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working distance
I was spurred on by the discussion on the definition of focal length(see thread:http://forums.dpreview.com/...forums/read.asp?forum=1002&message=25051350.

To look at the technical specifications for my AF Micro-Nikkor 60 mm lens once again. It specifies a 90.4 mm working distance. So I looked up 'working distance' and found the brief parenthetical definition: "camera-to-subject distance". So, I put my camera system (incl. Nikon D80) at approx. 90.4mm from the subject, a grid laid out in a 254 by 254 mm pattern.



The image in focus turned out to be approx. actual size, that is a magnification of X1. However, no way was the working distance 90.4mm or the 270mm of the focus ring reading. Any explanations? And any on what working distance really means and how to use it?.

Http://www.umefotographie.com..

Comments (6)

Gking wrote:.

Results: please seehttp://www.umefotographie.com/study.html?1191375454103The image in focus turned out to be approx. actual size, that is amagnification of X1. However, no way was the working distance 90.4mmor the 270mm of the focus ring reading. Any explanations? And any onwhat working distance really means and how to use it?.

The minimum working distance is measured from the sensor location (not the front of the lens) to the subject with the camera set to the minimum focusing distance (consider doing this manually and moving toward and away from the subject to get the subject in focus). Many cameras have a small symbol on the top of the camera at the sensor location..

Van..

Comment #1

John p vansteenberg wrote:.

The minimum working distance is measured from the sensor location(not the front of the lens) to the subject with the camera set to theminimum focusing distance (consider doing this manually and movingtoward and away from the subject to get the subject in focus). Manycameras have a small symbol on the top of the camera at the sensorlocation..

Yes. The focal plane symbol is usually a circle with a horizontal line slicing through it.Regards,Baz..

Comment #2

John p vansteenberg wrote:.

Gking wrote:.

Results: please seehttp://www.umefotographie.com/study.html?1191375454103The image in focus turned out to be approx. actual size, that is amagnification of X1. However, no way was the working distance 90.4mmor the 270mm of the focus ring reading. Any explanations? And any onwhat working distance really means and how to use it?.

The minimum working distance is measured from the sensor location(not the front of the lens) to the subject with the camera set to theminimum focusing distance.

Actually no, that's not correct. The minimum focusing distance is measured that way - from the focal pane to the subject. But the "working distance" in macro photography refers to the clearance between the front of the lens and the subject. It's not even the front of the front element that is measured, it is whatever is at the front of the lens - invariably the filter mount...

Comment #3

The technique is this:.

- Rest the camera flat on a table, it makes measuring easier..

- Choose a subject which is easy to focus on manually, and which will conveniently rest on the table. A box maybe, something of that sort..

- Switch the lens to MF and set it to the minimum focusing distance..

- Position the camera and subject so that the subject comes into focus. Doesn't matter whether you move camera or subject, whichever is convenient..

- Measure the distance from the focal plane (marked on the camera as mentioned in another post)..

- Measure the clearance between the front of the lens and the subject..

You should now have two measurements, one which agrees with the published 'minimum focusing distance' (which is probably also given on the focusing scale); and the 'working distance' (which should be 90.4 mm according to your source)...

Comment #4

Steve:.

You are exactly correct. Following your instructions, closest focusing distance matched (220mm), as did the working distance (90.4mm)..

-Garrisonhttp://www.umefotographie.com..

Comment #5

Gking wrote:.

Same as 'sensor location'?.

Yes.... or, more precisely, it is the front face of the sensor that is located at the image plane ... ('image' plane is interchangeable with 'focal' plane).Regards,Baz..

Comment #6

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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