How to align/crop multiple images as a unit?

kdog · December 26, 2009

Maybe a Photoshop guru can point me in the right direction here. Let's say I shot a sequence of some action. Could be a gymnast doing a trick for example. I shot it hand-held, so the images are not exactly aligned. What I want to do is align them, then apply the same cropping to all of them. By align, I mean that the stationary parts of the scene should end up in the exact same places from frame to frame, and only the subject itself appears in different locations from frame to frame since its moving. Then I want to crop them all exactly the same way. I think I need some sort of align and stack, and simultaneous cropping. Any takers?

Thanks!
-joel

BinaryFx · December 27, 2009

In all versions of Photoshop, this can be done manually by shift dragging one image over the next with the moVe tool (or copy/paste). Then change the second upper layer from normal blend mode to difference blend mode - a solid black layer content results if both layers have exactly the same content/alignment. Difference mode is great for aligning similar images (also perhaps adjust opacity).

CS3 Extended has a script - File > Scripts > Load Files into Stack.

Under the edit menu one can also find - Edit > Auto-Align Layers (auto option).

In CS4 Extended I think Adobe Bridge also has a Photoshop tool to do same/similar.

Anyway, once you have all the various layers loaded, you can find the best position to crop, making sure that you are happy with the crop position and image content. Crop with the crop tool or a marquee selection and Image > Crop.

Another option may be to save a selection of the crop area as an alpha channel, then load this as a selection and apply the selection as a layer mask to each layer.

Ruler Guides may also be of help when checking the crops of multiple layers.

Hope this helps,

Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

Richard · December 27, 2009

The Edit->auto-align feature is also available in the standard edition of CS3. Remember too that if you don't like the auto results, you can use the arrow keys with the move tool to nudge a layer one pixel at a time, up, down, left or right. Using that in combination with the difference blending mode that Stephen mentioned lets you fine tune the alignment.

kdog · December 27, 2009

Thank you Stephen and Richard, the load-images into layers, and auto-align layers worked perfectly, as did the crop.

Now here's a followup question. I played around with the difference blending mode, and was able to make a single image which shows the subject in the various poses throughout the scene. Very cool. The only trouble I have is where the snapshots of the subject happen to overlap in places. The difference in the overlap area is not desirable in that case and just makes a mess. What I would prefer is that the pixels in the overlapped area be replaced with the relevant pixels from the next layer in the stack. So the snapshot of the subject from one scene simply occludes the snapshot of the subject from the previous scene. I could accomplish this by manually blending the composition back with the correct layer to paint in the pixels and replace the messed up area. But I'm wondering if there's an easier way. Sorry if this question isn't clear. It's not a big deal because I have a way to fix the problems areas by manual blending like I mentioned before. No worries!

Thanks again, guys.
-joel

Richard · December 27, 2009

This sounds like a difficult problem to solve generically. I think it would all depend on the image and the differences among the layers. I would just use layer masks. Perhaps there's an easier way.

kdog · December 27, 2009

Richard wrote:

This sounds like a difficult problem to solve generically. I think it would all depend on the image and the differences among the layers. I would just use layer masks. Perhaps there's an easier way.

Should be possible, but it would probably require a blending mode that looked across three images rather than just two. I can't be the first person whose wished for such a thing.

kdog · December 27, 2009

BTW, the results from this operation are here: http://www.dgrin.com/showthread.php?p=1291231#post1291231

Richard · December 27, 2009

kdog wrote:

BTW, the results from this operation are here: http://www.dgrin.com/showthread.php?p=1291231#post1291231

So you want to create a single frame that combines the fox's position from each of the three frames but you don't know what to do about the areas where there is overlap. Is that correct?

BinaryFx · December 27, 2009

Joel, thanks for the link - it really helps...

Great shots mate!

