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Hi! This is Toby with HMC Electronics. We're going to be answering a question we often
get from clients, and it pertains to when talking about magnifiers. And that question
is: What is a diopter?
So let's talk first exactly as to what a diopter is. So a diopter is the measurement of a lens'
ability to bend light over its surface. Diopter is measured by the viewer--you--being ten
inches, 25 centimeters, away from the lens, and then taking the product--in this case,
a circuit board--and bringing it to the farthest distance where it is in a sharp focus. So
that's how you measure a diopter and that's what a diopter is.
Now let's talk a little bit about how that applies to us. So common diopter magnifiers
that you are going to see on our site are 3-diopter and 5-diopter. Okay, so what does
that mean to me? What is a 3-diopter? What am I getting?
So, a diopter is a power increase to the power of 25%. So a 3-diopter is a 1.75x lens. A
5-diopter is a 2.25 power of increase.
With regards to what the increase in power does to your working distance. The strength
of your lens--the diopter of your lens--and its working distance are directly tied. So
if you're working with a 3-diopter, you've got about 13 inches of working distance. You
got a 5-diopter, you're down to 8 inches of working distance. And as those continue to
increase, your working distance begins to shrink, which is why on an eye-loop--which
is a 7-power (25-diopter) lens--your working distance is nothing. You're right on top of
the product.
So when you're looking at your diopter, always think about how far you comfortably want to
be away from the product. And again, we're not talking about you, the viewer. You should
always be stationed 10 inches above the lens. It's how far your product can be from the
lens.
So how come HMC's site only shows these 3- and 5-power diopter lenses? Why can't I just
get a 10-diopter magnifier or a 20-diopter magnifier? Well, we're curving light. We're
bending light. We've got certain laws that we can't change here. The lens has to be thicker,
as it's more curved. It's going to get thicker and heavier. So that's one thing. A 10-diopter
or 20-diopter lens is going to be super thick, super heavy, and unfortunately have a really
bad working distance.
So let's go over it again: 3-diopter = 13 inches of working distance. 5-diopter = 8
inches of working distance. If you were to find a magnifier that had a 10-diopter lens,
you'd be down to around 4 inches of working distance. And not only that, the actual area
of the lens that would be in focus--that sharp focus point--would be very, very small.
So, for reasons of practicality, you'll see a number of the magnifiers on our site actually
have a swing away lens. You can have your 3- and 5-diopter for when you're doing your
general assembly, you've got great amount of working distance. But when you really need
to see a product, you've got this eye-loop that you can drop in, swing it over the product,
get right up on that eye-loop, take a look at what you're looking at. You're at a very
high inspection, you don't have any working distance, but it's not designed for that.