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next question in a long series of stupid questions; Microscopes

Posted by Liam Schofield  
Liam Schofield July 22, 2011 01:05PM
Hi All,

I'm in the market for a 'scope however, I'm not sure what the right one is for me. I've always assumed that a Stereo microscope is best for studying mineral specimens (Triocular for the attachment of my DSLR) however, I've recently found the higher magnification Metallurgical 'scopes and have been considering the possibility of going for one of these rather than the standard Stereo scope. However, I'm concerned about the suitability of such a device for the study of mineral specimens. Most seem to start at 40x magnification, which is about average for a Stereo microscope but the additional option of up to 400 and even 600x is quite appealing for those tiny, tiny crystals.

So, I'm hoping someone would be able to advise on this subject. Can anyone tell me, first and foremost, what the functional difference is between a 'metallurgical' 'scope and a standard Stereo 'scope, besides the increased magnification?

I don't have a fortune to spend and as much as I'd love to look at the really swish Zeiss equipment, it's just not feasible with my budget. However, if anyone has any recommendations, I'd also be appreciative of the help.

Many thanks in advance.
Ralph Bottrill July 22, 2011 02:06PM
Metallurgical microscopes are designed for looking at polished surfaces under reflected light, and are not much good with normal mineral specimens. They have a small working range and a very small depth of field also. You are much better off with a normal steromicroscope and incident light (they are also much cheaper).

David Von Bargen July 22, 2011 02:25PM
Once you get above 50x, the depth of field gets real narrow and most of the image is not in focus (photography with stacker software may make higher magnifications a bit more useful)
Liam Schofield July 22, 2011 02:35PM
That's very useful information, many thanks. So I'd be better off looking at a 20-60x zoom? Are the higher magnification Stereo Scopes worth looking at?
Alfredo Petrov July 22, 2011 02:40PM
Better start lower, Liam, like 10x, which most mineral collectors use more often than any other. I have 10x to 80x, but very rarely have occasion to use anything over 45x. Any higher magnifications have such small fields of view and depth of field that they become pretty useless for anything except dust particles, or organic tissues squeezed between glass slides.

(Incidentally, with regard to the title of your thread, I've been told many times that there is no such thing as a stupid question, only stupid answers :)
... and I hope I don't give those toooooo often. Nice to meet you in person at the Mindat party (sorry, conference) in Poland... may we have many happy returns!)

Edited 1 time(s). Last edit at 07/22/2011 02:44PM by Alfredo Petrov.
Robert Rothenberg July 22, 2011 04:17PM
Hi Liam,

I wish to differ with Alfredo. I collect at places where the crystals are very small (e.g. Varennes). I do most of my quick looking at 30x and often go quickly to 45 or 60. Much of my photography is at higher magnifications. So, I guess what you need will be based partly on what you are going to be looking at.

Liam Schofield July 22, 2011 04:33PM
And there in lies my issue, Bob. The problem is I would like to be able to look at Micro minerals (<500um) as well as the more standard sized micro mounts and possibly even larger samples. my current PoS 'scope is quite good with magnification but really lets the side down with the manual focus, laughable resolution and built in illumination. This was the reason I was drawn to the Metallurgical 'scopes, primarily because they offer the 20/40x magnification but also because they offer the higher magnifications as well. Now, if they are entirely unsuitable, then I'll discount them but it is where my question stems from. And the set up's i've looked at give a decent amount of reach, similar to the Stereo microscope- I.E some are mounted on bases that do not have any platform meaning larger samples could be placed underneath, if so required.
Jim Robison July 22, 2011 09:50PM

Gene Cisneros, who really knows scopes, gave some advice yesterday on another thread. An easy and relatively inexpensive way to increase your magnification range is to get something like a rougnly 7-55X zoom, (using a 10X occular eyepiece,) and then order a set of 20X eyepieces to double the range of your scope when you need to. As noted above, depth of field gets smaller and smaller, as does field of veiw, as you increase magnification.

You definitely do not want a flat field reflected light microscope.

Biggest hint I could give is to look carefully at the vertical focus range of the scope stand. Some chearper models only have a range of an inch or two. If you handle large size specimens, you will probably want more range. And consider, if your budget will support it, a two knob focus setup, with one for coarse adjustment, and the second for very fine adjustment, especially if you plan on spending much time looking at the little tiny stuff.

Happy hunting.
Jonathan Levinger February 04, 2012 12:50AM
There are plenty of good scopes available on eBay. I used to collect Microscopes but now for the lack of space I have sold most of them. I still have few on eBay listed along with many others from other vendors. I also have some more not listed yet.
Robert Simonoff February 04, 2012 03:34PM
I personally like the option of the 20x eyepieces - but it will confound your camera work, since the camera will not take the picture through your eyepieces. You want the camera, as closely as possible, to take the same photo your eye sees. This, as I have learned is a trick in and of itself!!!

