[OTHER] Exposure Bracket Function

hey guys. thank you for your dedication towards developing picamera2 further

[Exposure Bracketing]

from picamera2 import *
from time import sleep
from fractions import Fraction

# This script captures exposures with varying shutter time. 
# The frame rate needs to be longer than the exposure or it won't work. 
# The capture takes as long as the frame rate, so reducing the frame rate saves time for quick exposures.

with picamera2.Picamera2() as camera:
   
        camera.resolution = (4056,3040)
        #camera.framerate = Fraction(1, 2)
        camera.iso = 100
        camera.exposure_mode = 'off'
        camera.awb_mode = 'off'
        camera.awb_gains = (1.8,1.8)
        
        config = camera.create_still_configuration()
        camera.configure(config)
		
        camera.set_controls({"ExposureTime": 114, "AnalogueGain": 1})
        camera.start()
        camera.capture_file('0.jpg')
        print(camera.capture_metadata())
		
        camera.stop()
        
		
        camera.set_controls({"ExposureTime": 300, "AnalogueGain": 0.5})
        camera.start()
        camera.capture_file('1.jpg')
        print(camera.capture_metadata())
		
        camera.stop()
        
        camera.set_controls({"ExposureTime": 500, "AnalogueGain": 0.5})
        camera.start()
        camera.capture_file('2.jpg')
        print(camera.capture_metadata())
		
        camera.stop()
        
        camera.close()

Any suggestions for improving my python code in terms of smartness. All setting should remain constant expect for exposure time/shutter speed. For example FocusFoM, ColourGains, Colourcorrectionsmatrix, Lux seems to change in my series.

The idea is to generate a HDR Image via multi exposure fusion algorthmn. Use case for solar power prediction.

[davidplowman]

Hi, just a few things to comment on:

1. Setting properties with camera.iso = 100 is an idiom from PiCamera, not Picamera2. You need to set these values using (for example) camera.set_controls(...). In fact there is no ISO control in libcamera, you just set the (analogue) gain directly.
2. Same goes for those awb_gains, that’s a PiCamera thing, in Picamera2 it’s camera.set_controls({"ColourGains": (1.8, 1.8)}).
3. In a couple of places you set the analogue gain to 0.5. Actually values under 1.0 aren’t valid, I expect it reports "AnalogueGain": 1.0 instead?
4. The ColourGains and ColourCorrectionMatrix should stop changing, I’m guessing that you’re not setting the colour gains correctly (point 2 above.)
5. The FocusFoM and Lux values are merely outputs of the system measured from the image (the former is a local contrast measure but it depends on the pixel levels, the latter is an estimate of how bright a scene is). They shouldn’t affect processing if you’ve fixed the AEC/AGC and AWB.

[davidplowman]

I’m not quite sure what’s going wrong for you. I took your script, deleted all the stuff after the captures (which I can’t run anyway), and rolled them up into a loop, just so that I was editing less code. Here’s what I ended up with:

import time
from picamera2 import *

tuning = Picamera2.load_tuning_file("imx477.json")

t1 = time.perf_counter()

exposures = [50, 100, 150, 250, 400, 650, 1050, 1700, 2750]

def exposure_bracket():
    with Picamera2(tuning=tuning) as camera: 
        config = camera.create_still_configuration(main={"size": (1014, 760),"format": "RGB888"}, raw={"format": "SRGGB12", "size" : (2032, 1520)})
        camera.configure(config)

        for exp in exposures:
            camera.set_controls({"ExposureTime": exp, "AnalogueGain": 1, "ColourGains": (1.0,1.0)})
            camera.start()
            metadata = camera.capture_file(f"{exp}.tga")
            lux = metadata["Lux"]
            sens_temp = metadata["SensorTemperature"]
            camera.stop()
            print("Exposure:", exp, "lux:", lux, " sensor temp:", sens_temp)

exposure_bracket()

t2 = time.perf_counter()
print(f"Finished in {t2-t1} seconds")

For me this code works perfectly. It completes in just over 7s with no errors. I also tried running the exposure_bracket function using the multiprocessing module, and that too seems to work fine.

Are you able to try this?

I’ll also lock this thread so that the discussion can continue on the issue that’s still open, if that’s OK. Thanks!