Discrepancies in pixels following resizing

[Ozzie_Traveller]

G'day all

I'm playing with someone else's JPGs from a 5D-iii - each is 22mpx ex-camera, 5760px on the long side

There are 18 images in a pano and the poor old software / windows??? is crashing
I have used Elements to do a bulk resize down to 4000px on the long side and the pano software stitches quite okay with that size. However, upon looking into the open blue sky, I find a pixellated blue sky

Here's a 400px sample - darkened slightly to show it a bit easier


Q- what can I do to minimise or overcome the effect??

Thanks
Phil

[VTphotog]

This looks to me, more a case of jpeg compression artifacts, though it could be exacerbated by resizing.
I haven't used Elements in quite a while, but seem to recall there are a few different algorithms used for resizing. The faster ones sometimes can leave things looking a bit jagged. If the jpeg quality is set a bit low, that can also cause these type artifacts.
I would recommend going back to the original files and, if you can't get the results you want with Elements, use Irfanview for the resizing and compression (if needed). The Lanczos (I think I got that right) resizing algorithm is slow for large file sizes, but more accurate.

brian

[Ozzie_Traveller]

Thank you Brian

Thinking about this overnight [down here] I had come to a similar conclusion - so your comment confirms my suspicions

Yes, PSE did the bulk resizing quickly. I was thinking to redo it progressively - via a 10% reduction each pass till I got down to 4000px

I have Irfanview as well as PSE ... I'll give each a try and see how it goes

Thanks again
Phil