Difference between zoom, macro, and telephoto lens

[jsl]

Hiya all,

I'm fairly new to DSLR photography and was wondering whether someone can help me with this seemingly basic question. I think some of the categories overlap but I keep getting different advice/comments. Basically, what is the difference between zoom lenses, macro lenses, and telephoto lenses?

Is say a telephoto lens the same thing as a zoom lens? Are some telephoto lenses, macro lenses? Are all telephoto lenses, macro lenses?

A comprehensive clarification would be really helpful if that wouldn't be too much trouble.

Thank you all!

[inkista]

A zoom lens is simply a lens with a variable focal length. It simply distinguishes it from prime lenses, which have fixed focal lengths.

Prime lenses are an older, simpler technical design, and primes are often smaller, sharper, and cheaper than their zoom counterparts. They also have the largest maximum apertures. A prime with a maximum aperture that's f/2.8 or larger (smaller f-number) is also known as a "fast" prime, because the large max. aperture allows for faster shutter speeds.

The categories by focal length (smallest to largest) are:
ultrawide (~10-20mm)
wide angle (~17-35mm)
normal or standard (~30-50mm, depending on crop factor of sensor)
telephoto (~70-300mm)
supertelephoto (~>300mm).

Obviously, the crop factor of the camera has some determination on whether a lens is wide angle or normal, or normal vs. short telephoto, but these are the general definitions.

So, for example, Canon's EF-S 10-22 is an ultrawide zoom. The Distagon 21mm is a wide angle prime. Canon's 70-200 f/4L USM is a telephoto zoom. The EF 400mm f/5.6L USM is a supertelephoto prime.

A macro lens is a lens with the additional capability of being able to focus closely (this is usually done by introducing a floating element--a piece of glass that does NOT rack in and out with focus in unison with the other elements in the lens). The strict definition is a lens that can achieve 1:1 magnification--that is, the image on the sensor/film is the same size as the object itself. Most true macros are prime lenses. And most macros are extremely sharp because of the floating element.

And two more oddball lens types you may bump into:

A fisheye lens is one where the lens does not attempt to draw the light in a rectilinear fashion, but rather a curved one. It has a high amount of distortion, but also brings in a larger field of view than a rectilinear lens with the same focal length.

A tilt-shift lens is one that allows for lens movements, analogous to a view camera bellows, only with less freedom. Shifting is used for perspective correction, and tilt for changing the focus plane and controlling depth of field. These lenses are mainly used for product or architectural photography.

[TheManny]

I'll take a stab at this too (forgive me if this isn't as comprehensive as you would prefer)...

Basically, what is the difference between zoom lenses, macro lenses, and telephoto lenses?

Zoom lenses are lenses that have the ability to vary their focal lengths as opposed to a fixed focal length lens (or prime lens).

Simple enough right... the following two are a little bit more on the gray (grey?) side:

Macro lenses are lenses typically optimized to focus sharply on a relatively small area, usually used for close-up work.

Telephoto lenses are a specific construction of long (typically single) focal length photo lenses in which the "physical length of the lens is shorter than the focal length." A regular lens that has a focal length that is longer than what is considered "normal," is not necessarily a telephoto lens. A telephoto lens has to incorporate a rear lens group usually referred to as a "telephoto group."

Whew...

Is say a telephoto lens the same thing as a zoom lens?

By definition no, however non-telephoto lenses of long focal lengths are often informally referred to as telephoto lenses. The angle of view created by a telephoto lens is the same as that created by an ordinary lens of the same specified focal length.

Are some telephoto lenses, macro lenses? Are all telephoto lenses, macro lenses?

Again by definition, no. Although at the right distances, you can almost utilize a telephoto lens as a macro lens, however your area of sharpness would be hindered by a telephoto lens' area of focus.

Hope that sheds a little more light on the subject matter for you. Cheers!

[LoveDSLR]

A true macro lens is a flat field lens as well--suitable for photographing documents, stamps, coins, etc.

