Tagged Questions
1
vote
2answers
112 views
What happened to multi-focal lenses?
Apparently multi-focal lenses such as the Tri-Elmar 16-18-21mm went out of fashion but I was wondering if the reasons for that were technical or commercial.
Are multi-focal harder to build compared ...
4
votes
1answer
114 views
What factor determines the largest usable sensor size with a certain lens?
Reading this excellent answer about field of view, focal length and sensor size a new question came to mind.
From the drawn diagrams it is clearly visible that for the same focal length an increase ...
5
votes
1answer
147 views
Where exactly would the focal length of a lens in the ray diagram fall?
If a lens is specified as (EF 50mm f/1.8), where exactly is the 50mm distance if I were to show it in a ray diagram? Considering that a lens is made up of multiple elements, I could not find a ...
6
votes
1answer
307 views
Does focus breathing make a lens slower when close focusing?
I've heard that focal length of some lenses will become noticeably longer when focusing to a close distance, an effect called "focus breathing". Since f-number is focal length divided by diameter of ...
12
votes
4answers
3k views
How can a lens like a 18-55mm have more than one focal length?
How can a lens have a range of focal lengths? Shouldn't it be a single number?
Isn't focal length supposed to be fixed for a lens of a particular shape and geometry?
What am I missing?
How many ...
