Types of loupe, triplet loupes, magnification, price and quality, pictures, examples
A loupe is a small folding magnifier, typically 10X magnification (though it can be as low as 5X or as high as 30X). When examining marks on jewellery or the quality of gemstones, or anything small (stamps, coins, insect & plant samples, PCB solder joints...) a loupe is your most important tool, without being able to see, all other tools are useless. Scroll down to see why loupes vary in quality, and the meaning of a 'triplet' lens. Or if you don't wish to read any further, just select from one my list of recommendations:
The following is just a very approximate idea of the difference in quality between lenses. The pictures are 'approximate' because I've simply held my camera to each lens (not the best way to take a photograph), and photographs on a monitor are never as good as real life (you'll get a slightly better view if you click on each picture):
of a £3.00 loupe.
of a £6.00 loupe
of a £24.50 loupe
Just a tiny bit of distortion, good contrast
of an £89.00 loupe
The numbers: the first number is the magnification (e.g. 10X) and the second number is the diameter of the lens in millimetres (e.g. 20) - so 10X20 means 10X magnification with a lens diameter of 20mm. Some customers express surprise, when they receive a loupe, because the size is not as they had imagined (see our feedback!), it may be worthwhile looking at a ruler.
The most powerful (quality quite good, and you can keep them in focus if you have a steady hand): 15X12, £16.50 or 20X12 5-element, £19.50. There are many loupes that are larger and / or more powerful (see a selection) but you cannot maintain good quality and high power and large lens size, it simply is not possible (you would need a microscope). I do have my own collection of samples marked "30X" and "40X", but they are not! - they are usually between 8X and 10X. .
Budget, 10X12, £6.50 is the one many traders choose, because they keep losing them and don't want to spend much money and the quality is quite acceptable. Our most popular budget loupe is a 10X21, £4.50, I notice that, at our stand, customers who buy these never look through them, they just want the largest jeweller's loupe at the lowest price (you do, of course, get precisely £4.50-worth of lens...not to be confused with our £25.80 10X21, above). In this category I could also include (new for Summer / Autumn 2014) a range of English-made loupes by Gowlland, from 5X to 8X magnification.
Cheapies just like you see on eBay or in street markets, the specification looks good but you are not buying the best quality lenses [I would like to say, "you are buying the worst possible lenses" but my colleagues tell me I must never say anything negative about our products]: 10X15, £2.00; or 3 lenses on top of each other, combine to make 3.3X or 6.6X or (near enough 10X), £3.00; or Double Folding Magnifier, 2 lenses, 6X or 8X or (together) 14X, £5.00. But there is one I quite like, a larger magnifier (30mm), 2 lenses, 5X or 5X or (together) 10X, £4.50, it's a copy of a Bausch & Lomb magnifier and it is very nicely made.
Larger lenses come in many sizes and strengths, they are not, technically, "loupes", but if you want something larger (and, by definition, lower power) we do have quite a selection.
Must be more powerful, must be best quality? - choose a microscope.
The very simplest loupes contain just one lens; better loupes contain two (doublets), very good loupes contain three (triplets) and a very few contain five ("five element"). These lenses (elements) are placed on top of each other, and each corrects for the distortions of the previous. Since all the lenses are transparent, the overall appearance is of just one lens.
There is a company selling "triplet loupes" who have registered the trade name Triplet and who claim that only they sell genuine Triplet quality.They are correct in that, having registered the name Triplet, it is only they who sell their own-brand (being 'Triplet') - however their loupes are not triplets! - and the optical quality is so poor that the weaker loupes give a fuzzy image and the stronger loupes are so bad they are unusable.
Now I have no objection to other companies selling loupes, but registering the name Triplet and selling loupes that are not triplets...that is not right!
following example is of a a double loupe, one side is a 10X and the other
side is a 20X. They are identical in outer appearance, even the markings
("10X18, 20X12") are the same.
