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Wrong exposure when scanning truncated negative film (Nikon Coolscan V ED)



 
 
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  #1  
Old September 24th 10, 09:57 PM posted to rec.photo.digital
rwalker
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Posts: 484
Default Wrong exposure when scanning truncated negative film (Nikon Coolscan V ED)

On Fri, 24 Sep 2010 04:38:54 -0700 (PDT), Castor Nageur
wrote:

snip

* Please tell if you know a simpler/easiest way ?

Thanks in advance.


I sometimes get results like that. What I do is to crop the image,
and in Photoshop elements, I do, in order, auto contrast, auto color
correct, auto levels. Most of the time that gets me where I want to
be, but you can always do additional adjustments. I did that with
your image, and here is the result I get:

http://www.flickr.com/photos/51646689@N00/5021459976/

It took less than a minute.
  #2  
Old September 25th 10, 04:41 PM posted to rec.photo.digital
Dave Cohen
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Posts: 841
Default Wrong exposure when scanning truncated negative film (Nikon CoolscanV ED)

On 9/25/2010 9:56 AM, Castor Nageur wrote:
écrivait
:

What I do is to crop the image, and in Photoshop elements, I do, in

order, auto contrast, auto color correct, auto levels.

Applying 3 successive image processing will decrease the picture quality.
I was thinking of an analogical treatment instead of a digital one.
I hoped there was a way I did not found yet to auto-expose on a selected
scanner area.


The quality is only impacted when saving as jpg and that loss is grossly
overstated. I do avoid serial jpg saves.


  #3  
Old September 25th 10, 07:22 PM posted to rec.photo.digital
isw
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Posts: 212
Default Wrong exposure when scanning truncated negative film (Nikon Coolscan V ED)

In article ,
Castor Nageur wrote:

rwalker écrivait
:

What I do is to crop the image, and in Photoshop elements, I do, in

order, auto contrast, auto color correct, auto levels.

Applying 3 successive image processing will decrease the picture quality.
I was thinking of an analogical treatment instead of a digital one.


There's no reason to expect that an "analog" treatment would be superior
to a "digital" one. There's plenty of theoretical proof of their
equivalency.

Isaac
  #4  
Old September 25th 10, 09:46 PM posted to rec.photo.digital
Peter[_7_]
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Posts: 2,078
Default Wrong exposure when scanning truncated negative film (Nikon Coolscan V ED)

"Castor Nageur" wrote in message
...
rwalker écrivait
:

What I do is to crop the image, and in Photoshop elements, I do, in

order, auto contrast, auto color correct, auto levels.

Applying 3 successive image processing will decrease the picture quality.
I was thinking of an analogical treatment instead of a digital one.
I hoped there was a way I did not found yet to auto-expose on a selected
scanner area.



Where did you ever get that idea from?
Even JPEG takes a lot of opening and reopening before you have noticeable,
unintentional degradation.



--
Peter

  #5  
Old September 25th 10, 10:36 PM posted to rec.photo.digital
Ofnuts
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Posts: 644
Default Wrong exposure when scanning truncated negative film (Nikon CoolscanV ED)

On 25/09/2010 22:46, Peter wrote:
"Castor Nageur" wrote in message
...
rwalker écrivait
:

What I do is to crop the image, and in Photoshop elements, I do, in

order, auto contrast, auto color correct, auto levels.

Applying 3 successive image processing will decrease the picture quality.
I was thinking of an analogical treatment instead of a digital one.
I hoped there was a way I did not found yet to auto-expose on a selected
scanner area.



Where did you ever get that idea from?
Even JPEG takes a lot of opening and reopening before you have
noticeable, unintentional degradation.


Actually I did some tests and as long as you don't change JPEG
compression parameters and don't perform global edits (color balance,
contrast and such) there is no degradation at all even with very high
compression.

--
Bertrand
  #6  
Old September 25th 10, 10:47 PM posted to rec.photo.digital
Peter[_7_]
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Posts: 2,078
Default Wrong exposure when scanning truncated negative film (Nikon Coolscan V ED)

"Ofnuts" wrote in message
...
On 25/09/2010 22:46, Peter wrote:
"Castor Nageur" wrote in message
...
rwalker écrivait
:

What I do is to crop the image, and in Photoshop elements, I do, in
order, auto contrast, auto color correct, auto levels.

Applying 3 successive image processing will decrease the picture
quality.
I was thinking of an analogical treatment instead of a digital one.
I hoped there was a way I did not found yet to auto-expose on a selected
scanner area.



Where did you ever get that idea from?
Even JPEG takes a lot of opening and reopening before you have
noticeable, unintentional degradation.


Actually I did some tests and as long as you don't change JPEG compression
parameters and don't perform global edits (color balance, contrast and
such) there is no degradation at all even with very high compression.



Your statement is consistent with my understanding. Except that any time
pixels are dropped and restored the restoration is based upon assumptions
that may not be accurate.
The way I understand it is that the compression-decompression algorithm
makes assumptions about the color of the adjacent pixels and drops a lot of
the pixels that duplicate the ones that are kept. (If the sky is blue on one
location, nearby locations will also have a blue sky.) When you change the
adjacent pixels, the original assumptions are no longer valid and there is
degradation upon restoration.

OK gearheads! My above statement oversimplifies the problem. So you are free
to attack my statement and explain the algorithm in plain English, so even I
can understand the theory.

--
Peter

  #7  
Old September 26th 10, 12:11 AM posted to rec.photo.digital
Kennedy McEwen
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Posts: 639
Default Wrong exposure when scanning truncated negative film (Nikon Coolscan V ED)

In article ], isw
writes
In article ,
Castor Nageur wrote:

rwalker écrivait
:

What I do is to crop the image, and in Photoshop elements, I do, in

order, auto contrast, auto color correct, auto levels.

