2 ways to get 200X

[Jimbo]

When I finally get my scope I plan to replace the 100X objective with a 60X objective but it would be nice to have 200X but there is no room for another objective.
I’m thinking about getting some 20X eyepieces and that could give me 200X with a 10X objective.
Is there a drop in the quality of the image doing it this way? I know that mathematically you could get 1000X with a 40X objective and a 25X eyepiece, but it’s just not done this way.
Thanks for any info you can give me. Jim

[MicroBob]

Hi Jim,
all objectives have a combination of magification and resolution. You can enlarge the image as far as you want, but it is resolved only to a certain magnification. The weaker objectives generally can take more post magnification by the eyepiece. A 10:1 n.a 0,3 can offer enough resolution for 150-300x combined magnification. A 100:1 n.a. 1,3 can only support combined magnifications from 650x to 1300 times. So for your 10:1 stronger eyepieces might give a fairly good image. When you compare the image of a typical 10:1 with a 40:1 the weaker objective always gives the crisper image. This effect will be lost when using much stonger eyepieces.

BTW how many seats has your nosepiece and which objectives would you like to use? I use different objective combinations for different subjects and can select based on experience.

Bob

[Greg Howald]

Lots of folks just don't like 4x objectives. I have one scope where I use 10, 20, 40 and 60x. Then I don't exceed a 15 or 16x eyepiece because if I do so the resolution seems to suffer. I use higher Eyepieces for specific moments and not for general use. It is possible by getting clever with the optics to stack Eyepieces. If you do that you may acquire very high magnification but the resolution will be extremely poor and the amount of light will be very low. Just not a Good idea. Good luck with it.
Greg

[Jimbo]

Bob, I don’t have a scope yet, but I am planning to use objectives of 4X, 10X, 40X and 60X.
Greg, I never even thought about not using the 4X objective. This idea sounds interesting because I could buy a 20X objective and get 200 X that way.
More researching to be done on my part, thanks.

[PeteM]

My preferences - and likely those of many others?

- At least a five hole nosepiece coupled with good 10x widefield eyepieces. Later on interchangeable nosepieces.

- A 2x or 4x low power objective to scan large areas of the slide. The 2x and sometimes the 4x often require something like a flip top condenser - cheaper condensers often don't cover 4x well and 2x not at all. In addition, this better bridges the gap between typical stereo microscopes and compound microscopes.

- The addition of a 20x objective. It's very useful and just right for many subjects.

- A really good 40x objective - this magnification is where differences in quality are pretty obvious.

- An oil immersion 60x or 100x higher power (and higher numerical aperture) objective rather than a 60x dry objective. I find the cheaper dry 60x objectives disappointing. They get better with $$$ and cover slip correction, but by the time you fiddle with cover slip correction you might as well go for the slight inconvenience and significantly greater numerical aperture of an oil immersion objective.

- If photography or movies are a big part of the equation, a 60x oil immersion objective rather than 100x - assuming both have the same 1.25 / 1.3 / 1.4 numerical aperture. The 60x will have the same resolution, typically greater working distance under the cover slip, and essentially the same digital magnification capacity due to its equal N.A. and resolution.

I'm curious why there have been so many recent "I'm about to get a microscope" posters who want a 60x dry objective? I have multiples of various 60x objectives -- with and without cover slip corrections, with and without oil immersion, and even a couple with water immersion -- but only a really pricey Olympus dry 60x provides images comparable to a typical (far cheaper) oil or water immersion objective. I'd really urge new users to try oil immersion. It's not difficult and sort of like wanting to learn to drive a car, but vowing to never make a left hand turn because it requires a bit more care (for those of us driving on the right hand side of the road).

[Stomias]

Yeah, my B&L 20X eyepieces are OK but there is a noticeable drop in image quality. Fortunately my scope came with a five hole nosepiece with 5 objectives. I was looking around at 60x objectives too. I have yet to use my 100x objective and thought a 60x might be more useful. I also have 15x eyepieces.

[Placozoa]

I'm curious why there have been so many recent "I'm about to get a microscope" posters who want a 60x dry objective? I have multiples of various 60x objectives -- with and without cover slip corrections, with and without oil immersion, and even a couple with water immersion -- but only a really pricey Olympus dry 60x provides images comparable to a typical (far cheaper) oil or water immersion objective. I'd really urge new users to try oil immersion. It's not difficult and sort of like wanting to learn to drive a car, but vowing to never make a left hand turn because it requires a bit more care (for those of us driving on the right hand side of the road).

