Getting PS to replicate precise stitching on different sets of files

[ed_hurst]

<p>Hello all,</p>

<p>I recently took a sequence of shots at sunrise for the purpose of stitching. However, due to the contrast in the scene, every position in the sequence was also taken at 5 different exposures to allow me to do a manual HDR technique in which I layer the differently exposed files and then manually use layer masks to get the precise effect I want. I do not want to use conventional HDR as I dislike how it looks and want to control it all.<br>

My original intention had been to get PS separately to stitch together all of the files at a given exposure, layer those stitched files, then do the mask work at that point (i.e. on the layered set of stitched panorama files, each of which is at a different exposure). So, in other words, all the files taken at 1/125 would be stitched; so would all of those at 1/250 as a separate file, etc.; they would then be layered and align perfectly. Trouble is, due to the different detail visible in the files taken at different exposures, the stitching was not produced identically for the differently exposed shots. So the 1/125 stitched file did not match the shape and geometry of the 1/250 stitched file, etc. - which of course made simply layering those separate panoramas impossible, as they would not align.</p>

<p>So I then decided to do the laborious process of doing the layering and mask work on each set of identically framed (but differently exposed) shots, then flattening those files - to give a single sequence of shots that could be stitched. The trouble is getting those shots to have compatible density so that the stitching would work. That proved next to impossible. I could not simply match the opacity of the masks because the differently lit parts of the scene demanded different opacities of mask - but stitching them looked messy. The function within the stitching process that smooth out transitions still left banding/blotches, etc..</p>

<p>I can tidy all of that up, but it's a terribly slow and imperfect process.</p>

<p>So...</p>

<p>What I would like to do is to find a way of forcing PS to do it the way I originally intended. In other words, to take one sequence of the shots all exposed the same, stitch them, then get PS to stitch the other sequences of shots identically, so that I can layer the identically aligned panoramas (which will have different exposures) and simply work on one set of masks. As I said above, normally stitching the differently exposed sets of files does NOT have this effect - presumably because the dark and light files lack the detail in parts of the scene to make the algorithms work in an identical way and you end up with quite different (and hence not aligned) stitched panoramas.</p>

<p>Does anyone have any ideas how to get PS, having stitched one set of files, to apply the EXACT same geometry to another set of files so they perfectly line up (given that the files at the different exposures are perfectly aligned)?</p>

<p>Hope this all makes sense!</p>

<p>BTW - I am using PS CS5 (in case that makes a difference).</p>

<p>Thanks in advance for any advice.</p>

<p>Ed</p>

[sheldonnalos]

<p>Is it possible to do the inverse? Complete each HDR frame then stitch the final results?</p>

[ed_hurst]

<p>It is possible but, as my rather rambling explanation says (buried somewhere in that essay above) I have tried that, and getting the files to actually look comparable so that they stitch right is very tough. I really want to layer the stitched panos together and then do the HDR work on the masks...</p>

[tim_eastman]

<p>I don't know about Photoshop, but in PTGui you can create a template which should enable you to batch the panos. I know what you are trying to do. I agree that you have much more flexibility to control and fine tune your output if you have layered panoramas to work with. Often the question comes up, whether to HDR first or your approach. HDR can be hit or miss. In PTGui you can create .psd output. I also don't know about PTAssembler, which many use to generatewide angle panos, vs. spherical.<br>

Of course this does not help with CS5!</p>

[alan_cox3]

<p>Well, I don't know if there is a way to do exactly what you want in Photoshop. But here's what I've done to solve the same dilema. I go ahead and do the HDR on the multiple exposures first. Yes, that leads to exposure variations when merging to the pano.</p>

<p>I solve the exposure/contrast/hue differences using adjustments on the individual layers of the pano. The trick is to throw in <strong>an extra high contrast layer on the top</strong> of everything. It's only used to exagerate the differences in the other layers. Then after adjusting them to match by eye, the top layer is disabled/discarded. It's work, but the results can be worth it. Hope this helps.</p>

[ed_hurst]

<p>Thanks guys for the input. I have decided to try PTGui and see how that fares. I'll report back :-)</p>

[ed_hurst]

<p>It worked! PTGui is the solution to this little challenge. As described above, having created one stitched pano from a set of files all taken at one exposure, it allows the user to then stitch the other sets of files (in this case taken with different exposures) with precisely the same stitching parameters. With the first set, you define (partly automatically and, if necessary, with manual adjustments as well) 'control points' - and the stitching is done using those. The 'project' is saved, which allows you then to use the control points (and other settings) with the next set of files - creating identically stitched files.</p>

<p>This allows me to put the identically stitched, but differently exposed, panos into layers, then mask them off as desired within a single file.</p>

<p>In short, problem solved! Thanks guys for the fantastic advice.</p>

<p>Ed</p>