Best BD option for 50x on FF?

Have questions about the equipment used for macro- or micro- photography? Post those questions in this forum.

Moderators: rjlittlefield, ChrisR, Chris S., Pau

ray_parkhurst
Posts: 3129
Joined: Sat Nov 20, 2010 10:40 am
Location: Santa Clara, CA, USA
Contact:

Best BD option for 50x on FF?

Post by ray_parkhurst »

I'm struggling with image quality issues from my Nikon BD objectives. Purple/green fringes mostly. I've been working primarily with the 20x and 40x ELWD objectives, which are known to have these issues. Now that I've shifted from APS-C to FF, I'm thinking I want to go up a bit in magnification. My subjects are phono styli, which take up a very small area of the FF frame at 20x, and still fairly small at 40x. Below is the full frame view of a stylus, with 40x ELWD BD objective, single image, focused on the wear patch (the dark area at the tip). Below that is a 100% crop of the tip. These were taken with the A7Rm4, single image.
...
DSC00013_2.JPG
...
DSC00013_3.JPG
...
I'd like to have better color fidelity and better sharpness than this, and I'm thinking going up to 50x may help. I want to stick with BD lighting as it gives me the "ringlight" effect I need to properly highlight the contact patch. I will build my own BD illuminator for whatever size objective I end up with.

So which BD will give me a better result than the above? I see some Mitty 50X BD and HR objectives, with sufficient working distance. I need at least 10mm to clear the body of the cartridge, so the Mitties will work fine. As you can see from the above, I don't need sharpnes to the corners. Are there other options that will give a good result?

Any advice will be appreciated. It appears I can spend from ~$1k up to many $k on these objectives, and don't want to waste funds on the wrong purchase.

Scarodactyl
Posts: 1184
Joined: Sat Apr 14, 2018 10:26 am

Re: Best BD option for 50x on FF?

Post by Scarodactyl »

I wonder if you could use a small ring light for illumination, maybe with a reflector. They make fiber optic ring light guides that fit right around a mitutoyo, though the one I tried admittedly put the light at entirely the wrong angle and I haven't tried any more with it. I did just get a motic 50x and I could mess around with it on that if you're interested in results from that, at least once my system is set up again.

Lwd options are pretty limited 50x and above as I am sure you know. The best possible option has got to be the mitutoyo HR (and when isn't that the case?), and maybe some of the recent Nikon TU series and/or olympus lmplanfl after that. I haven't tried the lwd versions of the nikon or olympus, but my nikon tu fluor 50x bd and my olympus mplanfl 50x bd are both excellent, and others' tests of the mplanfl have suggested exceptionally broad coverage.
That said, I wouldn't sweat full frame coverage per se. If the corners don't matter then you can just use a longer fl tube lens to stay within spec. At this point your working distance has put a hard cap on NA, and your desired subject has a specific FoV need.

Edit:maybe an olympus neo splan ulwd 50x with a 2.5x nfk photo eyepiece? Extra mag but it would cover full frame and the cropped corners wouldn't matter so much. You'd need the correct tube lens in addition to the eyepiece but the illuminators with them built in are easy to get. Heck, I have a partial one you could have cheap. I havem't troed the ulwd one, but the normal neo splans are very good when used with the correct tube lens and eyepiece.

ray_parkhurst
Posts: 3129
Joined: Sat Nov 20, 2010 10:40 am
Location: Santa Clara, CA, USA
Contact:

Re: Best BD option for 50x on FF?

Post by ray_parkhurst »

The 30mm Angel Eyes ringlight might work. The 20mm is too small given the 13mm WD. The radius of the 30mm varies from 8.5-13.5mm, fairly wide. If the 50x BD is like the BD's I have, the illumination comes from a fairly narrow range around 45-deg, which is ideal for the application. Anyway, this may open up some non-BD options but I'd need to test the ringlight on a similar WD objective to see if it lights the stylus tip correctly.

ray_parkhurst
Posts: 3129
Joined: Sat Nov 20, 2010 10:40 am
Location: Santa Clara, CA, USA
Contact:

Re: Best BD option for 50x on FF?

Post by ray_parkhurst »

I went ahead and purchased a Mitutoyo 50x BD Plan Apo 0.55 objective, and built an illuminator for it. For the tube lens I used the "ITL 200" clone available on eBay. It gave the best result versus the various tube lenses I have, and seems to give excellent coverage across the FF frame.

The light cone from the 50x Mitty is "just right" and gives good contrast to the contact patch as well as overall even lighting. The 13mm WD is more than adequate.

33 shots at 625nm steps, though it was clear they varied a bit from that number. This was quarter steps with 1mm pitch and 400 step motor, but as we know microstepping is not perfect.

The IQ is better than the Nikon 40x BD ELWD I was using previously. Below is the same phono stylus tip shot with the 40x, though I did clean some gunk from the tip that showed up in the image above.