I know this one. Oliver stated on a couple of videos that:

1. Oil immersion is horrible. Its a nuisance to clean up, good chance you will dip a non oil immersion lens, and the gain in image quality is insignificant.

2. A 60x dry is way easier to use, offers comparable results, and has more working distance than a 100x immersion objective.

I took his advice and bought one myself actually.

[PeteM]

I'm curious why there have been so many recent "I'm about to get a microscope" posters who want a 60x dry objective? I have multiples of various 60x objectives -- with and without cover slip corrections, with and without oil immersion, and even a couple with water immersion -- but only a really pricey Olympus dry 60x provides images comparable to a typical (far cheaper) oil or water immersion objective. I'd really urge new users to try oil immersion. It's not difficult and sort of like wanting to learn to drive a car, but vowing to never make a left hand turn because it requires a bit more care (for those of us driving on the right hand side of the road).

I know this one. Oliver stated on a couple of videos that:

1. Oil immersion is horrible. Its a nuisance to clean up, good chance you will dip a non oil immersion lens, and the gain in image quality is insignificant.

2. A 60x dry is way easier to use, offers comparable results, and has more working distance than a 100x immersion objective.

I took his advice and bought one myself actually.

Well, we all owe Oliver a debt of gratitude for this site. However:

1) Oil immersion is no big deal once you get used to it.

2) A 60x dry objective simply doesn't offer "comparable results" to either a 60x or 100x oil immersion objective. Compared to a typical 40x (.65na) objective, a dry 60x (.80-.85na) offers about a 25% improvement in potential resolution. An oil immersion objective (1.25-1.3+na) offers about a 100% improvement in potential resolution.

As for working distance, let's take the specs for a bottom of the line Olympus UIS achromat objective (not plan). Their 60x dry has a NA of 0.80 and a working distance of .13mm. The cover slip thickness can play havoc with it. Their cheap 100x oil has a NA of 1.25 (more than 50% better) and a working distance of .10mm. That drop of oil makes it less finicky about cover slip thicknesses. Were we comparing something like a 60x Plan Fluorite oil we'd have it all - better working distance, way higher resolution.

We don't use oil immersion with beginners and small kids -- or even higher power objectives - because kids can be counted on to crash the objective through a slide, get oil on other lenses and so on. So, Oliver has a point. But for even a modestly interested hobbyist, the routine of adding a drop of oil to the slide, moving the oil immersion objective into that drop, and then blotting up after is no big deal if one actually wants to see significant detail beyond what a good 40x objective will do.

The real key to getting good images at high magnification is preparation of the specimen. Could be many minutes to hours of work to get something thinly sliced and under a cover slip. Once that's done, the extra few seconds to add (and later remove) a drop of oil to see (or image) that specimen at the highest budget-willing resolution is no big deal. At least, IMO.

[MicroBob]

If I had a 4-seat nosepiece and objectives 4,10,20,40,basic 60 dry,100oil I would use them like this:
First test basic 60 dry for advantages over 40 under practical conditions. If it shows that is can give a better image in certain situations:

botanic sections and plancton: 4,10,20,40
diatoms: 10,20,40,100oil (the beginner might better leave the 40 away due to the danger of dipping it in oil)
field use: 4,10,20,40 (and swap the 4 against the 60dry occasionally)

With diatoms the maximum resolution possible with a light microscope is always a hard limitation, even with oil immersion. So I would consider the 100 oil "everybodys race horse" in the stable here. With permanent mounts it is not that difficult to use and clean under controlled conditions in the home lab.

I use 3 5-seat nosepieces:
For quick scanning of slides and general use: 2,5 - 6,3 - 10 - 16 - 40 dry apo corr. with n.a. 0,95
For diatoms: 10 - 22oil - 50oil - 100oil
For phase contrast: 10 - 16ph2 - 40ph2 - 100ph3

Bob

[Heliozian]

Well that was all very interesting - thank you folks. I have a dry 60x lens (largely to avoid mess and fuss as I am almost exclusively using wet mounts of pond life) I'm not unhappy with it, was considering getting a 100x oil lens soon and now am realising that a 60 or 63x oil immersion might be as good or better and that I need to concentrate on NA rather than magnification - to be honest 60x dry is usually giving me a large enough image - it just lacks the clarity that I'd like. I have just looked for 60x OI lenses on ebay though and seen some prices which are both well out of my range and well beyond the range of what it is sensible to spend on this scope.

