How to pick the right interpolator?

[Peter A. Schaible]

I have no idea how to make an intelligent choice when I arrive at the
last step of PTGui and actually "make" the panoramic image. I get some
very good results, BTW, but it's all guess work.

Is there any place I read an explanation of how to pick the best
interpolator, and what Bicubic softer means vs. Lanczos16 (Sinc1024) vs.
Spline64, etc.

(BTW, I love this forum and have great admiration and appreciation for
all of you who share your wisdom so generously and unselfishly. Happy
Thanksgiving to all, even those outside the USA who don't observe our
national holiday!)

--
-- Peter

Peter A. Schaible



SunDance New Media
www.Sundance360.com

[Erik Krause]

Am 27.11.2013 14:47, schrieb Peter A. Schaible:
> I have no idea how to make an intelligent choice when I arrive at the
> last step of PTGui and actually "make" the panoramic image. I get some
> very good results, BTW, but it's all guess work.
>
> Is there any place I read an explanation of how to pick the best
> interpolator, and what Bicubic softer means vs. Lanczos16 (Sinc1024) vs.
> Spline64, etc.

Except for Nearest Neighbor the difference is subtle if visible at all
as long as you do a single interpolation as is the case for normal
panorama creation.

However, you asked for it: If you do a lot of consecutive interpolations
the differences get visible, as shown here:
http://photocreations.ca/interpolator/index.html
These examples are a bit outdated since they cover the original
non-antialiasing panotools interpolators. And most likely the bar image
(central column) for the three photoshop interpolators is wrong. But you
might get an idea.

In general the lanczos (sinc) interpolators are slightly sharpening and
can create echoes (like visible in the bar image) while the spline ones
are not. Hence the lanczos are best for landscape while the spline ones
are good for graphics. For interiors it depends. The higher the number
the better is the interpolator and the longer will it run.

The bicubic ones are universal, Nearest Neighbor is the fastest but
should only be used for previews and if images are not warped (f.e. for
batch merging to HDR). Bilinear is for low quality fast renderings.
Default is a good choice balancing quality and speed.

--
Erik Krause
http://www.erik-krause.de

[John Houghton]

On Wednesday, November 27, 2013 1:47:59 PM UTC, SunDance wrote:

Is there any place I read an explanation of how to pick the best
interpolator, and what Bicubic softer means vs. Lanczos16 (Sinc1024) vs.
Spline64, etc.

Peter, There's some basic advice given in the PTGui's Help pages: select the Create Panorama tab and then click Help->Help for this screen.

John 

[PTGui Support]

By the way, 'Default' simply uses Lanczos2 for normal images.

If the source images are 32 bit (.exr or .hdr) then Default maps to
Bicubic soft. This is because any interpolator with negative
coefficients will give artifacts when dealing with HDR source images.
Note that this only applies to hdr source images, not to bracketed sets.

Kind regards,

New House Internet Services BV
Joost Nieuwenhuijse

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PTGui - Photo Stitching Software

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[ravenfli...@gmail.com]

That was an excellent and extremely helpful answer. Thank you!