Some scopes have a zoom range 0.7x - 4.5x, but then you can attach a magnifier underneath, just above the specimen. So, with 10x eyepieces, a 2x underneath magnifier, and 0.7x-4.5x zoom you get up to 90x magnification. Then, at least with our scope, you must place a lens inline, in the trinocular tube to make it so that what your eye sees is roughly what your camera will see. Our inline trinocular lens is 1.9x. So one path of optics is: 10x -> 0.7-4.5 -> 2x and the other path is 1.9x -> 0.7-4.5 -> 2x

As for the amount of magnification, as long as you can back it off to a low zoom, I prefer to have a good amount available to me. So a 20x magnifier just above the specimen is a bad idea for all of the reasons the other have mentioned above, but I am finding 2x to be just fine (and it can be removed if necessary). I just shot a whole series of pictures at 90x for a presentation I hope will be given at the Rochester Mineralogical Symposium - and for 3-4 shots I wished I could go higher. But at that magnification, light becomes a problem as do vibrations. There is NO free lunch!

Jason Evans February 04, 2012 06:23PM
Hi Liam, I to have been toying with the idea of getting a scope, if i do eventually get one I am going for a Brunel MX6T or MX7T
My friend has a microscope from Brunel, although its a different type for examining mushroom spores so much higher magnification but he thinks its a good scope.
Now I have a few stupid questions of my own, I see a lot of people say its best to use lower magnification like 10x, I already have a 10x loupe so would it really be worth getting a microscope if i can get the same magnification from my loupe, what are the advantages of the scope? and also many of my specimens which have small crystals are matrix specimens, so is there enough space between the lens part and the base to put a matrix specimen in and to be able to focus in on the area where small crystals are?
David Von Bargen February 04, 2012 06:33PM
"what are the advantages of the scope?" - Much more comfortable. You can spend several hours at a scope and feel pretty decent after. With scopes you usually would have better lighting available, and you don't have to hold a specimen in your hand all the time.
Robert Simonoff February 04, 2012 07:10PM
There are other advantages to scopes over loupes including:

1) Working distance. Most loupes have a smaller working distance than a scope. Working distance is the distance between the specimen and the bottom lens of the scope. Our scope has a working distance of about 9 cm. So if the specimen surface is not even you can still look around.

2) Photography. While it is possible to photograph through a loupe it is much easier to do it through a scope - even if the scope doesn't have a trinocular tube. Of course it depends on your camera and set up.

3) Magnification. While 10x is a good magnification, it simply is not enough for everything, in my opinion. We have a 20x loupe that works nicely, but it still is not enough for everything we want to use it for. I have the utmost respect for people who say 10x is enough - I have no problem with that at all, so consider it preference that it is not nearly enough for our household.

Donald Peck February 05, 2012 07:30PM
Magnification up to about 40x is usually pretty good. Above 40x the depth of field is almost gone, and that obviates the purpose of a stereoscope. However, there are times when the need for magnification trumps the lost depth of field and I have run up to about 90x.

In any case, a scope beats a loupe hands-down. Incidently, I prefer fixed magnification to zoom.
D Mike Reinke February 05, 2012 08:54PM
Amazon has, under 'magnifiers' a TINY 45 power magnifier, that I took a chance on since I actually could risk $3.18 (for once) plus shipping. It's not bad. Certainly goes anywhere. It is better if you tear off the clear visor on the end. it does hurt the eyes after awhile.
Ron Layton February 23, 2012 04:05AM
Just a thought. I have an Amscope, made in China, from eBay that I bought years ago for $120. Its fixed 20-40-80x with two sets of eyepieces, 10x & 20x. I have made mine into a field scope since its light and small. I took all he electric lights and cord, transformer, etc to make it light and use portable LED's for field work. My big scope is made by Variscope in China. It is 8x to 40x zoom and I have bought an auxiliary 2x ocular for the tiny stuff. With the 10x eyepieces its great for day to day work and with the 20x eyepieces its good for ID and studying very small crystals. It is a big scope weighing about 15 pounds and its 20 x 10 x 8 inches. This one cost $357.00 postpaid all together and is worth every penny. Its not a Wild or Leica but on my budget it works just great for me. PM me if you want the seller.
Owen Lewis (2) February 23, 2012 11:05AM
Thoughts on magnification. The range you will tend to use depends on the types of subject you favour. I am constantly surprised at the amount of time I spend working at x10. My 'scope will zoom to x65 when using x10 eyepieces and, with a screw-in objective doubler, will go to x130 which I do occasionally use.

I also have a pair of x20 eye-pieces but would not care much if these left home. The extra magnification they afford is what is called 'empty magnification' i.e. you can see bigger but without seeing any more detail. To see more detail one needs to up the resolution of and/or the magnification of the objective lens. IMHO, x20 eyepieces should be used only by those whose 'scope will not accept an x1.5/2/3 auxiliary objective lens. If the latter facility is not built into your stereo 'scope, you can probably make an adapter to hold one if you are good with your hands and have the tools.

Don't forget your lighting. The light gathered by your 'scope reduces as an inverse square as magnification is doubled. This basic rule means that, even with the wonderful sensitivity range of our eyes, unless you have powerful and adjustable output lighting, you will see the field of view start to get appreciably dimmer with most subjects when working at about x40 or above. At x65 and above the effect becomes pronounced and, without auxiliary lighting, can make much useful work impossible. If one is going to want to work much above x40, something like a 150W source with cold light delivered directionally via fibreoptics (one or two) is a great help and should be budgeted for, I think.

Edited 1 time(s). Last edit at 02/24/2012 01:33PM by Owen Lewis (2).
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