab Event, in October with Scott Kelby. This isn’t an ad, it’s already sold out. I just love showing Wayne’s work, he is a great shooter and a dear friend.

Today I would like to do a little Tech Friday on Thursday. The question many photographers ask me is how do you know when it is time to buy a long telephoto lens and which one should I buy.
It’s a good question, so let’s talk about it.

First, what is a long piece of glass? The so called normal lens on most film cameras was a 50mm lens. The 50mm refers to the lenses focal length, which is a measurement of the lens elements in the system. On a film camera a 50mm lens made a photograph where objects were approximately the same size as seen with the naked eye. This would also hold true for digital cameras with sensors the same size as a piece of 35mm film. In the Nikon system some cameras have what are called DX sensors (currently D90, D300s, D40, D60, etc.), on those cameras, because the sensor is smaller, the “effective” focal length of a lens “appears” to be 1.5 times longer. For example, on a D90 with a DX sensor a 50mm focal length lens would produce and image in which the main subject would be 1.5 times larger than with the FX (35mm size) sensor, or like a 75mm lens.
This applies only to “apparent” magnification. Though it appears to lengthen a lenses focal length, it doesn’t, it simply crops out a smaller part of the scene.

So what effect does focal length have on the resulting image? If you photograph a person from ten feet with a 50mm lens on a FX sensor camera, the person would appear approx. the same size in the image as what you saw with you eyes. With a 100mm lens, the person apparent size would double. At 200mm, the person would double again, at 400mm they would double once again.
So every time the focal length doubles the subject size in the image doubles as well. Keep in mind with the DX sensored camera the subject starts out 1.5 times larger than you would expect because the lens and sensor size “crops” the image to 1.5 times larger. After that the same would be true about doubling of image size as the focal length doubles.

So when do you need a longer lens? When you want to get closer to the subject but may not be able to move physically closer. For instance if your in a Range Rover in Africa and want a closer shot of the lions face, but can’t (or shouldn’t) get out of the vehicle and walk up closer. The closer you want the subject to appear in the image, the longer the focal length.

Here are some common subjects and the focal length range most often used to photograph them;

Wildlife, mammals: 200mm to 600mm and beyond.
Wildlife, birds: 300mm to 600mm and beyond.
Sports: 180mm to 600mm and beyond.
Portraits of people: 85mm to 200mm.
Landscape photography: 70mm to 400mm.

This is a very limited list and opinions will vary widely on what lenses are best, but these can serve as starting point.

One thing is for sure, long glass is expensive and big. A 600mm f4 lens can cost up to $12,000.
and is a very large and heavy piece of glass. Consider carefully just what you will use a piece of long glass for, it’s a big investment. The Nikon 200-400 f4 VR lens is a favorite because it’s relative cost, around $6,000. is more reasonable, (a relative term), and it has a great range of focal lengths built into one lens. Also keep in mind that if you own a DX sensor camera the 200-400 would produce images much as if it were a 400-600 lens!

Long lenses are fun and expensive, so choose wisely. By-the-way, my long lens? I carry the
small Nikon 70-300 AFS VR lens (about $550.). It is a 70-300 on my FX cameras and a
105-450 equivalent on my DX sensor cameras. I find it covers almost all my long glass needs, is affordable, very sharp and if you break it, does not require a second mortgage on the house to
replace! Food for thought.

More food for thought, God loves you, love Him back…………….

the pilgrim