An Ultra-High-Speed Shutter Override! - Feature Requests - CHDK Forum
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An Ultra-High-Speed Shutter Override!

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Offline Woodsman

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An Ultra-High-Speed Shutter Override!
« on: 30 / November / 2007, 03:49:11 »
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This topic has been locked. Please see the thread titled "Whoa! ****MAJOR**** High-Speed Shutter-Speed Discovery!" in the "General Discusssion & Development" board for further discussion and input.



This one went from discovery to request to implementation to development so fast I wasn't sure where to put the related threads on it.



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I was going to move the thread about this discovery from the general discussion forum, but it appears to be missing from my view at the moment. (To more clearly show how it happens and how I verified it.)

Anyway, I found out that when using High-Speed Tv Bracketing that the shutter speed goes up to 1/6,400, 1/12,500, and maybe even 1/50,000 of a second at the other end of its extremes.

(hah, I just realized in all my other posts I was adding in an extra zero. My "excitement override" mode. LOL)

Could we have that shutter speed override too?

Since my photography covers many extremes, from astrophotography for night-sky shots (those new 65" shutter speeds are fantastic!) to trying to stop the motion blur of hummingbird's wings and insect's wing, I would LOVE having those high shutter-speeds at my disposal. Plus, I found out when they are overridden by CHDK then you aren't crippled to using only small f/stops too! Using f/2.7 at 1/12,500 is possible!

One important note, this high-speed override would have to start from 1/1600 on up, since the aperture limitation starts to kick in at any shutter speeds higher than 1/1600. If I set my camera on 1/1600 then I can use f/2.7, I can't use 1/2000 until I set the aperture to f/4.0. This way I could use my widest apertures using the camera's own shutter speeds. Unless there's a possiblity to also include an Aperture Override, then it might be more compatible with all the camera's auto modes?

One other request. Since the slow-shutter override is on a sub-menu selection of CHDK, it's difficult to find it when you need it, and it's easy to forget that you left it on, so when you start up your camera again it might still be in that mode. So.

1) could these overrides be made a top-level menu option? Easy to get to and see what they are set at for quick changing.

1b) could there be an option to have a small OSD icon showing to know you have shutter-override engaged?

2) could their status not be saved in CHDK.CFG when you power down? Or have the option to have that or not? (I just now realized that using a camera by remote it might be nice to have the camera power-up in those special shutter speeds.) (option 1b may be enough so this wouldn't be needed)

3) (please put the "reset to defaults" option on the debug menu so it's not so easy to accidentally reset all your CHDK options)

Thanks if you can do these things!

(EWAVR, (the CHDK genius), I hope you or someone can add this feature to your already remarkable slow shutter speeds.)

I just realized of another great use for this. My other digital cameras allow for a flash sync as high as 1/2400 shutter speed. We might be able to still use the flash at higher shutter speeds with this. Much will depend on how closely Canon sync'ed it to their own shutter-routine. My other camera has the flash-duration dead centered on the shutter speed. This could be a new level of high-speed flash-sync for Canon cameras. :)

I foresee a menu option like this, at the top of the main menu:

Shutter-Override: 65", 50", 40", 30", 25", 20", OFF, 640, 800, 1000, 1250, 1600, 2000, 2500, 3200, 4000, 5000, 6400, 8000, 10000, 12500, 16000, 20000  ....?

Usage:
Slow Speed
Higher-Speeds Flash Sync & F/Stop Limit Overrides
Ultra Speeds
« Last Edit: 04 / December / 2007, 18:30:50 by Woodsman »
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Offline Woodsman

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Re: An Ultra-High-Speed Shutter Override!
« Reply #1 on: 01 / December / 2007, 12:23:36 »
Is there a way that this feature could be implemented so that if we choose something like 1/6400 shutter speed, that this will be the starting point for High-speed Tv bracketing too? Or will this interfere in that? I'm guessing, hopefully, that it will just act as the starting point and HS Tv bracket will work as normal. Since there are no exposure metering features available that would take advantage of and suggest to us some proper exposures for their use, having HS Tv Bracketing would be a good way to find the right exposure, a test burst, to see what speeds would be best from the resulting HS Tv Bracketed sequence.

