Excellent idea... I've been looking at these pencams myself.
At 16:58 07-12-01 +0100, you wrote:
>A few weeks ago I broke down and bought a pencam as a quick and dirty way
>to record things for the Internet and simply whenever I was underway (I
>used to consider a camera working on film for the job but the instant
>readout appeals to me.)
>
>Well; I was lucky; the images were not so good and the problem seemed like
>poor focus, but it looked as if a bit of a rotation of the lens mount would
>fix the problem, so I grabbed a pair of sturdy tweezers and gave the mount
>a twist (it has a pair of tiny holes probably intended for exactly this
>job, but at the factory) As expected, the focus was quickly corrected; so
>why not add an adjustment so I could focus anytime I wanted!? It worked
>and it's not exactly camera making but modifying is close enough.
>
>The end result focuses to about 10 cm with a full turn of the lens,
>allowing pretty satisfactory close-ups while the work involved is small.
>
>For those who might be tempted;
>1) find or make a disk to become the "handle" and on which the calibration
>will be marked. My own was a gear from who knows what, with fine
>teeth. Material: cream-colored plastic. Metal would work as well, and a
>plain disk would be fine except the fine teeth are a nice substitute for
>knurling. The grip is good. I considered a washer but the only ones I had
>with a small hole and a suitable diameter were plated steel and I did not
>want the rust, but you may be luckier in locating a better one.
>2) Put in a central hole of a selected size and two small holes for
>mounting the disk to the lens mount. On my camera the holes on the mount
>are 8 mm apart and have 1.2 mm diam. A different model might use other
>values. (I have an Aiptek Presscam.) My screws are m1.4 so the holes in
>the disk are 1.5 diam.
>3) Deepen the holes in the lens mount. I removed the lens entirely and
>prayed I could guess a safe depth. I was lucky and struck no glass (I was
>a little afraid to remove the optics from the mount; that would be trading
>one kind of safety for another.) You may want to go to some UNC size if
>only those taps and screws are easily available. There is enough metal for
>holes about 3 mm or so deep, but that is a guess! Please do not just go to
>that depth and dash off an angry message if you bore a lens. (The back
>elements on my lens are much larger than the hole in the front so there is
>some danger.)
>4) Fasten your disk to the lens. Mark the distances for best focus. I do
>not have a reference line; I just use the edge of the viewfinder. You can
>add an official reference line according to taste. The easiest method to
>find the sharpest focus is to run the camera as a webcam, with the highest
>resolution, which will probably give rather slow response on account of the
>readout time over the USB port. You should keep the camera quite steady to
>get decent images because determining sharpest focus is not all that
>easy. My target was an Air Force 1951 chart but there are plenty of
>alternatives, some of which are likely to be better. The Siemens chart
>could be better; bring the sharp image as near the center as possible.
>
>The lens is fixed with a spot of "glue" to prevent wandering out of focus
>in the hands of the buyer. It takes some torque to remove the lens. Don't
>slip! You will mark up the lens mount, a not too professional style of
>working (I should admit, I have those marks, though they are hidden under
>my disk.) Clean off the glue before installing the lens.
>
>A full revolution covers from infinity to about 10 cm on my camera, making
>macro work possible. You do need to correct the parallax when observing
>through the viewfinder. (Reminds me of the "good old days", when I still
>had a Leica IIIF. You can get good results without an SLR or other ground
>glass focusing.) I was again lucky; my gear had a raised ring on one side
>and when this faces the camera it serves as a stop preventing me from
>turning much past "infinity". You might want to make something similar but
>better is to leave a little bump on your disk and arrange a stop on the
>camera body so the rotation stops at infinity and is confined to a little
>less than 360 degrees.
>
>The final result is a considerable increase in flexibility for not much
>work. I looked at the resolution on the Air Force chart and it was better
>than 400 lines (200 line pairs), so the optics on these cameras are not
>bad. (It is not trivial to measure resolution beyond a certain point and I
>doubt that the Air Force chart is the right tool. You can reach some quite
>different conclusions depending on just how the chart lines are aligned
>with the sensors pixels. (With a steady support I and patience, I can
>believe you could align the pixels with lines on some chart and see 640
>lines=320 line pairs in the final image, but is it worth the effort?)
>
>It is not a 5 megapixel camera but I am pleased by the photos but for about
>$50 I will not be too devastated if it falls into a pond or something
>similar. And it is compact compared to the megapixel wonders
>
>Have fun!
>
>Bob
>
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