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Old 08-25-2008, 10:11 AM   #1
Stephan.klose Stephan.klose is offline
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Default DNR applied to Blu Ray. What exactly does it mean?

In a recent review of "Sum of all Fears" i read "Heavy DNR, consistens edge enhancement... and so on..
In almost any review I read on High-Def-Digest the reviewers are complaining about DNR. The only thing I found in wikipedia about the subject were the following:" Digital Noise Reduction or DNR is a software program used to enhance the quality of digital photographic reproductions of either still or moving images. It is a tool especially useful to correct imperfections (such as film grain, electronic noise, film speckles, dirt, scratches, etc) inherent in the source material, in particular those from film negatives, photographs and other such copies.[1]"

So can someone explain to me why DNR is such a problem?
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Old 08-25-2008, 10:18 AM   #2
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Some people doing the encodes use it because they think there's too much film grain visible. Film grain also gets increased when multiple generation copies of a piece of film are made (so scanning the original negative would be better than scanning a multi-generation copy). How much visible grain there is also depends on what type of film was used etc.

The problem with using too much DNR (or if the DNR is badly done) it is that it can also remove details in the picture (in a way the film grain is the detail). Basically it's a bit like adding a "smooth" filter (sort of - so in a way I suppose it could reduce resolution).

If it's used too much it can make real people look like waxworks/cartoons/cgi (as well as there being less detail). If overused it can also make it look a lot less like the original film.

Last edited by 4K2K; 08-25-2008 at 10:44 AM.
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Old 08-25-2008, 11:25 AM   #3
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Quote:
Originally Posted by 4K2K View Post
Some people doing the encodes use it because they think there's too much film grain visible. Film grain also gets increased when multiple generation copies of a piece of film are made (so scanning the original negative would be better than scanning a multi-generation copy). How much visible grain there is also depends on what type of film was used etc.

The problem with using too much DNR (or if the DNR is badly done) it is that it can also remove details in the picture (in a way the film grain is the detail). Basically it's a bit like adding a "smooth" filter (sort of - so in a way I suppose it could reduce resolution).

If it's used too much it can make real people look like waxworks/cartoons/cgi (as well as there being less detail). If overused it can also make it look a lot less like the original film.
Excellent explanation!
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Old 08-25-2008, 12:37 PM   #4
Stephan.klose Stephan.klose is offline
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Quote:
Originally Posted by 4K2K View Post
Some people doing the encodes use it because they think there's too much film grain visible. Film grain also gets increased when multiple generation copies of a piece of film are made (so scanning the original negative would be better than scanning a multi-generation copy). How much visible grain there is also depends on what type of film was used etc.

The problem with using too much DNR (or if the DNR is badly done) it is that it can also remove details in the picture (in a way the film grain is the detail). Basically it's a bit like adding a "smooth" filter (sort of - so in a way I suppose it could reduce resolution).

If it's used too much it can make real people look like waxworks/cartoons/cgi (as well as there being less detail). If overused it can also make it look a lot less like the original film.
Thanks. But is there another way to remove flaws without applying too much dnr?
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Old 08-25-2008, 12:40 PM   #5
SS316SRV SS316SRV is offline
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Quote:
Originally Posted by Stephan.klose View Post
Thanks. But is there another way to remove flaws without applying too much dnr?
Flaws like what? DNR can be applied if only in a very little amount.
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Old 08-25-2008, 12:45 PM   #6
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Quote:
Originally Posted by Stephan.klose View Post
Thanks. But is there another way to remove flaws without applying too much dnr?
Flaws are usually removed by software, in witch there's a DNR option as well. So company use it, others don't. Most Universal Catalog release (that are on HD DVD) have been passed thru this software, but DNR was applied too. Look at the screenshot on AVSFORUM from U571, the Bluray version is noticably software and have less fine detail than the HD DVD, but there's also less dirt and spec..
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Old 08-25-2008, 01:58 PM   #7
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Quote:
Originally Posted by SS316SRV View Post
Flaws like what? DNR can be applied if only in a very little amount.
That's a good question. What do you determine to be flaws? If you mean speckles and dirt and such in the print, that's not done through DNR to my knowledge. Grain isn't a flaw, it IS the image in film-based movies.

I can already tell this is going to turn into another grain vs DNR thread, but the basic point to be made is that grain is an inherent part of film and the image.
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Old 08-25-2008, 05:01 PM   #8
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Quote:
Originally Posted by Stephan.klose View Post
Thanks. But is there another way to remove flaws without applying too much dnr?
1. You can use SOME DNR, but only put the knob at 1 or 2, instead of 9 or 10

2. You can go through the movie, frame-by-frame and touch things up as needed with a mouse or a pen and tablet, basically the same way you'd touch up a photo in Photoshop. Only there's 24 photos for every second of the movie.
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Old 08-25-2008, 05:20 PM   #9
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Quote:
Originally Posted by RazorFromHRSnet View Post
1. You can use SOME DNR, but only put the knob at 1 or 2, instead of 9 or 10

