Should the condenser diaphragm work when using DIC?

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farnsy
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Should the condenser diaphragm work when using DIC?

#1 Post by farnsy » Sun Jul 11, 2021 1:00 am

I purchased a microscope that has DIC capability and I am just getting familiar with it--I'm a beginner with DIC. DIC seems to be working at all magnifications but I have questions about its proper usage.

One thing about its build surprises me: the condenser that houses the Nomarski prisms is exactly the same as what is used for phase contrast. It just has the prisms in the location where the annuli would have been. The thing that strikes me as odd is that the condenser has a mechanism that prevents the use of the condenser diaphragm unless it is rotated to the brightfield spot. That makes sense for phase contrast but does it make sense for DIC? I can't see any reason why one would not use the condenser diaphragm while using DIC in the same manner as you would when doing brightfield. Am I right about that?

I could probably figure out a way to disable that mechanism and use the diaphragm, but presumably there was a reason they did not do that at the factor, right?

I might need a little coaching on the proper use of DIC in general.

PeteM
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Re: Should the condenser diaphragm work when using DIC?

#2 Post by PeteM » Sun Jul 11, 2021 3:40 am

You're right -- the condenser iris should work.

With phase contrast, many makers disable the iris on the positions where phase rings are located to avoid closing the iris down over them.

Sounds like the maker didn't want to go to the trouble of making a dedicated DIC condenser?

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75RR
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Re: Should the condenser diaphragm work when using DIC?

#3 Post by 75RR » Sun Jul 11, 2021 5:09 am

.
Agree that the condenser iris should be available with DIC, should you need it, though I must admit I use mine wide open.

Can you tell us the make and model - photo would be nice.
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
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farnsy
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Re: Should the condenser diaphragm work when using DIC?

#4 Post by farnsy » Sun Jul 11, 2021 5:41 am

In this forum, Chinese manufacturers are primarily known for their inexpensive mass-market microscopes. However, they do make higher-end scopes. I bought one of these. It's a BestScope 2081. The same scope is sold under the names AccuScope EXC-500, Nexcope E900, and Euromex Delphi-X Observer. Radical India makes one that appears to use the same body but I don't think it uses the same optics. Of course, each of these brands may do a few things a little differently. It uses Nikon-compatible objectives, made in the Novel Optical factory where many of Nikon's actual parts are made, so it has a ton of things in common with the Nikon Ci line--unfortunately the condenser dovetail is not exactly the same (I'll post on this separately). The prices are Chinese-level, so I was able to afford a set of great parts (DIC, a complement of phase objectives, all fluor and apo objectives, the polarization kit, the ergo head). Really good deal. Watch out for shipping, tarrifs, and lead-time, though.

I'm actually very happy with the scope, but there are a couple of auxiliary parts they just don't make. Like a NA 1.4 aplanat/achromat condenser, a 60x fluor objective, and a 100x fluor water immersion objective (I had to get achromat on these two. If I ever feel rich enough I may buy the Nikon versions of the latter two). And apparently the DIC condenser is a repurposed phase condenser. Not a huge deal but something to be aware of. I guess it will be nice if I ever need to center these prisms (har har). I will open up the condenser soon and see if I can easily remove the mechanism that disables the diaphragm.

I'll post a proper review of the scope soon in this forum. Still trying all the bells and whistles. Overall I really recommend it, for someone who wants to buy new and has some money but not enough for a mainline scope from the big four. I would take it over an Olympus CX43, for example, which is another scope I got quotes on.

ImageImage
Image

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75RR
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Re: Should the condenser diaphragm work when using DIC?

#5 Post by 75RR » Sun Jul 11, 2021 6:30 am

I will open up the condenser soon and see if I can easily remove the mechanism that disables the diaphragm..
Not sure that would work, in my condenser at least, each DIC port and the Brightfield port has its own iris diaphragm

It makes a kind of sense to build it without an iris diaphragm (i.e. making use of a ready made phase condenser)
if you don't think it is really necessary and want to save some money, however it makes no sense to have one built-in and disable it


"When the condenser iris diaphragm is adjusted to approximately 70 percent of the objective rear aperture size,
most high-performance de Sénarmont DIC optical systems produce excellent contrast.
However, these microscopes also perform superbly when the condenser diaphragm is opened to match the objective rear aperture diameter."


https://www.microscopyu.com/tutorials/o ... microscopy
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
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farnsy
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Re: Should the condenser diaphragm work when using DIC?

#6 Post by farnsy » Sun Jul 11, 2021 7:31 am

Here are the naughty bits.

Image

There is just one diaphragm, which is on the left piece here. The little screw goes around when you dial the diaphragm. It's attached to a spring that's attached to a lever, that is held in place by another lever-thing if the condenser is not set to the brightfield location (the inner metal ring on the right piece is thinner on one side. If I remove the screw, the spring, the ring, or either of the levers, I believe the diaphragm will work in any setting.

One actually wonders why they didn't just remove one or all of these pieces at the factory.

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Re: Should the condenser diaphragm work when using DIC?

#7 Post by Scarodactyl » Sun Jul 11, 2021 7:44 am

You got the Chinese DIC? Awesome! Finally we can get some handa on reports about it!

