UMP12K, ISO 800 | Sigma 35mm Cine, T1.5, 11.5° shutter angle (PNG, 4096x2160, 16bit)
It has been noted that color rendition might shift as the iris is opened or closed on certain lenses.
To see the extent our test lens might exhibit this issue, I shot a color chart at T1.5 and T9.7. This is the greatest delta I could achieve by only changing shutter speed and still exposing middle grey consistently.
UMP12K, ISO 800 | Sigma 35mm Cine, T1.5, 11.5° shutter angle (PNG, 4096x2160, 16bit)
UMP12K, ISO 800 | Sigma 35mm Cine, T9.7, 360° shutter angle (PNG, 4096x2160, 16bit)
Value differences were removed from images leaving just hue & saturation (to account for variations in exposure). Images were cropped to just the chart, blurred (gaussian blur, 5 pixels), then the edges were removed (to account for focus differences).
Color averaged between T1.7 & T9.7
Color differenced
Color differenced, exaggerated 200x
At least with this copy of this lens, the color differences as the iris is closed down are negligible. Based on these results I feel comfortable utilizing the aperture to better match sensor sizes for the blind test.
12K, 8K and 4K BRAW files on 4K timeline. Scaling set to "Scale full frame with crop". 300% crop.
UMP12K, ISO 800 | Sigma 35mm Cine, T11, 12K scaled to fit (PNG, 4096x2160, 16bit)
UMP12K, ISO 800 | Sigma 35mm Cine, T11, 8K scaled to fit (PNG, 4096x2160, 16bit)
UMP12K, ISO 800 | Sigma 35mm Cine, T11, 4K scaled to fit (PNG, 4096x2160, 16bit)
UMP12K, ISO 800 | Sigma 35mm Cine, T11, 12K 100% crop (PNG, 4096x2160, 16bit)
UMP12K, ISO 800 | Sigma 35mm Cine, T11, 8K 150% crop (PNG, 4096x2160, 16bit)
UMP12K, ISO 800 | Sigma 35mm Cine, T11, 4K 300% crop (PNG, 4096x2160, 16bit)