Yes two pairs of 5 dioptre glasses gives you 10 dioptres (maybe it's 5x5 so 25) doesn't it? I think that's getting to a decent magnification. Not sure exactly what power.Bahnstormer_vRS wrote: ↑Sat Mar 27, 2021 5:29 pmI've done that before now.exHowfener wrote:Does anyone here watch "The Repair Shop" on BBC1? There's a guy on the programme (a jeweller) who wears two pairs of glasses.
Taken an old pair of reading glasses and placed them in front of my regular Varifocal spectacles.
Guy
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Incoming from Watchgecko
Re: Incoming from Watchgecko
- H0rati0
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Re: Incoming from Watchgecko
not quite 10 dioptres because you get diffraction across the air-gap but pretty close. At that power, focus is achieved at 10cm because a dioptre by definition is the reciprocal of the focal length. Times magnification (magnifying power as opposed to power of lens) is more difficult because it depends on the distances between a "typical" eye, magnifier and object but typically 3-4X for 10 dioptres.
Thus more power (in dioptres) means you have to shorten the viewing distance, narrowing the field of view and in practice the lens has to be more complex because aberration (distortion) increases and it all starts going sideways.....
"There is no beginning to enlightenment and no end to training" - Dogen Zenji (1200-1253)
Re: Incoming from Watchgecko
I definitely find my 25x loupe set very hard to use. I get all types of aberration, and a very limited depth of field. I imagine that's the inexpensive lens design of my viewer. I notice a difference with binoculars. I have a lovely pair of 8x30 pentax binoculars, and the image is always crisp and clear. much more so than when I use other less expensive glasses.H0rati0 wrote: ↑Sun Mar 28, 2021 3:18 pm
not quite 10 dioptres because you get diffraction across the air-gap but pretty close. At that power, focus is achieved at 10cm because a dioptre by definition is the reciprocal of the focal length. Times magnification (magnifying power as opposed to power of lens) is more difficult because it depends on the distances between a "typical" eye, magnifier and object but typically 3-4X for 10 dioptres.
Thus more power (in dioptres) means you have to shorten the viewing distance, narrowing the field of view and in practice the lens has to be more complex because aberration (distortion) increases and it all starts going sideways.....
- H0rati0
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Re: Incoming from Watchgecko
Pentax do know what they are doing when it comes to lens design....though naturally the design of binoculars is a very different from a loup. For your 25x try holding it very close to your eye and then bring the object into focus. It will be very near the loup but that's how they are designed to be used - though as you say on a cheapo one the optics (aberrations) won't be anything to write home about.JAFO wrote: ↑Sun Mar 28, 2021 4:09 pm
I definitely find my 25x loupe set very hard to use. I get all types of aberration, and a very limited depth of field. I imagine that's the inexpensive lens design of my viewer. I notice a difference with binoculars. I have a lovely pair of 8x30 pentax binoculars, and the image is always crisp and clear. much more so than when I use other less expensive glasses.
"There is no beginning to enlightenment and no end to training" - Dogen Zenji (1200-1253)
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