OK, I read the FAQ's but did not find my problem.

I am using OS-X, LR, LRT and Starstax then Premier Pro to process Raw astro. timelapses. 

In some cases I get a big problem which involves the jpg image rendered for LRT changing size by one pixel.  This is enough to kill Starstax processing.

This has happened to four different processing flows now, and I note these common traits

1. The image is cropped 16:9 and varies in size, i.e. zooms in or out.
2. Crop size changes are correctly applied to Exifs by LRT
3. Crop is rotated also, and correctly carried out by LRT
4. All images have LR image distortion set to around +90 to correct for fisheye lens

LRT correctly produces jpg images at 4096 by 2304 pixels until some point when it jumps to 4096 by 2303.  It may do this often I do not know. It only becomes apparent when I make trails using Starstax which objects to any change.

Sequences processed in the workflow, but without crop rotations, do not cause a problem. 
So my hypothesis is a rounding error maybe in LRT when calculating crop corners ? Or do we have a problem with LR rendering ??


I would appreciate a solution because, as you can imagine, this takes a long time to diagnose and to work around.

Best regards

It's not possible to animate the crop without having such rounding effects in Lightroom. That's why I recommend to always export in full size and do any crop animation afterwards in the video editor.

OK, I thought as much.  

No more LRT crop animation for me then !!

It's unfortunately something I cannot change, it's just the way Lightroom crops to full pixels, I'm sorry.

Hi Gunther,

I know. It's inevitable. 

It only becomes a visible problem when I post-process LR. jpgs with Starstax.   So I will avoid the combination of crop animations and Starstax from now on.

Just to say that after a very big time-lapse of the milky way in transit, this problem occurred. Catastrophe! But we overcame it in the end by guessing that it was in fact a LR rounding error, and then by using brute force to make each LRT.jpg the same size. Got a solution, but stressful and it took all day !

This TL involved radial movement of the camera, tracking the Milky Way along the ecliptic all the night using a Radian, then in post an animated crop of milky way going from vertical to nearer horizontal, all done happily with LRT, then forced sizing of LRT.jpgs to make star trails forward and reverse motion. We got there in the end !  and flicker free too.

Thanks for the prompt response in any case.

I am going upgrade to LRT Prof. tonight for the additional features

best regards
Stars