A test and need for advice

On Wed, 30 Aug 2017 16:39:40 +1200, Eric Stevens
wrote:

Here in Auckland we are just coming out of winter in the easrly days
of spring. In the last two months we have had as much rain as Houston
has had in two days but we are fortunate that it rains into the sea on
each side of us. We are starting to get bright clear days with harsh
light which seemed to me to be ideal to try out Photoshop CC's HDR
capability (never having used it before). So, taking the local bus
(free to me) I finished up at Victoria park on the outskirts of the
CBD. Harsh light, naked deciduous trees and almost no wind. It seemed
ideal.

I was experimenting to hell so I set the D750 to Auto ISO, f8,
exposure bracketing in groups of 3 at +1EV, 0EV and -1EV. I hadn't
realised it but the exposure was still on -0.7EV from a previous
shoot. The lens was the Tamron 24-70 f2.8. The camera settled on an
ISO of about 1250 and a shutter speed of around 1/1000sec which suited
my shaky hands, and at continuos low I fired of bursts of three.

Everything I have read about HDR has told me that it is essential to
mount the camera on a tripod but I have had success in the past with
hand held HDR using Paint Shop Pro so had deliberately decided to not
use a tripod on this occasion.

The images were processed in Photoshop's 'Merge to HDR Pro' and saved
as PSDs. The PSDs were lightly edited using the ACR filter and
received sharpening from Smart Sharpening. I also removed perspective
distortion. Here is a typical result
https://www.dropbox.com/s/dif31zuit3zv3vp/HDR1.jpg?dl=0

The old building in the corner was extremely harshly lit and it could
really have used a wider range of bracketing, but still it worked. I
was most impressed by the resolved detail in the branches and twigs of
the tree. Photoshop has done a very good job of aligning three
slightly different images.

I think it looks very good.

I walked around the park taking a number of shots and as I got to the
end I had a bright idea. Could I construct a panorama from a number of
hand-held HDR shots? So I stood there at the end and, swivelling
around my hips, I took six sets of HDR shots. I processed them as
above and then put them through Photomerge. I ticked all the boxes and
the resulting entirely hand-held HDR panorama may be found at
https://www.dropbox.com/s/gjschkqxtl...rama1.jpg?dl=0
It's best to view it at full screen if you can.

I have one problem and at the moment I am not quite sure how to deal
with it. You will see that the image of the park gives the impression
that it is slightly dish shaped. What is the best way to flatten it?

The dishing may be due to the photographs being taken at 24mm. The
workflow I followed did not seem to enable me to make a correction for
lens distortion and this might be the root cause. I will continue to
experiment.

To me, it looks like the structures on the sides are tilted in towards
the viewer. It's very odd. I would guess that the problem is that you
stood in one place and panned. That's normal, of course, but I see
that furthest point of the grass - I guess you could call that the
horizon - on the left is centered, is much lower in the middle, and is
still below center on the right. So either that's an artifact of the
stitching, or you were moving the camera vertically as you panned. If
it's an artifact, I'd agree that it might be because of the 24mm lens,
along with the subsequent lens correction in post.

On Wed, 30 Aug 2017 16:52:17 -0400, Ken Hart
wrote:


--- snip ---

I have one problem and at the moment I am not quite sure how to deal
with it. You will see that the image of the park gives the impression
that it is slightly dish shaped. What is the best way to flatten it?

The dishing may be due to the photographs being taken at 24mm. The
workflow I followed did not seem to enable me to make a correction for
lens distortion and this might be the root cause. I will continue to
experiment.



Very nice.

I think your "dish-shaped" issue is a matter of perception.

As SD pointed out in another post, the shadow in the foreground
(bleachers?) emphasizes any "dish-shape".

Not bleachers - a motorway flyover.

Also, the second group of trees from the left appear to be leaning. But
at second look, I think that's the way they are growing: a short trunk
with large branches coming out at an angle. The building behind those
trees is plumb and square. Likewise the goal (?) at the far left, and
the building at the far right- both are straight vertical.

I enlarged the image until the foreground shadow was nearly gone, and
the image looked fine.

In short, as far as the "dish-shape" you complain of, I think you're
nuts! Crop off the bottom at a point about halfway up to the goal, and
it will be a fine panorama.

BTW, the cranes in the background to the right of the spire need to go
back to NYC. PeterN can help you with that!--

We wouldn't notice. There are a whole lot more around the city.

