Long-Exposure Continuous Shooting (for star trails or other uses)

bananaman

Hello!
I have recently figured out how to write a script that I've been meaning to do for a while.
It allows you to take any number of pictures, each with an exposure between 1 and 60 seconds (you pick the number of seconds)

This is useful for star trails or other astrophotography uses.
It was tested on the SD960IS, firmware 1.01d, but it should work on any camera.
This is written in LUA, so if you want it, copy it, paste it into a text editor (not a word editor), and save it as "whatever_you_want_to_call_it.lua"
Or, you can download the attachment.

--[[
@title Long-Exposure Continous Shooting
@param a Exposure Time (Seconds)
@default a 10
@param b Number of Shots
@default b 10
]]

--This is an array of TV96 values for exposure tomes 1-60 seconds.
--It is indexed by the exposure time in seconds.
expVAL = {0, -96, -152, -192, -223, -248, -270, -288, -304, -319, -332, -344, -355, -366, -375, -384, -392, -400, -408, 415, -422, -428, -434, -440, -446, -451, -456, -462, -466, -471, -476, -480, -484, -488, -492, -496, -500, -504, -507, -511, -514, -518, -521, -524, -527, -530, -533, -536, -539, -542, -545, -547, -550, -552, -555, -558, -560, -562, -565, -567}

--This is the main part of the script.
for i = 1,b do
print( "Shot", i)
set_tv96_direct( expVAL[a] )
sleep( 100 )
shoot()
sleep( 1000 )
end

Hope you enjoy it!

Star_Trails.lua

758b

lapser

Great job! You solved the problem of converting seconds to tv96. Here's a couple of suggestions:

What happens if the user enters 61 seconds? How about -1 seconds?

If you indent blocks of code, i.e. between "for" and "end", it makes it easier to read.

By using shoot(), you'll be re-focusing for each shot. You'll need to be in aperture priority mode, and fixed ISO to get consistent exposure for all shots.

It will take several seconds between shots this way, where the shutter is closed. This will produce dotted or dashed line star trails.

To solve both of these problems, you could shoot in continuous mode with just press("shoot_full"). If you want to count the number of shots, try using the function: get_exp_count().

waterwingz

lapser
What happens if the user enters 61 seconds? How about -1 seconds?

Looks like a great place to use the @value feature added in the 1.2.0 dev branch.

lapser

waterwingz
Looks like a great place to use the @value feature added in the 1.2.0 dev branch.

Good idea! I'll have to use it in the future. It looks like this option would do the trick:
@range x n m

waterwingz

lapser

waterwingz
Looks like a great place to use the @value feature added in the 1.2.0 dev branch.

Good idea! I'll have to use it in the future. It looks like this option would do the trick:
@range x n m

Even better for this application.

bananaman

I've re-done it with range, and setting ISO.
I don't need to screw with the aperture, as mine is one of the cameras that uses an ND filter.
Here is the new code:

--[[
@title Long-Exposure Continuous Shooting
@param a Exposure Time (Seconds)
@default a 10
@range a 1..60
@param b Number of Shots
@default b 10
]]

--This is an array of TV96 values for exposure times 1-60 seconds.
--It is indexed by the exposure time in seconds.
expVAL = {0, -96, -152, -192, -223, -248, -270, -288, -304, -319, -332, -344, -355, -366, -375, -384, -392, -400, -408, 415, -422, -428, -434, -440, -446, -451, -456, -462, -466, -471, -476, -480, -484, -488, -492, -496, -500, -504, -507, -511, -514, -518, -521, -524, -527, -530, -533, -536, -539, -542, -545, -547, -550, -552, -555, -558, -560, -562, -565, -567}

--This is the main part of the script.
for i = 1,b do
print( "Shot", i)
set_iso_real( 80 )
set_tv96_direct( expVAL[a] )
sleep( 100 )
shoot()
end

Hope you like it!
Thanks for the suggestions!

Star_Trails.lua

779b

lapser

bananaman
[code]
--[[
@title Long-Exposure Continuous Shooting
@param a Exposure Time (Seconds)
@default a 10
@range a 1..60
@param b Number of Shots
@default b 10
@range a 0..9999
]]

--This is an array of TV96 values for exposure times 1-60 seconds.
--It is indexed by the exposure time in seconds.
expVAL = {0, -96, -152, -192, -223, -248, -270, -288, -304, -319, -332, -344, -355, -366, -375, -384, -392, -400, -408, 415, -422, -428, -434, -440, -446, -451, -456, -462, -466, -471, -476, -480, -484, -488, -492, -496, -500, -504, -507, -511, -514, -518, -521, -524, -527, -530, -533, -536, -539, -542, -545, -547, -550, -552, -555, -558, -560, -562, -565, -567}
--This is the main part of the script.
--MUST BE IN CONTINUOUS DRIVE MODE
if(b>0)then
b=b+get_exp_count()
end
if(b>9999)b=b-9999 -- starts from 1 again
set_iso_real( 80 )
set_tv96_direct( expVAL[a] )
press("shoot_full") -- holds shutter down in continuous mode
repeat sleep(10) until get_exp_count()==b

[/code]
Hope you like it!

