I'm using CHDK on a pair of S5 IS cameras, as part of a book-scanning system (http://diybookscanner.org/forum), and because of the large number of pictures this generates, I've already worn out a couple of shutters, which cost me $130 each to replace -- almost as much as the camera itself, these days.
I see there are motion detection routines for taking pictures of lightning. I assume these keep the shutter open, as video mode would, and poll (clear?) the CCD at specified intervals, looking for a threshholded change. When it detects the change, the MD routine returns, and the calling script can elect to take a picture.
What I wonder is, is it possible to take a picture without flipping the shutter? Just leave the shutter open, as it is in the MD routine, and clear/collect/write the CCD to the SD?
Do you have a rough idea of how many exposures were on the camera when they wore out ? I think this would be of interest to many users.ISTR some users have put > 100,000 shots on their cameras with timelapse scripts.
MD watches the live view (the same thing you see on the display). When it detects motion, it triggers a normal shot, shutter and all. Lesson: lighting isn't as fast as you might think
A full readout must be quite long compared to video, which might cause trouble without the shutter (otherwise, why would Canon bother with a mechanical shutter at all ?)
However, I guess you could use relatively low light with the book scanner, so it might be OK.
I don't really know. I know I'd only put around 30,000 shots on them, but I bought both cameras "refurbished" from Canon, and I doubt that replacing a working shutter would be part of the refurbishing process. They may have had more than 70,000 shots on them when I got them. The reason I know I'd shot about 30,000 is that my counter rolls over at 10,000 shots, an event which requires special handling when I'm post-processing the images of the books. If you know of an internal counter which doesn't roll over, I'd be happy to take a look, but even if such a counter exists, it wouldn't surprise me if resetting that to zero WAS part of the refurbishing process.
You know, that's a good question. Why do they bother with a mechanical shutter? Video mode is obviously not closing the shutter for every frame, and my 2 MP phone camera doesn't employ a shutter at all.
I think you're probably right, that the higher resolution means it would take so long to write the data to the SD that the exposure would be compromised if the shutter didn't enforce a physical cutoff in light accumulation.
The more I think about it, the more I think I may need to wait for technological advancement to provide CCDs and memory storage which is fast enough to take high-res shutterless pictures.
There is a 'total shot' count display in the later pages of the vers.req info. It is quite possible that canon zeros it when when they service.
This PDF from Kodak describes some of the variations http://www.isgchips.com/pdf/Shutter_Operations_Kodak_App_Note.pdf
According to that document, the mechanical shutter is required because the CCD output is interlaced. If video mode is writing each interlaced stripe as a frame, that could explain why no shutter is required for video mode.
For my application, the subject will not change significantly between frames, so if I could only get video mode to write each interlaced stripe at maximum resolution (at a rate of one frame every five seconds, or even slightly slower if necessary) that would be a workable solution.
press("shoot_half")repeat sleep(1)until get_shooting() == truepress("shoot_full") -- start shooting by fully pressing the shuttertstart=get_tick_count() -- store exposure start timerepeat openshutter() --force shutter open even during photo readout sleep(1)until (get_tick_count() - tstart ) >= exptime release("shoot_full") -- release shutter buttonsleep(1)release("shoot_half")
I wouldn't think the full raw lines are ever available anywhere camera software could get them. My guess is something squishes them down to 640 pixels very early on. I would also guess that video readout just reads the same subset of the available lines over and over, so you even if you could get the full width lines, you wouldn't be able to build up the full frame.CHDK certainly can't get you anything like that today.
FWIW, I was curious what the photo would look like if the shutter was open during readout, so I modified my multiexp.lua script (which controls the mechanical shutter from Lua during long exposures) to call OpenMShutter in a loop while shooting:[...]It crashes with lens open right after the camera has closed the shutter for readout. Romlog points at MechaShutterActuator.c Line 158.So that was a failed experiment, but AFAIK you do need a mechanical shutter to black out the CCD during readout even if the scene is static, because the charge from distant pixels on a row is passed through pixels closer to the readout section and all pixels are still sensitive to light during readout. People with broken shutters have posted photos on this forum before, I think...
But the question is why did you have the cameras repaired if all you want is a camera with no shutter? Did they fail to an error code? My a570 has >120k shots on its counter. A very large portion of those were with manual focus and manual exposure in timelapses or motion detect, i.e. minimal mechanical movements (= minimal amount of clicking noises during/between shots).
If you have a camera with no mechanical shutter (or manage to override it open in CHDK -- this might be possible as we are already replacing some shooting related ASM code with our own) you could build a sturdier external one or have exposure controlled by switching lights on/off (or a flash) in a dark book container box.
With almost 4000 posts, I'm sure your guesses are better than mine, but what are they based on? If the camera software can't get to them, the implication is that JPEG compression for each image size is being done in hardware. While that may be true, it would surprise me.
I see values in str_list like JPEGBufferFull, JPEGBufferFullForMovie, and JPEGbuf.c, which suggest to me that software is involved somewhere along the line. It's possible I'm misunderstanding where str_list.txt originated.
I also looked for documentation of an openshutter() call, but all I could find was open-shutter.bas, which doesn't seem like the same thing.
In a perfect world, PB would stand for "picture buffer", and I'd be on the right track. Can you burst my thought balloon?
Quote from: fudgey on 15 / May / 2011, 12:38:41If you have a camera with no mechanical shutter (or manage to override it open in CHDK -- this might be possible as we are already replacing some shooting related ASM code with our own) you could build a sturdier external one or have exposure controlled by switching lights on/off (or a flash) in a dark book container box.Assuming I did that, can you suggest how I'd get a picture from the CCD to the SD? Are existing CHDK commands up to that task, or are "click" and "press" the only things that can currently accomplish it?
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