user22686: My subject was filmed in front of a green screen using a different lens than was used for the fake background image.
When she moves away from the camera, she looks like a giant against the background image.
Is there any trick in After Effects I can use to fake her distance from the camera so it looks more believable?
Cheers.

user24627: You can use CC_lens to change the appearance of your background so the focal length matches your plate more accurately.
If you have more time (and money) to spare, you can use software like PFtrack to follow the visual lines in both images to estimate the focal length. This would give you the opportunity to accurately distort the image so the focal-lengths match on a more accurate scale.

22686: <p>My subject was filmed in front of a green screen using a different lens than was used for the fake background image.</p>
<p>When she moves away from the camera, she looks like a giant against the background image.</p>
<p>Is there any trick in After Effects I can use to fake her distance from the camera so it looks more believable?</p>
<p>Cheers.</p>
 24627: <p>You can use CC_lens to change the appearance of your background so the focal length matches your plate more accurately.</p>
<p>If you have more time (and money) to spare, you can use software like <a href="https://www.thepixelfarm.co.uk/pftrack/" rel="nofollow noreferrer">PFtrack</a> to follow the visual lines in both images to estimate the focal length. This would give you the opportunity to accurately distort the image so the focal-lengths match on a more accurate scale.</p>
