Magnification Ratio Revisited (with pictures)

Please refer to these three photos:

 

http://www.flickr.com/photos/jwallphoto/sets/72157606008740576/

 

Adding the Raynox 250 (8-diopter) close-up lens, even with the Nikon 105 AF-D Micro set at infinity, clearly gives a

magnification ratio greater than the 1:1 allowed by the lens without the Raynox. But how do you calculate what the

magnification ratio actually is with the Raynox attached?

 

Thanks again!

I believe the easy way to calculate this is to photograph a horizontal mm rule, then divide the width of the camera sensor (or film width) by the number of mm.

First, the 1:1 picture with the naked lens does not seem a 1:1 magnification. A quarter is almost 24mm in diameter, so it should cover the whole long side of your photo (with a D200 APS-C sized sensor) at 1:1. Next, an 8 diopter lens should have a focal length of 1/8m = 125mm. If you set the lens at infinity, you should get 1: (125/105) magnification, which is roughly 1:1.25. That's what I see in the picture - the quarter doesn't quite cover the long side, but almost. At 1:1 it's a more complicated calculation that also depends on the position of the Raynox with respect to the internal construction of the 105mm lens and which is beyond my capabilities, sorry :)

Peter L., you are correct. I also thought it didn't seem right. So anyway, I get the Numb Nut Award of the day. The lens was set to Limit, which kept it from going to 1:1 even manually. D'oh!

 

When I redid the test with the lens set at Full, it did go to 1:1. With the Raynox added to the lens at infinity, it was less than 1:1, as someone calculated in the other thread. And the additional magnification of the Raynox with the lens at 1:1 was probably just over 2X, also as someone calculated.