Aligning Images?

Ive got a couple sets of images where I bracketed exposures for blending later, but somehow I either bumped the camera slightly in between or didn't tight down my tripod so they are just the smallest bit misaligned. I'm talking about a couple pixels. Auto align in cs4 can't quite align them. It seems to do a better job when there is a larger difference between the images. Anyone know of any plugins or techniques for doing this? Any info would be greatly appreciated.

Thanks.

Stack the two images on top of one another, then select the top layer and change the Blend mode form 'Normal' to 'Difference'. If the two images are not perfectly aligned, that layer will resemble an engraving, showing non-aligned pixels. Choose the Move tool, and use the arrow keys on your keyboard to nudge that layer one pixel at a time up/down/left/right. When they align perfectly, the top layer will turn black, which means that every pixel is now the same.
Change the Blend mode back to Normal, and you should be good to go.

I've used the Panotools "Align_image_stack" executable a few times and it worked great. Although I have never had an issue with CS4 that I can remember. Other HDR tools available probably have align features built in that may work better as well. I know with Hugin (a freeware one) you can actually set points and help guide it, but I've never done that.

You might want to look at the software list on this page and see if there's anything there that can help. (Note the "Align" column which indicates which programs can do that.)

If you are using photoshop CS you could use the auto align function. Stack the layers then select both layers. Under Edit ( I think, doing this from memory) there is a function for Auto align. It works well. I also change the opacity of the top layer to 50% to make sure things are aligned right when done. I had never thought of changing the blend mode to difference like John suggested, I'll try that next time.

If you are using photoshop CS you could use the auto align function. Stack the layers then select both layers. Under Edit ( I think, doing this from memory) there is a function for Auto align. It works well. I also change the opacity of the top layer to 50% to make sure things are aligned right when done. I had never thought of changing the blend mode to difference like John suggested, I'll try that next time.

Note that the difference blending mode will only really show black if the pixels are actually identical. For two different exposures being blended, the pixels will be colored to represent the difference. That may still be helpful, but it won't go black.

Good catch, David!

Thanks for the tips, appreciate it. I've been trying to just nudge the two images to get them aligned but the angle or something is just slightly off so its not possible to perfectly align them, looks like I'll have to do some warping.

Thanks again for the tips.

Jeremy, if they were taken at the same focal length and focus distance, they should also have the same warping - or very close to it - from the lens. In that case maybe one just needs to be rotated slightly relative to the other? You can use the "free transform" command to both slide and rotate a layer. I'm not sure if you can use the arrows to rotate though so you might have to carefully do it with the mouse.

Now if your focus shifted or the focal length shifted (or your tripod shifted) things could be tougher. Maybe a real stacking program would be in order where you can set points to tell it what should be aligned.

Well I'm not having any luck manually doing this, Does anyone know of a good stacking program? Hopefully that lets you save the two images separately after they have been aligned so that I can then blend them in P.S