Alignment – When it all goes wrong

Alignment

Something I have brought up in the past about over-shooting a scene –  taking too many exposures –  popped up last week in one of my images. I was shooting the ocean sunset and shot 6 exposures using AEB + EC (Auto Exposure Bracketing – Exposure Compensation) It’s a quick way to get 6 (usually 5 because one can be a duplicate) exposures of a scene without having to do much figuring.
When I got home I threw the 6 images into Photomatix Pro 4.1 and selected my usual alignment “Match Features”. I use this because often I have some complex objects in the foreground and I need them aligned as perfectly as possible.
I merged the image and what I got was this “widescreen” image. and you can see a misaligned  handrail on the right side.
?
What? I didn’t shoot widescreen! Going back and looking at the images I could see what the problem was as we can see here looking at the six exposures

The first two exposures are so under-exposed they have very little detail left in them for the software to find edges to align. (You can also have this probelm on an too over-exposed image that is totally blown out)
So the simple answer could have been to just eliminate those two exposures from the merge, they may not have had enough information – as is the case when people over-shoot a scene- to even be worthwhile putting in the mix.
So I did that and still using “Match Features” for the alignment mode, Photomatix perfectly aligned the image and did not crop off any part of the image
OK, great. But the truth is, the image did not have the color range I wanted especially in the dusk sky. So I went back and merged all 6 images again, this time choosing “Match Horizontal and Vertical shifts”. Because there was, even in the lowest two exposures a clear line for the horizon, this would be a good choice.
 
Using this method, I got a perfect alignment AND the full range of color and luminosity (and DR) that I wanted for the image.
Just another example that shows us that using the same setting all the time, even if we really like that setting, isn’t always the right choice. And that experimentation may be the best thing to do to achieve your final goal.
One final thing to note was that the image WITHOUT the two darkest exposures was actually darker than the one with all 6 images. (Both used the same tone mapping) this is because the software needed to bring some information down into the shadow area and it brought some of the midtones with it.
Hope that helps
PT

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