The fallacy of 35mm "equivalent focal lengths"

Started 3 months ago | Discussions thread
OP Tony Beach Forum Pro • Posts: 11,933
Re: The fallacy of 35mm "equivalent focal lengths"

mamallama wrote:

Tony Beach wrote:

mamallama wrote:

Tony Beach wrote:

Describing a lens as having an equivalent focal length is simply wrong. I can't make it any more concise than that.

Provide a concise precise technical definition of equivalent as you are using the term. That will save a lot of the round robin discussions that have taken place.

I just did.


Sorry, I should have been more clear.

If you have already stated it then copy and paste the precise definition of equivalent here.

My point is there is no such thing as an "equivalent focal length" because all focal lengths have their own unique characteristics.  By invoking one limited aspect of a focal length as its used on a given sensor the other equally important aspects of that focal length are explicitly being disregarded.

It's more accurate to say a focal length when used on a particular format has a particular FOV.

Our learned folks here at DPR use the term equivalent focal length in discussions and in their lens specifications. They are very definite in the definition of how they are using the term equivalent. It is not a fallacy. It is how the whole industry uses the term.

Now you are coming along claiming it is a fallacy. That is why I want to know your definition of the term.


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