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06/14/2006 12:46:55 PM · #1 |
Tried mixing two of my favorite techniquies infrared and panoramas, but I've having great difficulty blending exposures. As I get closer to the sun the IR levels must change drastically (but not uniformly), because the exposure levels change with less than two degree shift in the head. Needless to say I must compensate for this in PS not at the time of exposure.
Suggestions?
Technical details...
Nikon D70 with 45mm f2.8GN lens. 13-15 images (I cropped several times after stiching, so I'm not exactly sure). All exposures 2 seconds @ f11 iso200. Hoya R72 IR filter.
Original file 14775x2775 pixels.
Here are links to larger images than DPC allows... 1600 pixels or 1024 pixels wide |
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06/14/2006 01:09:10 PM · #2 |
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06/14/2006 02:15:24 PM · #3 |
Wow, you overlapped a lot! I wonder if some of the "exposure" difference were actually differences in off-axis light entering the lens (flare) as you approached the sun. I've seen that on visible light panos.
My way of dealing with this is a little tedious but effective. I put the pano together, and output it as a layered phtoshop .PSD file. I then select a frame to be the reference frame for exposure, typically near the center, and compensate the others to that. When required, as I think it is here, I make a gradient mask across the individual frame and apply curves selectively. On very difficult-to-match sections of sky, I will occasionally resort to broad-brush cloning at lowered opacity to broaden the transition, but only as a last resort. |
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06/14/2006 02:19:17 PM · #4 |
You did not specify what stitching software you used. Some work better than others. I have always read that you should avoid using polarizer filters for panoramas and that might apply to IR too. I actually thought of testing that theory with my polarizer last weekend, but didn't. Dang!
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06/16/2006 09:50:18 AM · #5 |
After further testing you were right kirbic, it was lens flare. I guess I never considered flare because of the lens I was using the 45mm f2.8GN. It has has only four elements and thr front element is recessed and the size of a penny, so if there ever was a flare resistant lens this is it. I just started using the Hoya R72 IR filter since it has a lower cut off point (720nm) than my B+W 093 (850nm) to keep exposure times shorter to reduce noise. I tried both the B+W 093 and the Hoya R72 in the same circumstances and the Hoya exhibited quite a bit more flare than the B+W. B+W makes the 092 which has a IR cut off of 650nm, so I might give it a try (outch$$). Or use a gel in the recess in front of the front element or on the rear like I do with the Peleng 8mm fisheye.
Although I've owned photoshop since version 3.0, I don't think I'm skilled enough to try Kirbic's suggested editing solution. After a couple of decades of shooting chromes I try to do as much in camera as possible. BTW I forgot to mention that I was using photoshop's photomerge to stich the photos.
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06/16/2006 09:59:01 AM · #6 |
| I use Hugin to stitch and Enblend to blend the exposures after stitching. It may work to hide the seams. |
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06/16/2006 11:44:01 AM · #7 |
Originally posted by hyperfocal:
... BTW I forgot to mention that I was using photoshop's photomerge to stich the photos. |
Ahhhhhh... Photomerge! That is your biggest problem. It doesn't blend luminosity or colors well at all. I've used Kirbic's solution for blending and also just plain old hand blending on single layer panos made with Photomerge before and "tedious" is mild way to describe how well it works. ;)
Just about anything else will be easier and do a decent job.
A free solution you might want to try is called "AutoStitch" and it works decently. It is a demonstration program put together by the researchers at the University of British Columbia that pretty much invented automated panorama stitching software. You can find it here:
//www.cs.ubc.ca/~mbrown/autostitch/autostitch.html
The "Hugin" and "Emblend" solution is a great and it is free but it is harder than all get out to install and learn to use properly. Believe me, I know, because it is what I primarily use now. If you got perseverence and technical savvy it is the way to go and it is certain it will fix your seam problem.
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