Rick, that looks good.
I'm hoping to be able to try out the Linos lens today.
Rick, that looks good.
I'm hoping to be able to try out the Linos lens today.
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
That is actually the principle are my friend has been working in, so he's already thickly involved in that topic.Originally Posted by marfa boomboom tx
Rick "who has seen GoogleMaps used to display microscope cross-sections of detached retinas and macular degeneration made by this particular expert" Denney
and the link I provided is to software that anyone can download and use... to do just what it says. Also, since it is source code, mods can be made. The point, my hope, was that anyone wishing to build is able to build onto existing. This was a pointer to an existing instance. A ready to use, to modify, to enhance. If your friend's students are building something, then, hopefully, they know about this already.
Rick, in your first paragraph you point out the requirement of 1 pixel distortion per tile for successful stitching. Using a 7000 pixel wide full frame sensor that would be .014% distortion along an edge. This seems an impossible requirement even if we consider that we try to match up two distorted edges with identical degrees of distortion at opposite sides of the frame. Most macro lenses, even the best might keep distortion down to 0.5% which would be 30+ pixels out of rectilinear along an edge. Using an auto fit algorithm assuming both opposite edges of the image are nearly of identical distortion (not possible), I suspect there would still be up to several pixels of mismatch along an edge (and not equal in X and Y). I suspect your 1 pixel requirement might need to be up to 10 pixels.
I am woefully inexperienced in stitching techniques but this makes sense to me. What thinkest thou?
Excellent to lay down some preliminary criteria for someone to work with.
Nate Potter, Austin TX.
Well, that was referring to the previous requirements I'd written which also required an 8.something-micron sensel. I was aiming at a 13-MP camera as the minimum camera.
So, writing the requirement to keep the distortion within any given number of pixels is a mistake--it's tainted by design and depends on a particular technology solution.
The Canon compact macro is tested at distortion better than 0.5%, but even with my 5D and its big sensels, that will be more than one pixel.
What I should have said is that we won't expect the stitching software to perform any corrections of geometric distortion. If any such corrections need to be made, they can be made in the pre-stitch batch process where I would also correct for falloff.
But that brings to mind something I didn't put in the requirements at all, which will be needed to correct these little errors: blending. But I know little about blending or what has been done, and so others need to add to what I've written about what the user will do for blending and therefore what is required of the software. What we don't want is for blending to reduce resolution, but I frankly have never used layer blending in Photoshop and don't know how it works.
Rick "needs are a model of what we do, not a prescription" Denney
You will never, ever see an error of one pixel. Such errors would only occur in the blended region, and would not interfere in any way with the stitching process. Visually they would simply be imperceptible.
The stitching software can perform geometric corrections quite easily, but with well corrected macro lenses, it's not likely to be an issue. Any software written or modified for this project needs to be fault-tolerant enough to deal with relatively large errors in alignment and correlation.
Ben, this is the interface of machine and software. The question is: How much precision in the machine can we expect in order to minimize manipulations of the image in the software. I know you say that these manipulations will be invisible, but at some point they will become visible, so there is a question of where to draw the line. It seems to me we can optimize the balance between machine precision and required software manipulation at the point where the cost of the former and the amount of the latter reach a joint minimum. There is no sense in asking the software to make manipulations when the cost of prevent the need for those manipulations is fairly minor anyway. Otherwise, how much fault tolerance do we need? Can we have enough so that a guy can plug any old lens and extension tubes onto his DSLR and hand-hold the camera for a series of images across the negative? Sure, I'm taking your statement to an extreme you did not intend, but if we don't establish boundary conditions, somebody will do just that.
Once I'm done with assembly, I'll be able to characterize what I think is a reasonable expectation in terms of machine precision. Peter could already do so. I doubt either of us are in the micron range, but we have taken inexpensive construction methods pretty far for all that.
So, we won't see an error of one pixel. Will we seen an error of 10 pixels? 100 pixels? What will it cost to keep the error below 100 pixels? (Probably we just need a tripod, a light box, and a roll of adhesive tape.) We know that it will cost a lot to keep the error down to one pixel--the lenses are not that good and none of us are likely to be able to construct a machine to that level of precision. But the important questions are not at 1 pixel or 100 pixels, but rather in the 10-pixel range. We don't know the answers to those questions yet.
One thing I do know: We will not achieve, using home building, what we aim for. So, we establish a high standard, just as we do with photography.
Rick "who has done a few panoramic stitches and is familiar with the effects of manipulations" Denney
It will be interesting to see if negative distortion correction is needed. No doubt this will depend on the lens, but with the light house picture and the 55mm micro it wasn't needed.
In perusing various forums, Microsoft ice works well with 20-25% overlap for a normal panorama and down to %5 overlap with a machine-based structured panorama, such as provided by a Gigapan. Since the distortion in our pictures is probably going to be even less, perhaps even less overlap would be ok. On the face of it, the less blending and geometric adjustment the software does, while still giving an acceptable result, the better.
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
Rick, I see your point, but I don't think we need to start with a theoretical ideal and work backward to achieving it. I think what we need are more empirical tests of the kind that Peter is doing. That's how we'll determine our required specifications and margins of error.
So far, it looks like off-the-shelf software can do the job, but it may help to have an application-specific version that's more suited to our purposes.
Is anyone here proficient with Photoshop scripting? Could a script be used to roughly position the tiles? If one only had to select a layer, change the blending mode to difference, and then tap the arrow keys a few times to get alignment, well, that wouldn't be too hard to do. I'd prefer it to manually adding control points in pano software.
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
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