Spot meter - Feature Requests - CHDK Forum  

Spot meter

  • 3 Replies
  • 1224 Views
Spot meter
« on: 06 / February / 2013, 15:14:19 »
Advertisements
If I use my handheld spot meter I know I am metering through a 1 degree field of view.

In my cameras a spot meter is much wider than this and varies with each camera.

I wondered if it would be possible for CHDK to have a means of metering the centre spot of the sensor at a given angular value, eg 1 degree.

This would help those of use that use zone metering.

*

Offline lapser

  • *****
  • 1093
Re: Spot meter
« Reply #1 on: 06 / February / 2013, 16:09:38 »
If I use my handheld spot meter I know I am metering through a 1 degree field of view.

In my cameras a spot meter is much wider than this and varies with each camera.

I wondered if it would be possible for CHDK to have a means of metering the centre spot of the sensor at a given angular value, eg 1 degree.
I can do that after the shot and return a Bv for any specified area of the picture. You can then use this value to take another shot.

Pre-shot metering isn't available yet. There's a pre_shot live histogram available, but that uses the full picture area. It might be possible to turn the pre-shot histogram into a Bv value. I'm not sure how accurate it would be, or how hard it would be to program.

But if you're willing to throw away one shot, and use the 2nd one, I should have something ready soon.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

Re: Spot meter
« Reply #2 on: 07 / February / 2013, 05:57:23 »
I wondered if it would be possible for CHDK to have a means of metering the centre spot of the sensor at a given angular value, eg 1 degree.

SDM already supports a spotmeter :-

uBasic command readYUV reads the luminance and UV chroma values from a 24 x 16 pixel area at the centre of the screen.

See 'readYUV' here http://stereo.jpn.org/eng/sdm/ubasic.htm .

Re: Spot meter
« Reply #3 on: 16 / August / 2013, 23:36:30 »
uBasic command readYUV reads the luminance and UV chroma values from a 24 x 16 pixel area at the centre of the screen.
See 'readYUV' here http://stereo.jpn.org/eng/sdm/ubasic.htm .
follow-up here :  http://chdk.setepontos.com/index.php?topic=8997.msg104158#msg104158
Ported :   A1200    SD940   G10    Powershot N    G16


 

Related Topics