35mm Lenses Tutorial and Guide

last updated Aug 16, 2011

v1.0, 2011.08.01 by Robert Giordano

 

This is an article about lenses for 35mm SLR and DSLR cameras. If you are learning photography or you just want to have a better understanding of different lenses and what to do with them, this guide is for you. I will not go into the history of different lenses or some of the many technical aspects of lenses that people obsess over.

If you have an SLR or DSLR (Single Lens Reflex or Digital Single Lens Reflex) camera, it means that you can attach various lenses to the front of it. It means that when you look through the viewfinder, you are actually looking through the lens. There are many, many lenses you can use with your camera. The question is, which one is the right one? The answer to this question will change depending on what you are taking pictures of, if the subject is moving or not, what time of day it is, and of course, your budget.

The Name of the Game

The first thing to learn is how lenses are named. The name of each lens tells you its Focal Length and widest Aperture. Along with these two critical pieces of information, are other letters and numbers that vary by manufacturer and describe extra features like auto focus. Here are a few examples of lens names (without the extra letters added by manufacturers):

50mm f/2.8
100mm 1:2.5
24mm f/2.8
12-24mm f/4
70-200mm f/3.5-4.5

The Focal Length comes first and is always expressed in Millimeters (mm). The Aperture comes next and is either expressed as an "F" number (usually written as a fraction, f/2.8) or a ratio like 1:2.8. When professional photographers talk about their lenses, they will say the Focal Length and the Aperture like, "Hey, did you see my new 105 F2? Its Amazing!" If you are a photographer's assistant, you have to be familiar with the names of the lenses a photographer has in his bag so when he says, "I need the 24" you know that he means his 24mm lens. If the photographer only has ONE 24mm lens in his bag (which will be 99.9% of the time), they usually won't bother to say the F number.

Focal Length

The Focal Length is a measurement. It is roughly the distance between the film or digital sensor in the camera, and the center of the main glass element inside the lens. I say "roughly" because the exact distance is calculated using the "rear nodal point" of the lens but I promised not to get into lengthy technical stuff. All you really need to know is that bigger Focal Lengths mean more magnifying power and smaller Focal Lengths mean a wider angle of view. A 50mm lens represents the middle or "normal" view where objects in the camera appear the same size as when you're looking at them without a camera. If you really want to get into all of the technical stuff, the following page is a good starting point: http://en.wikipedia.org/wiki/Focal_length

Some common Focal Lengths:

18mm
Super wide angle. Captures an entire scene, used for landscapes, architecture, etc.
24mm
Wide angle. Good for smaller scenes, large objects like airplanes or ships, group photos with 10 or more people.
50mm
A "Normal" lens, meaning no magnification. Used for journalism, medium sized objects like cars, small groups of people. See Normal Lens in the definitions below.
85mm
Subject will be slightly magnified. Good for small objects or object details, good for cropped studio portraits with 1-3 people.
105mm
Subjects magnified roughly 2X. Best for object details and studio portraits of an individual.
200mm
Subjects magnified 4X. Good lens for journalism and a good all purpose lens for medium distance shots. Not quite enough zoom for long distance shots.
300mm
Subjects magnified 6X. Good lens for journalism and fashion, greater depth-of-field to separate subject from background.
400mm
Subjects magnified 8X. Mainly used for sports and wildlife. These lenses can be very big and heavy.
600mm
Subjects magnified 12X. Mainly used for wildlife. These lenses are generally very large and expensive.

Lenses are available in many other Focal Lengths. A "Zoom" lens is one that can be adjusted anywhere between two different focal lengths. A "Prime" lens is one that is set at a fixed focal length and cannot zoom in or out. It would be awesome if there was one lens that you could adjust anywhere between 18mm and 600mm, but due to the current methods of lens construction, this isn't possible or practical. I used to have an expensive 18-200mm zoom lens (18mm to 200mm) and although it was really handy, my 24mm and 180mm prime lenses produced better quality images.

Focal Length Illustrations

The following scene was photographed with a number of different lenses. The camera was on a tripod and was not moved between shots. The focal length of the lens is given at the top of each image.

