« Quiet Time in the Loop - Dick LaRosa | Main | Julius Sumner Miller - John Dunn, Consultant Ambertec, P.E., P.C. »

March 31, 2012

Comments

John Dunn

Clearly (pun intended), this is a simplification of the topic. For a nice write-up in greater detail, take a look at:

http://en.wikipedia.org/wiki/Focal_length

George Storm

As you say - somewhat simplified.
Your photographer friend would have been on firmer ground if he had contested the equation: 1/u+1/v=1/f
For real (thick and/or multi-element) lenses the reference plane is not stationary and the magnification does not correspond to a constant focal length.

William Ketel

The fact is that as a number gets vary large, it's reciprocal does get very small, and if we are using fixed-point arithmetic the vary small number may indeed drop out, equivalent to becoming zero. So while a lens may not be focused on actual infinity, it can be focused on some point far enough away so that the difference is not measurable with common measurement procedures. In short terms, "close enough" to infinity.

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been saved. Comments are moderated and will not appear until approved by the author. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Comments are moderated, and will not appear until the author has approved them.

Your Information

(Name and email address are required. Email address will not be displayed with the comment.)

Editor

  Learn about our  

 free engineering 

consulting referral 

      service at:

 

  IEEE Consultant's 

      Network of 

     Long Island

 

We have over forty 

electrical, electronic, 

mechanical and 

software engineers 

with expertise in more 

than sixty-five categories 

of technology and business. 

All are members of the 

IEEE and adhere to the 

IEEE professional codes 

of ethics. 

No fee is charged for the

referral service. 

Each member is an 

independent consultant 

and negotiates his/her 

own consulting agreement.

 

Editor: Jerry Brown

Contributors:

John Dunn

Marty Kanner

Murray Kleiner

Dick LaRosa

David Pinkowitz

Carl Schwab

Gerry Bodner

Larry Rachman

 

Unless otherwise noted, 

reprinting or republication 

of anarticle on this blog is 

authorized by crediting the 

author and prominently 

displaying the following 

sentence at the beginning 

or end of the article,

including the hyperlink to

IEEE Consultant's Network 

of Long Island


"This report is republished 

with permission of IEEE 

Consultant's Network of 

Long Island"

 

Pages

Blog powered by Typepad

Enter your email address:

Delivered by FeedBurner