PanoTools NG:
Re: Some more tests on Optimal Cubefaces.
Erik Krause 2008-Nov-01 13:17:14
Am Friday, October 31, 2008 um 21:26 schrieb Hans Nyberg:
> I have made some more tests on the optimal cubeface sizes.
> http://www.panoramas.dk/cubefaces/
Nice test. However, we all know that using a large cube face size and
not allowing zoom in to 1:1 pixel display is a waste of bandwidth. It
is no surprise that viewing a panorama at a given zoom setting yields
the same quality as long as the cubefaces are larger than necessary.
Hence this test only shows the interpolator and anti-aliasing quality
of the viewer...
As for Ken's 70% rule: Your images show impressively that he is
absolutely right. However, the reason he gives (bayer interpolation)
needs a closer look: While it is true that color information is
upsampled this is not necessarily the case for brightness
information.
It depends on the used interpolation algorithm whether this affects
the output resolution or not. This is the reason why you sometimes
get a colored moiree if you shoot regular structures that are in the
range of sensor pixel density. And it is the reason (among others)
why different raw converters give different results.
Hence the quality loss if downsampling to 70% might depend on the
image content. Evenly bright images with a lot of color contrast
might not suffer at all, while almost black and white images might
suffer more.
All this gets more and more meaningless with digital cameras having a
pixel density (in some cases far) above the resolution of the used
lenses...
best regards
--
Erik Krause
Offenburger Str. 33
79108 Freiburg
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