Example of 18mm focal length, photo copyright 2011 Robert Giordano

Example of 24mm focal length, photo copyright 2011 Robert Giordano

Example of 50mm focal length, photo copyright 2011 Robert Giordano

Example of 105mm focal length, photo copyright 2011 Robert Giordano

Example of 300mm focal length, photo copyright 2011 Robert Giordano

Example of 600mm focal length, photo copyright 2011 Robert Giordano





Apertures and F-Numbers

The second distinguishing feature of a lens is its widest Aperture. This is given as an "F" number like f/2.8 or as a ratio like 1:2.8. Again, I'd like to skip as much technical jargon as possible. This number tells you how much light a lens will let into the camera. The LOWER the number, the MORE light it will let in. On most lenses, you can set the aperture to a number of different "F-Stops" to let in LESS light, but you can't make a lens let in any more light than its widest aperture. Let's say you had a choice between a 200mm f/4 and a 200mm f/2.8. The 200mm f/2.8 would generally be a much better lens. It might also cost twice as much because the glass elements would be twice as big, in order to let in twice as much light.

Aperture chart, copyright 2011 Robert Giordano

The Aperture Chart shows various apertures drawn to scale. As you can see, the LOWER F-Number represents the WIDER Aperture, which lets in MORE light. The following is a list of all the F-Stops you are likely to see on 35mm lenses:

f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64, f/90, f/128

Why should you want an f/2.8 lens instead of an f/4 lens? (or an f/4 instead of an f/5.6, etc.) Why do you want to let in more light? Since each F-stop in the above chart lets in TWICE as much light as the one after it, an f/2.8 lens lets in twice as much light as an f/4 lens. This means you can use a shutter speed that's twice as fast with your f/2.8 lens. This is good for shooting sports where things are moving fast. It also means you can shoot pictures when there isn't as much available light. This is good for shooting concerts or events at night when you may not be able to use a flash. This is why sports photographers always have those big huge lenses. They need lenses that let in as much light as possible so they can use faster shutter speeds and they can shoot games at night where stadium lighting isn't as bright as sunlight.

A wider aperture also increases the Depth-of-Field. In other words, it makes the background more blurry. Fashion photographers like this because it separates the model from the background. It also makes flat photographs look more three-dimensional. Food is often photographed with an f/2.8 or f/2 lens so that only a small detail of the food is actually in focus.

Cheaper zoom lenses may have an aperture range like f/4.5-5.6. When this lens is set to its smallest focal length, you'll have a maximum aperture of f/4.5. When set to its longest focal length, you'll only have a maximum aperture of f/5.6. That's not very good. Better quality zoom lenses will have a consistent maximum aperture throughout their zoom range. If you like math and you want to learn how F-Numbers are calculated and all of that stuff, see http://en.wikipedia.org/wiki/F-number.

There is one last point to consider. Because lenses with smaller F-numbers have to be made with larger pieces of glass, they also have to be made with greater precision and higher tolerances. This is why an f/2.8 lens is more expensive than an f/4 but it is also why the f/2.8 lens might produce sharper, better quality images. While this isn't true in every case, I've experienced it more often than not. Having a greater range of creative control is an important detail to any artist. It is why a painter will pay twice as much for one type of brush as opposed to another. It is why a photographer will pay more for an f/2.8 lens than an f/4 lens.

The "DSLR Crop Factor"

The sensor in many DSLRs is smaller than 35mm film. Its called the APS-C image sensor format. Nikon calls it the DX format while Canon calls it EF-S or APS-C. When you put a 50mm lens on an APS-C format camera, the image will look like you shot it with a 76mm lens. Why? Because the sensor is smaller than 35mm film, you are only getting the center section of the 35mm image that the lens is capturing.

To find the equivalent of a 35mm lens on an APS-C format camera, multiply the Focal Length by 1.5. For example, a 20mm lens becomes a 30mm lens. This is not good news when you need a wide angle lens. The best wide angle lens I've used is Nikon's 12-24mm f/4 which gives me the equivalent of an 18-36mm lens on a 35mm film camera. On the other hand, my 200mm lens becomes a 300mm and my 300mm lens becomes a 450mm. As you can see, there are advantages and disadvantages to the APS-C format. Some lenses are specifically designed for APS-C cameras. While they might also fit on a 35mm film camera of the same brand, they will usually vignette. Full frame 35mm digital cameras are available but they are generally a lot more expensive.

