DPReviewTV: What is diffraction in photography?

SteveC

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I hated things like Bessel Functions where we had to do calculations on those huge old mechanical calculators that could multiply and divide to many decimal places but we did it over and over and had to get every one of the many digits put in correctly. They were needed for wave propagation theory. In my case, it wasn't light waves, but electromagnetic waves.

Since slide rules were a critical tool for engineers at the time, we all had good ones. I still have a couple laying around, 59 years old this year, I bought them in the fall of 1961. I still use the triangular architect's scale I bought then, its right here in my desk. When calculators came out, a simple 4 function one cost something like $450. HP was king until TI came out with much less expensive ones that did not use reverse polish. I bought a SR50 instead of a HP35.

Reverse Polish is one of those things that make no damned sense (why in the hell would someone design a calculator to work that way?) unless you understand it's working on a stack. Then it not only makes perfect sense, but if you're clever enough you can do more complex things on it than you could with a "regular" calculator.

I had used plenty of non RPN calculators before entering college, but IN college, an HP41 became my companion. I still have it, but it's broken (there are shops out there that will repair them; it's on my to do list). I've told people that it should be put in my coffin with me.
 

AlanF

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Aug 16, 2012
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I hated things like Bessel Functions where we had to do calculations on those huge old mechanical calculators that could multiply and divide to many decimal places but we did it over and over and had to get every one of the many digits put in correctly. They were needed for wave propagation theory. In my case, it wasn't light waves, but electromagnetic waves.

Since slide rules were a critical tool for engineers at the time, we all had good ones. I still have a couple laying around, 59 years old this year, I bought them in the fall of 1961. I still use the triangular architect's scale I bought then, its right here in my desk. When calculators came out, a simple 4 function one cost something like $450. HP was king until TI came out with much less expensive ones that did not use reverse polish. I bought a SR50 instead of a HP35.
Put them in a display cabinet with your film cameras.
 
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stevelee

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I wondered if RPN might have been an overreaction from people who used to program in Lisp.

I use Casio calculators that use algebraic notation. They seem to follow it better than other brands I have tried that supposedly do the same thing.
 

SteveC

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Sep 3, 2019
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I wondered if RPN might have been an overreaction from people who used to program in Lisp.

I use Casio calculators that use algebraic notation. They seem to follow it better than other brands I have tried that supposedly do the same thing.

I hated my first experience with RPN, in junior high school. It was maddening and I had no idea why anyone would want to do it. In college though, I had been taught about stack architectures, and when I realized there was a four-layer-deep stack on HP calculators, it suddenly made perfect sense to me--I had a mental picture of how it worked--and four levels lets you do a LOT of algebraically complicated things without the use of a parenthesis key. A very simple example:

4 * (12+3) comes out as 4 (enter), 12 (enter) [don't do anything just yet, the stack has 4, 12 on it] 3 + [adding the 3 to the 12 and leaving the stack as 4, 15], then with the stack containing 4 and 15, you hit multiply.

Note, though that any stack based system has to have keys that swap the top two things on the stack and also one that does a "roll" of the stack (moving everything one position, and taking what's at one end (and about to be shoved off by the roll) and sticking it into the other.
 

stevelee

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Jul 6, 2017
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If I had encountered a pocket calculator in junior high, I wouldn’t have cared if I had to stand on my head to use it. As it was, I was in graduate school in Dallas when I was at a prof’s home when I saw one. His wife worked for a TV station, and she had a calculator from the station at home with her. It cost over $300 and would add, subtract, multiply, and divide in the simplest manner. I vowed that one day I would own one.
 
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Valvebounce

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Hi PBD, usern4cr.
Head over and have a look at Roger’s post to see just how misleading this can be! I found it enlightening and entertaining! o_O

Cheers, Graham.

Looking down a lens and trying to estimate anything is an exercise in futility as the lenses you are looking through change the very view of what it is you think you are seeing.
 
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usern4cr

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Sep 2, 2018
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Hi PBD, usern4cr.
Head over and have a look at Roger’s post to see just how misleading this can be! I found it enlightening and entertaining! o_O

Cheers, Graham.
Thanks, Valvebounce. I had read that post previously, and it's pretty amazing in how many steps & photos they took.
 
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