Lenses

Created April 10, 1999 Last Modified: January 30, 2000

About the camera itself: I have no idea how much or little you know about photography or about the basic operation of this camera, so I have to start out at the very basic stuff.

The magnification of a lens is defined by its focal length. If you look through a camera, you see an image in the viewfinder of whatever the camera is pointed at. With a very wide-angle lens, you could see the entire expanse of the Grand Canyon. With a telephoto lens, you could zoom in (like binoculars) on one Mule walking down the trail to the bottom of the Grand Canyon. The magnification is a function of the focal length of the lens.

Usually, the "speed" of a lens (just like films) is a reference to how much light it requires for an image to be recorded. A fast lens (or film) will allow you to take a picture in a situation where there is less light available than a slow lens (or film). The light gathering capability is related to lenses as a function of the maximum "F-stop" for the lens. I am not going to try to completely explain "F-stop" here, but I will give a simple quick explanation. For a complete description, see the Photography book that I highly recommend.

A lens that can open up to an F-stop of F-2.0 can gather twice as much light as a lens that can only open up to an F-stop of F-2.8. The F-2.0 lens is one "stop" "faster". It would allow you to use a shutter speed that is twice as fast as the F-2.8 lens. In some situations, that could be very important. In general, faster lenses are more expensive than slower lenses.

In general, there are two TYPES of lenses, ones with fixed focal lengths, and ones with variable focal lengths. There are generally five focal length RANGES of lenses. These are listed below.

Once you have done a lot of photography, you will begin to learn what types of pictures you will be taking, and that will drive your choices of type and focal length(s).

These are usually lenses that have a focal length shorter than 20mm. These are generally referred as "fish-eye" lenses because they tend to distort the image, very much like a standard peephole in a front door. They allow you to "see" a wide expanse of space in a very small area, but they tend to bend the view of objects.

These lenses tend to be expensive and very specialized. Once you have seen an image from a "fish-eye" lens, you will understand the limitations.

Wide-angle lenses are usually lenses that have a focal length between 20mm and 40mm. These are used mostly for scenic and landscape images, or wherever you want to capture a wide view of a scene. To capture the grandeur of the Rocky Mountains or a wide expanse of beach, you would want to use a wide-angle lens. When you look through a wide-angle lens, the image that you see will appear smaller than what your naked eye would see.

The most common wide-angle lenses are 35mm or 28mm. Once you get down below 24mm, you are getting into more expensive lenses, and their usefulness begins to drop off.

A "standard" lens is almost always a 50mm fixed focal length lens. It is called "standard" because when you look through one, the image you see will have the same perspective as what your naked eye would see.

Years ago, whenever you bought a camera body, it came with a standard 50mm lens. For many people, that was the only lens they ever used. Because of the natural perspective, it is still a very widely used lens in many fields.

Portrait length lenses are called that because their primary use was for taking portraits. In a normal portrait situation, a lens in this range would show one-third to one-half of the subject. That is perfect for a waist-up portrait. However there is no reason that you can't use a portrait lens for any type of pictures.

The most common portrait length lenses are 80mm and 85mm. I have an 85mm lens that I just love. It is a very fast lens, and I find it very useful for taking pictures in the low light situations such as indoor hockey games.

Telephoto lenses allow you to enlarge objects in the distance, much like binoculars or telescopes do. These lenses are useful for taking pictures of wildlife or anything that you cannot get close to.

Typical telephoto lenses are 300mm, 400mm and 500mm. Of course, as the focal length increases, the "speed" of the lenses generally drops, and the price generally increases. Fast telephoto lenses are significantly more expensive than slow ones. A 300mm F-2.8 lens may cost you ten times as much as a 300mm F-5.6 lens. I have a much more detailed page all about telephoto lenses.

I am into long lenses for many of the things that I photograph, but it all depends upon what you are into.

Zoom lenses are lenses that can be adjusted across a range of focal lengths. As a result of trying to operate across a range of focal lengths, zoom lenses tend to require more light to record an image. This is what we refer to as "slower". Zoom lenses are useful because they can give you a greater degree of flexibility, but they have their limitations. In general, zoom lenses do not render as sharp an image as a fixed focal length lens, which is optimized for a specific focal length. When you cover such a broad range of focal lengths with one lens, you begin to sacrifice a bit across all focal lengths. In general, zoom lenses are slower than fixed focal length lenses.