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Re: Should the condenser diaphragm work when using DIC?

#8 Post by viktor j nilsson » Sun Jul 11, 2021 8:58 am

I, too, am very excited to see how this will perform!

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Re: Should the condenser diaphragm work when using DIC?

#9 Post by MicroBob » Sun Jul 11, 2021 9:43 am

Hi,
the first two Zeiss 160mm DIC systems with common analyser prism used a revolver condenser with 3-4 prisms that already somewhat restiricted the aperture of the condenser, and there was a centerable condenser diaphragm available in addition. But setting up such a microscope needs a user who is willing to adjust all these knobs. Some users are less technical minded and would profit from a system with less adjustable settings, so it may be a sensible decision to cut a few corners.

Bob

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Re: Should the condenser diaphragm work when using DIC?

#10 Post by farnsy » Sun Jul 11, 2021 8:43 pm

I unhooked the spring from both things it was connected to and removed it. Now the diaphragm works no matter which position the condenser is in. That was easy. I don't know how many people will be in this circumstance, but now we know how to address it.

I'm thinking about removing the centering screws as well. They don't have any purpose in a DIC condenser. On the other hand, they aren't hurting anything.

Scarodactyl, this DIC kit is pretty good stuff at a good price (for what it is). The complete kit (upper and lower prisms 10-100, the polarizer, aluminum case, and the condenser) was just over $3000 new at the time I bought it. I'm not sure how to tell whether it's good quality or not. It works and looks like DIC. But I think I would need someone more experienced with DIC to evaluate whether it's better or worse than the system from another manufacturer--or at least to tell me what to look for. Hard to distinguish hardware shortcomings from user error. When I use it, the background is blue and specimens that would otherwise be transparent are shown in sharp relief, as are their organelles. I'm not sure whether I'm really using it as well as I could, though. Like, should the background be dark blue or light blue? By turning a dial it goes yellow. Need to do more research to know exactly how to get the most out of it.

When I was buying it, I saved some money by not getting the 100X prism ($420). My reasoning was that I never use 100X with my current microscopes and was not shelling out for the oil immersion 100X fluor. Oil immersion is just enough of a pain and hard enough to get working right (never worked well on my old scope) that I avoid it. Instead I got a 100X (achromat) water immersion objective, not knowing how good that is. It turns out, it's amazing! I keep a little dropper of distilled water by my scope and toss a drop on the condenser, bring it up to the slide until the water spans the distance, then I put a drop on the slide cover and rotate my 100X WI in and it looks great. It doesn't drag the slide cover around when I move it, it leaves zero messes, and works perfectly. When I want to rotate back, I lightly touch the drop with a paper towel. No other clean up to worry about. I don't worry about the drop on the condenser either...I often just forget about it. It leaves no apparent residue when it dries. Anyway, water immersion is awesome--it seems really silly to me that beginner scopes come with oil immersion, rather than water immersion, 100X objectives. Anyway, unfortunately BestScope doesn't have a fluor water immersion objective, so I can't use DIC with it even if I had the prism. Radial India and Nikon both have 100X fluor water immersion objectives, though, so I'm thinking about buying one (the radical india version is about $500). In that case I will really regret not having bought the 100X lower prism. I'm sure I could still get it but it but I don't know how hard it will be to install--I assume it has to be aligned perfectly and I'm not actually sure whether these prisms are cemented in place or screwed in or what. Lesson learned, but problem not yet fully resolved. I might actually end up sending the condenser back to BestScope and having them install it for me. That could take a while. I bought this microscope on April 22 and it was (mostly) delivered on June 18. Got the DIC kit a few days ago. Still waiting on a couple of items (100X darkfield condenser is the main one).

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Re: Should the condenser diaphragm work when using DIC?

#11 Post by Dubious » Sat Jul 31, 2021 3:34 am

So if I understand correctly, the $3,000 DIC kit was an upgrade option at the time you bought the BestScope 2081, and not a custom kit that they make to order for different microscopes?

farnsy
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Re: Should the condenser diaphragm work when using DIC?

#12 Post by farnsy » Sat Jul 31, 2021 3:45 am

Dubious wrote:
Sat Jul 31, 2021 3:34 am
So if I understand correctly, the $3,000 DIC kit was an upgrade option at the time you bought the BestScope 2081, and not a custom kit that they make to order for different microscopes?
Yes. The kit consists of a condenser with lower DIC prisms in it, a rotating polarizer, and two sliders that go into the nosepiece, which contain the analyzer and upper prisms. The condenser could be adapted to be used with another microscope without too much trouble. The sliders don't look like a standard size I'm familiar with but someone might figure out a way to use them in another system. They might sell you the kit if you asked them to, but it's intended for this particular microscope only and not designed to be easily adapted. In fact, its designed for their suite of fluorite objectives (they don't want you to use it with the achromats that the microscope comes with by default).

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Re: Should the condenser diaphragm work when using DIC?

#13 Post by farnsy » Sat Jul 31, 2021 6:04 am

Finally did a video review of the scope and DIC system. You can check it out if you want.

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