Can anyone teach me logarithms and place in computerless lens design ?

Mustafa Umut Sarac · Nov 22, 2016

My high school days wasted to listening Pink Floyd but not to courses and studying. Now I dont know anything about logarithms , effective calculations with it nor place in lens design with ruler ?

thank you very much who may want to make my day,

Umut
Istanbul

wiltw · Nov 22, 2016

Find yourself a public library to look up the topic! Greatly oversimplified, for log base 10...
Express the numbers in scientific notation (mantissa and exponent)
If we wish to multiply 4 * 5 =20,

Log 4 + Log 5 = Log 20
(0.6021 * 10^0) + (.0990 * 10^0) = Log 20
0.6021 + 0.6990 = 1.3011 = (0.3011 + 1) = (2 * 10^1) = 20

You need to know how to look up log values in a table, and the operations to perform for multiplication, division, and exponential values.

Use of a slide rule is actually nothing more than use of Logarithms, without the bother of tables to look up!

DREW WILEY · Nov 22, 2016

My math teacher hated me because he hated my brother and sister first. So I got loaned a damaged wooden slide rule guaranteed to give me bad grades. I other classes we had those big books with their log tables. In college I had a roommate who was a physics grad from CalTech and could simply rattle out log equations up to six or seven digits long, right out of his head, faster than most people can punch buttons. Amazing. But he couldn't even spell "was" or "that" correctly. He became a NASA rocket scientist, literally, but soon got bored with the job. As for me, I just keep a
basic fifteen buck log and trig calculator in the darkroom. Does everything I need. That gives me more time for photographing real logs.

David Lyga · Dec 17, 2016

Mustafa:

You have to know the 'base' (the number that you are multiplying) and you have to know the result. Then, the 'log' is simply the exponent that the base is raised by.

For example: log (base 2) of 8 is 3. In other words: 2x2x2 = 2 to the 3rd power = 8.
For example: log (base 10) of 10 is 2. In other words: 10x10 = 10 to the 2nd power = 100

Another way of saying this (and remembering, also) is:

The 'log' is the exponent that the base must be raised in order to achieve the result of 8. Therefore, the log (base 2) of 8 is 3 because 2 to the third power equals 8.

- David Lyga

Theo Sulphate · Dec 17, 2016

Type "understanding logarithms" into Google. Plenty of on-line resources.

paul ron · Dec 17, 2016

If you Are familiar with how to use a slide rule then google slide rule logs where you will get videos n tutorials on how to do it.

example
http://www.sliderules.info/a-to-z/background.htm

otherwise, your $10 scientific calculator can do it very simply in any base.

.

Nodda Duma · Dec 17, 2016

You just asked the equivalent of picking up a chunk of iron ore and asking how to turn it into a Toledo steel rapier. It takes years of study and practice to effectively design optics. There is no shortcut and...if it were easy everyone would do it.

Begin with a text on optics which describes raytracing. Like Hecht

Chan Tran · Dec 18, 2016

DREW WILEY said:
My math teacher hated me because he hated my brother and sister first. So I got loaned a damaged wooden slide rule guaranteed to give me bad grades. I other classes we had those big books with their log tables. In college I had a roommate who was a physics grad from CalTech and could simply rattle out log equations up to six or seven digits long, right out of his head, faster than most people can punch buttons. Amazing. But he couldn't even spell "was" or "that" correctly. He became a NASA rocket scientist, literally, but soon got bored with the job. As for me, I just keep a
basic fifteen buck log and trig calculator in the darkroom. Does everything I need. That gives me more time for photographing real logs.

I had a very nice slide rule and a very big log table. It may be 6x8 and 2 inches thick.

Dan Fromm · Dec 18, 2016

Chan, when I was an undergraduate I used my Chemical Rubber Company Handbook of Tables a lot. I don't miss the book or replacing division, exponentiation and multiplication with table look ups, addition and subtraction. And it has been centuries since I used a slide rule (= analog computer for division, exponentiation and multiplication). I don't miss my slide rules, even the cute little six inch P&E Model N600-T Log Log Speed Rule that's still in my upper left hand desk drawer.

RalphLambrecht · Jan 2, 2018

paul ron said:
If you Are familiar with how to use a slide rule then google slide rule logs where you will get videos n tutorials on how to do it.

example
http://www.sliderules.info/a-to-z/background.htm

otherwise, your $10 scientific calculator can do it very simply in any base.

.

how? mine only has the options of base10 and natural logs.

dasBlute · Jan 3, 2018

RalphLambrecht said:
how? mine only has the options of base10 and natural logs.

some old HPs have logbase(x), but you can do it yourself

logbase(x) = log10(x) / log10(base)

ex: log2(8) = log10(8) / log10(2)
= 0.903 / 0.301 = 3

Can anyone teach me logarithms and place in computerless lens design ?

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