Help removing seams while stitching panorama

Discussion in 'Digital Darkroom' started by gsbhasin, Mar 9, 2004.

  1. Hi,
    I stitched with 5 images. However I see visible seams in the final image. I stitched the images with Canon Stitching software.
    Attached is a ratherlarge image for clarity. I have placed red markers where seams are visible. I also adjusted curves so that they are more visible.
    How do i get rid of the seams? I have read somewhere using the Gradient tool?
    Thanks,
    Gurpreet
    007ea2-16983784.jpg
     
  2. I'm no expert on this.But for the skyline I would use the blur tool.I use adobe photoshop elements that came free with my scanner and the photo merge on there is amazing.I have tried only with black and white as of yet.But I tried saving the different pictures at different contrats e.t.c. and the photo merge changed everything to fit in.I have tried zooming in and I can't see the stitching line at all.
     
  3. If you find an answer, I am interested also. I tried stitching 5 B&W frames together using Photoshop CS. It left terrible looking seams. I have not found or figured out a way to clean them up yet. All 5 frames were shot with the same body/lens/film/exposure combination and then scanned sequentially with the auto gain turned off on a Canoscan FS4000US scanner.
    007ebq-16984684.jpg
     
  4. I don't stitch often but I have had the same problem. I use the stamp brush in Photoshop
    (or Photoshop Elements) to smoothen the transitions.

    You can minimize the differences if you set your camera in manual mode and use the
    same speed and aperture for all the shots.
     
  5. Hi. There's an answer for you that is straight-forward, though time consuming.

    You need to start with the pictures as separate layers in Photoshop. It's a major pain in the butt to fix a shot after you've stitched it.

    Figure out which shot gives the closest representation of the scene; i.e., the one whose colour you'll match the others to. Next, go to a layer whose seam butts up against this shot. Now go to your red colour channel and open the levels adjustment window. Match this shot as closely as possible to the main layer that we chose as the one whose colours we liked best, by sliding the arrows around (generally you'll just need to use the middle one). Go through each colour channel and do the same thing. At this point we are primarily concerned with the sky and are ignoring the fact that the buildings may look worse as the sky gets better. Then go back to the RGB setting and, using centre arrow on the levels settings, fine-tune the tone for the seam.

    This gets us a close match with the one side, though the side farthest from the seam will probably look washed out. To remedy this, make a layer mask (reveal all) and then drag a solid-to-transparent black gradient across the washed-out side of the pic, if necessary. Do another one across the entire pic and then go to edit>fade gradient (or SHIFT-CTL-F for PC) and drop the opacity to 60% or so - whatever looks right.

    Repeat the same steps for each layer and then merge them. Once you've done that, use your healing patch tool to clean up any visible joins you may have.

    If there are buildings or foreground that look terrible, our final step is to use the History Brush and paint over the adjusted buildings or foreground. This will take a while to get right and there may well be a better way. In fact, instead of this you might have selected the sky entirely to start with and then pasted only the sky sections into their own layers and avoided touching the buildings at all. You could look at different Blend Modes before you
    merge the two layers, too.
     
  6. Oh - after you've done all the colour correction and such, you can still use Canon's Photostitch with the corrected shots.
     
  7. Seam problems like those in the image sample can be due to light fall-off/vignetting and/or variations in exposure. It saves a lot of post processing effort if you give each image the same exposure and correct for vignetting before stitching. Then, the images should match reasonably well. Correcting seam problems is vastly easier if you use a stitching program that delivers a layered Photoshop .psd file. I use Panorama Tools, together with PTGui (a front-end gui interface that greatly improves the user interface). Panorama Tools will also give far more accurate stitching than the Canon program. It will correct lens distortions, give level and flat horizons, upright verticals, and enable multi-row stitching. There's also a plugin that can be used to correct images for light fall-off.
    The way to hide slightly visible seams in the sky is to feather the edges of the images using a gradient applied to the edge of a layer mask. (Panorama Tools will deliver the psd file complete with layer masks. If using the Photoshop stitcher, you can add the layer masks manually). See the tutorial blending technique for further details.
    As for getting images to match for colour and brightness, I find it easiest to match each of the red, blue and green channels of the psd file separately, viewing the images in b&w. Use the curves tool to get the highlights, shadows and mid tones to match. It often helps if a temporary curves adjustment layer is placed above the images so that the contrast can be increased and shadows brightened. When the images are a good match in all three channels, very minor tweaking with hue/saturation might be necessary to finish off.
    For Panorama Tools, see stitching tutorial. As alternatives to PTGui, there's PTAssembler and PTMac, and a new freeware program called Hugin.
     
  8. x

    x

    Another technique which can be used is as follows. You need to have a layered Photoshop output file and to have sorted out the major colour or brightness mismatches using the normal levels/brightness/colour correction tools. This is OK for small differences. Select a very large brush - 200 to 400 pixels or maybe even higher with soft edges e.g. 0% hardness. Apply a mask to the whole image if you don't already have one and then feather the edges by painting on the mask using black. This will "hide" the edges and gradually dissolve one layer into another.
     
  9. The Canon Stitching software is good for previewing panoramas, but for final work one option is to choose a good panorama, load all the images into photoshop and stitch by hand (mostly using the rubber stamp and the eraser.)

    There are dedicated software out there which should do a good job, but I haven't had time to test them and some definitely need better user interfaces.
     
  10. Thank you all. I forgot to mention that all images had the same exposure. No surprise seams occured because different areas actually had different illuminatio.
     
  11. I have not had good luck with Canon's stitching software. It puts horrible diagon seams across the image, even when the the exposure was set to manual, and the autofocus was turned off. I've gotten pretty decent results stitching images in PhotoShop Elements. I open a new document that is slightly larger than the finished panorama. I then open each image and copy it onto the new image. I find it easier to work right to left, overlapping the next image on the previous. Also, when I shoot the images, I tend to leave a lot of overlap. This allows me to crop an image to place the seam in a less conspicous place. Still, I've found it impossible to match up one image perferctly. That's where the clone tool comes in. The attached image is of a gallery opening that was shot handheld. You may complain about the perspective, but I don't think you'll find the seams. Good luck,

    Phil
     
  12. Phil, Of course you will find it impossible to align the images just using Photoshop. There's barrel distortion very evident, which will obviously cause problems. You really ought to try Panorama Tools (with PTGui or PTAssembler). It will align your images to an accuracy of a pixel or two over the overlap area, the barrel distortion will be eliminated and you can get all the verticals nicely vertical, all with little effort. Moreover, since you can have the output delivered in psd format, you can edit the layer masks to make the seams go exactly where you want. It does save an awful lot of effort and gives much better results into the bargain.
     
  13. Thanks for the info. I don't often shoot panoramas indoor because of the barrel distortion, but thought in this case it would be fun. I'll give your suggestion a shot!

    Regards,

    Phil
     

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