The Ikonoskop A-Cam is ready to shoot right out of the box and the new firmware, 1.28 has given us a new gamma curve that provides a more pleasing image before grading. I have noticed though that when shooting 12db gain at night there is uneven exposure in one of the quadrants of the sensor.
The A-Cam uses a CCD sensor made up of four quadrants that are “stitched” together to create a seamless frame. These quadrants come calibrated from the factory but with new firmware or shooting conditions may need to be readjusted. I had been happily shooting without noticing any problems until after a recent night shoot with the camera set to 12db gain, the highest setting, and 180 degree shutter.
When I reviewed the footage I could see the very faint outline of a square corner in the lower left quadrant which appeared darker in exposure. For a couple of minutes wracked my brain playing around with gamma and lift in Resolve thinking that I was trying to push this low light shot too much but then I hit me. I have never re calibrated the camera at the highest gain setting.
Yesterday I read the instructions in the manual… like most of the documentation from Ikonoskop its very sparse. I understood the basic principle though so I decided to go for it.
First step in the process is to turn the camera on and let it warm up for 20 minutes this ensures that you are calibrating correctly. While the camera is warming up prepare an evenly light white surface, I didn’t have a white card at my friends house so I used a piece of white paper illuminated with a task light.
After the camera has warmed up simply point it at the white surface and adjust the distance or zoom until the entire frame is filled. Use the menu navigation button and toggle to Maintenance>Calibrate>Recalibrate. The menu will direct you to adjust the aperture of your lens until the value is between 1800 and 2200. A number appears in red in the top left corner and goes up in value the more you open the lens and decreases as you close it.
The numbers jump around quickly so you have to adjust slowly. After you are in range the number will turn white, you are then prompted to press any button to activate the calibration. After you press the button you can see the quadrants lighting up with green pulsing lines.
The process is quick and then you are prompted to adjust the number to a value between 400-500. To achieve this number value you must close the lens down and then once the number value is correct it will show in white and you press any button and the calibration process begins again.
After the process has been completed you will be notified by a screen saying that it was successful. The menu will default back to the mainten menu so you have to navigate back to Calibrate>Save as Default.
If you want to create alternate calibration settings you have to select Calibrate>Custom Calibration.
Its important to know that calibration settings affect only the specific gain that the camera is set at. If you are experiencing quadrant issues at 12db then you only have to calibrate at that gain level. If you are having problems on the other settings then you will have to go through the process at each level to ensure proper calibration.
The whole process took about ten minutes from start to finish and this is something that you can easily do on set if you have to. If you are filming outside though you must use your ND filters since without them in sunlight at least here in California you won’t be able to close your lens down enough to reach the correct values.