Olympus-OM
[Top] [All Lists]

[OM] Magnification vs focal length, was: Moose Arrives In Maine - Locals

Subject: [OM] Magnification vs focal length, was: Moose Arrives In Maine - Locals Amazed
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Sat, 21 Sep 2013 15:20:37 -0400
I really have no idea if you're right or not.  I'm traveling at the 
moment but some time after I get home I plan to test this... not by 
moving a pixel width (which I can't measure) but by displacing the 
camera an easily measured distance.  I'll observe the movement of the 
image as produced by two lenses of different focal length set to 
appropriate distances and extensions to create the same magnification 
(or as close as I can get it).  We'll see whether the setup with longer 
focal length produces greater image motion even though at the same 
magnification.

But your wording below gives me some pause to ask:  What is the nature 
of the motion being measured?  Is it simple linear motion parallel to 
the subject?  Or is it angular motion about some (as yet) undefined 
center point such as the "no parallax point"?  If the latter then focus 
will change unless the subject is a circular track with radius = the 
object distance from the no parallax point.  Not significant for a one 
pixel motion but maybe significant for a 10mm image motion.  Can I do 
this with a simple X-Y slide or do I need a pano head?  Just askin'.

But it will be more than a week before I can do this.  Maybe you'll have 
done it before I can get to it.  I'll believe you... honest I will. :-)

Chuck Norcutt


On 9/20/2013 6:25 PM, usher99@xxxxxxx wrote:
> A bit more investigation shows that at pixel width "p", angular
> velocity of cam w, one pixel blur should occur at shutter speed of p/(f
> *w). No?
> Thus shutter speed required for a given blur is proportional to 1/f
> where f is the focal length. Magnification makes this more complex but f
> never drops out. Am getting to the 85% certain confidence level. This
> is either correct or not , there is no in between.
-- 
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/

<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz