Long lenses tend to be large and bulky. Many people tend to leave the longer lenses at home when they go out for a day trip. Nobody wants to lug around a big, heavy lens all day.
A TYPICAL 400mm LENS
The very good long lenses also tend to be quite pricey.
The longer the focal length of your lens the more steady the camera must be to avoid blurring the image.
A general rule in photography: Only hand- hold a lens when your shutter speed is equal to or faster than your lens focal length.
Example: A 200mm lens should not be hand held at speeds under 1/200th of a second. Any speed equal to or greater than the focal length should be fine.
As you can see most telephoto lenses will need to be mounted on a tripod for maximum performance. Now you not only have a large lens to lug around but also a heavy tripod.
One last point, no matter how good your lens is, when taking photos from a great distance your image is at the mercy of atmospheric conditions. Dust, haze and other elements can hamper your efforts of obtaining a sharp image.
TELE-CONVERTER / DOUBLERS
There are ways of getting around using telephoto lens.
A doubler or tele-converter magnifies the image; you attach the doubler to your lens. You then mount the lens to your camera body.
Example: 135mm lens with an added doubler becomes a 270mm lens.
There are different size converter such 3x tele-converters or smaller.
Tele-converter will degrade your image. You may be able to find a good converter with multiple elements, but any added glass to your lens will always degrade the image in some manor.
A 2X tele-converter M42 mount.
If you do decide to use a tele converter be aware that the converter will cause a loss of light. If your using a through the lens meter, such as the type found on most new SLR’s and DSLR’s you wont have to compensate for the loss of light. If your using a hand held meter then you have to make corrections for the light loss.
Example:
2X converter - open up 2 stops
3X converter - open up 3 stops
THE CAT LENS / MIRROR LENS
The Cat lens is a catadioptric lens. A catadioptric lens is a telephoto lens that uses a curved mirror to increase the size of an image.
The design of the Cat lens enables a very long focal length to be obtained in a short barrel. A 500mm Cat lens can be as short as 4 inches long. Compared to a normal 500mm lens, which can be as long 12 inches or more, this is quite an advantage.
A Cat lens does have a drawback. The best catadioptric lens does not produce as sharp of an image as the equivalent telephoto lens. Although with today’s technology some very good catadioptric lenses have been manufactured.
Catadioptric lenses do not have variable diaphragms. The aperture is fixed usually at f/8 or f/11 and cannot be adjusted.
An inconvenience? When I discuss depth of field the inconvenience will become apparent.
ZOOM LENS
Zoom lenses are quite convenient. A zoom lens will allow you to change focal length without changing lenses. A 35mm – 105mm zoom lens can be adjusted by simply turning the barrel in most cases; some lenses have a push – pull type adjustment.
Nikkor 35mm-105mm MF zoom lens.
Zoom lenses have a complex optic design causing most zoom lenses to be heavy and a bit bulky. Also, most zoom lenses are not as sharp at any given focal length as their fixed length equivalent.
There have been many changes in the design of newer zoom lenses. With the new computer designed lenses the optics and bulk have improved dramatically.. You can find some very sharp zoom lenses, but most of these come with a hefty price tag.
Some zoom lenses are designed with two separate control rings. One ring controls focus while the other focal length. Once you have set the focus you cannot accidentally change the focus while adjusting your focal length.
The push – pull zoom lens is a one-control ring function design. You twist the ring to focus and push or pull the ring to adjust focal length. It is very easy to lose your sharp focus while adjusting your focal length, so careful use is required for razor sharp images.
THE MACRO LENS
A macro lens is a close focusing lens. Some macro lenses will allow you to focus close enough to obtain an image that is about the same size as in real life.
Fujinon EBC 55mm macro 1:3.5 M42 mount
The relationship to the size of the image on film or digital sensor to the size of the actual object is called the reproduction ratio. A ratio of 1:1 (one to one) means that a life size image is produced on film/digital sensor. A 1:2 ratio means the image produced is one half the size of the actual object, and 1:3 is a one third the size of actual object.
Common terminology:
Macro lens – reproduction ratio of about 1:1
Macro- Focusing lens – reproduction ratio between 1:1.2 and 1:2
Close- Focusing lens – reproduction ratio between 1:2 and 1:4
A macro lens can be a lens of any focal length, although they tend to be of medium focal length. Common macro lenses may be a 55mm, 100mm, and 70-180mm macro zoom. This simply means that in addition to its focal length it can be used to focus closer than a standard lens to create life size images.
PORTRAIT LENS
A good portrait lens produces an image free of perspective distortion. We want the nose of the model to be proportionate to the models face. We also don’t want to flatten out the models face.
A good portrait lens will produce an image that flatters the model.
85mm to 135mm lenses should produce the most flattering images for portrait work.
A GOOD 35mm FILM PORTRAIT LENS
A GOOD PORTRAIT LENS FOR A CROP DIGITAL
Keep in mind that on a crop digital camera you have to multiply the focal length by the crop factor. So, a 58mm lens will function as a 87mm lens when multiplied by 1.5. This would make a good portrait lens on a digital crop camera.
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