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Offline Barney Fife

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Re: An Ultra-High-Speed Shutter Override!
« Reply #2 on: 01 / December / 2007, 13:17:51 »
P.S. Can these shutter speeds be given a uBASIC command for scripts?? The final icing on the cake!!

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Offline Barney Fife

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Re: An Ultra-High-Speed Shutter Override!
« Reply #3 on: 01 / December / 2007, 14:41:32 »
Here's some confirmation images. The only CRT monitor I have available at this time for tests is an old C-64 monitor that I'm using for a wild-life surveilance monitor hooked to an IR video feed.

Using fresh batteries and a cold CCD, I was able to duplicate the extremely short durations I experienced the first night. Up to a point. These didn't get down to the 1 to 2 scan line limits but close.

In any case, you'll see what I'm talking about. It now appears that the stops are not linear in high-speed settings. Notice the jump from the last 2. I was missing some frames (the camera's shutter not sync-ing to the display, so the 1/400,000 and 1/800,000 shots are missing. But I found the 1/1,600,000 frame intact. (in next reply, due to the 4 image limit per post)

Refer to filenames for the full stop jumps between exposures. I was using a High-speed Tv bracket step of 1 EV.

This first batch represents: 1/3200 (0EV), 1/6400 (+1EV), 1/12500 (+2EV), 1/25000 (+3EV)

« Last Edit: 01 / December / 2007, 16:29:16 by Barney Fife »
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Offline Barney Fife

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Re: An Ultra-High-Speed Shutter Override!
« Reply #4 on: 01 / December / 2007, 14:52:21 »
Here are shots taken at +EV values of 4, 5, 6, and 9.  (value 5 is missing due to shutter not triggering while scan lines were visible, and the stops +7EV and +8EV likewise)

The represents shutter speeds of: 1/50,000 (+4EV), 1/100,000 (missing) (+5EV), 1/200,000 (+6EV), and 1/1,600,000 (+9EV)

So you see, even though the number of scan lines don't add up, the number of them does decrease even when EV values exceed shutter numeric speeds of 1 MILLIONTH of a second. Numerically at least, if not in actual results.

To any developers, perhaps you can use these images and the number of scan lines as a way to better define the numeric progression of shutter speeds.

All in all, I count 13-14 scan lines in the 0EV image, and only 2 in the +9EV image. That's at least a FULL 4 stops! Coming in around 1/40,000 of a second. (Holy #*@&!) Can it be taken further than that? Why do I get the feeling it can. I still recall those first test images where I only got 1 or 2 dim lines.
« Last Edit: 01 / December / 2007, 16:30:48 by Barney Fife »
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Offline n6mod

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Re: An Ultra-High-Speed Shutter Override!
« Reply #5 on: 01 / December / 2007, 16:12:22 »
Thanks for the test images. I still need to shoot some test images of a spinning disc with a mark on it, because I think shooting a CRT isn't very useful at these speeds. I don't think it's possible to tell the difference between reduced aperture (because the shutter doesn't have time to open all the way) and reduced shutter time. Phosphor persistence just makes it too hard to tell what's really going on.

You say that you're using a C-64 monitor. That's NTSC, so we have some timings to work with. The horizontal scan rate for NTSC video is 15.734kHz. So any exposures taken at actual shutter speeds beyond 1/16000 would have less than a full scan line painted during the exposure. Yet even at 1/200000, I'm seeing two lines at equal brightness, which suggests that they were both painted while the shutter was open. (or 1/8000 shutter speed) This /is/ very fast, no doubt about it.

I'm not sure what you mean by the shutter "not triggering while scan lines were visible." Did these shots fire during vertical blanking? Or were you zoomed in on less than the full screen?

