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Author Topic: Lens Calibration - how far to go?  (Read 3716 times)

andyroo

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Lens Calibration - how far to go?
« on: July 11, 2014, 04:25:33 AM »
Looking for some feedback on my calibration methods. I am using a Canon D10, focused to infinity, and a 24" monitor. Fitting everything but aspect and skew. Pics are a bit blurry, but the more I take, the better my calibration gets. (lower Std Error). So far I've done seven batches of 11 to 61 pics (251 total) with power cycles between each one, over a few days. I wanted to investigate how error varied when combining pics through power cycles because I figured if my StdErr got worse it would mean my calibration wasn't stable between power cycles, and if it got better it would mean it was.

My calibration parameters are definitely converging on a value (hooray!) but I don't really know when I should stop. My last set of 61 pics dropped by StdErr by 12-13%, except for k4, which dropped by 24%. going from about 90-100 pics to 190 pics (comparing 6 previous) dropped my StdErr by about 30% except k4 by 50%.

Anyway, my values from various calibrations and combinations are shown in the table I attached as an image. Seemed easier than trying to format all this in a html/message table. right hand numbers are comparing calibration done with sets 1-6 with calibration done with sets 1-7, and computing difference in variables and % change in standard error (1 - (x/y)).

I am interested in any thoughts or suggestions on how I might know when i am done. I don't have a good feeling for what change in values (especially k1-k4) would be meaningless, and it looks like my error might keep going down for quite a while. If anyone familiar with Brown's camera model can plug numbers in or tell me how I might, in order to estimate when I should stop adding images, I'd be most appreciative.
« Last Edit: July 11, 2014, 04:28:47 AM by andyroo »

andyroo

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Re: Lens Calibration - how far to go?
« Reply #1 on: September 04, 2014, 08:39:13 PM »
Anybody? Suggestions? Thoughts? Critiques? Insults? Praise? It's so quiet here... I feel lonely and forgotten  :'(

holgar

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Re: Lens Calibration - how far to go?
« Reply #2 on: September 17, 2014, 02:29:06 PM »
I can only say that I am also interested. I am Just making some tests and also wonder about the error differences. I am new to this topic..but I would like to know what are tolerable Vallues here.
Below are my results....are these Ok? I use a Canon 5D Mark II with a EF24-105mm f/4l IS USM Zoomlense.
« Last Edit: September 17, 2014, 02:31:52 PM by holgar »