bclaff

Why not ask Dr. Han Q. Le ? He might feel this falls somehow under "fair use" but it would have been nice to ask.

FWIW, Studio scene Image Comparison Tool

I think this Tag is only accurate for Bulb mode otherwise the "nominal" exposure is reported. FWIW, if exposure time advances in stops then we might expect 10s to actually be 2^(3 + 1/3) = 10.08s T ...

Not for me. I never use the term viewpoint regarding photography.

The focal length doesn't change. You are simply cropping a smaller angle of view out of the lens and that smaller angle of view is *equivalent* to that of a lens with the focal length multiplied by ...

Strictly speaking perspective depends on the location of the entrance pupil of the lens (approximately where you stand), the angle of view (eg. focal length), and magnification (ie. distance to ...

Rectilinear lenses from the PhotonsToPhotos Optical Bench GOI Russar-21 133 degrees TH Swiss Irix 11mm f/4.0 126 degrees Canon EF11-24mm f4L USM 125 degrees Fisheye lenses: Patent , never produced? ...

Well, never the thin lens equations; they have a built-in assumption that pupil magnification is unity. Consider this: The light green ray is the chief ray. On the object side it points to the ...

Sorry but no; pupil magnification is required, the thin lens formula disregards it.

Yes, except you have left out pupil magnification. I prefer to think of it in term of magnification rather than distance. f / (1 + m / p) With m = f / x f / (1 + f / x / p) See Optics Primer - ...

Are you angry about some lens purchase(s)? Lie implies an intentional effort to defraud. You have no evidence of that. Focal lengths have always been rounded. And since they are often different as ...

I think you have this backwards and wrong. You cannot "compute" (effective) focal length from (effective) f# and magnification or Angle of View. Things like pupil magnification will trip you up. In ...

As I suspected ... not even close (patent is actually a 100mm f/2.5 macro)

Yeah, does not line up:

Related but not a match:

Not sure why that's directed at me. I know that. And so it follows that the focal length of a complete lens can be built up in this way. But what I do is use ray tracing on the whole lens prescription.

It's a real as any other focal length. It's just not the focal length for the lens as focused at infinity.

Let's be clear. Focal length is meaningful at any zoom/focus position for the lens. It is determined from rays that originate at infinity but the lens need not be focused at infinity.

As I said, I haven't entered it yet. But your definition of "correct" is much looser than mine. Different spacing requires a different optical prescription so I would not call that "correct" (a ...

Close but there are some significant spacing issues. Regards