Originally Posted by jsl;

Is say a telephoto lens the same thing as a zoom lens? Are some telephoto lenses, macro lenses?

May be the old Nikon AF Zoom-Micro Nikkor 70-180mm f/4.5-5.6D ED.

[Doug Pardee]

Originally Posted by jsl

what is the difference between zoom lenses, macro lenses, and telephoto lenses?

All of those terms have been "hijacked" and most people now use them to mean something different from the original meanings.


The modern, popular, but not technically correct meanings:

A zoom lens is one that is adjustable across a range of focal lengths.

A macro lens is one that can focus at fairly close distances (for taking pictures of bugs and the like).

A telephoto lens is one with relatively high magnification.


If you care about the original technical meanings:

A zoom lens is one that is adjustable across a range of focal lengths without disturbing the focus. Almost all of today's "zoom" lenses require refocusing when you change the focal length. The correct term for those lenses is varifocal. For still photography it's not a big deal, but for shooting movies the act of zooming in or out while filming a scene should not cause the subject to go out of focus.

A macro lens used to be generally understood to be a lens that could produce an image on the film—or sensor—that was at least as large as the object being photographed (obviously this would be at very close range). So a 1/2-inch long bug could be projected as a 1/2-inch long image on the film or sensor. Very few of today's "macro" lenses are capable of this "1:1" magnification.

A telephoto lens is one that uses a "telephoto group" of lens elements to allow the lens to be shorter than focal length would normally dictate. Many lenses that are called telephoto don't really have telephoto construction.


By the way, since it was mentioned in an earlier response… the term prime lens has also been hijacked. It is now generally used to mean a lens with a single focal length, more properly called fixed focal. Originally a prime lens was the main lens when using multiple lenses in combination. For example, if you mount a 70-200 zoom (ahem, varifocal) lens on a 1.4x teleconverter, the 70-200 is the prime lens while the teleconverter is the secondary lens. Similarly, if you fit a Canon 250D "close-up lens" to the filter threads on the front of your 18-55 lens, the 18-55 is the prime lens and the 250D is the secondary lens.

[jsl]

Thanks for all your comments! I found the wealth of information incredibly useful. I'm a pragmatic type of guy so I found the following really useful:

Originally Posted by Doug Pardee

The modern, popular, but not technically correct meanings:

A zoom lens is one that is adjustable across a range of focal lengths.

A macro lens is one that can focus at fairly close distances (for taking pictures of bugs and the like).

A telephoto lens is one with relatively high magnification.

Having said that, I really enjoyed reading about the background and history so thanks for that too!

On a related note, does anyone know what the mm numbers mean on a zoom/telephoto lens? E.g. what does 18-200mm actually mean? I used to think this was the distance between the first and last lens but looking at Canon L lenses, I'm not sure how this could be the case. Can anyone shed some light?

[dcclark]

Technically, the focal length (measured in millimeters) is the distance from the center of the objective (front) element of the lens, to the point of focus (basically, the sensor). However, modern lenses use all kinds of tricks which modify the focal length without actually having that much distance. So, basically, the focal length measurements are a handy way to compare the field of view of lenses, without having a whole lot of practical physical meaning.

[Doug Pardee]

Originally Posted by jsl

does anyone know what the mm numbers mean on a zoom/telephoto lens? E.g. what does 18-200mm actually mean?

It's a measure of the magnification power of the lens.

An object of size 'x' at a distance of 'x'—say, a building 500' tall photographed from a distance of 500'—will project an image on the sensor or film whose size is equal to the focal length (18mm for an 18mm lens, 200mm for a 200mm lens).

Object size divided by object distance equals projected size divided by focal length. At distance, anyway. At close range there is a bit of fudge factor needed to account for the incipient angles and for focal length change due to the focus adjustment.

There is a theoretical basis which is basically "the same magnification that a single thin lens would give when the distance between the thin lens and the imaging plane is equal to the focal length." This theoretical basis doesn't have much practical use, though.