Magnification question.

Hi Phil,
OK, With all 3 tubes with the 50mm you will get 1.36X mag,
With the same setup adding a 1.7x converter will give you 2.3 magnification

with a 105 your max mag with all 3 rings will be 1.65x mag, and with a 1.7 fitted you'll get 2.8x
Worth noting that the 105mm lens figures are probably not as accurate. This is due to the way a macro lens focusses the closer it gets. You might (probably) find the magnification for the 105 will be more than I have quoted here.

Some-one might be along soon to disagree, but I think these figures are a good estimate using the formulae I used to use when doing my medical forensic stuff. (Unless I've forgotten it all, and I am way off of course. Well it was a long long time ago !!)
 
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There are several 105mm options and the resultant maximum magnification will vary quite a lot between the them.

Two of Nikkor's previous versions (not the current VR) had focal lengths of 66mm ad 88mm when focussed at MFD. This large reduction in focal length will mean that the extension applied will give a greater increase in magnification.

Bob
 
Canon Bob said:
There are several 105mm options and the resultant maximum magnification will vary quite a lot between the them.

Two of Nikkor's previous versions (not the current VR) had focal lengths of 66mm ad 88mm when focussed at MFD. This large reduction in focal length will mean that the extension applied will give a greater increase in magnification.

Bob
Click to expand...

Bob... that doesn't really help me lol.
 
What Bob says it true, which is why I said in my post that the figures from the 105 will be a rough approximation.

I think part of the reason for the difference is that normal lenses do not change focal length very much going from infinity focus (where the focal length is measured) to minimum focus which is where they are being used for macro. This is not true for macro lenses where the focal length changes considerably, so my 105mm macro lens is actually about 78mm at 1:1 (approx).
However even using this revised focal length in the magnification calculations still gives numbers that are lower than actually observed.
 
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