Image Stitching Help

[Turnerea]

I stitched a number of images together with GIMP. This is a scaled down pano, hopefully its not too large displayed here.

My question is how should I approach trying to even out the lines where I've stitched the images together? I just did it by hand, they are in different layers. I'm not all that familiar with how to use the fact that they are in different layers to my advantage- I figure I need to somehow get information from both images into the section where they are merging. Any help would be greatly appreciated. I did try searching around a little for help online, but I'm not too familiar with the terminology I need to look up to tackle this problem.... thanks in advance for any help.

 

[Steph]

It looks like you changed exposure between frames. Did you keep shutter speed and aperture the same for each frame? I think it is going to be quite difficult to rectify the problem now (but then again I am not very good with post-processing).

 

[Turnerea]

Yes sorry I should have been more specific about how I shot it. I did keep it on Manual, so same exposure, and I had it set to a specific White Balance, so those settings should be ok. I did not use a tripod, and shot it "horizontal" which I know isn't ideal, but I figured this was just an experiment at how to do this....

 

[Ls3D]

This is where overlap helps as you can feather the layers into each other with a huge soft erasure.

Then dodge & burn as needed, typically also done with a huge soft brush and low values.

Even cloning in areas where it will not be apparent is workable.

PS and some other stitching apps try to do the blending for you, creating layer mask - but I like manual assembly also.

-Shea

 

[Turnerea]

Thanks... I checked out some of those tools... ended up doing a layer mask for each layer and painting with a big soft brush. I think what that did was sort of erase the part I painted from the new layer? Seemed to work pretty well! There is still one transition that needs work, but I just did this quickly to see what I could do. Thanks for the help.

 

[Ls3D]

Looking good! The layer mask is simply a non destructive way of editing as you can both paint to remove (black) and replace (white) the image by editing the mask. Take a look at your channels.

-Shea

 

[Turnerea]

Yeah, seems like a very useful tool... why does the "paint" tool remove pixels from the selected layer its masking though? Seems sort of backward.... though I see the black splotch I'm making, and it sort of makes sense... that's a 'mask' I take it....

 

[Ls3D]

A layer mask can be setup to reveal or hide all, basically inverting the controls if I'm thinking right..

File size gets a bit crazy, especially working at 16 bits per pixel.. so I usually commit the layers to save space, unless it is a paying gig or epic shot.

-Shea

 

[Turnerea]

Yeah the file size was throwing me off for a while. My first attempt I just tried to crate a blank canvas which was the sum of the dimensions (along the long direction at least). Which I realize would be too long because they overlap considerably, but GIMP crashed because it said the image size would be a few gigs!

So when I stitched this current picture together, I resized all my original photos down by 50%, then just opened the first one and added canvas to the right of it and pasted in the new image in a new layer, and just kept doing that. Is there an easier way?

I'm not too confident on all the terms for digital image size. But when I reduced the size by 50%, was I also changing the dpi? I realize the total number of pixels was cut in half in each direction, but I'm not sure how the program goes about actually doing the resize... I guess I'm just wondering if my method for throwing these together hurt the overall image quality.

 

[Ls3D]

Yes you threw half your data away, understandable if your machine is not up to the big stitch. I'm not going to get into DPI much, except to say turn off resample when adjusting to see how it really works.

I don't run Gimp but if you can right click a layer and choose duplicate, targeting the composite document - you can use less ram (no copy & paste, undo, etc) by letting the application read write the layer from disk (in theory).

Your workflow appears sound, and your thinking as well - so I'm sure you will adapt as needs and horsepower change.

-Shea