Can CHDK override lens sensors?

colorbroken

3

« on: 26 / December / 2008, 01:59:04 »

Advertisements

I don't know where else to put this, so I put it here. I'm a tinkerer, and can't stop thinking of ways to override or improve things already done. I like the CHDK system by the way, and thanks to everyone who works on it, it's outstanding, and just saved me $300 on getting simple RAW images.

The problem is this: I want to physically rebuild a camera so that it uses a stationary lens, like an old 1.8 lens for example. The issue is that if certain sensors in the lens don't activate when the camera is turned on, it will error and cease operation until you restart it.

I want to understand better how the camera makes these determinations, and if they can be overridden or skipped using firmware. If there is a set of focus sensors or zoom position sensors that can be removed physically, and removed in programming in the firmware, I'd be able to build customized little Canons with certain unusual image qualities and possible functions.

Any ideas or suggestions would be greatly appreciated. Happy Holidays, and much respect, -pete

p.s.-- shameless plug, you can visit ColorBroken.com to see what other ridiculous things I get into.

Logged

Microfunguy

4037

Re: Can CHDK override lens sensors?

« Reply #1 on: 26 / December / 2008, 06:28:46 »

Quote from: colorbroken on 26 / December / 2008, 01:59:04

I want to understand better how the camera makes these determinations, and if they can be overridden or skipped using firmware.

I am also interested in this but do not have the answer at present.

However, with the CHDK supported cameras there are other problems,
They all use use a tiny mechanical shutter to block the light AFTER exposure.
The aperture in that shutter will be too small for any add-on optical system.
It will also be extremely difficult to make one that is sufficiently fast.

The result (in bright light) will be images with strange colours and an interlaced effect.

It is far easier to work with a fixed focus camera (5MP ones available) but you still have the shutter problem.

David

Logged

colorbroken

3

Re: Can CHDK override lens sensors?

« Reply #2 on: 27 / December / 2008, 01:21:24 »

Crafty, but I think you're right, and I hadn't considered that. My impression was that the shutter speed itself is determined by the amount of time the sensor is allowed to capture and write a file. For example, if CHDK can record what, 1/20,000 of a second, it can't possibly be due to that little shutter alone.

My hope is that the sensor itself and programming attached will determine the shutter speed. If it turns out that is untrue, then I'll have to stick with my idea of converting Disc Film cameras, including the shutter units, into digitals, and just work with that.

Logged

Microfunguy

4037

Re: Can CHDK override lens sensors?

« Reply #3 on: 27 / December / 2008, 06:27:52 »

Quote from: colorbroken on 27 / December / 2008, 01:21:24

My impression was that the shutter speed itself is determined by the amount of time the sensor is allowed to capture

Yes, that is electronically controlled, the mechanical shutter is not used.

Quote

if CHDK can record what, 1/20,000 of a second

If it can. There is no convincing proof.

I have disassembled a Vivicam camera and removed the optical elements from the zoom.
There are just two fedback sensors.
One, a photo-interrupter, detects that the focusing-lens mount is docked at the home position.
The other, a photo reflector, detects that the zoom barrel is at the home position.
Hopefully, blocking the slot of the first and sticking reflective foil on the second should override them for startup.
If so, I will then remove the entire zoom assembly and fit a C-mount so that specialised lenses may be used.

Logged

colorbroken

3

Re: Can CHDK override lens sensors?

« Reply #4 on: 27 / December / 2008, 14:19:09 »

This is exactly what I had in mind, a C-mount install. I was looking for a Canon digital-zoom model to simplify the whole project, but even the D-zoom models have moving lenses, I assume for auto-focus.

The issue is still that there are certain devices in place that will not allow proper operation of the camera if they are not detected... that I recall anyhow. I have a 590 in the mail, I'll try it when I receive it. Thats why the question begs, are the sensor positions checked by software, or hardware? If the code can be changed to ignore the detection, then we can just remove the sensors in question and carry on. If it's hardware based, then yes, black tape will probably have to be employed.

Logged

Microfunguy

4037

Re: Can CHDK override lens sensors?

« Reply #5 on: 27 / December / 2008, 14:25:43 »

Quote from: colorbroken on 27 / December / 2008, 14:19:09

are the sensor positions checked by software, or hardware?

Presumably by both.
On power-up for example, does the firmware expect a docked zoom signal and then after attempting to move the zoom expect that signal to change ?

Only one way to find out.

You do not have these problems with fixed lens cameras.

However, they tend to have a tiny, thin IR-blocking filter as part of the lens and you will need to fit your own separate filter no more than 1mm thick.

On the zoom lens models, the filter tends to be larger and fitted over the sensor.

No need to provide your own.

Logged