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acdsee full screen display resampling quality lacking?



 
 
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  #11  
Old September 12th 04, 02:34 AM
HandyAndy
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On Fri, 10 Sep 2004 18:47:29 +0000 (UTC),
wrote:

One image I have, it was a huge scanned image, 4000x4000, in ACDSee,
there were a lot of rough edges that I can see, but on ThumbsPlus, the
image were reduced nicely and everything was very smooth and sharp. If
I shrink the image in using ACDSee to screen resolution, it is also
displayed smoothly.


First off, you can't compare two displays unless they are both
displaying at the same resolution. If you zoom in on the ThumbsPlus
display to the same level of magnification as you use in ACDSee
you'll see identical image quality, just as you noticed.

Second, any seasoned photographer and graphics editor knows to turn
off any display resampling so they can see the true resolution and
detail of their photos from the actual pixels. Image display
resampling methods alters this when you zoom in to view the photo.
It smoothes them out, makes them look much nicer than they actually
are. In effect, you're looking at your photos through rose-colored
glasses.

Unless you're using the software for a slide-show ONLY, there's
absolutely no reason you should turn on any resampling algorithms
for viewing your images. Turn off all resampling for image displays,
or you'll never see all the errors and faults in your photography
that everyone else will see when you send your digital photos to
them. They're not going to put on the same rose-colored glasses that
you are so fond of just to make your images look better. Resampling
methods should ONLY be used for upsizing and downsizing images for
final output, never at any other time.

I wonder how many people forget to turn it off image display
resampling in their browser when looking at camera test photos and
editing software reviews online? This probably accounts for much of
the conflicting opinions that I read. Opera browser allows me the
option to turn off resampling, that's why I use it.


  #12  
Old September 12th 04, 07:17 AM
Dave Martindale
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Posts: n/a
Default

writes:

One image I have, it was a huge scanned image, 4000x4000, in ACDSee,
there were a lot of rough edges that I can see, but on ThumbsPlus, the
image were reduced nicely and everything was very smooth and sharp. If
I shrink the image in using ACDSee to screen resolution, it is also
displayed smoothly.


It sounds like ACDSee uses nearest-neighbour resampling for quickly
resizing too-large images. I still use ACDSee Classic, and it certainly
does just that. While this might have been a good choice when the
typical computer had a 100 or 200 MHz CPU clock, it produces a number of
nasty artifacts, and is a poor choice today. With today's CPUs, it
makes sense to use a resampling algorithm that filters the image
properly while resizing it.

Irfanview gives you the choice of either method, and that's why my
default image-opening application is Irfanview, not ACDSee. Although it
takes a little longer for Irfanview to calculate a properly-resized
image, the result is often much better looking and worth the wait - even
on my ancient PIII-700.

On the other hand, when browsing through a directory full of images, I
still use ACDSee because its one-image read-ahead helps a lot, and when
I'm looking at lots of images the quality of each one isn't so
important.

I think ACDsee has not improved its resampling algorithm over the
years, at the time it was pretty good, but now comparing to other
applications, it's being to show its age...


Another interesting case is Photoshop. Years ago, Photoshop used only
nearest-neighbour resampling for screen display, but it tried to
display at sizes that used integer downsampling ratios (25%, 33%, 50%)
to minimize effects like discontinuities in diagonals. Then at some
version Adobe introduced the "image cache", which is really a image
pyramid, several copies of the same image resampled to several smaller
sizes. Photoshop uses this for displaying reduced-size versions of the
image when it can, giving cleaner-looking results that are more
representative of how the image would look if you really reduced the
image to that size.

Dave
  #13  
Old September 12th 04, 07:28 AM
Dave Martindale
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Posts: n/a
Default

writes:

One image I have, it was a huge scanned image, 4000x4000, in ACDSee,
there were a lot of rough edges that I can see, but on ThumbsPlus, the
image were reduced nicely and everything was very smooth and sharp. If
I shrink the image in using ACDSee to screen resolution, it is also
displayed smoothly.


