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Shot_histo help

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Online reyalp

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Re: Shot_histo help
« Reply #10 on: 15 / July / 2020, 13:49:34 »
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@c_joerg

Thanks; I’ll have a look.
If I understand correctly, you want to measure histogram values in terms of "stops" from white level. If so, rawopint https://chdk.fandom.com/wiki/Lua/Scripts:_Raw_Meter_Intervalometer also has examples.

from exp:init_frame()
Code: [Select]
self.white_level=rawop.get_white_level()
-- histo limits in shot histo units
-- lowest value to count as over exp, as shot histo value
-- = raw(ev(whitelevel) - margin_ev)/(2^(bpp - histo_bpp))
self.over_histo_min = bitshru(rawop.ev_to_raw(rawop.raw_to_ev(self.white_level)-self.over_margin_ev),rawop.get_bits_per_pixel() - 10)
-- highest value to count as under exp, as shot histo value
-- = raw(-margin_ev)/(2^(bpp - histo_bpp))
self.under_histo_max = bitshru(rawop.ev_to_raw(-self.under_margin_ev),rawop.get_bits_per_pixel() - 10)
Don't forget what the H stands for.

Re: Shot_histo help
« Reply #11 on: 15 / July / 2020, 14:39:33 »
@reylap

Thanks for the link to rawopint.

Had a quick look and realise I need to look/study it a lot more before I consider ‘exploiting’ bits of it.

For now, using get_histo_range approach is ‘good enough’ for my needs ;-)

Cheers

Garry

 

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