with the latest firmware updates the S1 is practically an S1H albeit with no internal fan and thus capped video file lengths however the video image quality is close to the Alexa LF and compared to
Sonya7Siii it is half the price, has superior codec (better colour science, more dynamic range 6K 10bit 200Mbit vs Ultra HD 8bit at 100Mbit) has better IBIS, better EVF, rear screens more readable in sunlight and below ISO 12,800 the S1 has the advantage in terms of creamy smooth low light results in 10bit V-LOG but the main disadvantage is the lack of PDAF autofocus on the S1. It is a more reliable video making camera than the Canon R5/R6
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