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DPChallenge Forums >> Hardware and Software >> CS4 Photomerge
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01/22/2009 01:08:37 AM · #1
When using photomerge, what characteristics of your source photos make them more or less able to be aligned properly? I am currently attempting to assemble one, and had zero troubles using all 24 images (I actually don't need to use this many, but when I took them I was ensuring that I had loads of overlap, thinking it would make this part easier...) when using the Auto layout, but none of the others ever seems to work, the program saying that it couldn't properly align the photos. The end result when this happens is a strip the correct length of all the photos, but all of them stacked directly on top of each other. Because performing such a large photomerge takes a bit, I'm trying to save myself some time by just messing around with it.
I know that there are lots of variables in images that could make the merging harder, but was wondering if there were some general guidelines.
The scene I am using is a landscape, and has sharply contrasting elements, so the alignment shouldn't be terribly difficult.
Would it improve things if I made a series of smaller pano's and then photomerged those resultants together?
01/22/2009 01:59:16 AM · #2
The first thing that can make a big difference is the focal length your shooting at. A wide angle lens is more prone to Parallax errors, or the change in position of foreground objects to background objects. This issue can be resolved by using a Panorama Head which you can set the camera to rotate around the nodal point (Point at which the light entering the lens crosses and becomes reversed and flipped upside down) of the specific focal length you are shooting at. This nodal point is what causes the parallax problems, the problems start to diminish the longer your focal length becomes. Secondly you want to have sufficient overlap in each image, typically 25% - 33% is enough. And lastly you want to make sure that the software has good reference points within those overlaps to make aligning easier, the more detail within the scene the better.

Having said that about the parallax issues a lot of the current software out there is doing a pretty good job at compensating for this. Extreme wide angle's will give you the most problems.
01/22/2009 02:37:16 AM · #3
Thanks for the reply- I was using the Sigma 10-20, and knew that distortion could throw things off. The scene in question does have large uniform areas (snow) but there are also very sharply contrasting areas throughout the entire scene. Overlap is not an issue here, either. I was also curious why the "Auto" layout function worked perfectly fine but then none of the others seemed to want to cooperate.
You mention that most software is compensating well- what I was getting at is why would CS4 compensate easily and fine for it's auto layout but not for any other layout option?
Are parallax errors magnified or decreased by using more or less images? IE- is it possible that software could "gauge" parallax better for adjusting if there are more photos and more overlap, or would this just confuse things?
01/28/2009 01:17:55 AM · #4
bump.....
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