First off, you can't compare two displays unless they are both
displaying at the same resolution. If you zoom in on the ThumbsPlus
display to the same level of magnification as you use in ACDSee
you'll see identical image quality, just as you noticed.


He's saying that, in the normal screen display mode, when both programs
are shrinking the image, ThumbsPlus produces better-looking results than
ACDSee - at the same resolution. The quality is not the same.
Then he says that, if you tell ACDSee to resize the image in memory,
actually reducing the number of pixels, it *does* do a good job of that.
So the "image resize" operator uses a good algorithm, but the "reduce
large image for screen display" does not.

Second, any seasoned photographer and graphics editor knows to turn
off any display resampling so they can see the true resolution and
detail of their photos from the actual pixels.


What are you talking about? It's not possible to see the whole image
at once *without* resampling it if it's larger than the screen.
Sometimes you may have a choice between poor (e.g. nearest neighbour)
and good (e.g. bicubic) resampling, but you've got to use some form of
resampling. The only way to avoid it is to view the image at 100%,
which is fine for looking at detail, but can't show you the whole image.
And it's the quality of the resampling that is in question here.

Image display
resampling methods alters this when you zoom in to view the photo.
It smoothes them out, makes them look much nicer than they actually
are. In effect, you're looking at your photos through rose-colored
glasses.


Huh? What size reproduction are you talking about?

Unless you're using the software for a slide-show ONLY, there's
absolutely no reason you should turn on any resampling algorithms
for viewing your images. Turn off all resampling for image displays,
or you'll never see all the errors and faults in your photography
that everyone else will see when you send your digital photos to
them. They're not going to put on the same rose-colored glasses that
you are so fond of just to make your images look better. Resampling
methods should ONLY be used for upsizing and downsizing images for
final output, never at any other time.


How would you suggest someone look at a whole image then? There are
times when it's appropriate to look at bits of an image at 100%, but
there are other times when it's appropriate to view it at 25% or
whatever gets the whole thing on screen.

I wonder how many people forget to turn it off image display
resampling in their browser when looking at camera test photos and
editing software reviews online? This probably accounts for much of
the conflicting opinions that I read. Opera browser allows me the
option to turn off resampling, that's why I use it.


Automatic resizing in browsers is a different issue. But I'd argue that
anyone doing critical image examination with a browser is making a
mistake. Better to save the image, then look at it in your favourite
image editor.

Dave
  #14  
Old September 12th 04, 06:14 PM
James Addison
external usenet poster
 
Posts: n/a
Default

Dave Martindale wrote:

It sounds like ACDSee uses nearest-neighbour resampling for quickly
resizing too-large images. I still use ACDSee Classic, and it certainly
does just that. While this might have been a good choice when the
typical computer had a 100 or 200 MHz CPU clock, it produces a number of
nasty artifacts, and is a poor choice today. With today's CPUs, it
makes sense to use a resampling algorithm that filters the image
properly while resizing it.

Irfanview gives you the choice of either method, and that's why my
default image-opening application is Irfanview, not ACDSee. Although it
takes a little longer for Irfanview to calculate a properly-resized
image, the result is often much better looking and worth the wait - even
on my ancient PIII-700.

On the other hand, when browsing through a directory full of images, I
still use ACDSee because its one-image read-ahead helps a lot, and when
I'm looking at lots of images the quality of each one isn't so
important.

Another interesting case is Photoshop. Years ago, Photoshop used only
nearest-neighbour resampling for screen display, but it tried to
display at sizes that used integer downsampling ratios (25%, 33%, 50%)
to minimize effects like discontinuities in diagonals. Then at some
version Adobe introduced the "image cache", which is really a image
pyramid, several copies of the same image resampled to several smaller
sizes. Photoshop uses this for displaying reduced-size versions of the
image when it can, giving cleaner-looking results that are more
representative of how the image would look if you really reduced the
image to that size.

