@reyalp As you may have spotted in the post above, I’ve made a first attempt at an ‘ETTR Meter’.
In attempting to understand the CHDK histogram, but not being a c programmer, I believe we might wish to tweak some of the CHDK manual…but I could be wrong ;-)
My understanding is that the CHDK histogram, eg see
https://photopxl.com/a-better-histogram/, does not show a stops based view, but a linear view, as shown in figure 4 in the link. Or does it show a gamma view?
If I look at the drawing code in the histogram.c, I come across this:
if (conf.histo_show_ev_grid) for (i=1;i<=4;i++) draw_line(x+(1+w)*i/5, y, x+(1+w)*i/5, y+h, FG_COLOR(conf.histo_color2));
That is, as I’ve speculated in my blog post, CHDK, like the Canon Histo, doesn’t divide the Histo into stops, but simply linearly across the Histo range, ie 0-255. Thus the right most divider line, is at 1/5 of the Histo range, which is at about 1/3 Ev down from highlight saturation.
If I’m right we may wish to make this clearer to the user, that the vertical grid lines are not stops.
But, as I say, I may be totally wrong ;-)
As usual I welcome your insight.
Cheers
Garry
