I worked out the magnification of the DFA 100mm (non-WR version) coupled with the Raynox DCR-250 using the practical 'ruler test' and thought others might be interested.
Short Version
As you move from infinity focus down to minimum focus, the magnification of this combo ranges from ~0.8X to ~2X and the working distance drops from 12cm down to 5.5cm.
Long Version
There is a great calculator
here, but it gets significantly off for the DFA100mm as the focal length changes throughout the focusing range (I figure it's approx. 75mm at min. distance) and the front element is deeply recessed. Test setup was simple, I lined the focus mark up with the different magnification markings on the focusing scale, moved until my subject (a ruler) was in focus using liveview, then measured things. All measurements are approximate. The Raynox was attached using a single 49-43mm step down ring.
Barrel Marking 1/x | FoV in mm | Magnification | Working Distance | Focusing Distance |
Infinity | 30 | 0.79X | 120 | 265 |
25 | 28 | 0.85X | 115 | 261 |
10 | 26 | 0.91X | 107 | 254 |
5 | 23 | 1.03X | 95 | 247 |
4 | 22 | 1.08X | 92 | 246 |
3 | 20 | 1.19X | 84 | 243 |
2.5 | 18.5 | 1.28X | 80 | 243 |
2 | 17 | 1.39X | 74 | 240 |
1.5 | 15 | 1.57X | 67 | 242 |
1.2 | 13 | 1.82X | 62 | 243 |
1 | 12 | 1.98X | 55 | 248 |
Column Notes: Barrel Marking 1/x - Magnification marked on the lens scale. "x=25" corresponds to 1/25= 0.04X magnification, "x=2" corresponds to 1/2=0.5X magnification or half life size, etc. I lined the focus mark up with the centre of the text on the scale. "x=Infinity" isn't marked on the scale, but this entry corresponds to Infinity focus.
FoV in mm - Ruler was in landscape orientation, that is, this measurement is the long side of the frame. Camera was APS-C k5iis.
Magnification - The long side of the k5iis sensor is 23.7mm, this column is 23.7/FoV.
Working Distance - Measurement from the front of the ruler to the front of the Raynox adapter in millimeters. This is how far the front of the camera is to your subject.
Focusing Distance - Measurement from the subject to the tripod socket (roughly where the sensor is) in millimeters. Note the trend as it goes down, then back up again as the focal length of the lens changes with the different focusing distances. Measurements are approximate, but you most definitely have to move the camera back out to maintain focus as you move from the "1/2" mark down to "1/1".
End Notes:
I think we'd get more magnification if the front element wasn't so deeply recessed, but it is what it is. It's kinda handy to be able to continuously range from ~0.8x to ~2x magnification with this setup (or just under life size to double life size), and also pretty convenient in practical use that the focusing distance hardly changes. The quality of this raynox is impressive, at some point I'll do a comparison at around 1X magnification using the adapter vs not using the adapter to see if I can tell which is which (I suspect it will be close).
Last edited by BrianR; 08-04-2016 at 03:35 PM.