Hi, Stefan,
i dont understand the new maximum aperture priority mode in the update. From the diagram in the pdf
http://www.ricoh-imaging.co.jp/english/support/digital/pdf/gr_vup_en.pdf
it looks like it is just going to keep f 2.8 out to 1/500 instead of closing down the aperture appropriately. doesn't this mean it will blow the highlights?
It's been about ten years since I considered exactly how programmed exposure curves work, and I don't know all the conventions on these. But let me try and help you to understand the chart, and in the process perhaps figure out the significance of the "maximum aperture" mode.
Basically the horizontal scale is of exposure time (shutter speed) and the vertical scale is of aperture (f-number).
The "input to the calculations" is the measured light value (scene luminance). That scale runs diagonally up and to the right. Various values along it are given by the diagonal lines (labeled at their leftmost ends).
This scale is labeled Lv when I would expect it to be Bv, so there is come curiosity there, but I will not deal with that right here. It should not screw up the principle I want to describe.
I believe that the heavy line is the "programmed exposure mode program line".
To understand how the chart works, let's work on the lower figure ("maximum aperture priority mode").
Imagine first that the measured scene luminance is LV1. If we look at that diagonal line and follow it to where it intersects the the heavy ("program") line, and then read the horizontal and vertical coordinates of that point,, we see that this would lead to a shutter speed of 4 sec and an aperture of f/2.8.
Next imagine that the scene luminance is much greater, say LV11 (10 stops higher). Follow the diagonal LV11 line until it intersects the program line. We see that for that scene luminance, the system would set a shutter speed of 1/250 sec and again an aperture of f/2.8 (a photographic exposure of 10 stops less).
Next imagine that the measured scene luminance is greater yet, say LV14 (3 stops higher yet). The same procedure will show us that the system would set a shutter speed of 1/1000 and an aperture of f/4 (a photographic exposure of 3 stops less yet).
Now consider a measured luminance of LV18 (5 stops higher yet). The same procedure will show us that for this, the system would set a shutter speed of 1/4000 and an aperture of f/8 (a photographic exposure of 5 stops less yet).
So we see that there is no "overexposure" over this 17-stop (131,000:1) range of scene luminance. The photographic expsure tracks exactly with scene luminance.
Comparing the two program lines, I note that in the "normal" programmed mode, when the scene luminance reaches LV 10, for the next some while, the decreases in exposure for further increases in luminance are done both through decreasing the exposure time and decreasing the aperture.
Then, at a luminance of LV 14, for a while the decrease in exposure is done only through change in exposure time, holding the aperture at f/5.6.
Then, for the next two steps in luminance, again the deceases in exposure are done both through exposure time and aperture.
Now lets look at the lower curve, for the "maximum aperture priority mode".
We see here that as the scene luminance increases, the aperture is kept at is maximum (f/2.8) [aha - that's the name of the song] and exposure changes are made only through decrease in exposure time for quite a while (up to where the exposure time is 1/500 sec).
So basically, the "maximum aperture priority" mode keeps the aperture at its maximum available value up to a higher scene luminance (by 2 stops), doing all exposure decreases by exposure time alone, than in the case of the normal mode.
I don't yet know what the dashed line is (likely, the boundary on what exposure combinations can happen), or the line full of little circles.
Hope this has helped some.
Best regards,
Doug