If you are not sure how to build a tube lens for microscope objective lens.We recommend this solution.
This package contain products as below
1, One piece of M42 to Canon EF adapter or M42 to Nikon AI adapter mount.
2, Three sets of M42 extension tube.Each set is about 5 cm long. If you need one more please visit https://www.wemacro.com/?product=m42-extension-tube42mm-x-1-0
3, Raynox DCR 150 with reversed adapter(Brand new)
4, One piece of M42 to RMS adapter or M42 to M26 .Please choose the thread type according to your objective lens.
5，One piece of black velvet （about 15cm*25cm ,approximate）Cut and Stick or just put the black velvet inside of the M42 tube.It can reduce the internal light reflection a lot in the lens and improve the contrast of the picture.
6,The height of sony E mount is 26.6mm.
The objective lens in the picture below is not included.
For the best image quality,it is better to set the raynox lens focus infinite .
The focus infinite distance from Raynox DCR 150 to camera sensor is 204 mm.The focus infinite distance from Raynox DCR 250 to camera sensor is 118 mm.(approximate)
The best M42 extension tube length = Raynox focus infinite distance(such as 204 mm or 118 mm) – Flange_focal_distance
Such as ,if your camara is Canon 5D2,and you use raynox DCR 150 reversed as tube lens, the best length of the extension tube = 204 mm -44 mm=160 mm.
Raynox DCR 150 is in reversed position.
There is a test about DCR150 reversed and normal setting comparison.The objective lens we use is Mitutoyo APO 5X with DCR150 with a APS-C camera.
Please download the file,zoom 100% compare the corner especially,and you will find REVERSED is BETTER than normal setting.
Testing image 10X with raynox 150 reversed,6micron step length ,31 pictures stacked.Resized only.By Canon 650D (click the picture for more details)
Testing image 4X with raynox 150 stacked.Resized only.By Canon 650D(click the picture for more details)