A Dremel will free-run at about 30000 RPM, or 500 rev/sec. In rough, back of the envelope terms, this means that 1/16000 (one NTSC scan line) will be about 10 degrees of rotation, and with no persistence to throw us off. 1/3200 will be about 40 degrees, so anything less than that is a real gain in speed.

Unfortunately, I'm away from home for the weekend, so it will be Monday night before I can test this.

In the spirit of reproducible results, can you post a pointer to the script you're running, and tell us what camera you're using? I have an S3IS and an A640 to test with (though my dad has the A640 right now)
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Offline a710is

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Re: An Ultra-High-Speed Shutter Override!
« Reply #6 on: 01 / December / 2007, 16:21:13 »
earlier I've layed a sticker on one of my cpu fan's blades but even at 1/2000s it came out pretty sharp
car turbos reach 100.000 rpm or more. if somebody has that, mark one of the blades of the air intake fan and do some tests
careful not to get your camera sucked in though :D
dentist drills can also be pretty fast
« Last Edit: 01 / December / 2007, 16:48:33 by a710is »
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Offline Barney Fife

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Re: An Ultra-High-Speed Shutter Override!
« Reply #7 on: 01 / December / 2007, 16:49:40 »
Quote from: n6mod on 01 / December / 2007, 16:12:22
I don't think it's possible to tell the difference between reduced aperture (because the shutter doesn't have time to open all the way) and reduced shutter time. Phosphor persistence just makes it too hard to tell what's really going on.

Well, I again have to disagree. Look at the brightness levels of the respective images. The brightness doesn't change by full stops, but the number of scan lines (speed) does. Though I agree, the phosphor persisitence makes this extremely difficult to tell exactly what is going on. I just know something is! And it looks oh so nice!

Quote
You say that you're using a C-64 monitor. That's NTSC, so we have some timings to work with. The horizontal scan rate for NTSC video is 15.734kHz. So any exposures taken at actual shutter speeds beyond 1/16000 would have less than a full scan line painted during the exposure. Yet even at 1/200000, I'm seeing two lines at equal brightness, which suggests that they were both painted while the shutter was open. (or 1/8000 shutter speed) This /is/ very fast, no doubt about it.
I'm not sure about that NTSC speed thing now that I think about it. It uses an S-VHS signal (NTSC) to drive an RGB display that might be running at 80kHz?. Damn, it's been so long since I knew the specs on that monitor. Anyway, I'm glad I mentioned the monitor because it gives everyone a timing clue if they can confirm its actual refesh rate, more than I myself would have bothered to work out the math for. I only know I used to use this to test shutter speeds of old film cameras in the past. To see if there might be anything wrong with their shutters and if they would reliably duplicate shutter speeds from one frame to the next. It can be very reliable for that, but we're not testing 1/125 shutter speeds anymore, so all I know is just extrapolation on old experience.

If you can look it up, it's a Commodore 1902-A, one of their better ones available at the time for 80 character CP/M and GEOS-RGB displays. I suppose you could partially guess the refresh rate by the 13-14 scan lines at 1/1600th shutter speed? Does that help?


Quote
I'm not sure what you mean by the shutter "not triggering while scan lines were visible." Did these shots fire during vertical blanking? Or were you zoomed in on less than the full screen?

Correct, the shutter fired during vertical blanking. And no, not zoomed in too much, I had the full face of the monitor well within the frame because I know they might show up top or bottom and I needed to increase my chances of catching them when the camera's shutter fired.

Quote
A Dremel will free-run at about 30000 RPM, or 500 rev/sec. In rough, back of the envelope terms, this means that 1/16000 (one NTSC scan line) will be about 10 degrees of rotation, and with no persistence to throw us off. 1/3200 will be about 40 degrees, so anything less than that is a real gain in speed.

Cool deal, looking forward to seeing something more reliable and exact than this.

