"Fixing" distortion?

I recently bought a 15mm full-frame fisheye, mainly for fun and
amusement, but it could be used for some serious wide-angles, also. I
have had thoughts about buying Canon's 24mm tilt-shift lens... someday.
I remember Bret rented one and decided it wasn't worth buying one.

I have been doing some reading and thinking and have started to wonder
if maybe using my 15mm, or any lens, and a program such as Image Align
might be a cheaper and reasonable alternative than the $1100+/- that
the tilt-shift lens would cost. Any thoughts or experiences?

TheDave© wrote:
I recently bought a 15mm full-frame fisheye, mainly for fun and
amusement, but it could be used for some serious wide-angles, also. I
have had thoughts about buying Canon's 24mm tilt-shift lens... someday.
I remember Bret rented one and decided it wasn't worth buying one.

I have been doing some reading and thinking and have started to wonder
if maybe using my 15mm, or any lens, and a program such as Image Align
might be a cheaper and reasonable alternative than the $1100+/- that
the tilt-shift lens would cost. Any thoughts or experiences?

My only thought on this is that as long as you're scaling "inward"
(compressing) to fix a distortion then no artifacts are made. But
anywhere where the distortion fix stretches outward then artifacts are made.

I don't know if for a fisheye that distortion fixes employ both, eg:
parts of the scene compress and other stretch to linearize the image.
If stretching is involved, then the overall image will have to be
downsampled to eliminate any 'stretch marks' in the image.

I received the following bit of spam the other day, maybe it can be of
use to you: http://www.imagetrendsinc.com/ There's a free trial. I have
no idea if it is any good.

Obviously a tilt-shift lens would be best, but in the Canon tilt-shift
lens I believe that also clips part of the image (??).

G'luck!

Alan.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.

I am increasingly of the Photoshop-fixes-everything persuasion: what the
picture looks like at the end is all that counts, not how you get there.
It is problematic to correct for all the distortion that a fisheye
introduces although there are programs and plug-ins that claim to do so.
However it is not difficult to correct for keystoning of architectural
subjects. Most often correction in more than one direction/dimension is
required but with practice this becomes less difficult.
It is important to include enough background in the original image because
of the cropping that will be necessary.
I do not see how making these corrections in Photoshop is any less valid
than making them with swings and tilts on the film plane.
People have to shed the mentality of how things were done prior to the
availability of digital tools. Swings/tilts, PC lenses are great but not the
only way to accomplish things.

bmoag wrote:
I am increasingly of the Photoshop-fixes-everything persuasion: what the
picture looks like at the end is all that counts, not how you get there.
It is problematic to correct for all the distortion that a fisheye
introduces although there are programs and plug-ins that claim to do so.
However it is not difficult to correct for keystoning of architectural
subjects. Most often correction in more than one direction/dimension is
required but with practice this becomes less difficult.
It is important to include enough background in the original image because
of the cropping that will be necessary.
I do not see how making these corrections in Photoshop is any less valid
than making them with swings and tilts on the film plane.
People have to shed the mentality of how things were done prior to the
availability of digital tools. Swings/tilts, PC lenses are great but not the
only way to accomplish things.



Photoshop can, to a great degree, substitute shifts, but tilts are are
another matter.

What isn't captured in focus in the beginning, can't be "Photoshopped"
afterwards.

I've never used a fisheye but correct perspective and WA barrel distortion
as a matter of course with Photoshop.
http://www.pbase.com/stanmore/image/72147131/original is a good example. If
I could afford a Canon 24mm TS lens I would get one because it would let me
compose 'perfectly' at capture
--
Simon



"TheDave©" wrote in message
...
I recently bought a 15mm full-frame fisheye, mainly for fun and
amusement, but it could be used for some serious wide-angles, also. I
have had thoughts about buying Canon's 24mm tilt-shift lens... someday.
I remember Bret rented one and decided it wasn't worth buying one.

I have been doing some reading and thinking and have started to wonder
if maybe using my 15mm, or any lens, and a program such as Image Align
might be a cheaper and reasonable alternative than the $1100+/- that
the tilt-shift lens would cost. Any thoughts or experiences?

Simon Stanmore wrote:
I've never used a fisheye but correct perspective and WA barrel distortion
as a matter of course with Photoshop.
http://www.pbase.com/stanmore/image/72147131/original is a good example.

I liked the way you removed the poster as well.

BTW, where ya been lately?

bmoag wrote:
I am increasingly of the Photoshop-fixes-everything persuasion: what
the picture looks like at the end is all that counts, not how you get
there. It is problematic to correct for all the distortion that a
fisheye introduces although there are programs and plug-ins that
claim to do so. However it is not difficult to correct for
keystoning of architectural subjects. Most often correction in more
than one direction/dimension is required but with practice this
becomes less difficult. It is important to include enough background
in the original image because of the cropping that will be necessary.
I do not see how making these corrections in Photoshop is any less
valid than making them with swings and tilts on the film plane.
People have to shed the mentality of how things were done prior to
the availability of digital tools. Swings/tilts, PC lenses are great
but not the only way to accomplish things.

I understand what you're saying, but I'm thinking more from a cost
perspective. *If* the same results could be obtained in the computer
with a particular software, then it would be much cheaper than buying
the lens, and I could get at it sooner because I can't afford the lens
right now.

In article , says...
I recently bought a 15mm full-frame fisheye, mainly for fun and
amusement, but it could be used for some serious wide-angles, also. I
have had thoughts about buying Canon's 24mm tilt-shift lens... someday.
I remember Bret rented one and decided it wasn't worth buying one.

I have been doing some reading and thinking and have started to wonder
if maybe using my 15mm, or any lens, and a program such as Image Align
might be a cheaper and reasonable alternative than the $1100+/- that
the tilt-shift lens would cost. Any thoughts or experiences?

You can fix perspective keystone distortion using Photoshop. I have
some tips on my web site showing several ways to do this.
You can also fix warp distortion as is caused by fisheye and
rotating panorama cameras using the free plugin Panorama Tools.
I show how this is done using cylindrical projections as well, to
correct spherical distortion the steps are the same you just pick
different options within the plugin.

It is also possible to approximate the shift in the plane of sharpness
which a tilting lens can perform. One uses a wide angle lens and tilts
the whole camera to bring the desired plane into focus. This shifts
the image to the edge of the frame. Then one crops out the portion
needed and makes any perspective adjustments. This is not exactly
the same as tilting only the lens and needs more magnification to
get to the same final size, but it is better than nothing.

--
Robert D Feinman
Landscapes, Cityscapes and Panoramic Photographs
http://robertdfeinman.com
mail:

Simon Stanmore wrote:
I've never used a fisheye but correct perspective and WA barrel distortion
as a matter of course with Photoshop.
http://www.pbase.com/stanmore/image/72147131/original is a good example. If
I could afford a Canon 24mm TS lens I would get one because it would let me
compose 'perfectly' at capture

A little cut and paste over the poster as well.

Color corrected or enhanced?

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.

Have been reading and posting Bret just not so much as a few years back when
it was much busier here
--
Simon


"Annika1980" wrote in message
ups.com...

Simon Stanmore wrote:
I've never used a fisheye but correct perspective and WA barrel
distortion
as a matter of course with Photoshop.
http://www.pbase.com/stanmore/image/72147131/original is a good example.

I liked the way you removed the poster as well.

BTW, where ya been lately?