Whoa! ****MAJOR**** High-Speed Shutter-Speed Discovery! - page 7 - Creative Uses of CHDK

GrAnd

916
[A610, S3IS]

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #60 on: 04 / December / 2007, 02:51:20 »

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I also tried to make fotos of my Dremel at 33000rpm by A610 without flash.
It looks like the shortest shutter speed is about 1/15000, because on shorter speeds there is no significant changes nether in sharpness nor in brightness of picture.
Here is the gallery with shots made with shutter speed from 1/2500 to 1/100000. I do not have any bright spotted light, so I used just 135W luminescent lamp. (Sorry, the interface of that site is in Russian, but filenames are self-explanatory)

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a710is

250
A710 IS

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #61 on: 04 / December / 2007, 04:18:22 »

so I guess we have a faster shutter speed, but the flash makes it even faster.
it would be interesting to find out just how fast the exposure is when the flash is also involved. the 30000 rpm dremel in that flash pic came out sharper than the one in GrAnd's pics

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a710is

250
A710 IS

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #62 on: 04 / December / 2007, 04:48:56 »

I'm asking again cause I've seen no answer:
is there a script that allows the user to set his own time? cause Fingalo's build only allows 1/10000 and I wanna take test shots at higher speeds. doing that in the tv bracketing is not the ideal way.

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GrAnd

916
[A610, S3IS]

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #63 on: 04 / December / 2007, 05:11:55 »

Quote from: a710is on 04 / December / 2007, 04:18:22

the 30000 rpm dremel in that flash pic came out sharper than the one in GrAnd's pics

Because xenon flash can achieve 1/100000.

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CHDK Developer.

a710is

250
A710 IS

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #64 on: 04 / December / 2007, 05:24:47 »

well in that case we can get 1/100000s pictures with the use of flash.

. even though the shutter time is longer, it's the lit interval that's gonna stay in the picture. now that's tight

« Last Edit: 04 / December / 2007, 05:26:38 by a710is »

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GrAnd

916
[A610, S3IS]

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #65 on: 04 / December / 2007, 05:25:47 »

Quote from: a710is on 04 / December / 2007, 04:48:56

Is there a script that allows the user to set his own time? cause Fingalo's build only allows 1/10000 and I wanna take test shots at higher speeds. doing that in the tv bracketing is not the ideal way.

I wrote my own. It's very simple, but it stand on the SD-card at home. So, I'll try to reproduce it here (may contain errors):

Code: [Select]

@title Custom Tv
@param a Start Tv
@default a 1084
@param b Finish Tv
@default b 1278
@param c Increment
@default c 32

while a <= b
  set_tv_override a
  shoot
  a = a + c
  sleep 300
wend

end

The start and finish Tv values are in 'PropertyCase's. How to convert Tv to PropertyCase value you can find the correspondence table on Fingalo's page. Or use this calculator.

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CHDK Developer.

a710is

250
A710 IS

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #66 on: 04 / December / 2007, 06:00:37 »

I've modified your script to this:

Code: [Select]

@title Custom Tv
@param a Start Tv
@default a 1276
@param b Finish Tv
@default b 1564
@param c Increment
@default c 32

while a <= b
  set_tv_override a
  shoot
  a = a + c
  sleep 300
wend

end

I now had a very adequate light source and the brightness keeps clearly decreasing until PropCase 1468 meaning basically 1/40000 I suppose

one thing I now noticed that I didn't know is that scripts remain in the camera's memory even when it's turned off and that also seems to be the case with the last zebra frame. the camera doesn't load a script from the SD when it turns back on, but from its memory.

« Last Edit: 04 / December / 2007, 06:03:07 by a710is »

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a710is

250
A710 IS

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #67 on: 04 / December / 2007, 06:34:02 »

the results aren't always consistent
the brightness in another light bulb test only seemed to decrease until 1/20.000

I did another test with sunlight (pointing at the -cloudy- sky)
first test the brightness kept decreasing until 1/20000
2nd test it decreased until 1/40000

however it happens that for example the 7th bracketed picture (1/40000s) is darker than the 4th (1/20000s), while the 5th and 6th are a bit brighter than the 4th or of similar brightness.

I guess in my cam's case the shutter override values that would need to be added would be the ones with these prop cases:
1308 ~1/12500
1340 ~1/16000
1372 ~1/20000
1468 ~1/40000

I wish that a script in which you can precisely set the shutter time would exist, and not bracketing, cause when bracketing you can hear the camera "getting tired" and working more and more slowly.
maybe it would go to even lower times if it wasn't bracketing

« Last Edit: 04 / December / 2007, 06:39:00 by a710is »

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GrAnd

916
[A610, S3IS]

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #68 on: 04 / December / 2007, 06:57:54 »

Quote from: a710is on 04 / December / 2007, 06:00:37

I've modified your script to this:

You needn't have modified my script to change the initial values. You could change parameters through menu.

Quote from: a710is on 04 / December / 2007, 06:00:37

one thing I now noticed that I didn't know is that scripts remain in the camera's memory even when it's turned off and that also seems to be the case with the last zebra frame. the camera doesn't load a script from the SD when it turns back on, but from its memory.

Nothing is kept in the memory. But script parameters are saved in the CHDK.cfg. If you loads an another script they set to default. But if you change the defaults in the script, they will not apply, because the script name is the same as before, and saved values will be used.

« Last Edit: 04 / December / 2007, 06:59:56 by GrAnd »

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CHDK Developer.

GrAnd

916
[A610, S3IS]

Re: Whoa! MAJOR High-Speed Shutter-Speed Discovery!

« Reply #69 on: 04 / December / 2007, 07:29:04 »

Quote from: Woodsman on 04 / December / 2007, 07:15:22

GrAnd? Is there a simple way where the calculated shutter speed in 1/seconds could be written to a file or displayed on the screen? (My math-brain ain't what it used to be for routines like that.)

Sure. You can find the formula in my xls-calculator.

To draw a Tv in the format "1/x" you have to calculate x using this formula:
x = pow(2, <propcase_value> / 96)
in other words, x = 2^{<propcase_value> / 96}
That's it. But you can't do this math in script due to absence of pow() function.

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