I did not check for exif, however the shots are great in terms of fixed white balance and exposure. This really helps. I presume shot from a tripod? Or was the burst that fast that you were using hand held? I notice some small movement between frames, which could be the wind moving the grass if you did shoot on a tripod?

Anyway, enough of my questions and musing...

I aligned all three images.

Setting each layer to darken layer blend mode worked a treat!

On the overlap, it is easy enough to hand paint the layermask.

I played with doing this with ChOps (channel operations), it was probably quicker and easier using hand painting. The basic mehtod was to have the upper layer in difference blend mode then take a merged copy, resetting the layer back to darken mode. Next I pasted this merged copy as a layer and duped the blue channel. I then trashed the merged copy layer. Back to the difference channel, a bit of blur, curves and paint finished it off. This isolated the overlap.

Anyway, I am not sure of the exact effect that you are after, attached is my initial quick take, using 25% and 50% opacity, one could also apply motion blur filtering to the ghosted layers as well.

Hope this helps,

Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

kdog · December 27, 2009

Richard wrote:

So you want to create a single frame that combines the fox's position from each of the three frames but you don't know what to do about the areas where there is overlap. Is that correct?

Yep, that's correct. I tried it again so I could show you what problem I was having, and now I can't get the blending to work the way I had thought it working. I thought using difference blends would work for this, but maybe not. Never mind.

kdog · December 27, 2009

BinaryFx wrote:

Joel, thanks for the link - it really helps...

Great shots mate!

I did not check for exif, however the shots are great in terms of fixed white balance and exposure. This really helps. I presume shot from a tripod? Or was the burst that fast that you were using hand held? I notice some small movement between frames, which could be the wind moving the grass if you did shoot on a tripod?

Anyway, enough of my questions and musing...

I aligned all three images.

Setting each layer to darken layer blend mode worked a treat!

On the overlap, it is easy enough to hand paint the layermask.

I played with doing this with ChOps (channel operations), it was probably quicker and easier using hand painting. The basic mehtod was to have the upper layer in difference blend mode then take a merged copy, resetting the layer back to darken mode. Next I pasted this merged copy as a layer and duped the blue channel. I then trashed the merged copy layer. Back to the difference channel, a bit of blur, curves and paint finished it off. This isolated the overlap.

Anyway, I am not sure of the exact effect that you are after, attached is my initial quick take, using 25% and 50% opacity, one could also apply motion blur filtering to the ghosted layers as well.

Hope this helps,

Stephen Marsh

http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

Thanks, Stephen! The images were already aligned using auto-align. Before the auto-align, they were really off. I was using a long lens on a bean bag, so it wasn't as stable as a tripod, and at 700mm, any motion is of course greatly exaggerated. So the auto-align and cropping was for the presentation in that thread.

I figured since I came this far, I'd also like to create a sequence shot exactly as you've done. However, I'd like to see it with all the shots at 100%.

I'm going to have to reread your post a few times and see if I can create this.

Thanks so much.
-joel

kdog · December 27, 2009

Ok, well it would have worked, except for that pesky overlapped area.

But... you taught me something very useful.

-joel

kdog · December 27, 2009

Ok, I fixed the overlap.

But... the overlap still kills the concept. Oh well, I have some newfound skills.

Thanks again, guys.
-joel

Richard · December 27, 2009

Here's a slightly different take:

This had the rightmost fox on the bottom layer in nornal mode. The center one was also in normal mode, but the background was masked. The leftmost was on top in darken mode with a little bit of masking to prevent the plants from overlaying the center fox.

The problem, as you see, is that now it doesn't look like a single-animal action sequence. Moral of the story: be careful what you wish for

.

kdog · December 27, 2009

Richard wrote:

Here's a slightly different take:

Oh yeah, that's an improvement. Very clever solution to the overlap problem by bringing the second guy into the foreground, Richard.

thumb That was also cool the way you eliminated the grass that got carried into the second figure.

But really you're right. The concept itself ain't quite right. :nah

How to align/crop multiple images as a unit?

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