Not Your Everyday Banana

by Bart Arondson

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I want to place a webcam between 6m (20ft) and 12m (40ft) from my subject and have a capture width of 3m (10ft). If I understand the formula, with an estimated sensor width of 8.46mm (1/3"), I need a variable focal length of 16.92mm-33.84mm (2x zoom).

All my searching has not produced a webcam which can do that (without digital software based zoom). So, I plan to try to custom "build" my own solution by taking the plastic casing off my webcam and attaching the sensor inside to a SLR lens. Here are my questions:

  1. Does the brand/quality/kind of lens I use for this, matter? The number of 16-34mm lenses available is staggering (with an equally staggering price range).

  2. How far from the lens should I put the sensor?

  3. Other than for protection, do I need some kind of special casing around the webcam/lens connection?

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4 Answers 4

I have been working on a project which also requires, more or less, a webcam with HD quality (something like 720p) and an optical zoom lens. There are such things for sale ... but they are industrial-strength, and industrial-priced, such as pan-tilt-zoom cameras for high-end videoconferencing equipment. And, of course, there are the commercial cameras that the TV broadcasters use. There aren't any such things in the consumer marketplace.

I found one guy who took apart a Sony camcorder and bolted its zoom lens to a standard webcam. He has a video of the process here: http://hackaday.com/2012/03/01/a-zoom-lens-for-your-webcam/ I did about the same thing: I also took the zoom lens out of an old Sony camcorder, and literally bolted it onto the circuit board of a Sony PlayStation "Eye" webcam (good electronics for $40), and "FrankenCam" works fairly well. The image is decent but washed-out. I need to work on aperture control. And I may need a better IR filter.

I found another guy who will sell you a Sony Playstation Eye webcam, installed in a case with a standard lens mount, here: http://peauproductions.com He also offers a low-pass filter that may help me with my image quality. I may try that if I can't get decent results on my own.

But I still think that we both could instead find an off-the-shelf camcorder, or digital camera, with a 'real-time' image feed. Many cameras and camcorders will support an external "AV feed", but all the ones I've seen, and bought, send out very poor video, usually broadcast-TV quality. I'm still looking for a good camera that will put out real-time HD video. For example, I have high hopes for the new Samsung Galaxy Camera, an Android tablet that thinks its a high-quality camera, which I just started to research.

Hope this helps.

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You will likely run into issues due to the extremely small size of the sensor and the much larger sensor that an SLR lens is designed for. In theory, you might be able to move it closer to focal point of the lens if the lens' design allows, but I'm not sure if it would even be able to focus.

You really probably either want a webcam that includes a built in optical zoom (not sure if such a thing exists) or an actual camera that supports use as a video capture device (which could be plugged in to the computer and used in place of a webcam.) I imagine you could find either a DSLR or simple point and shoot that would support this functionality and likely cheaper than the cost of buying a DSLR lens.

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I've looked for both of your suggestions, neither one exists that I can find. There are hacky suggestions for capture w/ a non-webcam but nothing reliable. –  just.another.programmer May 26 '13 at 21:47
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@just.another.programmer I know Canon DSLRs support a live feed of video via the EOS Utility and it appears that software can be used to make that output show up as a video capture device to Windows. Additionally, a quick google for Optical Zoom Webcam shows multiple results that appear to meet your needs. –  AJ Henderson May 26 '13 at 22:16
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In theory, there should be no problem. Just put your webcam sensor in the same distance as is the one in your DSLR. You must also cover the connection so no light other than from the lens can reach the sensor.

Maybe some extension tubes will help you if you find them in proper length.

The only issues I see are:

  • Setting up Aperture. You must have older lens with aperture ring since the new ones are operated from body. Canon's new lens have opened aperture as default, Nikon's have it closed.
  • Lens MFT. Using such small sensor demands good optics. Since your sensor will capture center of your lens where they are sharpest, this may not be much of the problem.

If you make it, please post some results here. This DIY project looks interesting :)

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What is your budget?

One approach is to get/buy/rent a DSLR that can provide a "live view" video feed. Then just use the appropriate tethering software. For my Canon 50D, which is a 5 year old camera, the standard Canon "EOS utility" will take the video feed on both Windows and Mac computers.

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