DIY Add on diopter

Started 9 months ago | Discussions thread
Stephen Barrett
Regular MemberPosts: 451Gear list
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Re: DIY Add on diopter
In reply to dickiedoo, 9 months ago

Hello dickiedoo,
Good job!
For an approximate measurement of the focal length, just hold your closeup lens close to a wall and adjust the distance until you get a focused image on the wall. Something outside a window will do, or even a lamp on the other side of the room.
The focal length is approximately the distance from the centre of the lens to the wall. You can improve the accuracy by repeating the measurement with the lens direction reversed and then averaging the two measurements. If you want the strength in diopters, that is given by:
diopters = 1000 / (focal length in mm)

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