RE: f number adjustment to increase light level

[Christopher Strevens <chris@xxxxxxxxxxxxxxxxx>]

In fact this was one of the first computer algorithms I wrote back in the ‘60’s when I started to study computing.

 

 

Chris

 

From: owner-photoforum@xxxxxxxxxxxxxxxxxx [mailto:owner-photoforum@xxxxxxxxxxxxxxxxxx] On Behalf Of Kim Mosley
Sent: 21 January 2011 03:52
To: List for Photo/Imaging Educators - Professionals - Students
Subject: Re: f number adjustment to increase light level

 

Here's o:p>

 

16 x 16 / 10 = 25.6    

Square root of 25.6=f/5 (rounded off)

 

Or suppose you are at f/8 and you want 4 times more light.

 

8x8 (or 8 squared) / 4 = 16

Square root of 16 = f/4

 

We are just talking about the area of the aperture, right?

 

No logs!

On Thu, Jan 20, 2011 at 8:31 PM, ADavidhazy <andpph@xxxxxxx> wrote:

I was intrigued by a statement I made during a review of a sample exam
session and this afternoon decided to find out what the new f# should
be given that one wants to increase the light level at the image plane
over that available at some starting f#. After 4 hours of pondering
came up with this (whole increments would be quite easy ...):

http://www.davidhazy.org/andpph/text-fnumber-aperture-adjustment.html

I am sure there are easier ways to do this and if so a hint would be
most welcome! Of course fractional or "decimal" f#s are not easy to set!

Andy

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Kim Mosley
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Website: http://kimmosley.com
Blog: http://kimmosley.com/blog