I have two questions. First - how awkward is oil immersion when using wet mounts? Does it tend to pull the cover slip around if you move the slide?
Second - My understanding is that if I use another manufacturer's lenses on my Motic BA310 as long as they are infinity lenses they should work but I will likely loose parfocality. As people seem to be saying that the oil immersion lens should be lowered onto the cover slip rather than swung onto it that makes rather less difference than if it was just swinging over like a dry lens. Are there specific things I'd need out look out for when buying a non-Motic lens beyond making sure it's infinity?

The Motic phase contrast 100x OI lens isn't cheap (well - it's cheap compared to some manufacturers but not cheap on my budget) so I wonder what the resolution difference is likely to be between the dry 60x brightfield lens which I have and a 100x OI phase lens used in brightfield which I'd like as it's likely to be the only OI lens I have for a while.

I hope that doesn't count as hijacking a thread which has already pretty comprehensively swung off topic

Any advice would be very helpful

All the best

Ian

[PeteM]

Heliozian -- If it's mostly pond critters, you might consider a higher power water immersion objective. Phil (Apo) apparently has a line on some affordable Chinese ones that might be parfocal (or easily made parfocal with thin parfocal shims). Lomo are the only other affordable choice I've seen and these are mostly shorter barrel objectives. Not sure how they'd perform on an extension.

You'd be right that oil immersion and a floating temporary cover slip aren't all that great a combination. Doable if you want to take an image, but an argument for one of the better 60x dry objectives with a correction collar. Like your experience, I don't find most of the affordable dry 60x objectives to be sharp enough to justify a full time home on a turret - especially if it means losing a 20x or 100x oil immersion objective.

Since pond critters need a bit of water to move under a cover slip, they tend to come in and out of focus. I find that a good 40x objective plus some contrast method provides adequate working distance and sufficient power. If you just want to see or image it larger, perhaps add an HDMI camera and 4K monitor and your existing 40x objective? What you'd lose in N.A. (.65na vs. .85 na) compared to a dry 60x you might gain in depth of focus. You could also try stopping down the 60x you have a bit - maybe marginally better than the 40x.

Are you using some method of enhancing contrast? That might make the biggest difference in perceived clarity.

[75RR]

When I finally get my scope I plan to replace the 100X objective with a 60X objective but it would be nice to have 200X but there is no room for another objective.
I’m thinking about getting some 20X eyepieces and that could give me 200X with a 10X objective.
Is there a drop in the quality of the image doing it this way? I know that mathematically you could get 1000X with a 40X objective and a 25X eyepiece, but it’s just not done this way.
Thanks for any info you can give me. Jim

On the subject of why not 20x eyepieces - see link for an old post on the matter.

https://www.microbehunter.com/microscop ... 460#p45460

[Placozoa]

Heliozian -- If it's mostly pond critters...

...You could also try stopping down the 60x you have a bit - maybe marginally better than the 40x.

I look at pond critters too, although I am not considering oil immersion at the moment.

What did PeteM mean by "stopping down"?

As for the original thread, yeah, use a 20x eyepiece and a 10x objective if you want. Your eyes should still be the weak link in that optical train so its fine. A 20x objective is pretty useful, get one of those too. My 2 cents.

[PeteM]

Heliozian -- If it's mostly pond critters...

...You could also try stopping down the 60x you have a bit - maybe marginally better than the 40x.

I. . .

What did PeteM mean by "stopping down"?

As for the original thread, yeah, use a 20x eyepiece and a 10x objective if you want. Your eyes should still be the weak link in that optical train so its fine. A 20x objective is pretty useful, get one of those too. My 2 cents.

I meant being sure the field iris (assuming there is one) is just barely outside the field of view and then (or only) closing down the condenser iris a bit. It will reduce the effective numerical aperture of the dry 60x a bit, but the advantages in reducing reflections and greater depth of field and contrast may be worth it in trying to track pond critters.

[BramHuntingNematodes]

Probably closing the condenser iris to reduce the NA but on increase the contrast.

[Placozoa]

Thanks Pete. My 60x has no field iris, I forgot that many high end objectives do have one.

As soon as you said it I felt silly, it was obvious. lol.

[viktor j nilsson]

Thanks Pete. My 60x has no field iris, I forgot that many high end objectives do have one.

As soon as you said it I felt silly, it was obvious. lol.

The field iris would be in the base, below your condenser, not in the objective. The field iris adjusts the size of the illuminated field (in the object plane), the conderser iris adjusts the acceptance angle (=numerical aperture) of the objective.