Diagram of 35mm Film vs. Nikon and Canon APS-C sensors, copyright 2011 Robert Giordano


More Terms and Definitions:

Aperture Diaphragm
This is a series of overlapping blades inside a lens than open and close to select the size of the opening, or "aperture" that lets light into the camera. The aperture diaphragm blades arranged in a circle is a common symbol in photography. The early James Bond films featured an aperture diaphragm in the opening credits.
Bokeh
This refers to the "look" and quality of the out-of-focus areas in a photograph. Many photographers use a wide lens aperture for a shallow depth of field. This technique separates the foreground subject from the background. The blurriness of the background can look completely different from one lens to another. Sometimes a photographer will choose a lens based on its bokeh as well as its sharpness. This happens frequently in fashion and product photography.
- Bokeh is influenced by the number and shape of the blades in the Aperture Diaphragm.
- The look of lens bokeh is completely different than using a blur filter in Photoshop. It is almost impossible to reproduce lens bokeh with software.
- For more information, see: http://en.wikipedia.org/wiki/Bokeh
Barrel Distortion
A type of distortion common to wide angle lenses is barrel distortion. Straight lines in an image appear to be slightly bulging out, like the lines of a barrel. Fisheye lenses use this type of distortion to the extreme but in rectilinear lenses, barrel distortion is not desirable. Pincushion distortion is the opposite of barrel distortion and makes straight lines look like they are bowed inward. Fortunately, barrel distortion can usually be corrected with software like Photoshop.
- For more information, see http://en.wikipedia.org/wiki/Distortion_(optics)
Chromatic Aberration
A type of distortion that appears as "fringes" of color along edges of contrast in an image. It occurs because different wavelengths (colors) of light will be in focus at slightly different points. While barrel and pincushion distortion can easily be corrected with software, chromatic aberration is almost impossible to correct. Lens manufacturers go to great lengths to minimize chromatic aberration by using special coatings and multiple types of glass elements within a lens. In general, cheaper lenses will tend to have more chromatic aberration because they lack these extra coatings and glass elements.
- For more information, see http://en.wikipedia.org/wiki/Chromatic_aberration and http://toothwalker.org/optics/chromatic.html
Fisheye Lens
A fisheye lens usually provides a wider angle of view by distorting the image into a circle. They were originally developed to take circular pictures of the sky from horizon to horizon (180 degrees). The extreme distortion of a fisheye lens can create interesting effects when used to photograph regular objects.
- Software exists that can "straighten" the lines in a fisheye lens image.
Macro Lens
All lenses have a limit to how close you can come to an object and still be able to focus on it. For example a 105mm lens might not be able to focus on objects that are closer than 2 feet away. A Macro lens is specially designed so it can focus on objects that might be only an inch away or less. Macro lenses are used to photograph very small objects with lots of detail. This includes insects, wristwatches, jewelry, electronics, and medical applications.
- Dedicated macro lenses will usually have the word "Macro" in their name. For example, you could own both a 50mm f/2.8 Macro lens and a regular 50mm f/2.8 lens.
- Some lenses are advertised as having "Macro" capability. This simply means it can focus on objects that are fairly close to the lens. This capability will vary from lens to lens. If you are shooting a lot of macro work, its best to buy a dedicated macro lens.
Normal Lens
A "Normal" lens is one that displays an image the same as you see it with your eyes. It doesn't magnify or make the field of view wider. The focal length of a normal lens is roughly the same as the diagonal measure of the film or digital sensor. For 35mm film, a 50mm lens is a common normal lens. For DSLRs with APS-C sensors, a 35mm lens would be considered normal.
Prime Lens
A "Prime" lens is a lens with a fixed focal length. In other words, you can't zoom in or out. If you can turn a ring on the lens to zoom in or out, its a Zoom lens, not a Prime.
- Prime lenses can be either Wide Angle or Telephoto.
- Prime lenses are generally sharper than Zoom lenses.
Rectilinear Lens
A rectilinear lens is one that keeps straight lines straight. It is the opposite of a fisheye lens. Wide angle lenses can be designed to be rectilinear but only the most expensive ones come close to being perfect. If you're shooting any type of architecture or interior, you'll need a rectilinear wide angle lens.
- See also Barrel Distortion.
Sharpness
The sharpness of a lens is both subjective and objective. People who upload their photos to Facebook, won't notice differences in sharpness that a person who makes 20 by 30 inch prints will.
- Generally, a Prime lens is sharper than a Zoom lens.
- An excellent article to read about sharpness is:
http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance
Zoom Lens
Any lens where you can vary the focal distance, or in other words, zoom in or out by turning a ring on the lens. If there is no ring on the lens that lets you zoom in and out, its a Prime lens.
- Zoom lenses will have the focal length range in their description, for example 18-105mm, 24-70mm, 12-24mm, etc.
- Zoom lenses can be either Wide Angle or Telephoto.
- Zoom lenses are generally not as sharp as Prime lenses but newer zooms from Nikon and Canon come very close.
- Some digital cameras have "digital zoom" but this has nothing to do with the lens and its more of a gimmick than anything. All "digital zoom" does is zoom in on the pixels of the digital image. It doesn't improve the image. Don't use digital zoom. Ever.

