SLR to Webcam Adapter

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My latest project is to develop an adapter so that Webcams can be fitted with SLR lenses. There are two main issues with this project. Firstly, each brand of SLR has a different mounting (often more than one per brand) and secondly the reference distance for each mount is different. The reference distance is the distance from the lens mount to the infinity focus plane, the place where the CCD must be. To complicate the issue each webcam  type has the CCD a different distance from it's mount. So you can see that there could be potentially hundreds of different adapter combinations required. 

Why use an SLR lens on a webcam. There are many reasons, not the least of which is just to see what can be done and explore the use of webcams. Even cheap SLR lenses have very good optics. They where designed to give a very flat field image over the entire 35mm film plain. The image in the center, where a webcam CCD resides, is therefore extremely good.  Telephoto lenses could be used for guide scopes and for applications where you want slightly wider Field of View (FOV) images of bright objects. Short focal length lenses like 50mm or even down to fisheye lenses can give webcams a reasonable FOV for wide field astro imaging. Note that even a 180 degree fisheye will only give a webcam a FOV of 40 to 60 degrees due to the small size of the CCD. There are also many terrestrial applications that could be explored.

Why not just use an SLR camera to T-Thread adapter and make a webcam to T-Thread adapter? It would be good however, the T-Thread ring is the wrong way around. It attaches to the camera body not the lens. 

Design issues

Mounting Issues:

Another issue is supporting the weight of the lens. The adapter has a flat machined in the bottom with a 1/4-20 threaded hole so that it can be attached to a tripod or telescope.  A 50mm lens would be OK and maybe even up to 135mm will work well on this mounting point. I have used a Nikon 70-210 zoom mounted on the tripod and it worked well. Some telephoto lenses have 1/4-20 tripod mounting attachments on them which would be good for heavier lenses. The bayonet mount will hold the weight of the lenses above. Bigger lenses could become a problem but they seem quiet strong and if handled gently would support bigger lenses.  I am looking at developing a universal holder for telephoto lenses that would clamp to the lens and provide at least a tripod mounting hole. More likely is the development of an aluminium clamp that attaches to the current adapter and has both a wedge fitting and tripod mount. But that is in the future. Please email me if you have any suggestions or questions regarding mounting.

Alignment:

The rotational alignment of the camera adapter and lens has been an issue. For the bayonet mounted lenses this is easier to solve, at least for the lens to adapter alignment. I have made my best attempt to get the adapter aligned correctly with the camera. It aligns with my version of the camera, but I am not sure if all the cameras are the same though so it may not align with your camera.   This is not a major issue in that it just means that the may not be tight when in the vertical position.  The M42 adapters are now aligned as well as the bayonet mounts. The thread starts in exactly the same place on every adapter, I love computers. (Once you get them working right)

Focus:

Normally an SLR lens infinity focus is set to be at the stop of the lens focus ring. The actual infinite focus point is determined by the length of the adapter and the exact position of the CCD within the camera. Given that I don't have total control of the CCD mounting and this may vary between cameras, even of the same model, I wanted to leave a little room for error. Also I think astronomy type users really want to be able to sweep the focus through infinity so that they can manually get a star in focus and confirm this visually rather than rely on the lens focus stop. So I have set the infinity focus position to occur before the stop is reached. I think this is the best solution and offers the astro imager the most flexibility. This means you will loose a foot or two in the close in focus range.

Development Status as at 30 July, 2008 :

To contain the problem a little I will initially be making the adapters for the most common SLR lenses and webcams. This will include C-Mount video cameras and probably the SAC7 and SAC8 cameras. The SLR lens mounts will be Pentax Screw and K series, Nikon, Canon EOS, and Minolta MD initially. The Quickcam series of camera is a problem from a vignetting perspective. Because the CCD is very deep within the camera body I don't thing these cameras will be suitable for use with SLR lenses. Given that each QC Pro version will require a different adapter and that it will most likely produce images with significant vignetting these adapters may never reach production status.

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Production and Ordering

Order adapters here: ORDER

This table shows the current production status.

NOTE: (1) The Minolta MD lens lock system is causing some difficulty at this time.

Ordering:

You can order the adapters that are in PRODuction from my normal order page. The part number appears in the table above.

Availability:

I am not planning to hold stock of these adapters because there are so many different combinations. I have developed the production process to support having a batch of blanks made which are common and then I can finished them off to meet a specific order. What this means is that from the time you place the order I need between one and two weeks to get the adapter finished. Then it will be another 5 to 14 days before it arrives at your place. During the initial stages this delay could be a week or two more because I am still setting up the production line. I appreciate your patience.

Price:

The initial run of adapters in each configuration will cost US$40. Once they are proven the price will have to rise to around US$50 to cover the cost of production.

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Comments - Suggestions - Questions:

If you have any comments, suggestions or questions please email me.