Now I think I realize what the issue really is: The preview does not work correctly! Sometimes the preview ignores your iso and lowers the preview gain in order to give you a preview that isn't overexposed. But sometimes it doesn't ignore the iso (for example high Iso) and can produce an overexposed...

So you've read back the gains for the last preview frame (we've already said preview frames do not have fixed gains) and written them to an EXIF tag. How does that help? The easiest way to read the debug is "strings foo.jpeg | grep exp", which will give you a line like dev=-1 mlux=-1 exp=199998814 ...

I just was able to get the gain in the exif data under "Copyright". I used camera.analog_gain and IFD0.Copyright and then I looked at the metadata. from picamera import PiCamera from time import sleep camera = PiCamera(resolution=(4056, 3040)) camera.framerate = 15 camera.iso = 100 camera.shutter_sp...

I haven't found a way to add analog gain and digital gain values to the exif data with Picamera. So I wasn't able to confirm the preview/exif theory. You can set analog gain and digital gain with Picamera though As far as I know this isn't possible. The Picamera documentation also says that this is ...

I haven't looked at the documentation regarding exif yet. I think the exposure compensation issue could be a different issue than the ISO / gain issue. All my tests were without exif. I tested exposure_speed , analog_gain , digital_gain either directly before the capture or directly after capture. T...

Looking closer, ISO does NOT lock gain during preview. It is fixed for the capture. Your tests are not taking captures. Yes, they are! Picamera can choose a different total gain at the same Iso. I just reproduced this again by adjusting the exposure time. At Iso 400 1/100s it chose analog gain 7.2 ...

But what about the issue that a fixed Iso leads to unpredictable gains? At a fixed Iso the total gain can vary significantly, no matter whether I use raspistill or picamera. My understanding is that the total gain should be constant and always the same at a fixed Iso. This is also described by the f...

I also just noticed that exposure compensation doesn't work correctly either. When I use exposure_compensation=0, sleep(5), exposure_compensation = -24 , sleep(5) , exposure compensation =0, sleep(5) , the overall gain can be different (for example lower) than if I just use exposure_compensation = 0...

You seem to be confused on what analog and digital gain actually mean. Analog gain is applied before the Analog to digital conversion process, ie before the AD conversion off the sensor. Digital gain is after and is best to think of it like boosting the EV exposure settings in a raw developing prog...

I also just noticed that the relationship between Iso and gain doesn't seem to be constant with picamera (I haven't tested raspistill) Now I used a fixed exposure time and Iso = 1600. Picamera chose an analog gain of 9.94 and a digital gain of 2. Then I took a photo again and used an exposure time t...

Even when I combine the night exposure mode with Iso 100, it doesn't want to choose a long exposure. My problem is that a correctly working Iso setting would reveal the brightness of the scene (if one knows exposure time and f-number), I guess this should make it much easier to adjust the automatic ...

Yes, raspistill doesn't choose a longer exposure time than approximately 1/15s, even at Iso 100 with bad f number. So the Iso setting simply doesn't work correctly, no matter whether I use raspistill or picamera (even when I adjust the framerate with picamera). No DSLR/mirrorless camera behaves like...

Hello, I am a total beginner. These are just my first days of learning Python. But my first impression is that the Raspberry HQ camera hasn't been implemented well. It seems to be a mess: -Raspistill uses different automatic exposure algorithm than Python, for example different shutter speed -Iso se...