Telecentric add-on with a a specifically designed add-on lens.
The Raynox 250 was kindly loaned from Torbjørn Rasch Pettersen
The add-on lens in question is a nice triplet sold as macro add-on, to be mounted in front of zoom lenses. The manufacturer claim low aberration and nice control of the astigmatism; we’re going to test that!
Recommended use with lenses of 75mm or more focal length, otherwise vignetting.
It has 39mm clear diameter and stated power 8 diopters (125mm focal length).
I’ve tested it in telecentric position over the two standard macro lens, Micro Nikkor 55mm f/3.5 and the Tamron 90mm f/2.8.
Compared to the previous 3D-printed lens holders, the Raynox with its spring adapter is a pleasure to use and also show excellent antireflection coating.
Image comparison
I’ve actually forgotten what was the f# for the Nikkor. Anyway.
The Raynox250 is indeed too small to cover the “wide” 55mm; otherwise seems to work very well.
Their DCR 5320 is larger but costs a fortune.
Nikkor-P + Raynox
The usual pupil
Estimated assembly parameters:
| Telecentric mount spacing | 65mm |
| Combined focal length | 37mm |
| Minimum magnification and front f# factor | 0.47 x |
| Nominal focus objective | 1:2 |
| Magnification x | 0.64 |
| Working distance mm | 45 (maybe, not measured) |
| IQ center f/4 | clean |
| IQ corners f/4 | Curvature, coma, astig |
| Usable field f/4 | 9 |
| IQ center f/16 | clean |
| IQ corners f/16 | pretty clean |
| Usable field f/16 mm | 27 |
| Distortion | no |
| Vignetting | yes |
Tamron90 + Raynox 250
Estimated assembly parameters:
| Telecentric mount spacing | 52mm |
| Combined focal length | 50mm |
| Minimum magnification and front f# factor | 0.78 x |
| Nominal focus objective | 1:1 |
| Magnification x | 1.25 |
| Working distance mm | 20 (maybe) |
| IQ center f/4 | clean |
| IQ corners f/4 | Curvature, coma, astig |
| Usable field f/4 | 9 |
| IQ center f/16 | clean |
| IQ corners f/16 | pretty clean |
| Usable field f/16 mm | 21 |
| Distortion | no |
| Vignetting | no |
Moral
If one doesn’t have a heap of doublets at home, getting this little thing sounds a good idea. I think it outperform all the doublets with the 90mm, although I couldn’t see a huge difference. Maybe better contrast. Some astigmatism, there is still, but likely depends on how this triplet was designed, likely to work with zoom lenses over very small format sensors.
And don’t forget that it mounts directly on the filter thread without much fiddling with adapters.
Thanks again to Rik Littlefield for the idea and Torbjørn Rasch Pettersen for the triplet loan!
Half cooked dreams by Giorgio Pattarini 