Over the years zoom lenses have gotten better in both their quality and their range. It is now possible to find lenses that zoom from 28mm or 35mm to 200mm and beyond. This is fabulous for giving you a tremendous range of focal length with one single lens. However, the tradeoffs mentioned above are simply magnified.

Most of the normal zoom lenses fall into the following ranges:

The combination of a lens from each of these ranges will give you good coverage for normal situations. (Personally, I strongly recommend that photographers back the two zoom lenses up with a 50mm fixed lens for those situations where the light is too low for the zooms.)

The Minolta 28-105i zoom lens is a very good lens. I use mine a lot, and I like it. Mine survived a drop on cement in Sedona and an unplanned dive in a lagoon once. It operates well across its entire range, and the zoom is fast.

I don't think much of the Minolta 70-210 lens. I bought one once just to give to my niece because they are inexpensive and plentiful at the swap meets. (I much prefer the 100-300 or 75-300 zooms, they are lighter, smaller, faster, and they zoom ~50% farther)

Minolta zoom lenses for the xi cameras have a "Predictive Autozoom" feature that I have always found to be really annoying. On the Minolta models, there is a switch on the barrel of the lens that selects between Auto and Manual. There is also a button right next to the switch that you can press. If you hold that button when you turn the camera on, it will turn the Autozoom feature off/on, with the display on top of the camera telling you. I would suggest that you turn the Autozoom OFF. Otherwise it is annoying as hell and eats batteries. I do not know if the aftermarket lenses have that feature.

Fixed focal length lenses tend to be faster than a zoom lens at the same focal length. Since a fixed length lens only has to work at one focal length, and there are fewer pieces that need to move, they can be more efficient.

A typical inexpensive 50mm lens will be able to work (take photos) in much less light than that zoom lens will.

I believe that the best scenario is one where you have a mixture of zoom lenses and fixed focal length lenses. Again, once you decide what kinds of pictures you like to take, you can do a better job of deciding what types and ranges of lenses that would best suit your needs.

According to many people, there really are only about three companies in the world that actually make lenses. That means that many "competing brands" of lenses are actually made by the same company. However, different lenses may be made to different levels of quality.

In my opinion, mixing and matching of components is a bad thing. I tend to use the Minolta brand lenses on my Minolta brand cameras as much as possible. They cost a little more, but I get some peace of mind. Many lenses from aftermarket companies are fine, but if there is ever an issue of function, the lens maker may claim that it is a camera problem, and the camera manufacturer may claim it is a lens problem.

Teleconverters are devices that add a multiplication factor to a fixed focal length lens. A teleconverter mounts between the camera and the lens. The most common teleconverters are doublers and x1.4. A doubler is a teleconverter that doubles the effective focal length of the lens attached. It also doubles the effective "F-stop" of the lens at each setting. A doubler would convert a 100mm F-2.8 lens into the "equivalent" of a 200mm F-5.6 lens. However, it will usually not be quite as crisp and clear as a real 200mm F-5.6 lens. You don't get "something for nothing", so for the increase in length, you pay for it by sacrificing image quality and speed.

A teleconverter is a relatively inexpensive way to get the benefits of a longer lens without the cost. If you have two fixed lenses, you may be able to use the teleconverter with both lenses, giving you roughly the equivalent of 4 different lenses.

Some high end expensive lenses (like APO telephotos) require specific teleconverters that cannot be used on normal lenses. I have a teleconverter for my 300mm F-2.8 lens, but it is the only lens that is will work with. However, by using them together, I have the "equivalent" of a 600mm F-5.6 lens that would have cost me 10 to 20 times the cost of the teleconverter.

Apochromatic coatings are usually used only on the higher end, more expensive lenses. (More to be added later)

(Section to be added later)

I ALWAYS recommend a screw-on filter on the front of every lens. Either a UV haze (80A) filter or a Skylight (1A) filter. It is always a good idea to have a filter on each lens. A filter can save you a lot of damage. A $10~15 filter will save the front of a $200 lens when dropped or bumped. Those filters do not significantly alter the image, but they can save you a lot of grief. I have had a couple lenses saved because I had a filter attached. I have had lenses that have been dropped, but sustained no significant damage because the filter took the brunt of the impact.

Feedback or comments? Mail to: John Schultheis /