ActionPhotos by Marianne

Home -> Tech Info -> Sensor Analysis -> First Measurements

To follow this example using your camera, first ensure that you have the required software set up as described in Getting Started. Note that this guide generally makes use of the batch files described there, so you will want to have those edited to match your camera's filenames and computer's drive-letter for your memory card reader.

A Few Tips

Before starting each test-image sequence, I like to set my camera to an empty folder and reset the file-number sequence so the sequence will always start with image number 0001. This allows me to use the same master batch file to process all of the image sets that will be taken.

Make sure your camera is set to take RAW, using Uncompressed 14-bit if that option is available. If using an FX camera, you can save storage by setting it to DX crop.

Step 1: Take a Saturation Sequence

The saturation point, or white point, is measured at your camera's base ISO setting. It is a reference level for determining the full-well count (FWC) for your sensor, as it makes no sense to take credit for the ADC full-scale DN if the ADC never puts out any DN values that high. We will determine the saturation point for each color channel by exposing the sensor beyond its capacity. On Nikon cameras, it is typically the green channel which is most limited, due to slight numerical up-scaling performed on the red and blue channels which cannot be defeated.

Point your camera at a blank-wall target or other suitable uniform target, illuminated as described in "Getting Started." Set a wide aperture and set shutter speed so the exposure meter shows about +2 stops overexposure. Then decrease shutter speed another 2 stops to achieve a +4 stops overexposure and take a photo. Decrease shutter speed another stop and take a second image.

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Last Update:  Apr. 3, 2012.