In each comparison you see a reference video on top and two versions of it below, A and B. All three play together and repeat.

• Pick the version that looks closer to the reference. Consider detail and motion.
• You can answer once the videos have played through once. Click the video, its button, or use the ← and → keys.
• Press ↑ to see the reference alone at full size, and ↑ again to come back.
• There is no "equal" answer. If they look alike, choose the one you think is closer.
• Changed your mind? Click an earlier square in the top strip to change that answer.

First you do 3 practice comparisons that tell you the right answer. Then the study has 34 comparisons and takes about 20 minutes. A few comparisons are checks with an obvious answer.

Please use a desktop or laptop computer and keep the browser window as large as possible: the videos are shown at their real size.

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