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Distortion fix formula/workflow for Tokina 12-24 AT-X Pro f/4?

 
 
k-man
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      04-28-2006
Hi:

I recently bought a Tokina 12-24 AT-X Pro f/4. Nice lens, especially
given the price. It's got some noticeable distortion, though,
particularly at the wide end. Anyone with any experience with this
lens care to share a workflow or Photoshop (I'm using CS at the moment)
formula that they've used or are using to help correct the distortion?
I've done a few by hand and it's not too terribly painful. But with
working with a lot of images of course any help is most welcome.

Thanks!
Kevin

 
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frederick
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      04-28-2006
k-man wrote:
> Hi:
>
> I recently bought a Tokina 12-24 AT-X Pro f/4. Nice lens, especially
> given the price. It's got some noticeable distortion, though,
> particularly at the wide end. Anyone with any experience with this
> lens care to share a workflow or Photoshop (I'm using CS at the moment)
> formula that they've used or are using to help correct the distortion?
> I've done a few by hand and it's not too terribly painful. But with
> working with a lot of images of course any help is most welcome.
>
> Thanks!
> Kevin
>

http://epaperpress.com/ptlens/
 
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k-man
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      04-29-2006
> k-man wrote:
> > Hi:

>
> > I recently bought a Tokina 12-24 AT-X Pro f/4. Nice lens, especially
> > given the price. It's got some noticeable distortion, though,
> > particularly at the wide end. Anyone with any experience with this lens
> > care to share a workflow or Photoshop (I'm using CS at the moment)
> > formula that they've used or are using to help correct the distortion?
> > I've done a few by hand and it's not too terribly painful. But with
> > working with a lot of images of course any help is most welcome.

>
>
> > Thanks!
> > Kevin

>
>
>
> http://epaperpress.com/ptlens/
>


Looks pretty slick. The Tokina's not in the database. But it looks
like I can submit photos for generating calibration and correction
values. Good tool.

Thanks.
Kevin

 
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2
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      04-29-2006
k-man wrote:

> I recently bought a Tokina 12-24 AT-X Pro f/4. Nice lens, especially
> given the price. It's got some noticeable distortion, though,


Gawd, that's horrible distortion. Even the fix leaves the contents (see the
lamps) skewed.


 
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k-man
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      04-29-2006

>
> k-man wrote:
>
>
> > I recently bought a Tokina 12-24 AT-X Pro f/4. Nice lens, especially >

> given the price. It's got some noticeable distortion, though,
>
> Gawd, that's horrible distortion. Even the fix leaves the contents (see
> the lamps) skewed.
>
>


I assume you're talking about the lamps in the PTLens "demo" pic.
Yeah, pretty bad. Only the center is really usable (to me anyway).
Fortunately, my pics don't start out anywhere near that distorted. I
tried the plug-in version on a test Nikon 12-24 pic I had taken and, at
least for that pic, PTLens seemed to work OK.

 
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bjw@mambo.ucolick.org
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      04-29-2006
2 wrote:

> Gawd, that's horrible distortion. Even the fix leaves the contents (see the
> lamps) skewed.


Assuming you're talking about the sample photo at
http://epaperpress.com/ptlens/
with the bikes in front of a wall, the original image appears
to be a section out of a fisheye image - both horizontal and
vertical lines are very curved. The corrected image is
rectilinear. The lamps look oval because objects at
the edge of a wide angle rectilinear image are stretched.
It is not a failing of the lens nor program, it's inherent
to rectilinear wide angle images. This is why, if you use
an extreme rectilinear wide angle to take a picture of a
group, the people at the edge will have egg-shaped heads.
(Well, will _look_ like they have egg-shaped heads.)

The original fisheye image makes the lamps look more
spherical, but straight lines running across large sections
of the image are obviously curved. You can't make a single
projection that works over wide areas, makes straight
lines straight, and preserves area/shape. It's the same
problem that makes it hard to represent the globe on
a flat map.

 
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frederick
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      04-29-2006
k-man wrote:
>>k-man wrote:
>>
>>>Hi:

>>
>>>I recently bought a Tokina 12-24 AT-X Pro f/4. Nice lens, especially
>>>given the price. It's got some noticeable distortion, though,
>>>particularly at the wide end. Anyone with any experience with this lens
>>>care to share a workflow or Photoshop (I'm using CS at the moment)
>>>formula that they've used or are using to help correct the distortion?
>>>I've done a few by hand and it's not too terribly painful. But with
>>>working with a lot of images of course any help is most welcome.

>>
>>
>>>Thanks!
>>>Kevin

>>
>>
>>
>>http://epaperpress.com/ptlens/
>>

>
>
> Looks pretty slick. The Tokina's not in the database. But it looks
> like I can submit photos for generating calibration and correction
> values. Good tool.
>
> Thanks.
> Kevin
>

The Tokina 12-24 is in the database, but maybe not against the dslr
model that you are using. It is there for Nikon, but I don't see it for
Canon. If you tell PTlens that you are using a Nikon, then it should be
very close - although the sensor size is different. (strikes me as kind
of odd, because I couldn't lay my hands on a Tokina with Nikon mount,
but the Canon mount ones seem reasonably readily available).
What PTLens is *exceptional* for is easy correction of more complex
distortion patterns, such as the "moustache" pattern seen on many of
these newer small sensor ultra w/a zooms, and wide/telephoto (17 or 18
to xx or xxx) zooms at the wide end.
Another interesting use for it, is to load an image of a grid pattern at
3:2 ratio, then see what all the lenses you might have ever wanted to
own are really like for distortion (assuming that the PTlens databse is
correct - which it seems to be for the lenses that I own). You see it
in "reverse" once "corrected" of course, but there are a few surprises
there. Distortion on some coveted (but older design) w/a prime lenses
is sometimes quite bad, and some of these newer zooms are very good.
 
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2
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      04-29-2006

"k-man" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
>
>>
>> k-man wrote:
>>
>>
>> > I recently bought a Tokina 12-24 AT-X Pro f/4. Nice lens, especially
>> >

>> given the price. It's got some noticeable distortion, though,
>>
>> Gawd, that's horrible distortion. Even the fix leaves the contents (see
>> the lamps) skewed.
>>
>>

>
> I assume you're talking about the lamps in the PTLens "demo" pic.
> Yeah, pretty bad. Only the center is really usable (to me anyway).
> Fortunately, my pics don't start out anywhere near that distorted. I
> tried the plug-in version on a test Nikon 12-24 pic I had taken and, at
> least for that pic, PTLens seemed to work OK.
>



 
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2
Guest
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      04-29-2006
<(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...

> It is not a failing of the lens nor program, it's inherent
> to rectilinear wide angle images.


It is inherent to a cheap, compromise designed "rectilinear" lens. That is
one crummy lens.





 
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2
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      04-29-2006
"frederick" <(E-Mail Removed)> wrote in message
news:1146299354.641509@ftpsrv1...

> [.,..] Distortion on some coveted (but older design) w/a prime lenses is
> sometimes quite bad, and some of these newer zooms are very good.


What OLD so-called w/a "prime lens" is coveted and still as bad as that? Who
would covet a lens that performs like that?

The zoomie in question is abysmal by any standard.

If you want outstanding w/a lenses, you have to go back to those that worked
without a mirror between the rear of the lens and the film or sensor. You
are doomed in the DSLR game.



 
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