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limiting min and max canon firmware shutterspeed

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Offline Mlapse

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limiting min and max canon firmware shutterspeed
« on: 07 / January / 2019, 15:29:37 »
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A while back I asked Waterwingz if he could alter UI so that it could exceed Canon's parameters, as I understand it cannot be done with scripts running canon's firmware.
this request is just the opposite.......
After thinking about it, i think it is more something to include in advaced image settings, i'm guessing the G series might have similar possibilitys.
That is, if there is interest from others....

Issue:
The M10 i'm currently testing has in P settings a range from 1/4000 to 30 seconds, especially the 30 sec is a bit much with an interval script...i obviously don't do astrophotography.

Request:
Would it be possible to create shutterspeed min and max settings that fall within canon's own min and max settings, like iso range settings?

I thought about testing it myself with an small, simple intervalometer script to see what would be optimal values.
i discovered i've got insufficient knowlegde to make it work, but it may give you an idea of what i am thinking of.

# low_limit_Tv      10     "Limit slowest shutter speed >" { Off 16sec 12 8 4 3 2sec 1.6 1.3 1sec 1/2sec}

-- speed table limit can be extended.
    speed_min =            low_limit_Tv
    speed_table_limit =    { 9999, -768, -576, -384, -288 -192, -96, -64, -32, 0, 96 }
    speed_min =            speed_table_limit[low_limit_Tv+1]

-- limits max exposure under canon firmware limits.
function limit_exposure()
    tv96current=get_tv96()
    if (tv96current <= speed_min) then
      tv96current=speed_min end
    return
end
 
« Last Edit: 07 / January / 2019, 16:01:30 by Mlapse »
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Offline reyalp

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Re: limiting min and max canon firmware shutterspeed
« Reply #1 on: 07 / January / 2019, 17:22:45 »
Quote from: Mlapse on 07 / January / 2019, 15:29:37
Request:
Would it be possible to create shutterspeed min and max settings that fall within canon's own min and max settings, like iso range settings?
I'm not sure I understand. If you are using a script, then the script can set the exposure however it wants.

CHDK currently cannot change what values the Canon auto exposure uses, so if a script changes one parameter, it must control them all. You can use Canon auto exposure to find out what the camera would have used, and then shuffle the values around using the APEX equation (see PDF at http://dougkerr.net/Pumpkin/#APEX for a good explanation).

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Offline Mlapse

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Re: limiting min and max canon firmware shutterspeed
« Reply #2 on: 08 / January / 2019, 02:47:21 »
Quote
I'm not sure I understand. If you are using a script, then the script can set the exposure however it wants.

CHDK currently cannot change what values the Canon auto exposure uses, so if a script changes one parameter, it must control them all.

So you are saying that it is not possible to send the original, possibly capped off Tv value back with the shoot command if it is a script that is running canon's firmware to calculate shoot conditions?
 
Then, read no further, I withdraw my request.

of intervalometers as far as i know only rawopint gives me the flexibility to limit exposure, correct me if i am wrong.
.....ok maybe also carlapse, but can't get that working to test.
i do not want to do a recalculation or change anything else, i only want to cap off exposure time to a preset point.
so images are still made, but getting (more) underexposed when they hit the cap.
it could also be helpfull if you shoot from a moving object. (f.i. limiting at 1/125 as minimum)
I can also imagine that people don't want a lapse recording in daytime shooting at 1/4000 continiously because of extra curtain wear, so that is why i think a cap at shortest shutter speed would also be helpfull...although this might also be solved by lowering iso speed. So in my opinion not nearly as interesting as limiting long exposures.
I would think it is something more people tend to use, if i'm wrong forget i ever asked.

at this moment if I run a canon firmware based intervalometer on my M10 at a sunset/sunrise it will never get dark at night with 30 seconds exposure...even at iso100. Not to mention the interval limit of >30sec.
« Last Edit: 08 / January / 2019, 07:39:54 by Mlapse »
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Offline Mlapse

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Re: limiting min and max canon firmware shutterspeed
« Reply #3 on: 08 / January / 2019, 13:55:42 »
i have found out a very weird thing on the M10...it is already in chdk in combination with canon's firmware (sort of that is)
so, put this request on hold, i'm going to test some more first
« Last Edit: 08 / January / 2019, 16:08:22 by Mlapse »
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Offline reyalp

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Re: limiting min and max canon firmware shutterspeed
« Reply #4 on: 08 / January / 2019, 17:26:15 »
Quote from: Mlapse on 08 / January / 2019, 02:47:21
So you are saying that it is not possible to send the original, possibly capped off Tv value back with the shoot command if it is a script that is running canon's firmware to calculate shoot conditions?
With script shoot(), you must set the exposure parameters before the half press starts, so you can't know what the Canon firmware would have used.

