The fallacy of 35mm "equivalent focal lengths"

Started 3 months ago | Discussions thread
Lee Jay Forum Pro • Posts: 54,144
Re: The fallacy of 35mm "equivalent focal lengths"

Tony Beach wrote:

Lee Jay wrote:

Tony Beach wrote:

ThrillaMozilla wrote:

Tony Beach wrote:

The fallacy of 35mm "equivalent focal lengths"

Sets up a straw man and imagines blowing it over with a single puff.

Look, it's good that you try to work through these problems in order to buy the right camera, but you haven't found a fallacy. It's more useful to ask questions than to tilt at windmills.

You can discuss or you can just troll.

I'm quoting this post in its entirety to take up as much of the remaining posting limit as possible.

Adding unnecessary text to your posts doesn't change the number of posts in the thread.

Regarding your counterargument, from your previous reply that I didn't bother to respond to since it was already covered in other posts here, your link does not appear to be to DPR (????), and given what amounts to the working definition of "equivalent focal lengths" (and I'm repeating myself here as it appears necessary to do so) compared to the "28-105mm equivalent focal length" DPR (and others) list for the S95 my NIKKOR 50/1.8D has a "50-150mm equivalent focal length" (see here).

Your 50-150 can have any equivalent focal length down to cropping it to a single pixel.

The number I arrived at was not random. The standard I'm using is the same one that would apply to the S95, so in that regard they are equally capable.

So, everyone everywhere should base their equivalent calculations on your S95?  That's silly.

Again, "equivalent focal length" is NOT ABOUT RESOLVING POWER!!! It's only about angle-of-view. Period.

I can apply whatever AOV I want after the shot is taken.


Resolution will be a big determinant in whether its useful or not;

And for different purposes, it will be different, which is why we don't use that as a standard.

so no, not one pixel, but enough to match the S95.

The S95 is not some sort of standard.

What you're talking about isn't "equivalent focal length", it's usually called "image scale" which is usually measured in arc-seconds per pixel.

It's funny you crossed that out, since you should have actually tried to learn what it said.  It's a common term in astrophotography.

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Lee Jay

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