Dave


I would invite you to send your thoughts and ideas to
and/or visit the forums at
http://forums.acdsystems.com and put a post up. I will forward your
posting to the appropriate people in ACD Systems.

Thanks for your comments,


--
James Addison
http://www.pjsoft.ca
  #15  
Old September 13th 04, 11:32 PM
external usenet poster
 
Posts: n/a
Default

HandyAndy wrote:

Second, any seasoned photographer and graphics editor knows to turn
off any display resampling so they can see the true resolution and
detail of their photos from the actual pixels. Image display
resampling methods alters this when you zoom in to view the photo.
It smoothes them out, makes them look much nicer than they actually
are. In effect, you're looking at your photos through rose-colored
glasses.


When I view my digital camera images, I view them full screen, fit to
screen, without any borders/windows to distract me. Unless you have
very large monitors that runs 3000x2000 resolution, you have to shrink
the image. When you shrink the image, resampling takes place.

Different program uses different methods to shrink the image. Using a
better algorithm does NOT mean you are looking at your photos through
a rose-colored glass, it actually gives you a much better
approximation of how the image is supposed to look when properly
scaled down to your screen resolution. With a properly calibrated
monitor, one should be able to see differences in resampling
algorithm, especially on some photos.

I'll even say that, using a bad resampling (fast) algorithm, you are
making your image worst than what it really is.

Unless you're using the software for a slide-show ONLY, there's
absolutely no reason you should turn on any resampling algorithms
for viewing your images. Turn off all resampling for image displays,
or you'll never see all the errors and faults in your photography
that everyone else will see when you send your digital photos to
them. They're not going to put on the same rose-colored glasses that
you are so fond of just to make your images look better. Resampling
methods should ONLY be used for upsizing and downsizing images for
final output, never at any other time.


Well, to me, when I view the image, I want it to look its best. I DO
want the "final output".

I think what you are basically saying is, if you edit the image, then
you better check the image at 100% view instead of relying on whatever
resampling algorithm the program uses...

Raymond
  #16  
Old September 13th 04, 11:32 PM
external usenet poster
 
Posts: n/a
Default

HandyAndy wrote:

Second, any seasoned photographer and graphics editor knows to turn
off any display resampling so they can see the true resolution and
detail of their photos from the actual pixels. Image display
resampling methods alters this when you zoom in to view the photo.
It smoothes them out, makes them look much nicer than they actually
are. In effect, you're looking at your photos through rose-colored
glasses.


When I view my digital camera images, I view them full screen, fit to
screen, without any borders/windows to distract me. Unless you have
very large monitors that runs 3000x2000 resolution, you have to shrink
the image. When you shrink the image, resampling takes place.

Different program uses different methods to shrink the image. Using a
better algorithm does NOT mean you are looking at your photos through
a rose-colored glass, it actually gives you a much better
approximation of how the image is supposed to look when properly
scaled down to your screen resolution. With a properly calibrated
monitor, one should be able to see differences in resampling
algorithm, especially on some photos.

I'll even say that, using a bad resampling (fast) algorithm, you are
making your image worst than what it really is.

Unless you're using the software for a slide-show ONLY, there's
absolutely no reason you should turn on any resampling algorithms
for viewing your images. Turn off all resampling for image displays,
or you'll never see all the errors and faults in your photography
that everyone else will see when you send your digital photos to
them. They're not going to put on the same rose-colored glasses that
you are so fond of just to make your images look better. Resampling
methods should ONLY be used for upsizing and downsizing images for
final output, never at any other time.


Well, to me, when I view the image, I want it to look its best. I DO
want the "final output".

I think what you are basically saying is, if you edit the image, then
you better check the image at 100% view instead of relying on whatever
resampling algorithm the program uses...

Raymond
 




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