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Emergency "Reading Glasses"

The pinhole in the "What's This" No. 360 reminded me of this tip.

Metal content: Reading a mike, the markings on a small drill bit, or a phone number printed on a tool supplier's business card......when you haven't got your reading glasses with you......and nobody is around to ask for help.

Use a "hand made" pinhole lens.

Cup your hand slightly and cross your thumb over your index finger. Roll and squeeze your thumb sideways until you can see light coming through a little opening (about .015" diameter) between your thumb and the place where your forefinger joins your hand.

Freeze your fingers in that position, bring your hand up to your eye and peer through that "pinhole". Put the thing you need to read about two inches in front of your hand and alter that distance until it's in focus.

Presto! Not much depth of field or angle of view, but if you only need to read a few characters it's much better than nothing.

I've always wondered how many millennia ago some poor bugger with deteriorating eyesight discovered that trick, using nothing other than the hand G-d gave him.

Jeff

Reply to
Jeff Wisnia
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Damn! That's clever! Thanks! :-)

-tih

Reply to
Tom Ivar Helbekkmo

I've been doing it all my life.

I'm not sure whether the effect is that of a pinhole lens or a stopped-down aperture.

Reply to
Jim Stewart

It's both: you get magnification because of the lens effect, and you get sharpness because of the depth of field of the small aperture.

-tih

Reply to
Tom Ivar Helbekkmo

Have to write this down that I dont forget. 8->

Nick

Reply to
Nick Müller

"Jeff Wisnia" wrote: (clip) Not much depth of field or angle of view, (clip) ^^^^^^^^^^^^^^ Thanks, Jeff. This is a good idea that is so old that I had forgotten it. I just tried it on some small type, and was able to read it at a distance of only about 3", with my glasses OFF. Any closer and my hand got in the way of the paper. BTW, I believe the depth of field is practically unlimited--that's one of the characteristics of a lens at small aperture, or a pin-hole. What IS limited is the amount of light, so you need to have good illumination.

Reply to
Leo Lichtman

this is how I read my clock radio in the middle of the night, when I don't want to wake up enough to put on my glasses...

Reply to
Emmo

Jeff's getting old, Jeff's getting old, na-na-na-naaa-naa-na!

Please post more geriatric tricks as I curse the bastards that print stuff smaller and smaller and with grey ink on slightly lighter grey paper...Mom told me I'd go blind.

OBTW, you're using a small aperature as the pin-hole effect produces an image upside-down.

Reply to
Tom Gardner

But, but, but how do you hold and read the dial calipers to get the .015"????? :-) Ken.

Reply to
Ken Sterling

It's both.

A pinhole can form an image like a lens, but unlike a lens it doesn't have a focal distance. It'll form an image at any distance, larger and dimmer for greater distances from the image plane.

A lens, including the one in your eye, forms an image by converging various rays coming from each part of an object into a corresponding part of the image plane or retina. The pinhole eliminates all but a very few rays from each part of the object, so no convergence is necessary. Therefore, the eye's lens doesn't have to focus, and aberrations have no effect.

Reply to
Don Foreman

"Tom Gardner" wrote: (clip) OBTW, you're using a small aperature as the pin-hole effect produces an image upside-down. ^^^^^^^^^^^^^ So does a lens, even the one in your eye, with or without the pinhole/small aperture.

Reply to
Leo Lichtman

The whole office had a good belly laugh! Thanks!!!

Reply to
Tom Gardner

Jeff, this also helps if you have cataracts, at least it's a crutch until you have a lens replacement. ...Been there, done that! :-)

Harry C.

Reply to
hhc314

Do you want to explain that in english? Looks like magic to me. ;-)

-- Mark

Reply to
Mark Jerde

I wonder if this is why people squint at hard-to-see objects.

Reply to
Artemia Salina

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