If you shoot using key presses, you can certainly modify the exposure after Canon AE, something like (Lua, off the top of my head, untested)
Code: [Select]
press'shoot_half'
repeat sleep(10) until get_shooting()

if get_tv96() > my_max_tv then
 set_tv96_direct(my_max_tv)
end
click'shoot_full'
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Offline Mlapse

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Re: limiting min and max canon firmware shutterspeed
« Reply #5 on: 08 / January / 2019, 18:06:32 »
ok, not possible, but...

i'm really onto something, it is going to take some time. to me, it looks like an interesting exploitable bug.
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Offline c_joerg

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Re: limiting min and max canon firmware shutterspeed
« Reply #6 on: 09 / January / 2019, 01:49:56 »
Quote from: Mlapse on 08 / January / 2019, 02:47:21
I can also imagine that people don't want a lapse recording in daytime shooting at 1/4000 continiously because of extra curtain wear, so that is why i think a cap at shortest shutter speed would also be helpfull

On short exposure times, not the curtain wear is the reason. They should try to follow the 180 degree shutter technique
https://forum.lrtimelapse.com/Thread-interval-shooting


If I understand @lapser correctly, then the life of the shutter is significantly reduced at shorter exposure times. Whenever possible I use an ND filter.
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Offline reyalp

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Re: limiting min and max canon firmware shutterspeed
« Reply #7 on: 09 / January / 2019, 23:14:51 »
Quote from: Mlapse on 08 / January / 2019, 18:06:32
ok, not possible, but...
Perhaps it doesn't work the way you expected, but it is absolutely possible to adjust exposure after canon AE. You just have to script the shot using key presses rather than shoot()
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Offline Mlapse

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Re: limiting min and max canon firmware shutterspeed
« Reply #8 on: 10 / January / 2019, 02:54:23 »
Quote
Perhaps it doesn't work the way you expected, but it is absolutely possible to adjust exposure after canon AE. You just have to script the shot using key presses rather than shoot()
I had no expectations on how it is done, i am still at the point of can it be done.
Is there a script available that uses key presses in that way?

What i'm hoping to achieve is  that my M10 shoots something that looks like the S95 shoot in this picture (where brightness of pictures followes the bv line)... but then with a user defined max exposure...the S95 is alas (or is that lucky?) bound to 1 second max exposure.
there was a time i was hoping the s95 max exposure could be increased to f. i. 1.3, 1.6 or 2 seconds. Ideally going from 1/125 to max exposure would be 1 to 3 steps brighter.
but with the M10 it is the other way around, and i thought that would be easyer, because it stayed withing canons settings instead of going beyond.
 
with 30 seconds exposure, the reults don't look like expected. it isn't really getting dark anymore. it just seems to move from sun to equally strong artificial light.
« Last Edit: 10 / January / 2019, 04:46:52 by Mlapse »
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Offline reyalp

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Re: limiting min and max canon firmware shutterspeed
« Reply #9 on: 10 / January / 2019, 16:41:43 »
Quote from: Mlapse on 10 / January / 2019, 02:54:23
Quote
Perhaps it doesn't work the way you expected, but it is absolutely possible to adjust exposure after canon AE. You just have to script the shot using key presses rather than shoot()
I had no expectations on how it is done, i am still at the point of can it be done.
Is there a script available that uses key presses in that way?
I'm not aware of any intervalometer scripts that do single shots like this, but there are plenty that modify exposure in half press. rawopint is an example.

It really shouldn't take much more than the snippet I posted earlier, something like

Code: [Select]
function my_shoot()
 press'shoot_half'
 repeat sleep(10) until get_shooting()

 if get_tv96() > my_max_tv then
  set_tv96_direct(my_max_tv)
 end
-- ... more exposure limits if you want
 click'shoot_full' -- implicitly releases half
 repeat sleep(10) until not get_shooting()
-- you might want to add some additional hard coded delay if you really need the shot to be finished when the function returns
end
Then replace shoot() with my_shoot() in your favorite shoot() based script.

A long time ago, CHDK didn't allow setting exposure using the normal override functions in half press (edit: although you could do it by fiddling propcases). A method I used to get a similar result was to press half shoot, release, get the exposure values, modify exposure, and then do shoot(). This was slower but worked fairly well as long as the scene didn't change too fast. But there's probably no reason to do this with modern CHDK.
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