First image is the FF shot at 10.8%, followed by a 50% redux crop around the tip, then a 100% crop of just the tip.

edited to add: I forgot to white balance with the new illuminator, which is why the background is blue versus grey in the earlier images.

Comments welcome.
...
21-12-06_085240_M=B_R=8_S=4_4.JPG
...
21-12-06_085240_M=B_R=8_S=4_1_4.JPG
...
21-12-06_085240_M=B_R=8_S=4_0.JPG

Scarodactyl
Posts: 1184
Joined: Sat Apr 14, 2018 10:26 am

Re: Best BD option for 50x on FF?

Post by Scarodactyl »

Nice! I agree it's a big step up (as it had better be given what they go for.) Seems like a good solution overall.

ray_parkhurst
Posts: 3129
Joined: Sat Nov 20, 2010 10:40 am
Location: Santa Clara, CA, USA
Contact:

Re: Best BD option for 50x on FF?

Post by ray_parkhurst »

Scarodactyl wrote:
Mon Dec 06, 2021 12:04 pm
Nice! I agree it's a big step up (as it had better be given what they go for.) Seems like a good solution overall.
The purple/green CA is gone, but I do still see some magenta/green in the 50x image. This was a stack while previous was a single image, so not directly comparable I suppose, but is this to be expected from the 50x Mitty? It is a little sharper given the slightly larger NA, but the main reason for getting it was to improve the CAs. They are better, but should/could they be even better than this? I guess the tube lens could be causing some issues as well. Would I expect better performance from a Raynox vs the "ITL200"?

Sorry for so many questions. This is the first time I've worked at these mags, and with infinite optics other than experimentally. With this objective I'm committed to infinite.

I did build a new stacking rig for the A7Rm4, and it seems to work well at 50x, with reliable sub-micron steps and reasonable stability. Settling time after a shock is ~0.5sec. This is a bit slower than my last rig, and I need to see if I can find the culprit, but it's pretty decent and does not make stacks take too long. Reason for bringing this up is that the new rig is Arca plate-based, and I see offerings from both mjkzz and WeMacro for complete infinite systems with integrated Raynox tube lens. Mounting to the Arca plate by clamps would be simple, and allow an interchangeable system with my modified bellows. So...has anyone used one of these systems? I'll need to see how each of them works with M42 threading as the illuminator I built for the 50x is M42-based.

Scarodactyl
Posts: 1184
Joined: Sat Apr 14, 2018 10:26 am

Re: Best BD option for 50x on FF?

Post by Scarodactyl »

It matches with my memory of the 50x copy I had, or rather it seems less pronounced in your examples, though I think that copy may have been an underperformer and I sold it off as such a long time back. It resembles what I've seen in some other 50x objectives. You of course have a subject that's going to highlight it quite a bit. Usually extra fine stepping helps (or rather, my imperfect hand stacking makes it worse) but you're obviously already handling that. I'll hopefully be able to try my Motic 50x in a week or so, fingers crossed, and I'd be happy to report back.

ray_parkhurst
Posts: 3129
Joined: Sat Nov 20, 2010 10:40 am
Location: Santa Clara, CA, USA
Contact:

Re: Best BD option for 50x on FF?

Post by ray_parkhurst »

Scarodactyl wrote:
Mon Dec 06, 2021 5:26 pm
It matches with my memory of the 50x copy I had, or rather it seems less pronounced in your examples, though I think that copy may have been an underperformer and I sold it off as such a long time back. It resembles what I've seen in some other 50x objectives. You of course have a subject that's going to highlight it quite a bit. Ussally extra fine stepping helps (or rather, my imperfect hand stacking makes it worse) but you're obviously already handling that. I'll hopefully be able to try my motic 50x in a week or so, fingers crossed, and I'd be happy to report back.
Sounds good, I'm looking forward to any results with the Motic.

I think this objective is OK (ie not damaged) as it's a bit sharper than the Nikon 40x, with much less CA. I'm just wondering if a Raynox would improve what CA is present.

I suppose it's not an easy thing to photograph a diamond. Some of the "CA" may not actually CA, but a phenomenon of the subject. I'm not 100% sure how to tell.

Scarodactyl
Posts: 1184
Joined: Sat Apr 14, 2018 10:26 am

Re: Best BD option for 50x on FF?

Post by Scarodactyl »

Incidentally, I saw thsi come up on ebag and it had me thinking.
https://www.ebay.com/itm/Mitutoyo-Objec ... 4733072598
Obviously the resolution isn't higher and you get smaller coverage, but the color correction is probably specced better to match the magnification, only the center matters here and the wd is still 13mm. This might be the only instance where this particular model would have the right set of features for a serious photomacrography project.
Not that you're likely to be in need of another solution any time soon, it just fired some neurons.