[Jimbo]

Thanks all for a lot of info I need to digest.
75RR, the “watered down whisky “ analogy made a lot of sense, thanks.
Many of you use the na of the objective in your calculations and I haven’t even delved into considering that. You guys gave me lots of formulas to use, and I think I will reread all those links many times to get all this clear in my head.
I remember when my 8” reflector telescope arrived the secondary mirror was loose! Rather than calling the manufacturer I decided it was time to really learn how to line up ( collimate) the mirrors. It took me a while, but it really helped me learn about the light cone, and how the center of the image is clearer than the edges. Microscopy seems a little more complicated as far as optics, but I like to learn new things. Wish I had my scope so I could be experimenting now, but all things come to he who waits.
Thanks, Jim.

[Heliozian]

Are you using some method of enhancing contrast? That might make the biggest difference in perceived clarity

Many thanks for your suggestions Pete

I am trying pretty much everything and, on occasion, confusing myself silly and going back to basics!

I have a 10 and 40x phase both of which are good for some things but not others. Great for flagella and bacteria but not so good for the crowded inside of a cell where the halos just tend to interfere with each other. I also have 4, 20 and 60x brightfield lenses.

I'm aware that my wet mounts are never going to be the clearest when the water layer gets a bit thick so I'm trying to keep the water layer reasonably thin. I'm playing with the camera software (Motic Images Plus 3) on the basis that sometimes it might be better to keep the condenser diaphragm more open (for better resolution) and use the software to tweak the contrast. I don't enjoy the effect of closing down the condenser diaphragm too much so I'm tending to do that with great caution or not at all. I do keep the field diaphragm stopped down pretty well and usually focus it but then there are times when I play with adjusting the condenser to see what happens.

I'm also playing with oblique illumination and the idea of putting a diffuser in the light path with very variable results. I need to play more but what I'm finding is that different samples - even seeing different details in the same sample - benefit from different illumination. And when I've got a nice illumination set up with one objective it often doesn't translate to another objective so it can be back to square one. I do enjoy being able to take a decent photograph but there are so may people on the web with such stunning results that I don't even try to compete - I'm more interested in observation and, hopefully, identification so teasing out little details is more important than trying to get great depth of field for photography.

I take your point that it's sometimes better to avoid going straight to the 60x objective which I do tend to do.

There are so many variables and I am, for now, so inexperienced! I may be best playing with what I've got for a while longer to clarify what it might be useful to spend money on - particularly if wet mounts are likely to be an utter pain with oil immersion.

Another line of enquiry (which I think you hinted at) is around camera resolution. I watched Oliver's video about working out optimal camera resolution in relation to NA. My camera should be able to pick up all of the available detail but I'm not convinced that it does. I'm slightly sceptical about that particular video so I might try to get hold of a mount which will let me get my old Cannon 500d onto the trinocular head to test whether I'm missing detail with my 3 mp camera.

Many thanks for you time and suggestions - water immersion, 40 or 60x oil immersion, all things I hadn't thought of and interesting considerations. There are so may different techniques and different people prefer different techniques. At the end of the day with what I have at the moment I get to look down the scope and to be thrilled and excited by what I see which is all I'm after really - the rest is just detail!

[Crater Eddie]

I might try to get hold of a mount which will let me get my old Cannon 500d onto the trinocular head to test whether I'm missing detail with my 3 mp camera.

My little 3mp USB camera provides pretty good resolution, but lacks in dynamic range, which I believe is a common flaw of all such cameras.
CE

[Heliozian]

I guess that's the point really - my 3mp USB camera has pretty good resolution - I just wonder whether it's missing a bit. It's fair but . . .
Hence my desire to test that by comparing with a higher resolution camera. I may well be being rather optimistic and it may be that what the camera is catching is all there is. Either way I'll keep on enjoying the wiggly wonders

[AntoniScott]

Most of my microscopy is of insects. This doesn't necessarily require very high magnification. 200x is usually the highest magnification I will ever use for observing insect parts. There are a few ways to obtain this 200x magnification.

My main concern is "working distance", the space between the objective glass and the specimin. A 10x objective usually has a long enough distance between the objective and the specimin so as to pose no problems accidentally touching the specimin. If I use a 20x eyepiece I get the desired 200x. Granted there is some insignificant image degradation.

If I use a 20x objective, the problem of small working distance can be significant because there is a chance of touching the specimin by accident. I was able to obtain a 20x objective (by Edmond) that has a long working distance, well suited to my needs. If I use a 10x eyepiece I get better image quality than a 10x objective with a 20x eyepiece.

I do have an Olympus 20x objective that offers superb image quality but at the expense of very short working distance. This objective is more suited to prepared slides with coverslips, not for use in examining specimins without coverslips.