Make RC focus on smoother areas

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    ssh4

    What you mean focus?
    More looks like you have problem in overlap, iso noise or sharpness of your images than in detected features on your images.
    To clarify your problem please show your camera placement, inspector and align settings.

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    Götz Echtenacher

    Hi Tom,

    I think it all comes down to the (hear-say) fact that RC chooses the best features / tie points first. So you are probably stuck with this behaviour as long as there is any significant  amount of ideal surface left. Window frames like yours are notoriously difficult, especially when coated with a semi or full gloss paint, which almost any of them are.

    Can you show some of the results you got?

    I myself have come to terms that there are just some elements on buildings, where you cannot expect a perfec, or even any result at all. Just now I am struggling with a roof where there are some very smooth tiles between old decayed and mossy ones. Many of the smooth ones have holes in them, even though they are almost exclusively in the foreground, where the resolution is better than further away and also the angle is better. I was already at full length of my 9m pole, so nothing I could do to prevent this. But it also happened with much better angles at lower parts of the roof. I can't explain it but it would take too long to optimize so I am either just going to leave it like that (as a natural restriction of the technique, like window panes) or brush it up a bit in IPS.

    Also, this time I got a flaws in some window and door embrasures, since they are made of a rather homogenous artificial stone. So even though I took all the images at an angle to prevent that, and usually the resolution should have been fine, there are still issues like that which can throw a pebble in the clockworks.  :-) You can see that it's exactly like your issue - no TPs at the embrasures (the black door is good enough) but plenty on the plaster. As you can see, I've tried CPs, but they are all fine as it is. It's really only the lack of TPs on certain areas. Again, I am going to smooth this over in IPS by overlaying orthophotos at different levels, since the flaws are only on the outer edges.

    Thinking about it, maybe raising the max repro error along with the preselector could aleviate that. But since I wouldn't want to mess up the whole rest of the model, I would need to do it locally, which means quite a bit of additional work...

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    Tom Foster

    Gotz, what's your setup with the 9m pole? Is the pole just hand-held from the ground, or part of some tripod? Do you rely on large aperture/fast shutter, for hand held sharpness? What then about low ISO necessary for low noise? Do you remote-view the image as well as remote shutter, focus, zoom etc? What about vertical and horizontal pan of the camera? Sounds like some sophisticated power-rig up there!

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    Götz Echtenacher

    Hi Tom,

    the Pole is handheld. I used it with full (or almost full, since technically it's 10m) extension for the first time for this project and it is borderline. With the added overlap of the missing meter, there was enough stability (if you can call it that) to be just able to take good shots. At full length it needed ALOT of patience to wait for it to stop shaking like crazy. Never mind the strength needed to haul this beast around (even with less than 500gr overall payload) and prevent it from falling like a tree, which did not do any good to my old injured shoulder, I can tell you. I am also toying with a tripod solution, but to be honest that adds up so quickly costwise that I will probably rather go for a drone instead at some point. Because the height limit of even the best pole is easily reached by many of my projects...

    I relied on image stabilization plus large aperture, since this is necessary for a good DOF anyway, there is nothing to lose. I do not compromise with ISO as long as it can be helped. My lowest is 200, so I leave that. Thinking about it now, I did reach the limits at the end of the cloudy day with shutter speeds as low as 1/10th (only the very last ones), so I could have helped this by switching to 400 or 800. But that would have meant to ground the whole contraption one more time which is really tricky since it bends about a meter and behaves quite unpredictably. It's an aluminum window cleader rod though and there are more convenient carbon fibre poles out there that can be extended much more easily since the sections are much smaller.

    Anyway, the results were still good though because I got almost all of my 12mpx images with the full 40k tie points, only the ones with about a third sky had less. This is a good indicator for sharpness, since blurry ones will get a recognizably lower number. Ther was only one bad one, but that was so blurry that it must have been an accident...

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    Götz Echtenacher

    Oh, there is more...  :-)

    I have a tablet for remote control which I mount on the rod.For horizontal pan I use the very sophisticated technique of turning the rod around it's axis.  ;-) And the vertical is just a simple joint that I have to adjust at the ground. Since the project was a rather simple barn, that was not so big an issue, although I would prefer something more sophisticated. I was always toying with the idea of a gimbal at the top, but that just adds potential for errors. Keeping it simple has its advantages too.

    And no, no power rig but cheap and basic, but with a good cost-benefit ratio!  :-)

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    Tom Foster

    Great info. For v different purpose (solar power reception) I messed with a 5m (effective) fishing pole which was verrry bouncy but at least was portable! Drone makes so much sense, for so many reasons. Even indoors I'm thinking, where lots of close up hi def photos may prove necessary to make sense of smooth surfaces, if flight path and shot locations/directions can be automated ... click click click ...

    One thing, surely DOF requires v small aperture not large ('pinhole' gives infinite DOF) which means slow shutter, exacerbated by need for small ISO. So you find image stabilisation is OK - I thought it was a no-no.

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    Götz Echtenacher

    I mean high aperture number! Small opening, yes.  :-)

    No big issues with stabilization so far - it's like the rest, if it works for you, do it. On a pole, there is no other way if you need to go below, say 1/60 exposure. A trade-off, as always.

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