Quote
In the spirit of reproducible results, can you post a pointer to the script you're running, and tell us what camera you're using? I have an S3IS and an A640 to test with (though my dad has the A640 right now)

No script. Just CHDK alone and my finger on the button.

CHDK Settings:  Misc Settings > Tv Bracketing Value = 1EV / Override Shutter Speed = OFF

S3 IS Settings:
ISO800
High-speed Continuous On
Manual Mode
Shutter speed to start out = Oh [admin: avoid swearing please], I'm glad you asked this! I just now realized I started out at 1/1600! Not 1/3200!

I chose 1/1600 because then I could use a wider aperture of:

F/Stop = f/2.7

Okay, knock off my values by 1 full stop.   :(  How sad is that?? Let's chalk this up to my original "Excitement Override" mode. ;D

Then just focus on your speed test object and hold down the shutter.

If you test this, please see if you can go beyond an 18-shot sequence of Tv bracketing, to see if the shutter speed gets even faster. The problem is that the other end of the exposures gets so long so quickly that you have to wait a long time before you get back to the high speed exposures as they alternate from slow to fast shots.

« Last Edit: 01 / December / 2007, 17:02:17 by Barney Fife »
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Offline emu

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Re: An Ultra-High-Speed Shutter Override!
« Reply #8 on: 02 / December / 2007, 07:42:06 »
Quote from: Barney Fife on 01 / December / 2007, 16:49:40
If you test this, please see if you can go beyond an 18-shot sequence of Tv bracketing, to see if the shutter speed gets even faster. The problem is that the other end of the exposures gets so long so quickly that you have to wait a long time before you get back to the high speed exposures as they alternate from slow to fast shots.

what can we learn seeing this problem - we need a tuned Tv bracketing mode that has more manual controll (e.g. stop at 1" on the slow side of the game and go on on the other side) - I think the pros here might be able to do that!? 8)
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Offline Barney Fife

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Re: An Ultra-High-Speed Shutter Override!
« Reply #9 on: 02 / December / 2007, 08:22:51 »
Quote from: emu on 02 / December / 2007, 07:42:06
Quote from: Barney Fife on 01 / December / 2007, 16:49:40
If you test this, please see if you can go beyond an 18-shot sequence of Tv bracketing, to see if the shutter speed gets even faster. The problem is that the other end of the exposures gets so long so quickly that you have to wait a long time before you get back to the high speed exposures as they alternate from slow to fast shots.

what can we learn seeing this problem - we need a tuned Tv bracketing mode that has more manual controll (e.g. stop at 1" on the slow side of the game and go on on the other side) - I think the pros here might be able to do that!? 8)

Well, now with Fingalo's new build I found out last night that the Tv bracketing when turned on used the shutter-override speed as its starting point! So you can start out at 1/10,000 second setting and let it bracket quite a bit before the camera slows down into the slower shutter speeds. So that's a way cool feature included. When in doubt on what exposure to use set a high shutter value and start up Tv Bracket mode, then count off how many frames from the first one is the best exposure. Since there's nothing in these cameras that could advise proper exposure at these speeds. It'll be a big help having those two features work together like this. (Now I'm hunting around trying to find things to shoot in high shutter speeds. :D )

As for true shutter speed, this is still going to require someone testing the absolute top limits available (as well as the accuracty of those already available) by someone with better tools, and someone who knows more than I do on the best way to accomplish this. When I look back on how many errors I made just in reporting these high shutter speeds (due to excitement mostly), I'm not to be trusted with any test results anymore. LOL ;D


But now that I remember, last night I got to thinking...

Fingalo?? Would it be possible to include more than just that 1EV value in Tv Bracketing? HDR photography is sometimes best with +2EV steps. Could that option be extended from 1/3, 2/3, 1, to include 1+1/3 (or 4/3), 1+2/3 (or 5/3), 2EV?

Would be NICE!


« Last Edit: 02 / December / 2007, 08:27:39 by Barney Fife »
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