A split layout lets viewers compare two states or options. It works best when the images are genuinely comparable and the divider does not become more prominent than the subject.
Match the conditions
Use similar framing, scale, and lighting when the comparison is meant to show a real difference. A dim distant photo beside a bright close-up may exaggerate the contrast without explaining the actual result.
Label only what is ambiguous
A short label can distinguish option A from option B or an earlier state from a later one. Avoid burying both images under explanatory sentences. The visible difference should do most of the work.
Check the implied claim
Ask what a viewer would conclude from the two halves. If the image suggests a transformation, confirm that the video demonstrates it under the conditions implied. Keep the original comparison frames so another editor can understand how the thumbnail was assembled and assess whether the balance is fair.