Panoramic Color Blending

[jpl]

So I made my first attempt at a panoramic shot last night (first attempt at HDR on the second one too!). I'm pretty happy with the results except for an exposure and/or color issue . If you look at both this shots you will see a color mismatch in the sky in the center of the image (well it may be too small to see here in the first image, but you should be able to see it in the second). There are rather distinct vertical lines through the sky on both sides of the largest building in the image where the color of the sky gets darker. What is strange is that these lines do NOT fall on the source image edges. My guess is that they fall where PS decided to stitch the image.

http://jpl.smugmug.com/photos/310363620_4K8td-L.jpg
Horizontal panoramic, 5 frames combined, severely cropped

http://jpl.smugmug.com/photos/310360779_9K5Bn-L.jpg
Vertical panoramic, 15 frames, 5 views of 3 exposures each, HDR, cropped

Anyway, I'm a completely PS newbie so I was hoping you guys could suggest a technique for me to blend those vertial lines out of the sky. I've tried copying the sky to another layer and adjusting it there before blending it back into the background and some other things but nothing I've done seems to make it better. So what can I do in PS to fix this?


As a secondary question, what can I do to prevent this from happening next time? I shot RAW, A mode, +1, 0, -1 exposures, F5.6. I didn't lock my WB setting but I went though the images and made sure the WB was the same on all of them before I combined them (it was). I couldn't use my AE-L function because I was shooting 3 exposures for each frame (or could I have used it)? I'm shooting a Nikon D40 so the exposure bracketing for the HDR was manual.

[David_S85]

You're on your way with these, so good on ya for beginning the pano thing.

You best bet in the future is to shoot full manual. That is... focus to infinity and then turn off the autofocus. Then set manual aperture and shutter. Also lock the WB setting (if you're shooting and processing in RAW, the WB shouldn't matter - just process WB identically). Overlap each shot by about 25-30%. The exposure bracketing you did is always a good idea, but for that to work more quickly, you'd probably need to be in aperture priority mode rather than futzing with the controls in the dark.

I like to make an exposure test run in aperture priority checking what the camera will do with the shutter speeds as I pan around - then I average those when I switch to manual, making a decision on what works best in the brightest shot. That procedure works better in the daytime - night shots will take more practice and YMMV.

And then, I also will bracket the shots - just in case. There's a lot that can mess up a pano (like people, cars and stuff moving through the shots). Just think it through and shoot a few sequences. Sometimes I don't notice those darned moving objects until I get home and look at the pics.

[jfriend]

I was going to say the same thing as David. Put the camera in full manual mode. Look at the meter in your camera viewfinder and adjust aperture or shutter until you have a centered meter reading (indicating a proper exposure). Then scan the whole scene to see if you get significantly different metering any place else in the scene by just watching the metering reading in the viewfinder. If you do see significantly different metering somewhere else in the scene, then you'll have to decide what best to optimize for. In the daytime, I usually want to preserve highlights (thus underexpose the areas without highlights). In the nighttime, you may want to let bright lights blow in order to preserve detail in the dark areas.

Since I'm always going to combine a set of shots that were all taken with the same exposure, if you think you need to bracket, I'd just take 3 separate pano sequences, each at a different exposure rather than taking one shot at 3 exposures, then the next, then the next and so on. That will help you better with moving objects (less time between the first and last shot in a sequence). Of course, this is my personal opinion - it can be done either way.

[dbd]

There is nothing in your pictures to indicate that the differences in sky light aren't real and not an artifact. Wide views subject us to the risk of varying lighting. An unlit lake or greenbelt behind one portion of an urban panorama can yield a much different skyglow than well lighted concrete parking lots behind another portion.

Both pictures show considerable differences in characteristics of the sky in different regions. One of the impacts of the processing to render a true HDR image to the limited LDR range we view on our moniters is that differences that were outside of our ability to resolve have been brought into a range where we can recognize the differences. That may have happened here.

Your response to the sky differences may still have to be found in PS, but you've also gotten some good advice on panorama shooting anyway.

Dale B. Dalrymple
http://dbdimages.com