Image File size is worryingly small after switch to PILimage save

[quitmeyer]

I have 9000x6000 resolution photos I'm taking with the Arducam 64mp camera on a Rpi4. Earlier I was taking photos via

old way

        request = picam2.capture_request(flush=True)
       request.save("main", filepath)

(full script https://github.com/Digital-Naturalism-Laboratories/Mothbox/blob/main/Software/scripts/TakePhoto_HDR.py)

and it would save an image that was about 7-10mb each

Now (for speed reasons and because I'm bracketing photos), I save my photos in two loops, one to where i capture a request and then save it as a PILimage and append that image to a list, and the second loop to save those images to disk

but now all the photos are only like 2-3mb each. and so it seems like a big red flag something is going wrong! Anyone know a better way I can save these images that keeps their full quality? Or maybe my original method was just inefficient? (im guessing not)

new way
loop 1

      request = picam2.capture_request(flush=True)
       pilImage = request.make_image("main")
       PILs.append(pilImage)

loop 2
img.save(filepath,exif=exif_bytes)

full photo script https://github.com/Digital-Naturalism-Laboratories/Mothbox/blob/main/Software/TakePhoto.py
(Full loops)

for i in range(num_photos):
        #middleexposure = camera_settings["ExposureTime"]
        
        picam2.set_controls({"ExposureTime":exposure_times[i] })
        print("exp  ",exposure_times[i],"  ",i)
        #picam2.set_controls({"NoiseReductionMode":controls.draft.NoiseReductionModeEnum.HighQuality})
        picam2.start() #need to restart camera or wait a couple frames for settings to change

        time.sleep(exposureset_delay)#need some time for the settings to sink into the camera)
        
        flashOn()
        request = picam2.capture_request(flush=True)


        if not onlyflash:
            flashOff()
        flashtime=time.time()-start

        pilImage = request.make_image("main")
        PILs.append(pilImage)
        #image_buffer = request.make_array("main")
        #requests.append(image_buffer)
        
        #print(request.get_metadata()) # this is the metadata for this image
        metadatas.append(request.get_metadata())
        request.release()

        picam2.stop()
        print("picture take time: "+str(flashtime))
        
    # Saving loop (can be done later)
    i=0
    for img in PILs:  
          exif_data=metadatas[i]
          pil_image = img
          # Save the image using PIL to get the image data on disk
          folderPath= "/home/pi/Desktop/Mothbox/photos/" #can't use relative directories with cron
          filepath = folderPath+computerName+"_"+timestamp+"_HDR"+str(i)+".jpg"
 
        
          print(exif_data)
          print(camera_settings.get("LensPosition"))
          #https://github.com/hMatoba/Piexif/blob/3422fbe7a12c3ebcc90532d8e1f4e3be32ece80c/piexif/_exif.py#L406
          #https://piexif.readthedocs.io/en/latest/functions.html#dump
          zeroth_ifd = {piexif.ImageIFD.Make: u"MothboxV3",
              }
          exif_ifd = {#piexif.ExifIFD.DateTimeOriginal: u"2099:09:29 10:10:10",
            #piexif.ExifIFD.LensMake: u"LensMake",
            piexif.ExifIFD.ExposureTime: (1,int(1/(exposure_times[i]/1000000))),
            piexif.ExifIFD.FocalLength: (int(camera_settings.get("LensPosition")*100), 10),
            piexif.ExifIFD.ISOSpeed: int(camera_settings.get("AnalogueGain")*100),
            piexif.ExifIFD.ISOSpeedRatings: int(camera_settings.get("AnalogueGain")*100),

            }
          gps_ifd = {
           #piexif.GPSIFD.GPSVersionID: (2, 0, 0, 0),
           #piexif.GPSIFD.GPSAltitudeRef: 1,
           #piexif.GPSIFD.GPSDateStamp: u"1999:99:99 99:99:99",
           }
          first_ifd = {piexif.ImageIFD.Make: u"Arducam64mp",
             #piexif.ImageIFD.XResolution: (40, 1),
             #piexif.ImageIFD.YResolution: (40, 1),
             piexif.ImageIFD.Software: u"piexif"
             }
          
          exif_dict = {"0th":zeroth_ifd, "Exif":exif_ifd, "GPS":gps_ifd, "1st":first_ifd}
          exif_bytes = piexif.dump(exif_dict)
          img.save(filepath,exif=exif_bytes)
          print("Image saved to "+filepath)
          i=i+1

[quitmeyer]

Ok, i think i solved it!
I didn't know the PIL image save feature had a "quality" command, and that the default is low-ish (like 50)

and so i changed my line of code to
img.save(filepath,exif=exif_bytes, quality=95)

and it seems to be saving normal file sizes. If i crank it to 100, the files sizes get quite big (like 22mb), but 95 seems to be around the same as before.