extra long exposures (split from: Hardcore modding on a A530, thanks to CHDK!

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Offline ewavr

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Regarding the sensor exposure, it may be that the sensor has a 16b internal counter, in 1ms increments, so 65 seconds is the most it can get until the timer overflows. I don't see any other reason why it would stop at this magic number.

Of course, this is software-only limitation.
For example, picture taken with 150s exposure (without dark frame subtraction) - http://ewavr.nm.ru/chdk/for_test/IMG_0260.JPG (4 Mb).
Image quality is really horrible.

How? This is my secret  :).

Well, we call modified SetShutterSpeedWithMecha() (more precisely, modified sub_FFCA4008) in capt_seq_hook_set_nr():

void capt_seq_hook_set_nr(){
 .....
 sub_FFCA4008_my(-694);  // = 150s
 .....
}

sub_FFCA4008_my is exact copy of sub_FFCA4008, except:

ROM:FFCA4060                 MOV     R0, R4         
ROM:FFCA4064                 BL      sub_FFCA5104 ; convert Tv in APEX units to microseconds; limitation is here! 
ROM:FFCA4068                 MOV     R4, R0         

replaced with

                 "MOV     R0, R4\n"
              //   "BL      sub_FFCA5104\n"
                 "LDR     R0, =150*1000000\n"  // exposure time in microseconds
                 "MOV     R4, R0\n"

Of course, this is quick working example only, not complete solution.

edit:

Finally I did it for A710 private build (http://trac.assembla.com/a710/changeset/42).
Here is 160s exposure time with dark frame subtraction : http://ewavr.nm.ru/chdk/for_test/IMG_0271.JPG
Image quality is still very bad.
« Last Edit: 02 / April / 2009, 20:59:55 by ewavr »

RaduP, yes, on the LCD and the 114/500 telescope (f/4.4 theorical) I can see stars up to magnitude 5 and a little more. Open cluster M7, its brighest stars appear in real time.

ewavr: THIS IS GREAT! I wonder if it's possible to do the same on my A530. Tell me, if it is possible, what can I do to change the exposure time? I'm not a programmer guy, however I'll take a look at your work.

Leo

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Offline ewavr

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I wonder if it's possible to do the same on my A530.

I'm very unsure about a530, it have different from a710 firmware structure  :(.
Here is test version - http://ewavr.nm.ru/chdk/for_test/a530.zip
Set in extra photo operations:
 - shutterspeed enum type = Factor
 - Value factor = desired factor (10, for example)
 - 0verride shutter speed = desired shutter speed (10, for example; total time in this case is 100s)

If in this case exposure time is still 64s, please write bug-report.
« Last Edit: 03 / April / 2009, 05:14:15 by ewavr »

Man, you are AWESOME!

It worked right away. I loaded the CHDK like always, and setted the new exposure times, as follows:

30 secs - OK
60 secs - OK
90 secs - OK (!!)
120 secs - OK
180 secs - OK
240 secs - OK
300 secs - OK
480 secs - OK (8 minutes exposure time!!)

Didn't tried more time.

The extended exposure times, I believe, is a feature that must be on the official CHDK releases.

Here I attach some images, with the amp off at ISO 100

A big thank you from Argentina!!


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Offline PhyrePhoX

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niiice.
leonardo - adding this to the main chdk branch certainly would/will take a while, as only a few people are able to do it, as it involves asm "magic" and most certainly a lot of time.

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Offline ewavr

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Didn't tried more time.

I tried even 10 minutes exposure (+10 minutes dark frame) - http://ewavr.nm.ru/chdk/for_test/IMG_0276.JPG (ISO80, F/8). In this mode battery life is 5-10 shoots  :D.

Quote
The extended exposure times, I believe, is a feature that must be on the official CHDK releases.

This is a lot of work  :(. Now I can add to "official" release a530 and a710 only (diff is attached).
If somebody really needs this feature, please report me via PM or forum.

edit: edit. edit. edit.
« Last Edit: 03 / April / 2009, 21:32:20 by ewavr »

Thanks ewavr.

If you ever need to do beta testing on other camera models, I have a lot of astro-friends that shoot with A570 (mostly) and A620.

Regards, Leo

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Offline RaduP

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Would it be possible to post some long exposure stuff converted from RAW? In the pictures you posted (the 10 minutes exposure), there is a lot of noise sharpening, so 1 bad pixel affects 10-20 pixels.


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Offline fudgey

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I'll try this out for a570 100e today, at first glance it looks very similar to a710 (will update later, I'm posting this to prevent unnecessary duplicate work).

edit: I just did my first 120 second exposure on a570is 100e. :xmas
I'll need to test it a bit more, clean up the code and see if 101a can use the same or almost same code before I post it.
« Last Edit: 04 / April / 2009, 12:05:53 by fudgey »

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Offline ewavr

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Would it be possible to post some long exposure stuff converted from RAW?

RAW is not better than JPEG.
Here is DNG for 10 min exposure - CRW_0276.7z - 6.25MB

 

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