Super CCD Measurements

Camera Article
 
Super CCD Measurements

Additional details about test data results of Fujifilm super CCD cameras (S5 Pro, S3 Pro…)

The measurements for Fujifilm Super CCD cameras are qualitatively different from those for other DSLRs, given that the Fujifilm Super CCD cameras sensor uses super CCD technology: instead of just one sensor, two sensors (of 6Mpix each) are interleaved on the die.

Each sensor has a Bayer structure, rotated by 45°. However, one has large pixels with sensitivity comparable to any other DSLR sensor, and the other one has smaller pixels with much lower sensitivity (about 4 f-stops). The advantage of this second sensor is that while highlights might be burnt on the large pixels, they still contain some information on the small pixels. This means that a significant gain can be expected in dynamic range.

This special “dynamic boost” mode is available for ISO settings lower than 800.

In order to be able to compare the Fujifilm Super CCD cameras data with that of any other sensor, we had to adapt our standard protocols:

  • We measured ISO sensitivity on the large pixel sensor (with dynamic boost off). While this is not compliant with ISO standard 12232 at saturation, in this particular case the norm is not adapted and would be very confusing for the user.
  • We considered the sensor as equivalent to 6Mpix. Under normal shooting conditions, the small sensor is indeed too noisy to provide any details.
  • We chose the most favorable noise curve: we considered larger pixels for low and mid-tones, and smaller pixels when the large pixels saturate.
  • We measured SNR 18% at 18% of the large pixel dynamic, which corresponds to equivalent exposure with the other sensors.

Our results showed:

  • A very large increase of dynamic range below ISO 800 (when dynamic boost is available).
  • A slight increase of tonal range and color sensitivity below ISO 800.
  • Unchanged SNR 18%.