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Re: [OM] I must admit

Subject: Re: [OM] I must admit
From: Jim Nichols <jhnichols@xxxxxxxxxxxxx>
Date: Tue, 9 Feb 2016 18:17:29 -0600
Looks like a very good test pattern. I suspect that your photo was better than theirs, which appears to be a poorly joined 3-panel pano.

Jim Nichols
Tullahoma, TN USA

On 2/9/2016 6:12 PM, Chuck Norcutt wrote:
And here's the actual school. You may have to rotate around to find it. It has turquoise panels. <https://www.google.com/maps/@42.1005948,-76.0495774,3a,75y,176.58h,85.68t/data=!3m6!1e1!3m4!1ssewFktFBNda38zwapVTxVQ!2e0!7i13312!8i6656!6m1!1e1>

On 2/9/2016 7:01 PM, Chuck Norcutt wrote:
I did that in Endicott, NY.  You can be sure it wasn't done in February.
:-)

On 2/9/2016 4:24 PM, Jim Nichols wrote:
Hi Chuck,

It was too cold for me to go out and be as industrious as you.  I
settled for a framed painting on the living room wall.  Shot square on
and centered, it worked pretty well.

Jim Nichols
Tullahoma, TN USA

On 2/9/2016 2:35 PM, Chuck Norcutt wrote:
I wasn't aware that Picture Window Pro was now doing that.  I used to
use PTLens by ePaperPress.  It's a Photoshop plug-in that has
distortion profiles for lots of lenses which are provided by users of
the software.  I've provided profiles for most of my own lenses which
includes a lot of OM Zuikos as well as Canon mount Tokinas and Tamrons.

The procedure involves photographing an architectural subject with
very square lines.  The author was pleased with my test shots since he
said they were very easy to work with.  I chose a late 1950s 3-story
grammar school building whose exterior was largely straight aluminum
beams encompassing large windows and colored aluminum panels
separating the glass.  Vertical and horizontal lines all over the
place and very square.  He then does measurements from the images to
develop a distortion profile for the lens and at various focal lengths
for zooms.

PTLens is still available <http://epaperpress.com/ptlens/index.html>
You can get a free trial version that will correct 10 images.  After
that you need to buy a $25 license.  Here's an interesting comparison
between PTLens and Photoshop lens correction.  PTLens is superior in
some cases. <http://epaperpress.com/ptlens/lensCorrect.html>

Chuck Norcutt


On 2/9/2016 11:15 AM, Jim Nichols wrote:
Thanks, Moose. I use Picture Window Pro 7.0 as my image editor. I dug
into the documentation and found that I can take a sample image made
with a given lens, pull a broken line to the edge that I want to
straighten, hit compute, and it will calculate polynomial
corrections to
remove the barrel distortion.  This can then be saved for that lens,
and
recalled any time the correction is required.

With a few iterations, I got a perfect match to the in-camera JPG
image.  While not an automatic solution, it only adds one step to my
work flow, and only for problem images.

It will even work with fisheye lenses.

Jim Nichols
Tullahoma, TN USA

On 2/9/2016 3:14 AM, Moose wrote:
On 2/8/2016 9:58 PM, Jim Nichols wrote:
If I may join this thread, I must admit that I learned something new
(to me) today.  I have noticed that, starting with a RAW file, I
sometimes get some barrel distortion when capturing horizontal lines with the X-E1 and 35/2 lens. When I look at the camera-produced JPG,
most of the distortion is missing.  I concluded from this that the
lens corrections are missing from the RAW files.

Is this correct?

Yep, it's a RAW file, and thus not processed to correct the linear
distortion, or anything else. The information to make the corrections is in the RAW file. The RAW converter makes the correction as part of
the conversion from RAW to general purpose formats.

In the case of µ4/3 RAW files, Oly Viewer 3 and ACR/LR automatically
make the corrections, and in fact, that can't be turned off. So their
outputs exactly match the JPEGs that were corrected in camera. DxO
Optics Pro doesn't use the manufacturers' settings, but uses their
own, from their own testing, and one may turn correction on and off.
In limited testing, their corrections were better than the defaults in
ACR.

I know exactly nothing about Fuji RAW files and conversion, but there
is undoubtedly a way to make distortion correction a part of the
conversion process.

Straight Lines Moose




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