How to make the best use of my new Olympus 20/0.40 ULWD?

[pulsar123]

It looks like I got a real bargain with my recent purchase of a second hand Olympus objective - ULWD Neo SPlan 20x/0.40 infinity/0 f=180. I only got it for 93$ US with shipping, and I strongly suspected that there would be a catch - either it's mislabeled, and it won't be an ULWD, or it's in a bad shape. I just got it, and it is exactly what the ebay listing said, and also in almost pristine condition. I think this happened because the ebay title didn't mention the ULWD bit (but the included photo clearly showed the full labeling). BTW the ebay seller was highly reputable. This demonstrates the value of checking not just titles, but also photos of ebay items.

And now I have to figure out how to make the best use of it. I want to use it with my FF DSLR camera Canon 6D, using focus stacking technique. (I have a stacking rail of my own design - Fast Stacker, https://pulsar124.wikia.com/wiki/Fast_Stacker). My only experience with microscope objectives so far was a Nikon 10x/0.25 160/0. I used it with a double set of extension tubes.

The Olympus is my first experience with an infinity objective. How should I use it? My understanding is that I need a 180mm tube lens, correct? I have two choices - Canon 135mm f2L, and Canon 70-200mm f4L. The second choice (set at 180mm) would be the best one, right? I ordered three step down filter adapters, to go from 67mm down to the Olympus' 26mm. I am afraid this might not work well - Olympus seems to use 0.70mm pitch (from my measurements, using a pitch match tool from my tap and die set), whereas the 26mm adapter is likely using 0.75mm (standard M26). As it will take a while to get the adapters from China, for now I'll try to print a plastic (ABS) one using my 3D printer, just for experimenting with the objective.

Another point - it looks like I won't be able to use the tube lens autofocus to do focus stacking, correct? I read somewhere that the image quality degrades a lot when the tube lens is used not at infinity focus. That'd be a pity, as I could use in-camera focus stacking capability (with Magic Lantern firmware). Meaning that I'll have to use my Fast Stacker, pushing it to its limits (formally it's smallest step is 1.25 um, and I need 3 um for the 20x/0.40 objective).

Finally, is there a way I make use of the light conduit (reflector) built into the objective? That'd be very cool - so I wouldn't need this space consuming arrangement I have (external flash with a softbox). Perhaps a bunch of tiny LEDs stuck at the back of the objective? It'd be tough, given that the objective should sit very close to the tube lens. And I definitely don't want to accidentally damage my expensive tube lens. Anyone tried something like this?

[ChrisR]

it looks like I won't be able to use the tube lens autofocus to do focus stacking, correct? I read somewhere that the image quality degrades a lot when the tube lens is used not at infinity focus.

It's well worth a try. Theoretically yes, the tube lens should be at infinity, but you should find the quality doesn't fall so fast that it's useless.

I had a try a long time ago with poking LEDs around a BD objective. It "worked" but it needed much brighter LEDs.


With an ULWD it's probably not really necessary.
If you can unscrew the outer part of the objective, you may find you have much better access for lighting.
A Nikon BD ELWD :

[Lou Jost]

Just a reminder-- there is nothing special about the rated 180mm tube lens focal length, except that this is the focal length that gives the rated magnification. Using a lower focal length could even improve the image quality, if the FOV of the objective is wide enough or the sensor is small.

With high m, the problem with using the lens for focus stacking is that the focal range of a lens is too small to permit deep stacks. At 20x it might be ok for very flat subjects. Otherwise you'll need to use the rail.

[ray_parkhurst]

I had a try a long time ago with poking LEDs around a BD objective. It "worked" but it needed much brighter LEDs.

I do this today with a BD Plan 20, and use it for taking pics of phono styluses (stylii ?). I needed a "ring light" to properly image the wear patterns, and this technique does the trick. I'm looking now for a small COB ringlight that will fit inside a BD objective. I found one made for a flashlight, but it's a little too small.

[Saul]

Mitutoyo BD COB version with the Optiphot adapter

[ray_parkhurst]

Mitutoyo BD COB version with the Optiphot adapter

That's a big objective! I assume the ringlight is a "40mm", with ~50mm OD?

[JohnyM]

What does "COB" stands for?

[ray_parkhurst]

Chip On Board. Instead of the individual LED's having phosphor applied to them, the LED's are placed on the board first, then the phosphor is applied to the board. This improves the uniformity and efficiency of the LED system and allows shapes to be made more easily.

[Saul]

Mitutoyo BD COB version with the Optiphot adapter

That's a big objective! I assume the ringlight is a "40mm", with ~50mm OD?

OD is 40mm.
I have unfinished project for Nikon BD (26mm thread), used smaller SMD type 15-17v LED

[ray_parkhurst]

Looks like some work I did to build a similar SMD ringlight! Seems many of us had the same idea.

The 40mm Angel Eyes works well for me in other apps, but for the BD I'm worried I won't get much of the light "down the tube". Maybe a light guide, with reflective sides?

Would be super cool to have a generic adapter that would work for the BD objectives, and have good performance.

[Saul]

Looks like some work I did to build a similar SMD ringlight! Seems many of us had the same idea.

The 40mm Angel Eyes works well for me in other apps, but for the BD I'm worried I won't get much of the light "down the tube". Maybe a light guide, with reflective sides?

Would be super cool to have a generic adapter that would work for the BD objectives, and have good performance.

Yes , you are right ...
I ordered some clear filament for the 3d printer , plus Rust-Oleum 267727 Specialty Mirror Spray - it should work
No idea how efficient it will be, but it is worth to try ...

[pulsar123]

Wow, great points from everyone - thanks a bunch!

I wonder if my objective can also have its outer shell unscrewed - I tried by hand, but it's either too tight or is not supposed to be unscrewed.

Even with ULWD having a built-in LED light would be superconvenient. I'll be looking into it. I already have an experience building an LED ring light for Laowa 15mm f1:1 (WD=5mm, with the lens diameter ~65mm!):

https://pulsar124.wikia.com/wiki/LED_ri ... macro_lens

[pulsar123]

I finally arrived at a reasonable setup for my new (to me) microscope objective Olympus ULWD Neo Splan 20x0.40 infinity/0 f=180mm. I did solder an LED ring to be used inside the objective, but for now decided to use an external LED light, with a 3D printed cone light diffuser.

I am using the objective on top of my Canon 70-200 f4L lens (on full frame camera). At 200mm I am still getting a bit of black corners, but nothing major.

Below are the first 3 tests, all using my own design Fast Stacker focus stacking rail (using it for the first time with 2.5um steps - seems to be doing very well), with 200-300 shots per stack. (I am using Magic Lantern's electronic shutter on my Canon 6D to avoid wearing off the shutter mechanism.)

What do you think of this objective performance? It does look a bit less sharp (in relative, not absolute units) than my Nikon 10x0.25, which is expected. And I think the sharpness drops faster towards the edges, which is likely the price to pay for the ULWD feature. Which is great BTW - it's 11mm, with the frame size 2.4x1.2mm, so one can do pretty deep stacks without cropping frame much.

A small ant:

Extreme macro at 20x by SyamAstro (700,000 views - thank you!), on Flickr

A ball pen:

Extreme macro at 20x by SyamAstro (700,000 views - thank you!), on Flickr

A CPU pin:

Extreme macro at 20x by SyamAstro (700,000 views - thank you!), on Flickr