Question for Don - Scan Twice

[DBM]

Don,
I read in another thread where you state you scan your slides twice.
Scan once for shadows and once for highlights. Can you explain how you
adjust the scanning software for each scan and then how you combine the
scans. I use a Coolscan IV scanner with Nikonscan software and Photoshop
Elements for my editor.

DBM

 

[Roger S.]

I believe Don will recommend this program:
http://hdrshop.com/

I recomend the free demo "combine two exposures" feature of this
program:
http://www.hdrsoft.com/

Scan at max resolution and set the cropping area to maximum. Try a
nominal exposure and then one that is way overexposed. Merge in the
above software and then edit in Photoshop.

 

[Bart van der Wolf]

I believe Don will recommend this program:
http://hdrshop.com/

It is not *his* program, but he has recommended it in the past. It is
a useful program to create/view an HDR composite from multiple
differently exposed LDR images.

Basic HDRShop shortcomings IMHO are lack of alignment/registration
functionality (=essential !), and 8-b/ch LDR output if you want
anything else than an HDR output, therefore Tiff output is
8-bit/channel.

I recomend the free demo "combine two exposures" feature
of this program:
http://www.hdrsoft.com/

Yes Photomatix does, amongst other things, produce a 16-b/ch "blended"
composite from multiple exposures, *AND* it aligns them before doing
so. A potential drawback (it depends on the input dynamic range
offered) is that the result may (need to) be somewhat tonemapped to
fit the High Dynamic Range in 16-b/ch. That would introduce some
non-linearity in Linear Gamma Raw scanner data, if that's an issue for
the intended use.

The Photomatix results are quite useful, if alignment is good. It also
allows to produce an HDR composite which would then be post processed,
e.g. with Photoshop CS2 or other HDR aware tools.

Scan at max resolution and set the cropping area to maximum. Try
a nominal exposure and then one that is way overexposed. Merge
in the above software and then edit in Photoshop.

The scan exposure difference needs to be within reasonal levels,
because excessive overexposure may lead to other image artifacts. So a
lot also depends on the film in question, and the actual exposure
level of that image. Slide film e.g. has very poor color accuracy in
its deepest shadows.

Bart

 

[Don]

It is not *his* program, but he has recommended it in the past.

Roger did not say it was my program. Calm down Bart and *read*!

And I did not "recommend" it but only offered it as a fully functional
yet free solution for people to get their feet wet.

You get too easily overexcited when you see a message from Don.

Basic HDRShop shortcomings IMHO are lack of alignment/registration
functionality (=essential !), and 8-b/ch LDR output if you want
anything else than an HDR output, therefore Tiff output is
8-bit/channel.

Of course, you're wrong because the algorithm HDRShop is based on
incorporates automatic alignment.

And you know you're wrong, Bart, because I've already explained it all
to you several times in the past and below you'll find an example.

You really need to stop obsessing with Don's messages or, at the very
least, calm down before commenting.

I know... The last thing people who are overexcited want to hear is
that they need calm down first... ;o)

Don.

---start---

That tells more about your "experience" than about HDR Shop:

--- start ---
...it does not scan precisely the same area of each negative relative
to the extents of the image. To counteract this effect, we
geometrically registered the images to each other using normalized
correlation to determine, with sub-pixel accuracy, corresponding
pixels between pairs of images.
--- end ---

"Geometrically registered images...", "using normalized
correlation...", ***with sub-pixel accuracy***... Need I say more?

I won't even bother with:


because is just plain silly. It's like saying a 4000 dpi scanner
"doesn't allow" 100 dpi scans.

Don.

---end---

 

[Randy Howard]

Roger S. wrote
(in article

I believe Don will recommend this program:
http://hdrshop.com/

I recomend the free demo "combine two exposures" feature of this
program:
http://www.hdrsoft.com/

Scan at max resolution and set the cropping area to maximum. Try a
nominal exposure and then one that is way overexposed. Merge in the
above software and then edit in Photoshop.

What's wrong with doing the HDR merge in Photoshop?

 

[Bart van der Wolf]

SNIP

What's wrong with doing the HDR merge in Photoshop?

1. It assumes one has access to Photoshop CS2
2. HDR merge in Photoshop converts the input to 8-bit/channel images,
which implicitly 'requires' the image to be gamma adjusted. That makes
it a bit more difficult to calibrate exposure levels, IOW reconstruct
the OECF (Opto-Electronic Conversion Function).
3. Alignment in Photoshop fails on large pixel size images on my
system (maybe I need more system memory, maybe the first PS
incarnation of HDR merge needs a bit more work).

On large pixel size images, it is usually not sufficient to only
translate (shift) images into registration. A very small rotation will
become a significant pixel rotation offset as the distance from the
center of rotation increases.

