Infinity Subject Distance on various cameras.

cppasm

« on: 18 / January / 2012, 08:28:15 »

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Hi.
Can somebody post here value from Property Case 65 (0x41) when camera is set to manual focusing mode and manually focused to infinity?
You can see this value in the Menu->Debug->Show PropCases when page number is set to 6.
I am especially interested in values from G12, SX30 and SX40.
Most cameras have infinity value equal to 65535 (0xFFFF), but it looks like this was changed in newer cameras.
This is required to properly store subject distance in the DNG metadata.

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TobiMarg

Re: Infinity Subject Distance on various cameras.

« Reply #1 on: 18 / January / 2012, 13:34:19 »

Hi
I have a SX230HS. The smallest value from Property Case 65 is 99 and if I focus to infinity it is -1.

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philmoz

3385

Re: Infinity Subject Distance on various cameras.

« Reply #2 on: 18 / January / 2012, 14:08:31 »

Quote from: cppasm on 18 / January / 2012, 08:28:15

I am especially interested in values from G12, SX30 and SX40.

Infinity = 4294967295 (0xFFFFFFFF) on these cameras (and the IXUS310).
CHDK treats the value as a signed int so displays it as -1.

Previously the CHDK code assumed subject distance was a 16 bit value and locked the maximum override value sent to the camera to 65535. This caused problems on my cameras - especially the superzooms.

I suspect most other new cameras are the same; but I can't test them which is why I made the change configurable and only enabled it for mine.

The change is discussed here http://chdk.setepontos.com/index.php?topic=2509.105

Phil.

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CHDK ports:
sx30is (1.00c, 1.00h, 1.00l, 1.00n & 1.00p)
g12 (1.00c, 1.00e, 1.00f & 1.00g)
sx130is (1.01d & 1.01f)
ixus310hs (1.00a & 1.01a)
sx40hs (1.00d, 1.00g & 1.00i)
g1x (1.00e, 1.00f & 1.00g)
g5x (1.00c, 1.01a, 1.01b)
g7x2 (1.01a, 1.01b, 1.10b)

cppasm

Re: Infinity Subject Distance on various cameras.

« Reply #3 on: 19 / January / 2012, 06:36:41 »

Thanks guys.

Quote

Previously the CHDK code assumed subject distance was a 16 bit value and locked the maximum override value sent to the camera to 65535.

It indeed was 16-bit unsigned integer as I can see in disassembler and native firmware reported 0xFFFF when manually focused to infinity, even if value was read as 32-bit integer.
Looks like it was changed in newer cameras, because I've disassembled SX30 firmware and it uses 32-bit value.

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