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Here are examples of results from high-quality cameras. Click on the thumbnails below to view full-sized images.
 |  Results for jpeg image from high-quality (Canon 90mm Tilt/Shift) lens |
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The differences between the DR of the two lenses (medium and high quality) seems to be minor when compared to an image from a low-cost “black-box” camera we recently received.
The low-quality (SNR = 0dB, labeled Low ——— ) DR is measured as 148dB—an astonishingly high number; DR from slope is 66dB—much lower than several quality-based DR measurements (and lower than the slope-based DR for the 90-mm T/S lens). Note that the two darkest patches don’t appear on this plot because their densities (8.184 and 8.747) are beyond the 160-dB limit of the plot. (A 160dB is a range of 100 million to 1—more than expected from any sensor or camera. Put another way, if one photon were to reach the darkest patch, the lightest patch would set the chart or sensor on fire).
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In Imatest 5.2, the Options II window (accessed from the button at the lower-right of the Imatest main window) offers a choice of whether to limit quality-based DR to slope-based DR. When the box is checked, the limit appears in the results display.
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Key takeaways—Flare light was not an issue with the high-quality DSLR/mirrrorless lenses we tested in the past, but it has become a major factor limiting the performance of recent low-cost lenses intended for the automotive or security industries. We have seen examples of how flare light can improve traditional DR measurements while degrading actual camera DR. Our approach to resolving this issue is to limit quality-based DR measurements (the range of densities where SNR ≥ 20dB for high quality through SNR ≥ 0dB for low quality) to the slope-based DR. This works because, for patches beyond the slope-based limit (where the slope of log pixel level vs. log exposure drops below 0.075 of the maximum slope):
Limiting quality-based DR in this way significantly improves measurement accuracy, and perhaps more importantly, can help prevent inferior, low-quality lenses being accepted for applications critical to automotive safety or security. |