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SX230 1.01A CHDK .jpg files too small

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SX230 1.01A CHDK .jpg files too small
« on: 31 / March / 2013, 08:36:26 »
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First: thanks to everyone who works on making CHDK possible, very much appreciated.

On my SX230 everything works as described except the Override JPG Quality option.  Whether I set this to Superfine, Fine, Normal or Off the resulting CHDK files are always about the same size and are always somewhat smaller than the non-CHDK mode Canon Normal files and much smaller than the Canon Fine files.

Close inspection of the CHDK jpgs does reveal less detail than the same picture at Canon Fine.

As an example I just took six pictures, tripod mounted, same exposure and zoom settings at the following settings and got file sizes (MBs) as follows:

CHDK mode:
Superfine - 1.88
Fine - 2.11
Normal - 1.85
Off - 1.85

Canon mode:
Fine - 4.63
Normal - 2.33

The camera was in Canon Normal compression during the CHDK part of the test.

Is this a bug that could be fixed, or is it possibly user error on my part?  I'd really like CHDK files of at least equal quality to Canon Fine.  Thanks,

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Offline srsa_4c

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Re: SX230 1.01A CHDK .jpg files too small
« Reply #1 on: 31 / March / 2013, 11:29:30 »
On my SX230 everything works as described except the Override JPG Quality option.  Whether I set this to Superfine, Fine, Normal or Off the resulting CHDK files are always about the same size and are always somewhat smaller than the non-CHDK mode Canon Normal files and much smaller than the Canon Fine files.
That's an unfortunate side effect of the memory allocation method this CHDK port has to use. See the camera's porting thread (use print view for better overview, search for "exmem").
Depending on what you use CHDK for, you may get away with a special build of the development version of CHDK (with exmem disabled). This might not be stable due to the low amount of free memory on this camera. If you'd like to try, just ask.

Re: SX230 1.01A CHDK .jpg files too small
« Reply #2 on: 31 / March / 2013, 13:20:23 »
I have two main intents for using CHDK 1) RAW capture and 2) HDR.  However since CHDK captures a jpg image with each dng that jpg allows me to use it instead of the extra effort of manipulating the dng if it suits (which is usually with higher iso pictures where generally I can't do better than the Canon jpg processing, and usually do worse).  So I'd like to have a high quality jpg available in CHDK mode so I could just stay in it instead of shifting in and out.

So if the build you're talking about would fit that purpose I'd like to try it.

Thanks,

Re: SX230 1.01A CHDK .jpg files too small
« Reply #3 on: 31 / March / 2013, 13:54:52 »
CHDK mode:
Superfine - 1.88
Fine - 2.11
Normal - 1.85
Off - 1.85

Canon mode:
Fine - 4.63
Normal - 2.33
There is something very wrong here if  Override JPEG Quality [ Off ]  produces a jpg any different than when CHDK is not even loaded!

Update : a quick look at the code in shooting.c  suggests that once you have change the quality to anything other than Off,  then I think you will need to reset the camera after you return it to the off position.  Setting a different quality value changes a PROPCASE value,  but setting it to Off does not reset that value.
« Last Edit: 31 / March / 2013, 14:01:02 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16


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Offline reyalp

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Re: SX230 1.01A CHDK .jpg files too small
« Reply #4 on: 31 / March / 2013, 14:00:02 »
On my SX230 everything works as described except the Override JPG Quality option.  Whether I set this to Superfine, Fine, Normal or Off the resulting CHDK files are always about the same size and are always somewhat smaller than the non-CHDK mode Canon Normal files and much smaller than the Canon Fine files.
That's an unfortunate side effect of the memory allocation method this CHDK port has to use. See the camera's porting thread (use print view for better overview, search for "exmem").
Wow, I somehow missed that the first time around. That's very bad, CHDK not using any overrides should not affect image quality. This should be documented prominently only the camera wiki page and notes. This should also be checked on other cameras that are forced to exmem.

@sx230user
Using the current autobuild, run the following lua script and report the value. This will tell us how much canon heap is available, which will tell us whether a non-exmem build is feasible:

Code: [Select]
print(get_meminfo('sys').free_size)
Don't forget what the H stands for.

Re: SX230 1.01A CHDK .jpg files too small
« Reply #5 on: 31 / March / 2013, 14:02:05 »
Wow, I somehow missed that the first time around.
See the edit to my previous post - its been in CHDK for a long time I think.
Ported :   A1200    SD940   G10    Powershot N    G16

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Offline reyalp

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Re: SX230 1.01A CHDK .jpg files too small
« Reply #6 on: 31 / March / 2013, 14:03:34 »
Here is the post from funnel describing the issue http://chdk.setepontos.com/index.php?topic=6397.msg83414#msg83414
Don't forget what the H stands for.

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Offline reyalp

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Re: SX230 1.01A CHDK .jpg files too small
« Reply #7 on: 31 / March / 2013, 14:04:37 »
Wow, I somehow missed that the first time around.
See the edit to my previous post - its been in CHDK for a long time I think.
Correct, that's a known defect of the quality override code, but not related to the issue that srsa is describing.
Don't forget what the H stands for.


Re: SX230 1.01A CHDK .jpg files too small
« Reply #8 on: 31 / March / 2013, 14:06:42 »
Correct, that's a known defect of the quality override code, but not related to the issue that srsa is describing.
Yes - but it does explains why sx230user got the wrong jpeg size when he had the override set to [ Off ].
Ported :   A1200    SD940   G10    Powershot N    G16

Re: SX230 1.01A CHDK .jpg files too small
« Reply #9 on: 31 / March / 2013, 14:38:33 »
I have two main intents for using CHDK 1) RAW capture and 2) HDR.  However since CHDK captures a jpg image with each dng that jpg allows me to use it instead of the extra effort of manipulating the dng if it suits (which is usually with higher iso pictures where generally I can't do better than the Canon jpg processing, and usually do worse).  So I'd like to have a high quality jpg available in CHDK mode so I could just stay in it instead of shifting in and out.

So if the build you're talking about would fit that purpose I'd like to try it.
You don't need a special build.  Based on the previous posts,  just leave the Override JPEG Quality set to [ Off ]  (reseting the camera if you needed to change it to be Off) and you should get the normal Canon quality.
Ported :   A1200    SD940   G10    Powershot N    G16

 

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