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I have a somewhat unusual need - I've got a webcam with a fixed, plastic lens that's focused on anything >40cm away. I need to be able to focus on things that are 5-20cm away. I'm not worried about permanence of mount, ease of use or anything like that. What I've tried is the magnetic add-on lenses they make for iPhones like this. The problem is that the macro lens is effectively a 10x zoom, which is way too much.

Do they make macro lenses in that form factor that are 2 or 3x? What other options do I have?

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Here's how you could refocus a Logitech C310 webcam:

Open it up:

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Lens held on by two screws:

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Lens removed:

enter image description here

Lens itself:

enter image description here

All you need to do is slightly increase the space between the lens and the sensor. If you loosen the screws slightly, the space may be enough to bring the focus where you want it, or for a more preeminent solution you could add small pieces of paper as spacers between the lens mounting points and the circuitboard.

Just be careful about dust, my webcam was ruined by creating this series of images because of the dust that fell on the sensor. I didn't care though because it's used for computer vision, not art, and computer vision doesn't care about dust.

  • I'll try it on a 310. On my c110 the lens is epoxied onto the sensor :-/ – kolosy Mar 1 '15 at 22:11
  • also works with c270. used cable cutter to break dab of glue the unscrewed easily (no force). now will smaller scan QR codes – Mr Mo Nov 13 '17 at 13:47
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Under the plastic cover, most webcams have a screw-thread mount for the lens to set focus at time of assembly; it's usually easy to remove the cover and set the focus as needed.

You could also use any low power positive lens as a macro lens, e.g. inexpensive one or two diopter glasses, with some sort of temporary mount. Not pretty, but OK for brief use. You could purchase a two-diopter 10-mm-or-so lens from Edmund Optics, but that might be pricey.

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Let me take Ryan's answer a step further. I also have a C310 and had a closer look at the lens:

There's a little spot of hot glue or something. I used a razor to cut this loose and then found that with a some force you can screw the lens off:

So basically I can now adjust the focus in a wide range. Here's a macro of one of the little screws that you can see in Ryans post:

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