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 _______________________________________________ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