Lou Jost
Posts: 5401
Joined: Fri Sep 04, 2015 7:03 am
Location: Ecuador
Contact:

Re: Best BD option for 50x on FF?

Post by Lou Jost »

That reminds me, I have the Mitutoyo 50x G Plan Apo and it is chromatically extremely well corrected.

Scarodactyl
Posts: 1184
Joined: Sat Apr 14, 2018 10:26 am

Re: Best BD option for 50x on FF?

Post by Scarodactyl »

I'm a ways off from up and running but I had a chance to try my motic 50x eith simple ad hoc lighting. It definitely shows axial ca, and much more than your mitutoyo. More like the nikon, though it will depend how well it stacks out I guess.

ray_parkhurst
Posts: 3129
Joined: Sat Nov 20, 2010 10:40 am
Location: Santa Clara, CA, USA
Contact:

Re: Best BD option for 50x on FF?

Post by ray_parkhurst »

Scarodactyl wrote:
Sun Dec 19, 2021 8:25 pm
I'm a ways off from up and running but I had a chance to try my motic 50x eith simple ad hoc lighting. It definitely shows axial ca, and much more than your mitutoyo. More like the nikon, though it will depend how well it stacks out I guess.
Thanks for that.

The 100x idea is interesting, given the small required image circle, but the NA is the same. If I could get higher NA with same working distance I'd go for it, but perhaps that is an optical impossibility.

Scarodactyl
Posts: 1184
Joined: Sat Apr 14, 2018 10:26 am

Re: Best BD option for 50x on FF?

Post by Scarodactyl »

Scarodactyl wrote:
Mon Nov 29, 2021 6:39 pm
I wonder if you could use a small ring light for illumination, maybe with a reflector. They make fiber optic ring light guides that fit right around a mitutoyo, though the one I tried admittedly put the light at entirely the wrong angle and I haven't tried any more with it.
I was reminded of this recently and decided to try it again. I am not sure why my initial impression of the ring light was so poor, because the ring light gives me what looks like very acceptable epi darkfield illumination with my mitutoyos.
This is how the ring light looks:
Image
Very slightly loose on the objective until the set screws are tightened.
Two example wafer shots with brightfield and darkfield:
Image
Image
Image
Image
It worked on my 5x, 10x and 20x. I haven't tried it on my thorlabs 2x yet.I have also found it gives some interesting (if flat) illumination on other subjects, a bit different from the interesting (but flat) of coaxial illumination.

blekenbleu
Posts: 75
Joined: Sat May 10, 2008 5:37 pm
Location: U.S.
Contact:

Re: Best BD option for 50x on FF?

Post by blekenbleu »

I still toy with the same challenge, although often distracted.
Experiments show substantially different focal distances e.g. for red than green and blue:
LCR.jpg
https://blekenbleu.github.io/microscope/#RGB

Since color seems not particularly relevant for phono needles,
IMO better results used green LED illumination and only green pixels from camera raw
instead of blue LED and pixels, having first supposed that shorter wavelengths would improve resolution,
but that may have been compromised by relatively sparse blue pixels in a Canon 20D sensor.
Direct projection to a Canon M60 mk II may address that blue pixel sparsity issue,
but a Nikon Metaphot BD frame is still undergoing resuscitation to use with an RGB pin spot for illumination.
https://blekenbleu.github.io/microscope/Nikon/Metaphot/
https://blekenbleu.github.io/microscope/pinspot/

Dialing in appropriate per-primary MTF compensation remains another opportunity.

For better full color images, perhaps
separately focus bracketing red, green and blue exposures,
then merging and color balancing those images
based on exposures of a gray card with the same equipment and settings...
Metaphot, Optiphot 1, 66; AO 10, 120, and EPIStar 2571
https://blekenbleu.github.io/microscope

ray_parkhurst
Posts: 3129
Joined: Sat Nov 20, 2010 10:40 am
Location: Santa Clara, CA, USA
Contact:

Re: Best BD option for 50x on FF?

Post by ray_parkhurst »

blekenbleu wrote:
Tue Sep 06, 2022 7:38 am

Since color seems not particularly relevant for phono needles,
IMO better results used green LED illumination and only green pixels from camera raw
I've been doing something similar with the Nikon objectives. The result is only slightly sharper, but significantly less distracting since the color fringes and shifted hues are eliminated. I am ultimately hoping to get color fidelity since color does have value, especially if I shoot more than just the very tip. By shooting around 20-30x, I get the entire stylus tip, plus a chunk of the cantilever. There is an aesthetic aspect to the photos that is squelched by eliminating color. From a different perspective, shooting at too high magnification is also detrimental to the aesthetics, making the image overly technical. High mag and no color, while fine for forensic work, is somewhat unpleasant to look at.

Post Reply Previous topicNext topic