Need to adjust diopter when switching focus distance? (1 Viewer)

[Eric_D]

Equations work without data.

That is like stating "Internal combustion engines work even without fuel".

In the equation 1/f = 1/d1 - 1/d2 you still have to insert two known values (data) to determine the third unknown!

Call me a 'general algebraist' or 'algebraic generalist'? Let us 'dance on pinheads' together.

The Wiki page for Keplerian telescope doesn't even have the equation!
If you visualise a graph, you don't need data.

I mentioned "1%" above, but I need not have. I made it up.

If you are zooming down a steep hill with no brakes, a fuel-less engine will still 'work' for engine braking, I guess ...​

Although the road is working on the engine, rather than vice-versa. A 'reciprocating' engine, if you like ...​

I am tempted to try the physical experiment, not just the thought-experiment. Rather than judging focus by eye, using a 'booster' as suggested up-thread (to reduce effects of eye-focussing) I would use a manual camera and lens (digiscoping) to give an 'objective' measure of focus-distance, and magnification by pixel-counting. Data, if you like!

This conversation could get quite "Alice in Wonderland":

"I mean what I say, so I say what I mean"​

"I see what I eat, so I eat what I see"​

"Words mean whatever I want them to mean"​

Or philosophical

"Is the Thames the channel in the ground, or the water that flows through it?"​

"Can you step into the same river twice?"​

 

[Eric_D]

There is a pair on that auction site that seems to use matched magnification as a selling point ... printed on the top end plate.
Royalcraft "magni-matched" 7x50 binoculars

 

[WJC]

There is a pair on that auction site that seems to use matched magnification as a selling point ... printed on the top end plate.
Royalcraft "magni-matched" 7x50 binoculars

Only 2 - 3% of the population have the same dioptric strength in each eye.