The spire is the 'Sky Tower' which is 1076 ft tall. They used a tower
crane on that when they built it. The antennae mast weighed 170 tons
and need a special crane on the top of the tower to hoist it into
place. That crane needed an even taller tower crane to dismantle it
and get it down. I believe that was at a height approaching 1300 feet
and there were days when the crane driver could not see the ground.
through the clouds.
--

Regards,

Eric Stevens

On Wed, 30 Aug 2017 16:39:40 +1200, Eric Stevens
wrote:

--- snip ---

I have one problem and at the moment I am not quite sure how to deal
with it. You will see that the image of the park gives the impression
that it is slightly dish shaped. What is the best way to flatten it?

The dishing may be due to the photographs being taken at 24mm. The
workflow I followed did not seem to enable me to make a correction for
lens distortion and this might be the root cause. I will continue to
experiment.

I have found rthe answer and more importantly I have found the
question. :-)

As part of the expedition which gave rise to the original question I
tried a vertical merge of oak trees on a neighbours property. My merge
of the park was carried out using Photoshop's 'auto' setting. This
time I tried each of the manual settings individually to se what
affect they had. Here are the two images which were merged:
https://www.dropbox.com/sh/g4n6b47kt...2eZCzAjUa?dl=0

There are seven different merge settings in Photoshop: 'Auto',
'Perspective', 'Cylindrical', 'Spherical', 'Collage' and 'Reposition'.
A jpg of each of these may be found at
https://www.dropbox.com/sh/oeqxn5r1w...OF11RKvxa?dl=0
The individual images are named according to the setting used to
produce them.

It is clear that 'Cylindrical' and 'Spherical' introduces curvature
and, presumably, so too does 'Auto'. To check this out I went back to
the original merge of the park and did it again, this time with merge
set to 'Perspective'. Here is the resulting image:
https://www.dropbox.com/s/11cp5ejwn1...ctive.jpg?dl=0
Here it is when straightened up and cropped
https://www.dropbox.com/s/qg8k1rah47...rama2.jpg?dl=0

It is apparent that apart from variation of the shape of the objects
merged into the final image the horizontal and vertical scales can
become distorted. That last photograph should be about 50% wider and
so too should be the Sky Tower.

Final comment: after making the merges of the park photographs I tried
to save the images as PSD files. I was unable to manage that as the
file size exceeded the 2GB limit of Photoshop. I don't know what the
size of the target file would have been but the process of panorama
merging seems to require a lot of space. I would have thought that
with 32 GB of available memory I would have had available space but
there still seems to be some 32 bit software lurking at the heart of
64 bit Photoshop.
--

Regards,

Eric Stevens

On 08/31/2017 08:33 PM, Eric Stevens wrote:
On Wed, 30 Aug 2017 16:39:40 +1200, Eric Stevens
wrote:

--- snip ---

I have one problem and at the moment I am not quite sure how to deal
with it. You will see that the image of the park gives the impression
that it is slightly dish shaped. What is the best way to flatten it?

The dishing may be due to the photographs being taken at 24mm. The
workflow I followed did not seem to enable me to make a correction for
lens distortion and this might be the root cause. I will continue to
experiment.

I have found rthe answer and more importantly I have found the
question. :-)

As part of the expedition which gave rise to the original question I
tried a vertical merge of oak trees on a neighbours property. My merge
of the park was carried out using Photoshop's 'auto' setting. This
time I tried each of the manual settings individually to se what
affect they had. Here are the two images which were merged:
https://www.dropbox.com/sh/g4n6b47kt...2eZCzAjUa?dl=0

There are seven different merge settings in Photoshop: 'Auto',
'Perspective', 'Cylindrical', 'Spherical', 'Collage' and 'Reposition'.
A jpg of each of these may be found at
https://www.dropbox.com/sh/oeqxn5r1w...OF11RKvxa?dl=0
The individual images are named according to the setting used to
produce them.
It is clear that 'Cylindrical' and 'Spherical' introduces curvature
and, presumably, so too does 'Auto'. To check this out I went back to
the original merge of the park and did it again, this time with merge
set to 'Perspective'. Here is the resulting image:
https://www.dropbox.com/s/11cp5ejwn1...ctive.jpg?dl=0
Here it is when straightened up and cropped
https://www.dropbox.com/s/qg8k1rah47...rama2.jpg?dl=0

How about "Collage" and "Reposition" settings? They still to do well
with your tree.

It is apparent that apart from variation of the shape of the objects
merged into the final image the horizontal and vertical scales can
become distorted. That last photograph should be about 50% wider and
so too should be the Sky Tower.

Agree that everything is stretched vertically ("skinny")

Final comment: after making the merges of the park photographs I tried
to save the images as PSD files. I was unable to manage that as the
file size exceeded the 2GB limit of Photoshop. I don't know what the
size of the target file would have been but the process of panorama
merging seems to require a lot of space. I would have thought that
with 32 GB of available memory I would have had available space but
there still seems to be some 32 bit software lurking at the heart of
64 bit Photoshop.



--
Ken Hart