What does mm mean on lenses. What is it actually measuring

[Dao]

So my question was not that simple at all.

The question is simple, because the answer is the focal length.
Or effective focal length since lens has multiple elements and each of them has it's focal length.

But of course, if you ask what is focal length, that's different story.

 

[bentcountershaft]

<puts serious hat on for a moment>

Isn't advertised focal length at least partially more of a marketing ploy than actual fact though? Something akin to not all 70-200's are created equal as some are closer to 170/180ish on the long end or whatnot. I'm fairly certain I've read that somewhere but can't remember if it was a credible source or not.

<removes serious hat due to poor fit and extreme heat buildup>

 

[Village Idiot]

Hey now.. that sounds dirty!!

I was an electrician's helper. I had experience.

Arent you supposed to shut off the power when you mess around with the socket?

Nah, just make sure you try not to touch the live part with something conductive, like a screw driver or a finger.

 

[vtf]

I was an electrician's helper. I had experience.

Arent you supposed to shut off the power when you mess around with the socket?

Nah, just make sure you try not to touch the live part with something conductive, like a screw driver or a finger.

That's why we call my Father-in-law "Sparky".

 

[MissCream]

God the poor guy can't even ask a question anymore!

 

[subscuck]

God the poor guy can't even ask a question anymore!

Yeah, credibility kinda cuts both ways.

 

[Dao]

<puts serious hat on for a moment>

Isn't advertised focal length at least partially more of a marketing ploy than actual fact though? Something akin to not all 70-200's are created equal as some are closer to 170/180ish on the long end or whatnot. I'm fairly certain I've read that somewhere but can't remember if it was a credible source or not.

<removes serious hat due to poor fit and extreme heat buildup>

Yes, the advertised focal length may not be the actual focal length.
In this article, assuming the data are correct, it shows that 18-270mm is actually a 18-230mm while the 18-250mm is actually a 18-220mm ....

Also, I remembered one forum member took 2 photos with 2 lenses at the same location. One with 24-70mm at 70mm and the other is 70-200mm at 70mm. The photos looks different as far as angle of view concern. So yes, focal lengths of lenses are different.

 

[MissCream]

God the poor guy can't even ask a question anymore!

Yeah, credibility kinda cuts both ways.

True, I think his best bet is to delete his account and start over.

 

[behanana]

I'm sad, the basic question still hasn't been answered, mm on a lense is the same everywhere else. It stands for milimeters and is a metric unit of length measurment. I'm such an ass.

 

[Bitter Jeweler]

True, I think his best bet is to delete his account and start over.

Ooh! That's a great idea! We should all make new accounts and see how long it takes us to figure out who each other are.
We all have our tells, don't we?

 

[Derrel]

<puts serious hat on for a moment>

Isn't advertised focal length at least partially more of a marketing ploy than actual fact though? Something akin to not all 70-200's are created equal as some are closer to 170/180ish on the long end or whatnot. I'm fairly certain I've read that somewhere but can't remember if it was a credible source or not.

<removes serious hat due to poor fit and extreme heat buildup>

"Is this tinfoil hat yours, Benny?"

Anwayyyy, yes, focal length is usually within 10 Percent of specified.

 

[subscuck]

God the poor guy can't even ask a question anymore!

Yeah, credibility kinda cuts both ways.

True, I think his best bet is to delete his account and start over.

Like Karissa?

 

[sleist]

God the poor guy can't even ask a question anymore!

The problem is he asked a question that has likely been asked and answered thousands of times before in the interwebs.
A google search would have given him the correct answer in any language he wanted faster than posting it in a beginners section of a photo forum.

Very few people have unique problems or questions.

RTFM*, then JFGI**, then ask for clarification on what you don't understand.

Failing to do even the smallest amount of research on your own is just lazy and will dictate how far you get in anything - not far at all.

* read the f'ing manual
** just f'ing google it

 

[fokker]

So my question was not that simple at all.

That was kinda my point. Nobody wants to sit here typing a novel about a complicated subject when it has been written about already by people who actually know what they're talking about. By posting your 'simple' question you've effectively just asked someone to google your own question for you and spoon feed the answer to you like the baby you are, and you've managed to create another 5-page greasy horror show in the process. Congratulations, troll.

 

[fokker]

God the poor guy can't even ask a question anymore!

The problem is he asked a question that has likely been asked and answered thousands of times before in the interwebs.
A google search would have given him the correct answer in any language he wanted faster than posting it in a beginners section of a photo forum.

Very few people have unique problems or questions.

RTFM*, then JFGI**, then ask for clarification on what you don't understand.

Failing to do even the smallest amount of research on your own is just lazy and will dictate how far you get in anything - not far at all.

Bingo