PDA

View Full Version : digital pinhole - another take- DIY



pekar
04-12-2006, 12:00 PM
Hi,
I've gotten the bug to make a pinhole from a point & shoot digital camera.
I've dismantled a Pentax Optio S with a broken lens/shutter. The camera should be functional otherwise.
The problem I'm having is that the camera wants to turn on, and the gear to extend the lens goes for about 15 seconds and then the camera shuts off. Does anyone know how these cameras sense that the lens is fully extended and prepare to take a picture?
Is this even a good idea? I've also come to realize that this camera may never work again due to the broken shutter. I had assumed that a digital camera wouldn't need a physical shutter, but I might be wrong there. Gear resistance has been ruled out, I suspect either there is another sensor (light or physical), or possibly something optical that tells the lens to stop extending.
Has anyone done something like this? I'm familiar with the SLR bodycap digitals, I just want to play around with inexpensive P&S. Perhaps a simpler camera (fixed lens) would be an easier hack. I had wanted to use the night scene mode to capture pinhole images with this camera.
Suggestions?
Thanks,
Pekar

timeruinsbelief
04-12-2006, 01:46 PM
if it is anything like the flatbed scanners i have dismantled, it would be a physical resistance i.e. the scan head reaching the other end of the scanning bed. would it be possible to re-assemble the zoom mechenism/ lens housing but with the lens and shutter yanked out?

ImageMaker
04-12-2006, 01:50 PM
Given you took the lens off, if you haven't discarded the parts you might want to look for a tab, contact, actuator, etc. on the extending part of the lens that could trigger the camera to "know" the lens is extended. On my digital, there's a sort of "lens cap" that retracts when the lens extends, though I don't know if that action is mechanical or actuated electrically separate from the lens extension. My camera, though, doesn't seem to use a physical shutter for exposure, because it uses the LCD as a viewfinder (actually, it has an optical viewfinder as well, and can be used with the LCD completely turned off, but few will use a digital like a film camera willingly).

If you find the sensor, you'll probably have to manually trip it within the correct time frame, since the camera will expect the lens to open after power up, and close after power down. And unless you can disable autofocus from the menus, you might find you can't get the camera to expose even if you can fool it into thinking the lens is extended.

DSLRs work better for this stuff, because they're mostly independent of the lens for the camera's functions, but also because they have larger sensors; most DSLRs have an APS-C sensor, about 18x24 mm, IIRC, while even a 5 megapixel consumer digital will have a sensor only 1/3 inch diagonally, possibly smaller if the camera is very compact (phone cameras might be as small as 1/4 that size, or about 2 mm diagonal), which could be limiting for pinhole because the sensels will be a lot smaller than the minimum resolution available from the pinhole (i.e. you might find you get no improvement in image quality above the camera's minimum resolution).

Second choice after a DSLR, and FAR cheaper, would be the earliest consumer digitals, with fixed lenses, relatively large, low-resolution sensors by today's standards, and the IR filtration in the lens instead of over the sensor. Pull the lens off one of these, and you can have all kinds of interesting fun. If I had an alternate webcam, I'd probably try to finally figure out how to remove the lens on my Creative WebCam Go; except for its poor low-light performance, it ought to work *famously* with a pinhole of around 10 mm projection distance and IR-pass filter... :)

pekar
04-12-2006, 08:59 PM
I broke enough of the lens mechanicals that reassembly isn't an option. Resistance is futile on the drive gear, it is very strong.
There are three clues.
1. The base ring gear has a small mirror on the outside surface. I cannot see an obvious sensor to interact with it.
2. The only electronics that have obvious connection were the shutter/iris. The lenscap was mechanically opened.
3. A second gear was driven by the ring gear that adjusted the optical gearfinder. There could be a sensor in this mechanism, but I can't easily reconnect it to the drive gear. It doesn't appear to respond at the extremes, and may only have been used during zooming.

ImageMaker
04-13-2006, 12:33 AM
Your second gear probably drove the optical zoom in the veiwfinder to keep it synched with the lens zoom. Sounds like yours is very much like mine (though I hope older; mine was $300 about 18 months ago!). The mirror on the ring gear is likely for something in the camera that reads the zoom or focus (possibly from a distance, with considerable precision), and may be the source of your problem; is it possible you could remount just the ring gear?