Achro vs. Plan Achro vs. Plan Apo stereo CMO objectives?

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
Post Reply
Message
Author
PeteM
Posts: 2983
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Achro vs. Plan Achro vs. Plan Apo stereo CMO objectives?

#1 Post by PeteM » Sat May 15, 2021 9:21 pm

I'm hoping that someone with more experience can give an indication of what one gains with better corrected CMO stereo objectives?

Most of my somewhat better CMO scopes (e.g. Wild M3C, Wild M8, Nikon SMZ-10) have achro objectives and achro supplemental lenses. They're generally fine for viewing, with "doming" clearly visible at lower magnifications. The M8 and SMZ-10 seem to hold up (visually) nearly to 80x and the doing isn't particularly objectionable for most biological specimens. I don't expect any of my current crop of CMO objectives to be particularly good for photos - but wonder if plan objectives might do significantly better.

The upgrade to a Plan objective (Leica, Wild, Nikon, Olympus) seems to be $250 or so. The upgrade to a Plan Apo likely $450 up.

Would either a Plan or a Plan Apo make a dramatic improvement in photo quality? I'm thinking more of biological specimens -- where resolution probably trumps field flatness. FWIW, the Wild M3C allows putting the camera through the center of a CMO objective -- one might hope it could nearly equal a microscope??

Perhaps another question - given a Plan Apo objective in a CMO scope, but likely achro optics in the magnification changer - do significant chromatic aberrations still creep in?

User avatar
mrsonchus
Posts: 4175
Joined: Tue Feb 03, 2015 9:42 pm
Location: Cumbria, UK

Re: Achro vs. Plan Achro vs. Plan Apo stereo CMO objectives?

#2 Post by mrsonchus » Sat May 15, 2021 9:57 pm

Hi, hmmm the plan 1x CMO of my SMZ800 shows no doming at all but I'll go back tomorrow and have a very close look just to make sure.


nikon smz800 (11).jpeg
nikon smz800 (11).jpeg (101.18 KiB) Viewed 1978 times
John B

Scarodactyl
Posts: 2775
Joined: Sat Mar 03, 2018 9:09 pm

Re: Achro vs. Plan Achro vs. Plan Apo stereo CMO objectives?

#3 Post by Scarodactyl » Sat May 15, 2021 10:01 pm

You will definitely notice a difference. Achro CMOs will tend to have very distinct lateral CA, particularly at higher magnifications. I found this particularly noticeable in photos on the wild M3 and the MZ6 with an achro objective.
That said, I would be surprised if you had an achro rather than a planachro lens on your M8. They only made the one plan 1x objective for them, though later Leica M80 objectives would fit so in theory you could have an achro off of one of those?
The relay optics don't seem to have nearly as much of an effect on color correction as the objective.
Nikon apo objectives are probably the cheapest option of the bunch, deals for under 400 sometimes crop up. The doming problem was solved in the SMZ-10a which is a generation earlier than the 800 (around thr same time Wild released their improved M3s which had optional plan objectives).

PeteM
Posts: 2983
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: Achro vs. Plan Achro vs. Plan Apo stereo CMO objectives?

#4 Post by PeteM » Sat May 15, 2021 11:40 pm

Thanks for that (as usual) informative reply. Much appreciated.

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Achro vs. Plan Achro vs. Plan Apo stereo CMO objectives?

#5 Post by apochronaut » Sun May 16, 2021 3:25 pm

Pincushion distortion is easy to induce by messing around with eyepieces.

Rorschach
Posts: 334
Joined: Sun Mar 10, 2019 11:44 am

Re: Achro vs. Plan Achro vs. Plan Apo stereo CMO objectives?

#6 Post by Rorschach » Tue Jun 22, 2021 6:42 am

My experience is mainly with Wild stereos. The doming effect of the achros disappears completely with the plan and planapo objectives. There's also a marked increase in resolution and, in the case of the planapos, a very visible reduction in chromatic aberrations. The only problem with the 2x planapo is the very short working distance, so the 1x planapo is my general 'go to' lens. I do have a 1.6x Plan as well for intermediate use at slightly higher magnifications.

One older scope to consider is the Wild M7S, because it has the objective slide option that is very beneficial for photography (i.e. centers the CMO objective on just one light path, effectively making the instrument a macroscope of sorts). The objective is not replaceable and is only achro but some people consider it to be semi plan.

Post Reply