Here is an example crop of a 5 image merge* from HSDShop, and an
example crop of the same 5 images, merged* by Photomatix:
<http://www.xs4all.nl/~bvdwolf/temp/HDR-merge.jpg> .

* Both automatically merged HDR images, received exactly the same
tonemapping adjustment in Photoshop CS2 to allow 8-b/ch display.

Whatever auto-alignment HDRShop used (it can't be controlled by the
user), IMHO it failed, where as under the same automatic conditions
Photomatix succeeded.

And this is what the entire image would look like, without:
<http://www.xs4all.nl/~bvdwolf/temp/Bridge.jpg> ,
and with the tonemapping applied:
<http://www.xs4all.nl/~bvdwolf/temp/Bridge_tonemapped.jpg>

Bart

 

[Randy Howard]

Bart van der Wolf wrote

SNIP

1. It assumes one has access to Photoshop CS2
Ok.

2. HDR merge in Photoshop converts the input to 8-bit/channel images,
which implicitly 'requires' the image to be gamma adjusted. That makes
it a bit more difficult to calibrate exposure levels, IOW reconstruct
the OECF (Opto-Electronic Conversion Function).

I guess I'm going to have to go study some more, never heard of
OECF before now.

3. Alignment in Photoshop fails on large pixel size images on my
system (maybe I need more system memory, maybe the first PS
incarnation of HDR merge needs a bit more work).

On large pixel size images, it is usually not sufficient to only
translate (shift) images into registration. A very small rotation will
become a significant pixel rotation offset as the distance from the
center of rotation increases.

Here is an example crop of a 5 image merge* from HSDShop, and an
example crop of the same 5 images, merged* by Photomatix:
<http://www.xs4all.nl/~bvdwolf/temp/HDR-merge.jpg> .

Is that the same sort of problem you see with Photoshop's
built-in (CS2)?? I haven't heard anyone report anything like
the top half of that image with CS2 before.

Whatever auto-alignment HDRShop used (it can't be controlled by the
user), IMHO it failed, where as under the same automatic conditions
Photomatix succeeded.

And this is what the entire image would look like, without:
<http://www.xs4all.nl/~bvdwolf/temp/Bridge.jpg> ,
and with the tonemapping applied:
<http://www.xs4all.nl/~bvdwolf/temp/Bridge_tonemapped.jpg>

Looks a bit too washed out to my eye.

 

[Don]

What's wrong with doing the HDR merge in Photoshop?

There are number of issues. I don't think Elements (which is what DBM
asked about) has HDR merge. Indeed, only the latest versions of PS
have some HDR support, AFAIK.

But there are problems with that too because I remember reading that
CS2, for example, does the same thing as HDRShop. It can open 16-bit
files but it converts them to 8-bit before (HDR) merging.

Also, I don't think PS does any alignment either.

But as someone who still uses an ancient PS6 (because it does all I
need) I'll let others fill in the details re capabilities of more
recent PS versions.

Don.

 

[Randy Howard]

Don wrote

But there are problems with that too because I remember reading that
CS2, for example, does the same thing as HDRShop. It can open 16-bit
files but it converts them to 8-bit before (HDR) merging.

Also, I don't think PS does any alignment either.

It does have an option to do alignment, but I don't have any
sample images right now that need it to test with.

But as someone who still uses an ancient PS6 (because it does all I
need) I'll let others fill in the details re capabilities of more
recent PS versions.

Well, I just downloaded Photomatix Pro, and using the sample
images it ships with, I did a quick test with Combine and
HDR/Tone Map and compared that to what Photoshop CS2 would do
with the same source images. Suffice it to say that CS2 was
slain badly.

So, I decided to try the Photomatix tone mapping plugin for CS2
and see how it did with an HDR generated with CS2. When I did
that with the same images, when I selected the Photomatix
plugin, it actually looked slightly better than the Photomatix
Pro generated image while I was in preview, but once I hit "ok"
to let it churn, the resulting image turned out very, very dark.
However, I converted the image back down to 16-bit per channel.
Looking at the histogram (not available in 32), it was basically
only HALF of the normal range. No idea what I did wrong, but
that is clearly not the expected result.

Then I tried an "Auto Levels" on the same image, and the result
was considerably better than that generated by Photomatix Pro on
its own. (As the preview showed earlier before I committed it)
I wouldn't call either of them "perfect", there is a bit of
color banding in the left half of the sky around where the sun
has blown it out, with slightly different effects in each
version.

I suspect I could tweak around on the settings to try to make
the standalone app work better, but already having CS2, it
doesn't seem to make a lot of sense. So, now the question is,
is there any reason to buy the complete PhotoMatix Pro
application (for some other features I'm not yet aware of), or
just spring for the Photoshop plugin, which seems to work very,
very well, at least with the sample images.