Applying 3 successive image processing will decrease the picture quality.
I was thinking of an analogical treatment instead of a digital one.


There's no reason to expect that an "analog" treatment would be superior
to a "digital" one. There's plenty of theoretical proof of their
equivalency.

Show me the theoretical proof that digital processing a scan which has
been underexposed by several stops, due to the missing part of the frame
in this case upsetting the scanner auto-exposure, is in any way
"equivalent" in quality to correctly exposing it in the first place.

If your claim was in any way true there would be no need for scanners to
have more than 1-bit ADC resolution, since it would be possible to
extract the full dynamic range, colour depth and signal to noise ratio
by digitally processing that single bit image.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
  #8  
Old September 26th 10, 12:17 AM posted to rec.photo.digital
Ofnuts
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Posts: 644
Default Wrong exposure when scanning truncated negative film (Nikon CoolscanV ED)

On 25/09/2010 23:47, Peter wrote:
"Ofnuts" wrote in message
...
On 25/09/2010 22:46, Peter wrote:
"Castor Nageur" wrote in message
...
rwalker écrivait
:

What I do is to crop the image, and in Photoshop elements, I do, in
order, auto contrast, auto color correct, auto levels.

Applying 3 successive image processing will decrease the picture
quality.
I was thinking of an analogical treatment instead of a digital one.
I hoped there was a way I did not found yet to auto-expose on a
selected
scanner area.


Where did you ever get that idea from?
Even JPEG takes a lot of opening and reopening before you have
noticeable, unintentional degradation.


Actually I did some tests and as long as you don't change JPEG
compression parameters and don't perform global edits (color balance,
contrast and such) there is no degradation at all even with very high
compression.



Your statement is consistent with my understanding. Except that any time
pixels are dropped and restored the restoration is based upon
assumptions that may not be accurate.


There are no "assumptions", only computations :-)

The way I understand it is that the compression-decompression algorithm
makes assumptions about the color of the adjacent pixels and drops a lot
of the pixels that duplicate the ones that are kept. (If the sky is blue
on one location, nearby locations will also have a blue sky.) When you
change the adjacent pixels, the original assumptions are no longer valid
and there is degradation upon restoration.


Everything happens in a 8x8 block. The contents of a block are totally
immune from the content of the adjacent blocks. And if nothing changes
in the block, the re-computation yields the very same numbers than the
contents of the block where decoded from.

OK gearheads! My above statement oversimplifies the problem. So you are
free to attack my statement and explain the algorithm in plain English,
so even I can understand the theory.


Check Wikipedia. More than you want to know


--
Bertrand
  #9  
Old September 26th 10, 12:25 AM posted to rec.photo.digital
Kennedy McEwen
external usenet poster
 
Posts: 639
Default Wrong exposure when scanning truncated negative film (Nikon Coolscan V ED)

In article , Castor Nageur
writes
rwalker écrivait
:

What I do is to crop the image, and in Photoshop elements, I do, in

order, auto contrast, auto color correct, auto levels.

Applying 3 successive image processing will decrease the picture quality.
I was thinking of an analogical treatment instead of a digital one.
I hoped there was a way I did not found yet to auto-expose on a selected
scanner area.


Just turn the auto-exposure off and use a fixed, if necessary manually
adjusted, exposure for the entire roll of film. The reason that the
CS-V has 14-bit ADC is to accommodate the huge dynamic range of slide
film. Colour negative film has nowhere near that dynamic range, little
over 2D, and this will easily fit within the 4.2Dmax of the scanner,
irrespective of any exposure errors on the original film image itself.

If it was slide film, or non-chromagenic B&W, that you had this problem
with then there would be no work around to the manual exposure, since
slide film utilises the entire density range of the scanner. However,
with colour negative film, autoexposure for each frame is just a waste
of scan time.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
  #10  
Old September 26th 10, 03:40 AM posted to rec.photo.digital
James Nagler
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Posts: 70
Default Wrong exposure when scanning truncated negative film (Nikon Coolscan V ED)

On Sat, 25 Sep 2010 17:47:40 -0400, "Peter"
wrote:

"Ofnuts" wrote in message
...
On 25/09/2010 22:46, Peter wrote:
"Castor Nageur" wrote in message
...
rwalker écrivait
:

What I do is to crop the image, and in Photoshop elements, I do, in
order, auto contrast, auto color correct, auto levels.

Applying 3 successive image processing will decrease the picture
quality.
I was thinking of an analogical treatment instead of a digital one.
I hoped there was a way I did not found yet to auto-expose on a selected
scanner area.


Where did you ever get that idea from?
Even JPEG takes a lot of opening and reopening before you have
noticeable, unintentional degradation.


Actually I did some tests and as long as you don't change JPEG compression
parameters and don't perform global edits (color balance, contrast and
such) there is no degradation at all even with very high compression.



Your statement is consistent with my understanding. Except that any time
pixels are dropped and restored the restoration is based upon assumptions
that may not be accurate.
The way I understand it is that the compression-decompression algorithm
makes assumptions about the color of the adjacent pixels and drops a lot of
the pixels that duplicate the ones that are kept. (If the sky is blue on one
location, nearby locations will also have a blue sky.) When you change the
adjacent pixels, the original assumptions are no longer valid and there is
degradation upon restoration.

OK gearheads! My above statement oversimplifies the problem. So you are free
to attack my statement and explain the algorithm in plain English, so even I
can understand the theory.


Trying to re-educate you on all your wrong assumptions would be like trying
to explain physics to a slug in a garden--pointless and not worth anyone's
time.

 




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