I'm finishing out an Optiphot, for which I currently have the 5x and 10x BD (210mm) objectives. I'm thinking that I want the 20 and probably the 40 or 60 for now, but I'm wondering about future-proofing.
For the 210 tube length, setting aside ELWD and non-Nikon objectives, I basically have 4 options: BD, ED, and BD DIC, plus adapted M is a 4th which might make sense for a higher-power objective for transmitted light. The apos are probably not in the budget for now. So ... are the ED optics a worthwhile upgrade from the BD version? They're fairly rare. How about the DIC versions? I assume those are basically BDs with strain-free glass, which might be interesting for polarization, if not DIC?
Since this has been a reflected scope, I don't have a condenser. The 1.25 Abbes seem to be cheap an common. Is there any compelling reason to switch to something like the .9 Achro if the scope won't be used much for transmitted light, especially with high powers and oil immersion?
Finishing Optiphot - BD vs ED, condensers?
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Scarodactyl
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Re: Finishing Optiphot - BD vs ED, condensers?
I had trouble finding a deal on a DIC 5x BD so I just got a normal BD 5x and it worked just fine for DIC, easily as good as the DIC 10x, 20x and 40x I had on there. I suspect you'd need an anomalously bad copy strain-wise for it to be a significant issue but I haven't exactly sampled a lot of them either.
I hadn't even heard of the ED variants before this thread. The BD ones are pretty good on lateral chromatic correction, but have noticeable axial CA. Maybe the ED version helps with that.
Adapting on m plans is not a bad idea--epi darkfield is pretty niche, and I wasn't super impressed with how it performed on my optiphot (though I did have DIC on that one, so it was mostly redundant). High power transmitted light is probably going to be limited to lower magnifications unless you look at a lot of coverglass-free crystallization slides or something like that.
And of course in non-nikon options, there are Akashi/Mitutoyo finite 210 objectives off of a line of hardness testers which might be viable. I haven't tried those myself but they are sometimes kind of cheap and they seem to be internally corrected like Nikons.
I hadn't even heard of the ED variants before this thread. The BD ones are pretty good on lateral chromatic correction, but have noticeable axial CA. Maybe the ED version helps with that.
Adapting on m plans is not a bad idea--epi darkfield is pretty niche, and I wasn't super impressed with how it performed on my optiphot (though I did have DIC on that one, so it was mostly redundant). High power transmitted light is probably going to be limited to lower magnifications unless you look at a lot of coverglass-free crystallization slides or something like that.
And of course in non-nikon options, there are Akashi/Mitutoyo finite 210 objectives off of a line of hardness testers which might be viable. I haven't tried those myself but they are sometimes kind of cheap and they seem to be internally corrected like Nikons.
Re: Finishing Optiphot - BD vs ED, condensers?
To add,
- I have one Nikon "ED" objective and don't see a dramatic difference between it and their regular "BD" version. Given their rarity, seems to me you just look for what's available, in good condition, at a fair price. Perhaps the ED at a slight premium if you happen to find one.
- Also have a couple Akashi M Plan 210mm objectives (BF only) and they seem just fine.
- Same experience with Nikon's better objectives, even when not marked for "DIC." They've worked OK for both simple polarizaiton and DIC.
- I'd agree that if you had DIC (which also gives you a polarization option), the need or desire for DF would diminish and you could go with regular M Plan objectives.
- Sounds like a cheaper 1.25na Abbe condenser would be fine, since you say you're not going to use it much; and mostly for lower magnifications.
- I have one Nikon "ED" objective and don't see a dramatic difference between it and their regular "BD" version. Given their rarity, seems to me you just look for what's available, in good condition, at a fair price. Perhaps the ED at a slight premium if you happen to find one.
- Also have a couple Akashi M Plan 210mm objectives (BF only) and they seem just fine.
- Same experience with Nikon's better objectives, even when not marked for "DIC." They've worked OK for both simple polarizaiton and DIC.
- I'd agree that if you had DIC (which also gives you a polarization option), the need or desire for DF would diminish and you could go with regular M Plan objectives.
- Sounds like a cheaper 1.25na Abbe condenser would be fine, since you say you're not going to use it much; and mostly for lower magnifications.