Look at the PICTURE ON THE LEFT. It has two single lenses, not 'triplet', not '5-element'. On the metal casing of the magnifier the big lens is marked "10X Triplet" and the small lens is marked "20X, 5-element" - this is completely untrue, one is 7X and the other is 10X. The 7X lens is OK in quality (for a 7X), the 10X lens is such poor quality that it is virtually unusable. When I say, 'virtually unusable' I mean that only the very middle of the lens can be made to focus but most of the image will be fuzzy. This is not (as many people think) a fault of their eyes, but simply because the lens quality is poor. We sell this loupe for £5.00.
Now look closely at the PICTURE ON THE RIGHT (you may have to click on it to enlarge), the left lens is a triplet, it is made of three lenses ("elements") cemented together (you can see where they are joined), the right hand lens is a 5-element (two of the lenses are each made of two lenses joined together, and the third is a single lens, all very precisely separated with metal spacers). We sell this loupe for £30.00.
Please do remember that when you use these loupes (without taking them apart!) you can't see how many lenses there are in each section, because each lens (element) is transparent. It is the number of elements and the quality of the lens that makes good or bad quality.
So as you see, we offer all qualities from street market / eBay quality to true professional quality, "you pays your money and you takes your choice".
On this website I have divided our dozens of models into the following categories:
10X magnification. This is the standard strength for hallmarks on jewellery and other small marks, diamonds and gemstones, stamps, coins and banknotes, insect and plants samples, paper and fabrics.
Dual magnification, where lenses slide on top of each other to give a selection of magnifications
Loupes that clip to spectacles, (actual loupes, not 'eyeglasses')
MAGNIFICATION (more information in the article, How to Choose a Magnifier)
As regards magnification, there are very few uses for anything more powerful than 10X.
For extra power you might want to try a 15X (I'd recommend the 15X12, i.e. 15X magnification, 12mm diameter lens), if you go for a larger lens (e.g. 15X21) the optical quality will not be as good. A 15X lens needs a steady hand to keep it in focus.
If you have to read particularly small laser-engraving on diamonds (writing that is a fraction of a millimeter in size) then do go for a 20X, for quality I prefer the smaller 20X12 5-element loupe to the larger sizes. But, generally, 20X is too powerful, you lose image quality and focusing is very difficult.
By the time you get up to 30X you are asking the near-impossible, though we do sell one, a 30X18 triplet. You will have to hold the lens about 8mm from the object (to get it to focus) and it will go out of focus if you move the lens 2mm closer or 2mm further away, and the image will appear be dark and it will be distorted around the edges - because it simply isn't possible to make good loupes this powerful....though, all this said, our 30X is actually a 30X, unlike most loupes I see at fairs and markets which are marked "30X" but are really 8X or 10X.
If you want a loupe more powerful than 30X - you are just being silly, you need to go for a microscope. We do sell a tiny (not much larger than a loupe!) microscope which is 45X magnification. It includes its own powerful adjustable light, because, at this strength, the lens must be almost touching the object, and this makes everything too dark to see unless you have a powerful light - which this little microscope does. Because it must be held so close, it is really only suitable for flat objects, e.g. stamps and coins; the very surface of plant or insect samples; documents, photographs and banknotes (you'll see the dots that make up the print).
It is better, of course, to go for a full-size microscope, prices from £139.00 to £1400.00.
How to choose a magnifier (plus everything you would ever want to know about magnifying lenses)
How choose a binocular headband magnifier (from simple hobby model to a professional surgeons / dentists models)
How to choose a magnifier for the partially sighted (specialist low vision aids including lenses and video magnifiers)
How to choose a video magnifier (from small pocket-size electronic readers to a large table model)
How to choose a UV loupe (ultra violet light)
Calculator (Excel format) - enter the magnification, it tells you the working distance, or enter the working distance, it tells you the magnification.
How to choose a stereo binocular microscope (all sizes and magnifications)
Professional USB microscope attachment (it replaces the eyepiece of your microscope)
QUICKTEST, Watford, WD18 8PH, Tel. 01923 220206, email info(at)quicktest.co.uk