 

[Bart van der Wolf]

SNIP

Is that the same sort of problem you see with Photoshop's
built-in (CS2)??

No, Photoshop just complains it cannot process/complete the alignment
task, and stops.

SNIP

Looks a bit too washed out to my eye.

Yes, I agree (a slight S-shaped "Curves" correction afterwards would
solve it though). But since tonemapping is highly tunable, one can
create whatever rendering looks pleasing.

Bart

 

[Bart van der Wolf]

SNIP

So, now the question is, is there any reason to buy the
complete PhotoMatix Pro application (for some other
features I'm not yet aware of), or just spring for the
Photoshop plugin, which seems to work very, very well,
at least with the sample images.

The Photomatix Pro demo will still offer some alignment functionality,
the available exposure blending methods offer a non-watermarked
result, and you can produce an HDR file if you want.

For HDR postprocessing, tonemapping is the art part of the workflow.
Before spending money on the Photomatix plug-in, you may want to also
checkout the FDRCompressor Plug-In:
<http://www.fdrtools.com/fdrcompressor-plugin/fdrcompressor_plugin_e.php>
It looks a bit simple, but produces nice results.

Bart

 

[Don]

It does have an option to do alignment, but I don't have any
sample images right now that need it to test with.

That's OK. As I say I only have PS6 and do the merge using my own
program which does the complete transformation, not just a fixed
offset alignment.

That's because (after extensive testing) I've determined that the
misalignment is not uniform and fixed across the whole image but
varies on *both* vertical and horizontal axis!

The stepper motor speed is not constant as it travels across the film
(as expected) but, apparently, the whole assembly also "wiggles"
causing differences on the other axis as well (which I didn't expect).

Well, I just downloaded Photomatix Pro, and using the sample
images it ships with, I did a quick test with Combine and
HDR/Tone Map and compared that to what Photoshop CS2 would do
with the same source images. Suffice it to say that CS2 was
slain badly.

Like all leaders (quasi monopolists) in any market PS is dragged
kicking and screaming to add new features and does that, grudgingly,
only when they perceive the competition to be a potential threat and
they can't hold back the progress anymore. :-(

That's another reason why I decided to "roll my own". I didn't like
the fudging many programs/methods do (e.g. blurring the border between
the two images to hide the color imbalance). I wanted a perfect color
match so I could use a hard edge, as well as the ability to control
exactly where in the histogram the border is, as well as move it.

Don.

 

[Randy Howard]

Don wrote

Like all leaders (quasi monopolists) in any market PS is dragged
kicking and screaming to add new features and does that, grudgingly,
only when they perceive the competition to be a potential threat and
they can't hold back the progress anymore. :-(

Ummm, I think you snipped too early. The above wasn't actually
written correctly. The first comparison was photoshop without
tone mapping (just the merge to HDR part). If Photoshop has a
built in "tone mapping" feature, I haven't found it yet. That
comparison is where CS2 fell flat. Later on in the post I
describe using the Photomatix tone mapping plugin, and how that
gave *better* results than Photomatix pro alone on the same
sample images.

That's another reason why I decided to "roll my own". I didn't like
the fudging many programs/methods do (e.g. blurring the border between
the two images to hide the color imbalance). I wanted a perfect color
match so I could use a hard edge, as well as the ability to control
exactly where in the histogram the border is, as well as move it.

Sounds like an interesting project.

 

[Bart van der Wolf]

SNIP

If Photoshop has a built in "tone mapping" feature, I haven't
found it yet.

As soon as you change the mode from 32-bits to 16 or 8-b/ch, you'll be
presented with several options.

Bart

 

[Randy Howard]

Bart van der Wolf wrote

SNIP

As soon as you change the mode from 32-bits to 16 or 8-b/ch, you'll be
presented with several options.

Hmmm... I need to spend more time with it, obviously.

 

[Randy Howard]

Bart van der Wolf wrote

SNIP

The Photomatix Pro demo will still offer some alignment functionality,
the available exposure blending methods offer a non-watermarked
result, and you can produce an HDR file if you want.

I just tried running a batch of four very large images --
48-bit, 4800dpi scans of 35mm slides with different amounts of
exposure changes during the scan process. Photomatix took
forever to complete, despite having dual processors and 4GB of
RAM, but it did manage to do a nice job with the colors overall,
but zoom'd in at 100%, it has little 'clouds' of color, as if
the alignment (which should have been at least close since the
scanner wasn't touched between passes) didn't quite sync up the
4 images properly.

I'm going to have to try this with some digital images,
hopefully it will be easier to get the pixel alignment better
that way.