Looks good. I modified it slightly to work in continuous mode, but haven't tested it. Be sure the camera is in continuous mode before starting the script, or it will take one picture and hang. You can add a test for this if you like.

get_exp_count() goes from 1 to 9999 on my camera, and back to 1. It corresponds to the file name of the jpg, i.e. img_9999. So if you set the number of shots to 0, it will take pictures until you interrupt the script by pressing the shutter button.

If you want a shorter script, you can skip the shot counting and just end with:

repeat sleep(100) until false

Intheswamp

Beware...first time poster here. 😉

I stumbled upon CHDK a few weeks ago and it has breathed life into my lowly A1200. 😀 My thanks to everyone who works and has worked on this project!

I'm no computer expert but I did manage to load v1.00C onto a card and I'm figuring out how to use some of the different scripts. I was wanting something to give me long exposure times and also continuous shooting for catching lightening strikes and possibly star trails and meteors. I have managed to get bananaman's scripts working including the one where he adds the ISO statement.

When I try to use lapsers script, though, I run into an error...

:19: 'then' expected near 'b'
PRESS SHUTTER TO CLOSE

Is the A1200 simply not a camera that can use this script or is something 'off' about the script?

Thanks,
Ed

ETA: Ok, my camera had the 100c firmware and I installed CHDK onto it...I'm learning. :😀

ahull

Looks like you may not have copied the whole script... can you post what you tried to run here, and let us know which post you fond the script in, so we can get a better understanding of the issue.

Intheswamp

The reply just above my first post...#6 I believe, is where I got the non-working script. Looking at it I don't see an "end" statement (I guess it needs one?) so it may just be a portion of a script that Lapser intended to post as an example to bananaman...I may have taken something as being a script, that wasn't. 😳 I'm guessing from the error I received that a 'then' statement is needed in line #19. I'm no code write...just an 'anklebone connected to legbone' kind of guy. 😳 Thanks for your help. Ed

--[[
@title Long-Exposure Continuous Shooting
@param a Exposure Time (Seconds)
@default a 10
@range a 1..60
@param b Number of Shots
@default b 10
@range a 0..9999
]]

--This is an array of TV96 values for exposure times 1-60 seconds.
--It is indexed by the exposure time in seconds.
expVAL = {0, -96, -152, -192, -223, -248, -270, -288, -304, -319, -332, -344, -355, -366, -375, -384, -392, -400, -408, 415, -422, -428, -434, -440, -446, -451, -456, -462, -466, -471, -476, -480, -484, -488, -492, -496, -500, -504, -507, -511, -514, -518, -521, -524, -527, -530, -533, -536, -539, -542, -545, -547, -550, -552, -555, -558, -560, -562, -565, -567}
--This is the main part of the script.
--MUST BE IN CONTINUOUS DRIVE MODE
if(b>0)then
  b=b+get_exp_count()
end
if(b>9999)b=b-9999 -- starts from 1 again
set_iso_real( 80 )
set_tv96_direct( expVAL[a] )
press("shoot_full") -- holds shutter down in continuous mode
repeat sleep(10) until get_exp_count()==b

Intheswamp

Hmm, well I tried modifying the scrip by inserting the red words...

if(b>9999) then b=b-9999 -- starts from 1 again
set_iso_real( 80 )
set_tv96_direct( expVAL[a] )
press("shoot_full") -- holds shutter down in continuous mode
repeat sleep(10) until get_exp_count()==b
end

It gave no error but simply resulted in a quick

***STARTED***
***FINISHED***

and no pictures taken. Can you tell I know nothing about writing scripts? (But I'm willing to learn. 😀 )

reyalp

Intheswamp
...
It gave no error but simply resulted in a quick
[code]***STARTED***
***FINISHED***[/code]
and no pictures taken. Can you tell I know nothing about writing scripts? (But I'm willing to learn. 😀 )

That script will do nothing if the b is less than 9999, since you've put the entire body inside the if statement.
What you probably want is

if(b>9999) then
 b=b-9999
end

You can probably find some beginner Lua tutorials on the web, it's used for many things other than CHDK.

Intheswamp

But reyalp, I had made those changes as mentioned above but it still didn't work. ???

Should there be spaces in between some of the statements.

Such as:

'if (b>9999)' rather than 'if(b>9999)'

??

waterwingz

I fixed the two syntax errors in the @parameters section.