2. You can go through the movie, frame-by-frame and touch things up as needed with a mouse or a pen and tablet, basically the same way you'd touch up a photo in Photoshop. Only there's 24 photos for every second of the movie.
Criterion does that with their MTI Digital Restoration System
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Old 08-25-2008, 06:39 PM   #10
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The problem I have with DNR is that when companies like Warner use it needlessly. By removing the grain you can remove quite a bit of detail as well. Now I don't think this is a bad thing used correctly say for restoring Citizen Kane or Casablanca. WB apparently used it on Batman Begins, now here us where I start having a major problem with it when Batman Begins was made in 2005 which leads me to assume that the print was immaculate, applying DNR to Batman Begins I would guess just removes detail. Blu Ray is all about detail in video and audio!
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Old 08-25-2008, 06:53 PM   #11
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Quote:
Originally Posted by Canada View Post
The problem I have with DNR is that when companies like Warner use it needlessly. By removing the grain you can remove quite a bit of detail as well. Now I don't think this is a bad thing used correctly say for restoring Citizen Kane or Casablanca. WB apparently used it on Batman Begins, now here us where I start having a major problem with it when Batman Begins was made in 2005 which leads me to assume that the print was immaculate, applying DNR to Batman Begins I would guess just removes detail. Blu Ray is all about detail in video and audio!
+1
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Old 08-25-2008, 11:01 PM   #12
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Apparently Gangs of New York on Blu-Ray has had a lot of DNR applied to it and it is supposed to look very crap. Try renting it to see.
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Old 08-25-2008, 11:38 PM   #13
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The thing that most people fail to realize, 90% of all Blu-ray Discs have had some DNR used on them.

Many people think that DNR is a one level, nuke everything approach.
Wrong!
*They* can use it sparingly and clean up the excessive noise and grain and the image is still sharp.
Or... they can get stupid with it and make the whole picture as soft as an upconverted DVD.

There are a few discs that should have a bit more DNR ran over them. I don't care what anyone says!

Others, we have all seen where a blind man was apparently at the controls of the DNR and hosed a decent movie.

There! I said it!
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Old 08-26-2008, 12:56 AM   #14
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The problem with heavy levels of DNR on film is that the software removes information it shouldn't (like very fine detail) when it removes the grain. It is true that DNR is more common than widely thought on Blu-rays, but a few titles have had horrendous applications of it. It's a tool that can be used effectively but a heavy hand with it can ruin a BD transfer.
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Old 08-26-2008, 01:35 AM   #15
Anthony P Anthony P is offline
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exactly. The issue is that DNR removes "noise" noise is any fine detail which the algorithm thinks is not right, that fine detail could be damage to the film (extremely bad), could be unwanted grain (bad),... but it can just as easily be freckles on a face that is far enough away or other details which are the raison d'etre of HD. When you do it (at any level) you get rid of both the good and the bad and you don't have a choice of what is removed. IN essence DNR smoothes the pic to make consecutive pixels it thinks should be the same, the same. DNR is also sometimes used to simplify an image in order to be able to use lower BW when encoding. DNR in and upon itself is not bad and its selective use can improve the PQ, but no one discusses that aspect because it is harder to catch (not to mention that you can never be sure it was DNRed and not manual). DNR gets the negative vibe because people bring it up when it was used to mess up the movie.
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Old 08-28-2008, 01:22 AM   #16
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The best use of DNR is really to just eliminate things like moire, which come when details fall between two pixels in the frame, the bouncing back and forth between the two different pixels makes a rainbow shiny kinda thing. You may see it sometimes on TV if you see someone who has a jacket with little checker boxes or a houndstooth pattern on it, stuff like that.
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Old 08-12-2009, 12:26 PM   #17
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DNR is a digital process that always kills detail, delivering a picture that is far from the original. Understood this, is hard to find reasons to use it.

The thing is that you can substract detail with your TV/projector sharpness adjustments, but you can't recover it, so the best way is to not mess with the picture and put it in the disc the way is meant to.
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Old 08-12-2009, 03:09 PM   #18
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Quote:
Originally Posted by Deimos View Post
DNR is a digital process that always kills detail, delivering a picture that is far from the original. Understood this, is hard to find reasons to use it.

The thing is that you can substract detail with your TV/projector sharpness adjustments, but you can't recover it, so the best way is to not mess with the picture and put it in the disc the way is meant to.
Yes, DNR always reduces details. After application of too much DNR, to compensate for the reduction of the details, another evil process called edge enhancement (EE) is applied. This can lead to a disastrous situation and generate electronic like images with hollows around the edges. Such images will look horrible especially on larger screens.

However, DNR has been used in moderation in some cases without removing too much details to improve the overall appearance of the picture even on larger screens.
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Old 03-25-2014, 03:44 AM   #19
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Does DNR automatically effect an entire frame of a film or does it "sense" noise and focus only on that?
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Old 06-22-2014, 07:09 PM   #20
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Emulsional Rescue: Revealing ‘The Godfather’”, an extra on the Godfather collection, goes over multiple technical issues of restoration. I found it very interesting.
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