Measuring distance for macro

[titrisol]

Having a brain-fade moment and need help.

I setup a Nikon D70 in a copy stand, with a light table at the bottom in my effort to digitiza MF negatives.
Maybe crude but it seems to work.
However, I'm using a AIS Micro Nikkor 55/2.8 and can;t get it in focus correctly. How should I measure the distance, from the end of the lens barrel or from the film plane?

Thanks

 

[David A. Goldfarb]

Film plane typically.

That's actually a very effective method of digitizing negs that you can't otherwise scan.

 

[titrisol]

thanks! I'll try that tonight.

Getting the light table was my main problem but I found one in surplus from a medical facility closeby (I guess it was used for Xrays) and it's pretty big (11x14)

 

[David A. Goldfarb]

I've used an 8x10" Logan 5000K light pad, which was pretty cheap--around $60 if I remember correctly.

 

[titrisol]

Thanks David,
I think it worked:
(there was a url link here which no longer exists)

PS. I hope you had a good deal on that Vitessa of yours.... I'll rememeber it as "the one that got away" for a long time

 

[Jim Noel]

To answer your question, you need to measure from lens to subject to determine magnification and exposure compensation.

 

[Ole]

To answer your question, you need to measure from lens to subject to determine magnification and exposure compensation.

If that were the question, he'd have to measure from the rear nodal point of the lens. That may be inside the lens, but doesn't have to be. Most macro lenses are symmetrical however, so the front and rear nodal points will be at the same distance from the aperture. Exact data should be available from the manufacturer.

 

[Jim Jones]

To answer your question, you need to measure from lens to subject to determine magnification and exposure compensation.

A simple way to determine magnification is to measure the height of the in-focus subject field and divide that into the height of the focusing screen. Determining exposure with the camera's meter is probably as easy as any method. Rulers have been available (or can be calculated and printed) that give magnification and exposure compensation when they are focused on. The formula for exposure compensation (E) is E=(M+1) squared where M is the magnification ratio (from www.macrophotography.org).