Exposure / Gain shift

[soulearth]

Hi,
I find the idea of keeping the brightness level by changing the gain or exposure excellent. On the other hand, I expected to find an equivalence that works both ways.

Here is an example:
If I choose exposure 180s and gain 101 the tool gives me the equivalent exposure 21.2s and gain 250.

So if I chose 21.2s and gain 250, I thought I would find my values from the start but no. If I choose 21.2s and gain 250, the tool gives 65.3s at gain 101!

init.png (8.85 KiB) Viewed 496 times

after_move1.png (8.88 KiB) Viewed 496 times

After reset :

init2.png (8.9 KiB) Viewed 496 times

after_move2.png (8.78 KiB) Viewed 496 times

Another thing, the same conversion done several times does not always return the same result. There are small differences. Is this normal?

Best regards,

[admin]

Hi,

ah, that's interesting...

The small errors are kind of expected - there are probably rounding errors happening behind the scenes, so when you see 21.2s, is it 21.15 or 21.24s? The big error isn't, and doesn't seem to happen so much if you just move the slider in increments (click left or right of the position), but does if you drag it. I suspect that the current implementation is letting the rounding errors build up too much due to 100s of updates while dragging.

I will investigate - I use it lots and want it to work correctly

Robin

[soulearth]

Hi,
Small errors are +/-5 for both exposition and gain. Bigger than a simple rounding but consistent with previous value.

But I always dragged the slider and not clicked. So it's not impossible that the problem is there in both cases.

Regards.

[admin]

Hi,

I had a look and it was a build up of rounding errors - every time the slider is moved a bit it tries to adjust the gain/exposure for that small change, but the *gain* value gets rounded off each time.

I changed the code so that all the calculations are done from the 'reference' gain and exposure values (those with the shift control set to zero) and everything works with both dragging and clicking to each side.

Thanks for reporting - with the way I use the control, it was close enough to make it unlikely that I would notice.

cheers,

Robin

[soulearth]

Great. I can't wait to install the next version.

Regards.