Measuring the impact of flare light on dynamic range


The dynamic range of recent HDR image sensors, defined as the range of exposure between saturation and 0 dB SNR, can be extremely high: 120 dB or more. But the dynamic range of real imaging systems is limited by veiling glare (flare light), arising from reflections inside the lens, and hence rarely approaches this level. Veiling glare measurements, such as ISO 18844, made with black cavities on white fields, result in large numbers that are difficult to relate to dynamic range. Camera dynamic range is typically measured from grayscale charts, where veiling glare depends on the design and layout of the chart, leading to inconsistent results. (more…)

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Using the DarkWorld chart mask

This post is meant to help with the correct setup and operation of the new DarkWorld Chart Mask

The DarkWorld mask pairs with the Imatest 36 patch Dynamic Range Test Chart and frame to block additional light from entering the camera. This allows for more accurate measurements by reducing the flare light coming from the target. Tests with transmissive targets should be performed in a completely dark environment with no ambient lighting apart from the light box.

DarkWorld Chart Mask Setup

If you have previously ordered a Dynamic Range Chart, setting up the new DarkWorld chart mask is as easy as 123! Each DarkWorld chart mask comes with six strips of Velcro. If you order the frame and mask together, you will not have to worry about applying these strips yourself.

Step 1: Verify that you have a new DarkWorld chart mask and a 36 patch dynamic range chart with a frame, as well as six strips of Velcro: 2 soft, non adhesive-backed strips and 4 smaller, rough adhesive-backed strips.

Step 2: Place the chart mask in the frame, and apply the 4 rough velcro strips by peeling off their adhesive backing. The Velcro is best placed in the vertical center, on both the left and right side. They should be placed end to end with a small gap to prevent interference when applying and removing the mask. 

Step 3: Firmly apply the soft, non adhesive-backed strip to the velcro on the chart mask. That’s it! Now you can ahdere the hanging tabs to the frame or peel them off to remove the Chart mask. 

The assembly is now ready for testing with an ITI Lightbox! Simply slide the frame into the rails on the front of the lightbox, and follow the intructions for using Multicharts to measure the dynamic range of your camera system with a single image. 

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