What Lenses Should I Buy?

I've been asked this question so many times that I decided to make the following list...
(I only use Nikon cameras and lenses so all of the examples are Nikon)

If you're a ___A___,
you should have ___B___
for example, ___C___
because ___D___

A. Photojournalist
B. 2 camera bodies, one with a wide angle zoom lens and the other with a telephoto zoom lens, one external flash, a notepad and a car charger for your cell phone.
C. Nikon 17-35mm f/2.8 and Nikon 80-200mm f/2.8
D. you need to have a minimal amount of gear you can keep with you 24 hours a day. You'll need a wide angle lens for entire scenes, and a telephoto lens to get crime scene photos from a safe distance. You'll need two camera bodies because you'll be shooting the action as its happening and you won't have time to change lenses on a single camera body. You'll need a notepad to write down the captions that your editor will demand from you later. You'll need to keep your cell phone charged at all times.

A. Landscape/Travel Photographer
B. 1 camera body, and an assortment of prime lenses, a good tripod, and survival gear.
C. Nikon 10.5mm f/2.8 fisheye, Nikon 12-24mm f/4, Nikon 20mm f/2.8, Nikon 35mm f/1.8, Nikon 50mm f/1.8, Nikon 105mm f/2.8
D. the lanscapes aren't going anywhere so you have time to select the right lens for the scene, and prime lenses will provide sharper details, especially if you want to make prints larger than 8 x 10. You'll need the tripod if you want to shoot long exposure scenes at night. You'll need survival gear because you'll be out in the middle of nowhere, sleeping on the ground so you can get that amazing shot at 5am.

A. Fashion Photographer
B. 2 camera bodies, several normal to telephoto prime lenses, an assistant, and an agent.
C. Nikon 85mm f/1.8, Nikon 180mm f/2.8, Nikon 300mm f/2.8
D. you'll need to use longer focal length lenses to make the models look as good as possible. You'll need an assistant because you have to give these models your full attention. You'll need an agent because, out of the 3,000,000 photographers that want this job every year, maybe 10 get paid to do it.

A. Concert/Club Photographer
B. 2 camera bodies, one with a wide angle zoom lens and the other with a telephoto zoom lens, one external flash, and a notepad.
C. Nikon 12-24mm f/4 and Nikon 80-200mm f/2.8
D. you'll want the minimal amount of gear because you could be on your feet for 6 to 12 hours straight, depending on the length of the event/concert/rave/etc. You'll want the widest angle lens you can get for impressive shots of the crowd, as well as a good telephoto for shots of the band/performer/DJ/etc. You'll want two camera bodies because you won't want to switch lenses back and forth a million times during the show. You'll want a flash to get photos of hot girls/guys/whatever in the crowd and you'll need a notepad to write down their phone numbers.

Conclusion

If you're a serious photographer, you should really strive to have the best set of lenses you can afford. Camera bodies come and go, and they are always being updated. That $1600.00 camera body you buy today might be obsolete in a few years but your 80-200mm f/2.8 can serve you for a lifetime if take good care of it. You can take a great picture with a cheaper camera body and an excellent lens, but the fanciest, most expensive camera will still take a mediocre picture with a cheap lens.

Please leave comments below if you found this article helpful, if you spot any errors, or if you think I should add anything else.

thanks!





[2 Comments]


  

Marty Hunter

26 Oct 2012 11:10pm

"Very helpful! I am fairly new to photography and have not found a better tutorial than this anywhere! The pictures that are provided with the information really brings the lesson to life for me because it make is so much easier to understand. I have a much clearer idea of the basics and what camera + camera lens to look for when i go buy my equipment, Thank you very much!"
 


  

Andrew Frazer

29 Jun 2012 5:58pm

"This was very helpful! Thanks for laying it out so simply, especially with the photos demonstrating the different lenses. I have just upgraded to a NEX5N from compact cameras, and this article will help me choose some vintage lenses to go with it. Thanks very much!"
 

  

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