On Tue, Jul 19, 2016, at 21:56, Torsten Bronger wrote:

> Matthias Andree writes:
>
> > I also looked through the older materials on calibration and have
> > been scratching my head over the illumination of vignetting test
> > images, how do you get good ones.
> 
> It is less critical than it seems.  A diffuser in front of the lens
> is always necessary, but in contrast to earlier texts of mine, I now
> think it can even be paper (if absolutely level of course).  The
> actual ilumination should not cast a visible gradiant of the
> diffuser but unless somebody points a laser pointer to it, I think
> this will work in all practical cases.

I found another interesting possibility for this recently, in the form of OLED 
mobile device screens. As mentioned in the existing tutorial, backlit displays 
don't make good sources of even lighting, but the OLED display on my current 
phone does a great job of this, as it turns out, when set to display an 
all-white screen[1]. Of course, it helps that my micro four-thirds lenses have 
fairly small front elements... and you would want to make sure your device 
screen is actually flat...

Anyway, I'll try to get to some of the calibration chores too, pending updated 
hugin instructions.

[1] handy android app for full-white screen: 
https://f-droid.org/repository/browse/?fdid=org.bc_bd.mrwhite

-- 
jys

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