README walking through the settings in the tuning file, and initial thoughts

2025-10-16 18:45:07 +01:00 · 2025-10-16 18:45:07 +01:00 · b47413100e
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+# A list of all the settings in a IMXxx.json:
+
+## version:
+
+I assume this needs to be 2.0
+
+## target
+
+Needs to be bcm2835
+
+## Algorithms
+
+### rpi.black_level
+
+contains one key-value pair. `black_level: 4096`
+
+### rpi.dpc
+
+Defective pixel correction, default off(?)
+
+### rpi.lux
+
+For light sensors, not used. Can be emptied?
+
+### rpi.noise
+
+```
+"reference_constant": 0,
+"reference_slope": 3.67
+```
+
+### rpi.geq
+
+Two elements. offset should be 65535 in all cases we've found. Slope unknown
+
+### rpi.sdn
+
+Spatial denoise. Warning on startup asks us to move it into rpi.denoise, even if empty
+
+### rpi.awb
+
+Auto white balance. Even though we don't use it, camera can't start without it being minimally populated, which is quite a lot
+
+### rpi.alsc
+
+Auto lens shading correction is calibrated by our microscope, and one suggestion is to ship this as a flat table (all 1s) and use that to check if the microscope is calibrated.
+
+`n_iter: 0` (not adaptive)
+
+_If we provide a flat one, then reset and disable flatfield correction will do the same thing. I'm also not sure these are persistent if you run one of them, then `ofm restart`_
+
+### rpi.contrast
+
+`ce_enable` should be 0 (disabled). Gamma curve linear or not is an open question
+
+### rpi.ccm
+
+We only want to ship one temperature. Currently it's 5000K, the temperature of the LED. However, the diffuser might affect this.
+
+Different for HQ and version 2 cameras: currently we take the temperatures either side of 5000K from `/usr/share/libcamera/ipa/rpi/pisp/imx219.json` or `/usr/share/libcamera/ipa/rpi/pisp/imx477.json`
+
+Python code:
+
+```
+import numpy as np
+
+temps = {4650:
+        np.array([
+            2.18174, -0.70887, -0.47287,
+            -0.70196, 2.76426, -1.06231,
+            -0.25157, -0.71978, 1.97135
+        ]),
+        5858:
+        np.array(
+        [
+                2.32392, -0.88421, -0.43971,
+                -0.63821, 2.58348, -0.94527,
+                -0.28541, -0.54112, 1.82653
+        ])
+    }
+target_temp = 5000
+temp_low, temp_high = sorted(temps.keys())
+alpha = (target_temp - temp_low) / (temp_high - temp_low)
+
+print(alpha)
+
+ccm_interp = (1 - alpha) * temps[temp_low] + alpha * temps[temp_high]
+print(np.round(ccm_interp, 6))
+
+temps = {4559: np.array(
+                        [
+                            2.15423, -0.98143, -0.17279,
+                            -0.38131, 2.14763, -0.76632,
+                            -0.10069, -0.54383, 1.64452
+                        ]),
+        5881:np.array(
+            [
+                2.18464, -0.95493, -0.22971,
+                -0.36826, 2.00298, -0.63471,
+                -0.15219, -0.38055, 1.53274
+            ])
+    }
+target_temp = 5000
+temp_low, temp_high = sorted(temps.keys())
+alpha = (target_temp - temp_low) / (temp_high - temp_low)
+
+print(alpha)
+
+ccm_interp = (1 - alpha) * temps[temp_low] + alpha * temps[temp_high]
+print(np.round(ccm_interp, 6))
+```
+
+This will be superseced by using a MacBeth target.
+
+### rpi.sharpen
+
+Currently empty. Sharpening might be something to add in post processing, but not here I expect.
+
+### rpi.hdr
+
+High dynamic range. Not relevant for us. Currently a short snippet.
+
+### rpi.sync
+
+Syncronising between cameras. Not something we're looking at anytime soon.