In this article, we report on the development of a novel, video-based measure of teachers' moment-to-moment noticing as knowledge-filtered perception. We developed items to capture teachers' perception of similarity of their own teaching to the teaching shown in three short video clips of authentic classroom instruction. We describe the item design and relate teachers' moment-to-moment noticing to their reflective noticing as measured by judgements of similarity teachers provided after viewing each video. Consistent with theory, correlations were of moderate size and provided evidence that the measures captured somewhat different information. We suggest that the difference can be explained by different cognitive processes: the moment-to-moment measure primarily captured noticing as a function of bottom-up (nonconscious) processes, while reflective noticing engaged top-down (conscious) processes. We conclude by considering strengths and limitations of this novel approach and the usefulness of differentiating between bottom-up and top-down processes to characterize existing measures of teacher noticing.