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Finding a manual focus adapter for a fixed focus phone camera?
Finding a manual focus adapter for a fixed focus phone camera?
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Old 6th December 2017, 10:38 AM   #31
Ron E is offline Ron E  United States
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Join Date: Jun 2002
Location: USA, MN
Quote:
Originally Posted by realflow100 View Post
Is there no product I could buy specifically for this purpose ANYWHERE?
I just want a manually variable customizeable focus lens that i can adjust on the fly.
preferably something that just clips on and has a knob on the side of the lens that adjust the focus?
post 29 is the same as post #1 - absolutely no progression from the information you have been given.
Businesses exist to make money, they don't make money by making a product to fix an issue that affects very few people.

Look at the bottom of this page:
schoolphysics ::Welcome::

You find a well-known formula there: 1/F = 1/f1 + 1/f2 - a/f1f2

If you buy two lenses and separate them by a distance "a", you can create many focal lengths. If you buy two lenses and mount them to a helical focusing mechanism that varies the distance between them, you can create a variable focus lens. You have to be smart about what you choose for f1, f2 and a.

I have a feeling you will want perhaps a 0.25 diopter lens, with a focal length of 4meters (4000mm) You will probably want one of the small lenses to have a positive focus, and the other to have a negative focus.

lets try a +50mm and a -50mm - now for some math!
1/4000=1/50-1/50-a/(-50*50)
1/4000=-a/-2500
4000=2500/a
a = 2500/4000 = 0.625mm
I did that in my head, can you believe that?

Lets say you wanted a 0.5diopter lens, with a focal length of 2000mm with the same lenses - the separation distance would then be a=2500/2000, or 1.25mm.

I have a question for you though: Is it weird that I use the capacitance meter setting on my DMM to check LED's?
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Old 11th December 2017, 03:10 PM   #32
realflow100 is offline realflow100  United States
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why are you asking the same question i asked back to me?
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