[HDR-photo] Starting out...

[Ferrell McCollough]

Roger,
Have you been successful with method #2? I haven't had success although the 
PM tutorial uses the method. It doesn't work because the blending process 
that creates a seamless pano changes the tonality of the image. If tonal 
adjustments are made then the merge to HDR process gives poor results. 
Perhaps I'm attributing my poor results to the wrong process?

Ferrell





----- Original Message ----- 
From: "Royce Howland" <royce at cospring.com>
To: "High Dynamic Range Photography" <hdr-photo at hdr-photography.com>
Sent: Sunday, February 11, 2007 9:58 AM
Subject: Re: [HDR-photo] Starting out...


> John Callan wrote:
>> Hello everyone
>> My name is John Callan and I am a photographer working in France.
>
> Welcome!
>
>> At the moment I am using CS2/Bridge from where I select images and
>> import them into "Photomatix". I then stitch them together with Realviz
>> stitcher. The results are okay but I just know that I'm doing it wrong !!
>> Any help or advice no matter how small would be very gratefully received.
>
> First off, if the end result looks good to you then you can't be doing 
> things too "wrong". :) However there may be some room for technical or 
> workflow improvements.
>
> There are three main ways to tackle the process for HDR panoramics:
>
> 1. HDR first, then stitch, which you are doing now. Since stitching can be 
> a beast on low contrast images, this avoids the problem by stitching only 
> once on the final resulting tone mapped image which likely has good 
> contrast through-out. The down side is that tone mapping may produce 
> contrast and color variations in each individual frame, even if the 
> original exposures were all taken on manual with identical shooting 
> parameters. If so, then the stitcher may not be able to blend regions very 
> well and the final image may look like a patchwork of different hues and 
> tones. Not much you can do about this except a lot of painstaking 
> corrective work in Photoshop.
>
> 2. Stitch first, then do HDR. As mentioned in #1, stitching low contrast 
> images can be a pain. Depending on your image bracket sequence, you 
> probably have at least two low-contrast series -- the most underexposed 
> series, and the most overexposed series. Some stitchers support running 
> multiple stitch projects of different input files using the same control 
> points and other parameters. If you have one of those stitchers, you can 
> use the image sequence with the best over-all contrast (hopefully it has 
> good contrast in all important areas) as your first project to set up all 
> control points and blending parameters. Then use that project file to 
> stitch all of the remaining series. Once all stitches are done, do the HDR 
> processing once on the pano's, and all tone and color work should look as 
> seamless as possible across the field of view. The downside is that if the 
> control point set ends up not being a good match for all of the bracketed 
> series, you won't find out until you've tone mapped and see ghosts, 
> shadows and other irregularities where the original stitches don't overlap 
> precisely. Then you have to go back to the control points and fine tune 
> them, then re-process everything from the beginning.
>
> 3. HDR and stitch in one go. As far as I know, only Autopano Pro supports 
> this option right now. You can feed it your entire set of bracketed pano 
> images, and it will stitch and merge them all into an HDR image, then 
> output a tone mapped file. If you prefer to use a different HDR tool for 
> merging and/or tone mapping, you can configure Autopano to emit separate 
> TIFF images, one for each exposure value. The benefit of this over #2 
> seems to be improved accuracy since the stitch can take all frames into 
> account at once. Plus you're only doing the stitch once, so fewer 
> opportunities for a "user error" to cause a problem and have to start the 
> whole thing over.
>
> In the past I have normally used #2 with Panorama Factory, and a lot of 
> work fine tuning my stitch parameters -- sometimes having to run the 
> process from start to finish more than once. Lately I've been evaluating 
> #3 and probably will switch to Autopano Pro as my main stitcher.
>
> I have discussed #1 and #2, as well as HDR topics in general using 
> Photoshop and Photomatix, in an article found here:
> http://www.naturescapes.net/072006/rh0706_1.htm
>
> Royce Howland
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