devignette and panoramas - ball park figures

[pco98]

New to devignette tools and experimenting a bit. Shooting with a full frame sensor (5D) and L lens. Would like to get some ball park settings until I get more experience myself.

Am doing some panoramics in PS so the vignette effect is more of an issue than with single frames. At the moment I'm going from vignette darkness halos to devignette lightness halos. I'm presuming it's vignetting but could the blending option also cause it? In some panoramics (nice blue sky ones) I'm getting good merging without adjusting vignetting. But I have some sunrise one with red mountains and white hazy sky which is causing really nasty blend seems, especially when I go at it with curves to bring out the contrast. So I'm not really sure if this is vignette or blending issue.

What settings in PS do people tend to use - guess this applies more to those shooting full frame. Easy with the midpoint and more amount or... So far I've left the midpoint and move the amount +4/5 max - so fairly conservative.

Even better, does someone have some recommended default settings in PS for any of the following Canon lenses (assuming full frame usage):

EF 24-105mm L IS f4
EF 70-200mm L IS f2.8
EF 16-35mm L f2.8
EF 50mm f1.4

I guess aperture affects this so maybe there is no ideal setting - I bring it up because I see PS has a set lens default option.

Thanks,

Ross

[bill t.]

I shoot lots of panos with both primes and zooms.  I have never done any vignetting corrections.  As you mention some types of scenes are much harder to blend that others.  By far the most effective technique I know to overcome the numerous issues blamed on "vignetting" is to simply shoot very large overlaps in those problem situations, as much as 50% or even more.  This gives blending algorithms plenty of headroom to play with.  An extra minute at shooting time can sometimes save hours of painful PS work.

PS can be used to make reasonably good panos, but programs like PTGui are radically better and will save a lot of post processing time.  Coupled with the free "Smartblend.exe" as the blender option, it's hard to beat.  If you have a lot of panos to crank out at once, PTGui's batch processing is a big plus.

[Panopeeper]

By far the most effective technique I know to overcome the numerous issues blamed on "vignetting" is to simply shoot very large overlaps in those problem situations, as much as 50% or even more

This is the best recipe for disaster. Just the opposite: the smaller the overlap, the less problem with the optical vignetting, causing banding in the sky.

However, in some cases nothing helps but very small aperture, not the shortest focal length of zoom lenses, and, well, vignetting correction.

[marcmccalmont]

I have had very good luck using DxO as a RAW converter prior to stitching with the 5D and 24-105 (good vignetting and distortion correction). Also holding the camera vertical instead of horizontal helps too.
Marc

[Geoff Wittig]

Your lenses are part of the problem. Both the 24-105 and the 16-35 vignette pretty badly unless you stop down a bunch. I own the 24-105 and it's a great "walk-around" lens, but I use the 24-70 lens for stitching for this reason.  For the 16-35 distortion and edge sharpness issues make it unattractive for stitching.

You can get around this by using Adobe Camera Raw to "develop" the raw files and undo the vignetting; the info tool will show you when you've succeeded in removing most of it. Then you can stitch the resulting TIFFs.

[AlanG]

There recently was another thread asking similar questions. I suggested that users try Autopano software and I posted some samples.  I do a lot of QTVRs and other panos and that's what I use.  It solves all of the vignetting and blending issues automatically.

I've included a few additional casual samples that were shot handheld without using a pano head. The ballpark photos were shot with a Canon SD800 and the Metro station was shot with a 5D and 24-105.

Autopano has several blend modes. I used Smartblend on these.  It can work from jpegs, tiffs or raw images.

[AndyF2]

New to devignette tools and experimenting a bit. Shooting with a full frame sensor (5D) and L lens. Would like to get some ball park settings until I get more experience myself.
[{POST_SNAPBACK}][/a]

Hmm, being an XTi and "pro-sumer" grade lens user, I'm slightly surprised an L lens is giving vignetting problems.  Full frame and L is what I expect to move to in about 3 years so I would not be happy to run into this.

However, a technique I used to correct vignetting from a Canon A1 ( [a href=\"http://www.amazon.com/Canon-Panorama-Waterproof-Camera-Battery/dp/B00016QMDW]http://www.amazon.com/Canon-Panorama-Water...y/dp/B00016QMDW[/url] ) to make this pano http://www.pbase.com/andy_fraser/image/76517078 from 9 negatives was to take two shots straight up to a clear blue sky, the second shot after turning around 180 degrees (but still take the shot straight up).  Convert them to monochrome, and combine them.  The reason for taking two shots, is the graduation of light across the sky changes so the 2 combined images should produce a symmetrical mask.  

This gives a correction mask for that specific particular camera & lens.  I used that as a control layer to brighten up the corners of each image before merging.  Without this, there were quite dramatic dark scoops across the upper and lower edges.  Sorry I can't give more details such as what type of correction layer I used, but this method may give you a more specific correction mask for each lens.  Experiment to see which type of layer gives the results you like.

In fact, just looking at the mask may tell you what kind of vignetting you have and whether a certain amount of overlap will avoid it.
Andy

[Panopeeper]

Curvilinear distortion is not an issue if using a decent stitcher; it's the stitcher's task to take the distortion into account when warping the frame.