There are plenty of ways to make your images look weird. Some of the perturbations are due to sneaky little things that Adobe Photoshop, Adobe Lightroom and/or Adobe Camera RAW might be doing to the data. We already talked about the “cooking” that is applied by default to RAW images and why letting that cooking stand unchallenged may be a bad thing. We’ve even warned you about Blur and Jaggies that may NOT in fact be in your images.
Recently Dan Barr asked us what we thought was causing a problem in his stacked star trails. If you read the title you’ve probably already figured out the culprit… Lens Correction! You may not notice anything weird if you process only a single image, but what if Star Trails, or image stacking are what floats your boat?
Notice the strange pattern in the upper left. This image is cropped from a larger image. Image by Timbo2013
Look in the upper left of the image above. That cross hatching is one possible artifact.
Why does this happen? The lens correction is a mathematical model that moves pixels around. Not surprisingly, since the images change – even if slightly, the results vary slightly, too.
How do you fix the problem? Don’t mess with your images before you stack them. Save the lens correction, contrast adjustments and other tweaks for after you’ve finished stacking.
Here is a before and after comparison:
Notice the odd “Moire” like pattern above and to the right of the mountain? (Image courtesy of Dan Barr)
It’s a little subtle. Here is the weird part close up – notice the vertical undulations? The oddness somewhat resembles sensor banding noise except when you look at a larger scale, the lines are concentric.
By redoing the stacking operation without performing lens correction, Dan was able to get an image without the waves:
Stacked first, then adjusted – no moire!
With the strangeness vanquished, Dan was able to improve the brightness and contrast as well.
An example of Moire-like patterns from Darrell (thanks, Darrell for posting it)
I suffered the same. I had no idea then I found this page with the solution works for me as well.
THANKS A LOT! I AM REALLY-REALLY GRATEFUL!
Switched on lens correction in Ligthroom caused the moire like problem for me.
No lens correction before stacking and no moire like problem :):):)
That makes sense, thanks for the post. My question is then, how do you apply the lens corrections after stacking images? Starstax generates a JPG image, so re importing to lightroom and attempting to use lens correction does not work… Thanks!
Automatic lens correction may no longer work, but you can still configure it manually.
Hi,
I’m having this problem too, (though not with every stack). Tried to avoid any lens correction, but after converting my ORF files from camera to DNGs using Adobe DNG converter and opening them in CameraRaw (9.1.1) it says that a built-in lens profile for deformation correction and chromatic aberration has been applied. Then, stacking the photos in PS CS6 using lighten blend mode brings up the moire pattern… Same with Starstax when using tifs… Not with Sequator, but the colors look weird.
Any idea how to make it work in PS? Or could there be something wrong with the source frames themselves? Like possible tripod instability (frames don’t look shaken though)?
Thanks for any suggestion.
Seems like the problem is in the conversion to DNGs (or in the case of Starstax the conversion to TIFF). I stopped using Photoshop about 2 years ago and canceled my subscriptions, so I can’t really troubleshoot the Adobe system any more. (I use Affinity 2 these days).
But if you send me a private link to two or more of your ORF (Olympic RAW) files, I can give it a try in affinity 2 to see if it occurs there. Use{@}[STARCIRCLEACADEMY](.) but with all the useless punctuation removed.
Finally, it’s possible that Olympic Raw files are not REALLY raw.