Minimum focus distance - industrial definition?


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zoossh

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Nov 29, 2005
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#1
It is a little confusing here for me.

By right, minimum focus distance should be measured from the nodal point of the lens to the subject in focus, although some mentioned it can be measured from the front of the lens to the subject in focus.

Does all brands follow the first definition (from nodal point) in their specifications? Or to the fellow seniors here, does any brands use the 2nd definition for their specification?
 

giantcanopy

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Feb 11, 2007
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#2
Working distance is from front element to the subject.

Ryan
 

zaren

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Oct 27, 2003
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#3
It is a little confusing here for me.

By right, minimum focus distance should be measured from the nodal point of the lens to the subject in focus, although some mentioned it can be measured from the front of the lens to the subject in focus.

Does all brands follow the first definition (from nodal point) in their specifications? Or to the fellow seniors here, does any brands use the 2nd definition for their specification?
what is the "nodal point" of the lens?
 

giantcanopy

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Feb 11, 2007
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#4
Image of the aperture as seen from the front of the lens.
also referred to as the entrance pupil ( the exit is vice versa ).
All light rays shld pass thru it, with the principal ray cutting thru its centre
In filmology, knowing the nodal point enables u to pan the lens about it without displacing the subject.
 

gooseberry

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Mar 11, 2004
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#7
Most manufacturers will quote the minimum focus distance as the distance from the subejct to the focal/film plane. Don't know of any manufacturers that will use a different definition.

The distance from the front of the lens to the subject is referred to as the minimum working distance (different from minimum focus distance above), not all manufacturers will specify this.

Also, your use of "Nodal" point of a lens is incorrect. The Entrance pupil (http://en.wikipedia.org/wiki/Entrance_pupil) and the Nodal point (http://en.wikipedia.org/wiki/Cardinal_point_(optics)#Nodal_points)
 

zoossh

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Nov 29, 2005
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#8
Most manufacturers will quote the minimum focus distance as the distance from the subejct to the focal/film plane. Don't know of any manufacturers that will use a different definition.
ic. you mean they usually add the image distance and object distance together for the shortest focal length of the lens?
 

imouyang

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Oct 17, 2004
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#9
MFD is the distance from subject to film plane... This is true for most if not all manufacturers... Also, on cameras, the film plane is being marked out near the hot shoe area(A white line in Canon's case)... Thus the MFD is measured from this 'white line' to subject...

Working distance as mentioned by giantcanopy is the distance between the subject and front element of the lens.... This term is quite commonly used in macro photog where being too close to ur subject (too short a working dist) can alarm ur shooting subjects...
 

lsisaxon

Senior Member
Nov 29, 2004
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#10
It is a little confusing here for me.

By right, minimum focus distance should be measured from the nodal point of the lens to the subject in focus, although some mentioned it can be measured from the front of the lens to the subject in focus.

Does all brands follow the first definition (from nodal point) in their specifications? Or to the fellow seniors here, does any brands use the 2nd definition for their specification?
The markings on the lens is graded in distance from the film plane to the subject.
 

lsisaxon

Senior Member
Nov 29, 2004
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#11
does all brands follow this convention and quote their MFD from the front element?
No, that's just the working distance. AFAIK, the convention for focusing distance (lens marking) is always to the film plane. There is a standards body governing all these conventions. CIPA is one of them. http://www.cipa.jp/english/index.html
 

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