I have been making some shots with multiple exposures to overlay. This is something I have posted about before and the shots here are similar to those from before. However, this post is less about the shots and more about the post processing I used. Previously I opened up all of the shots as layers in a single file and then auto-aligned them. Once done, I then used the Auto Blend functionality to show each shot o the aircraft in place.
This was a lot quicker than my previous approach and was something I picked up from posts on photographing star trails. However, recently, I have not been as happy with the results as I should have been. Some of the planes, particularly those near to the edges, had some odd artifacts appearing. Also, if there were any overlaps, the blending masks could give some weird effects. Therefore, I have taken a different approach for a while. This is slower, I admit, but I think it gives a better result.
Once the alignment of the images is done, I hide them all except the bottom layer by Alt clicking on the eye beside the last layer. Then I add the next layer up back in but mask it out completely. A white brush on the mask then allows me to paint back in the new aircraft positions. This is a bit laborious but it does allow you to decide exactly what you want in and what you don’t. if one file is not helpful to the composition, you can easily ignore it.
If the layers are not all exactly aligned from shooting on a tripod, you will also get gaps at the edges on different layers. You can also fill these in by brushing in the layers that provide the right coverage and get a complete image. Once you are happy, flatten the whole thing and you are done.