Alley in Pisa, Italy

by Lars Kotthoff

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8
votes
6answers
811 views

Why is focal length measured in millimeters?

Why is focal length measured in millimeters?
4
votes
3answers
388 views

What does it mean that a lens is x millimeters?

Every lens has different focal length in terms of millimeter so if I have a 100mm lens, what does that refer to? Does it mean the length of the lens itself is going to be 4 inches long, or does this ...
2
votes
3answers
5k views

What is the relationship of aperture, focal length, and ISO in a SLR?

I was using Nikon digital camera, and recently bought a Canon 550D. I am totally new to SLR. I am not familiar with SLR terms: Aperture, focal length and ISO, and their relation to one another. What ...
12
votes
4answers
2k views

What is a normal lens?

I've heard people call 50mm lenses "normal lenses". For a lens to be considered normal, does it have to be exactly 50mm or is there some leeway? Does the normal focal length depend on crop factor of ...
4
votes
3answers
2k views

What is the meaning of single focal length?

The Nikon AF-S DX Nikkor 35mm f/1.8G is described as a single focal length lens: http://www.nikon.co.in/products.php?categoryid=1014. What does that mean? What are its disadvantages as compared to ...
4
votes
3answers
8k views

What does “the telephoto end” and “the wide angle end” of a zoom lens mean?

In the Canon Rebel T3i Manual, page 59, it's mentioned that "If you have a zoom lens, use the telephoto end to fill the frame with the subject from the waist up." Same note on page 61 and another one ...
8
votes
3answers
829 views

How can a 24-70mm and a 10-22mm both be “wide angle” lenses?

I've been looking at a 10-22mm lens for my Canon T2i. I've also come across some other "wide angle" lenses, like the Sigma 24-70mm F2.8. I don't understand how a wide angle lens can have such high ...
13
votes
3answers
2k views

What is a parfocal lens and how beneficial is it to photography?

I heard someone say that after using a parfocal lens for the first time, they would never switch back. What is a parfocal lens, how is it different from any other lens, and what are the advantages and ...
11
votes
4answers
859 views

What does 'Equivalent to 1.6x the focal length of the lens' mean?

In the specifications of Canon 550D, about the lens the following is mentioned LENS Lens Mount EF/EF-S Focal Length Equivalent to 1.6x the focal length of the lens Now this is really ...
45
votes
5answers
9k views

What is “angle of view” in photography?

I read on the Lens Buying Guide @ neocamera: Focal-length determines the angle-of-view seen through a lens for a given sensor-size. With a full-frame sensor a lens gives the same angle-of-view ...
18
votes
4answers
492 views

Is there construction-agnostic term for a lens with a long focal length?

Turns out that telephoto refers to a specific construction of a long-focal-length lens, i.e., one where the lens is physically shorter than the focal length. Is there a generic term for referring to ...
20
votes
4answers
3k views

What is focal length and how does it affect my photos?

What is focal-length? Are focal-length and zoom synonymous? How does the focal length of a photo affect it?