Retry specific images in alignment?
Answered
Is it possible to retry some images that don't align, only with different settings?
I have a few images that don't align, but they are very close to other images that do align and there (visually) appears to be enough information to go on. In one case it detects 3400 some odd features, but only has 9 tie points. I have had good luck with increasing the maximum number of features per mpx and max total features. I wanted to try re-aligning the missing images either with a different approach or increased settings or even manual placement. Is any of this possible or is it better just to count those as lost?
I have a few images that don't align, but they are very close to other images that do align and there (visually) appears to be enough information to go on. In one case it detects 3400 some odd features, but only has 9 tie points. I have had good luck with increasing the maximum number of features per mpx and max total features. I wanted to try re-aligning the missing images either with a different approach or increased settings or even manual placement. Is any of this possible or is it better just to count those as lost?
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Hi Neil
try recommend to change only this values:
Max features per image - amount of all detected points in image
Preselector features - how much from the max features will be used in alignment
Detector sensitivity - sensitivity of point detection
try use 40k/20k then 80k/40k and eventually 160k/80k
If want not align all the imgs can use ControlPoints to put it together
https://www.youtube.com/watch?v=d8naLEtLqDY
But even from my experience if get say 5% not aligned imgs its OK. best if try to understand what was the cause ( low points detected= featureless subject or not good angles between the images or etc ) -
Wonderful! Thank you for the additional information and video. The video helps quite a bit!
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So "160k/80k " means
Max features per image = 160k
Preselector = 80k
:?:
And does "Detector sensitivity" has to be higher or lower to get more images aligned? -
Hi Akiro
Yes you understand it right
So "160k/80k " means
Max features per image = 160k
Preselector = 80k
the detector sensitivity is useful when say set 160k points and you get say 100k points per image detected ( "every" img get just around this points detected ) so you can set higher sensitivity and it will try detect more points.
But more detected points with higher sensitivity mean it will detect even "weaker" points" so its cannot be directly said it help better align.. because weaker points mean weaker alignment results.. -
Dang, and I played with the mpx value instead of the preselector.
That explains why it didn't improve much. :-)
What does that do then - is that points per megapixel?
So is the limit whichever value is reached first, per image or per mpx? -
Hi Götz
What does that do then - is that points per megapixel?
Max features per image = 160k its the MAX points per image :D
Preselector = 80k = it take from the 160k points 50% = 80k points so its take the "better" 80k points
max features per Mpix = default value is 10k, its say as its name how much points can be detected per Mpix.
if set say 20k it will try ( and highly probably NOT success except the image have a very features rich subject surface texture there ) detect 20k points in one Mpix so it sooner fill the limit on max features per img = 160k/20 = 8Mpix of whole image so it can be just small part of image with detected points...
if set higher it detect a LOT of ( not useful ) points in small areas that will cause alignment stability issues = harder to align properly. so its advisable to not to play too much with this settings at all.
if get alignment issues PM me with screenshot of the scene so can give advice what can help out... -
Hey Wishgranter,
your offer is much appreciated!
Since I understand the variables better now I am confident that I will be able to get better results on my own.
If not, I might still get in touch... :) -
OK.. :D
feel free to ask if stuck somewhere... -
Holy Moly, that was it!
Set to 40k/20k and got 399 of 404 in one component!
Yay!
Now I will do the same with the main set... -
Götz Echtenacher wrote:Dang, and I played with the mpx value instead of the preselector.
That explains why it didn't improve much. :-)
Same here... :mrgreen:
Thanks again Wishgranter! It works great now! 8-) -
Brilliant insight and the only explanation I've found of Max features per mpx, which I've found has no effect - here's why.
Is it fair to say, as guideline, that Max features/mpx should be based on:
Max features/img / Image size mpx = Max features/mpx?
e.g. 160k / 20.2mpx = not more than 7.9k Max features per mpx?
Then the Align default settings of 10k Max features/mpx and 40k Max features/img, would be right for images of not less than 4mpx?
And that with Align default setting of 10k Max features/mpx, with 12mpx images Max features/img should be not less than 120k?
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