--[[
@title Long-Exposure Continuous Shooting
@param a Exposure Time (Seconds)
@default a 10
@range a 1 60
@param b Number of Shots
@default b 10
@range b 0 9999
]]

--This is an array of TV96 values for exposure times 1-60 seconds.
--It is indexed by the exposure time in seconds.
expVAL = {0, -96, -152, -192, -223, -248, -270, -288, -304, -319, -332, -344, -355, -366, -375, -384, -392, -400, -408, 415, -422, -428, -434, -440, -446, -451, -456, -462, -466, -471, -476, -480, -484, -488, -492, -496, -500, -504, -507, -511, -514, -518, -521, -524, -527, -530, -533, -536, -539, -542, -545, -547, -550, -552, -555, -558, -560, -562, -565, -567}
--This is the main part of the script.
--MUST BE IN CONTINUOUS DRIVE MODE
if(b>0)then
  b=b+get_exp_count()
end
if(b>9999) then b=b-9999 end -- starts from 1 again
print("exp:",expVAL[a])
sleep(2000)
set_iso_real( 80 )
set_tv96_direct( expVAL[a] )
press("shoot_full") -- holds shutter down in continuous mode
repeat sleep(10) until get_exp_count()==b

It mostly works as long as you have the camera set to Continuous shooting mode.

However, in testing on two different camera models, I noticed that it sometimes does not set the shutter time correctly. I get 1/20 of a second rather than 5 seconds for example- the correct exposure was 1/20 so the camera is shooting without the override..

If I immediately rerun the script, it shoots with a 5 second exposure on the second try and every subsequent try. Changing the shutter time sometimes causes it to shoot at 1/20 the first time and then back to the new time after that.

Strange.

reyalp

Intheswamp
But reyalp, I had made those changes as mentioned above but it still didn't work.

So, there were even more problems.

Should there be spaces in between some of the statements.

http://www.lua.org/manual/5.1/

edit to be slightly more helpful:

In general, whitespace doesn't mater in Lua, unless it is necessary to distinguish keyword or variable names

if(b>9999)then
if ( b > 9999) then
if b>9999 then

are all equally valid.

ifb>9999then

isn't, because it would be trying to compare something called ifb to 9999then (which isn't even a valid name)

If you do something like that, you would generally get an error of some kind rather than the script just not doing anything.

reyalp

waterwingz
If I immediately rerun the script, it shoots with a 5 second exposure on the second try and every subsequent try. Changing the shutter time sometimes causes it to shoot at 1/20 the first time and then back to the new time after that.

I would expect this has something to do with the fact it doesn't pre-shoot, just does shoot_full immediately.

waterwingz

reyalp
I would expect this has something to do with the fact it doesn't pre-shoot, just does shoot_full immediately.

I tried this :

press("shoot_half") 
repeat sleep(50) until get_shooting() == true
set_iso_real( 80 )
set_tv96_direct( expVAL[a] )
press("shoot_full") 
repeat sleep(10) until get_exp_count()==b
release("shoot_full")
release("shoot_half")

but it did not override the exposure time at all ???

reyalp

waterwingz

but it did not override the exposure time at all ???

The override functions need to be called before half_shoot.

waterwingz

reyalp
The override functions need to be called before half_shoot.

Thanks - I always get confused about that. Seems like the half_shoot is where the camera decides on the exposure and focus settings, so you'd want to insert the overrides after that?

waterwingz

That seems to be better. First time I ran the script it shot at 1/20 rather than 10 seconds. But now I can't repeat that. Might be confounded at this point with whatever philmoz found in the script parameters "bug".

--[[
@title Long-Exposure Continuous Shooting
@param a Exposure Time (Seconds)
@default a 10
@range a 1 60
@param b Number of Shots
@default b 10
@range b 0 9999
]]

--This is an array of TV96 values for exposure times 1-60 seconds.
--It is indexed by the exposure time in seconds.
expVAL = {0, -96, -152, -192, -223, -248, -270, -288, -304, -319, -332, -344, -355, -366, -375, -384, -392, -400, -408, 415, -422, -428, -434, -440, -446, -451, -456, -462, -466, -471, -476, -480, -484, -488, -492, -496, -500, -504, -507, -511, -514, -518, -521, -524, -527, -530, -533, -536, -539, -542, -545, -547, -550, -552, -555, -558, -560, -562, -565, -567}
--This is the main part of the script.
--MUST BE IN CONTINUOUS DRIVE MODE
if(b>0)then
  b=b+get_exp_count()
end
if(b>9999) then b=b-9999 end -- starts from 1 again
print("exp:",expVAL[a])
sleep(2000)
set_iso_real( 80 )
set_tv96_direct( expVAL[a] )
press("shoot_half")
repeat sleep(50) until get_shooting() == true
press("shoot_full") 
repeat sleep(10) until get_exp_count()==b
release("shoot_full")
release("shoot_half")