Sunday, November 11, 2007

Stitching Update

It's been some time since I have written about stitching, but despite owning a 1Ds2, I continue to stitch on a regular basis. There seems to be a lot of talk of needing shift lenses to stitch and nothing could be further from the truth. In reality, camera rotation stitching works just as well as shift image stitching. Sure there's more processing but don't forget that in rotating the camera, you never have to approach the edge of the image circle. As far as ease of processing, I continue to use PTGui.

I have used Photoshop to do some stitching but have not found it as reliable as PTGui - there's nothing worse than spending several hours working on an image only to find that there's a discontinuity in the stitch that you hadn't noticed, and now it's back to the drawing board. I like the fact that PTGui gives me feedback on the success of my efforts - a good stitch, or not so good, or poor, and I can check the alignment of the control spots (matching pairs of points in adjoining images). Most of the time I get a perfect stitch first time out, but with close work and really wide angle work, finding that nodal point becomes more critical and so sometimes the alignment isn't perfect. Photoshop just goes ahead and does the best it can, PTGui warns me that there are problems and even shows me where they are located.

As I never do more than a single row stitch, taking the stitching images is no great chore, using my RRS nodal point slider and a levelling head under the ball head so it rotates horizontally. I normally just eyeball the lens, knowing ahead of time roughly where in the lens the nodal point is and if the camera is aiming up or down (so the ball head leans forward or back), I adjust the slider accordingly so that the nodal point is vertically over the centre of the ball, not the actual clamp.

When stitching with the camera aimed really down or up, one does need to take into consideration that at either end of the image, you have angled edges to the stitched image. Since you have to crop this to a rectangle (assuming you are a traditionalist), you need to include a bit more to the left and right to allow for this cropping. You'd have to do the same if you shot a single image aimed up or down if you later plan to correct vertical perspective in photoshop since filter/distort/lens correction will also give you angled sides when you dial in the change in perspective.

The only limitations in stitching for me are water, where waves can be tricky to blend - especially organized waves like the ocean, or where I need to blend images for depth of field or for increased dynamic range, in which case I usually won't stitch, though occasionally it's worth the effort.

As a landscapist, I find there really aren't any medium and far distance images in which it isn't worth the effort to stitch.


doonster said...

Interesting that you post this. I wrote a post about my panorama techniques here.

I have similar experiences to you, even with multi-row images.

Anonymous said...

have you tried stitching with CS3, its much better than CS2 and I find it never fails on a single strip and gives great results.


George Barr said...

I was in fact referring to CS3. Initially it seemed to do a great job stitching, but then I started to find some failures, not always immediately which is really frustrating.