Reduction lens/sensor size

[Sauerkraut]

I'm planning on buying a used Canon EOS T3i to T6i or the SL2 DSLR. Sensor size for these cameras is ~ 22.3mm x 15mm.

There is a specific C-mount adaptor made for my Omano OM139 trinocular bright field microscope. It has a 0.5x reducing lens.

https://www.microscope.com/accessories/ ... 139-t.html
(description incorrectly states OM139 is a stereoscope)

The description says it's ideal for 1/2" sensors. Will this c-mount still work well with the larger sensor sizes? It might be nice to have a c-mount adapter specifically designed for my scope.

Thank you for any input.

Heather

[75RR]

This article by Charles Krebs and the links in it should help you choose.

http://krebsmicro.com/relayDSLR/relayoptics1.html

[jfiresto]

I'm planning on buying a used Canon EOS T3i to T6i or the SL2 DSLR. Sensor size for these cameras is ~ 22.3mm x 15mm.

There is a specific C-mount adaptor made for my Omano OM139 trinocular bright field microscope. It has a 0.5x reducing lens.

https://www.microscope.com/accessories/ ... 139-t.html
(description incorrectly states OM139 is a stereoscope)....

If the microscope is modern enough to not need a compensating, adapter, the other way to do it, is to buy a simple, 1X adapter – which is generally cheap and well nigh optically perfect, because it has no optics – and choose a used camera to match the adapter. I am trying this, now, and it looks like it will work out very well.

[Scarodactyl]

The .5x is definitely not suitable for a dslr. It is for cameras with a tiny sensor, actually reducing the already small size of the image circle to fit it. You would ideally need about a 1.6x for a crop sensor, though this magnification is almost never actually available. 1x will vignette badly on aps-c. There are some cheap Chinese 2x dslr eyepiece adapters out there which have gotten decent reviews and have the right optics in them, though I am not sure how easy lne would be to moubt on your given trinoc port.

[jfiresto]

... There are some cheap Chinese 2x dslr eyepiece adapters... though I am not sure how easy lne would be to mount on your given trinoc port.

I should have qualified my above suggestion, likewise, but fortunately I don't expect anyone will pursue it.

[Sauerkraut]

Thank you, all. I'll scrap the the 0.5x reduction lens idea and look for something more fitting, like a 1x or 2x adapter. Worst that can happen is another epic fail that can be added to my growing collection.

[jfiresto]

Some call that gaining experience. What is best is to gain it from others' epic fails.

On that note, I had a nice one, yesterday, trying to make a combined USB data and remote shutter release cable for a lately acquired Olympus camera, as no one seems to offer one. "All" I want to do is add three little wires to the camera-side connector of a data transfer cable. Three destroyed cables later, I believe I have found the tools for the job, which most importantly include a stereo microscope. (The wires and connector are pretty small and encased in plastic.) Fortunately, it was cheaply won experience.

[Hobbyst46]

Thank you, all. I'll scrap the the 0.5x reduction lens idea and look for something more fitting, like a 1x or 2x adapter. Worst that can happen is another epic fail that can be added to my growing collection.

Not everything can be forseen, there are simply too many variables in the world of classical optics, so almost every reasonably-priced solution (I mean, costing less than hundreds of $) is a compromise. Some non-fitting pieces of equipment today might be revealed as project savers in the future.

I note this interesting current thread, for example:
viewtopic.php?f=9&t=7628
Perhaps the solution (when found) will be generic, not case-specific.

BTW: I seem to remember a Microbehunter Youtube video by our dear admin Oliver, from 1-2 years ago, where he showed how to couple a DSLR to an Omano microscope. I might be wrong.

[Sauerkraut]

Thank you, John for the giggle (so many of my experiments start out with "All I want to do is...") and Hobbyst46.

I'll see if I can find a specific Oliver video on the Omano. In the meantime, I'm modifying a generic microscope/telescope adapter that works via the eyepiece and a cell phone. The one Oliver uses in his camera-connecting video is slick, but not available in the US. The ones available here are clunky, such as this beast which needs to go on a diet:

https://www.amazon.com/gp/product/B00OX ... UTF8&psc=1
This one weighs 365 grams/0.8046 lb.

I'm hoping to post a pic or two of my modified set up if it turns out well and is determined it could help someone else. The idea will be to have a dedicated 10x eye piece attached to the adapter so it can just be swapped in for a pic with minimal hassle and adjustment.

Heather

[Hobbyst46]

Hi Sauerkraut,
The post: viewtopic.php?f=9&t=7628
just reminded me of the known method of direct projection. It can be done on the trinocular head with a normal 10X eyepiece. The eyepiece is raised above its normal position within the photo tube, by means of a short "collar" (made of cardboard or thin flexible plastic or very thin flexible steel sheet), such that the top end of the eyepiece rests a few (say, 8-10)mm above the top of the photo tube. The camera body is connected by any mechanical adapter to the photo tube, with/without support by the eyepiece itself (I can provide more details if interesting).
This trick has been mentioned, e. g. by David Walker in microscopy-UK, and by Pau and others on the photomacrography forum. I tried it in the past and the results were not as good as in afocal mounting. In particular, because of the small change of the optical tube length, or some other reason, only the center of the FOV was free from pincushion distortion and chromatic aberration. On the other hand, this trick eliminates the need for a special 2X relay lens. But others use it with possibly good results. So, only a plain eyepiece in the photo tube is needed, and not a relay lens. It might be interesting to compare this trick to a generic relay lens.