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Discussion Starter · #1 ·
i was ready to pull the pin on a HLN617W after seeing one briefly in a store but after reading a few posts here and a subsequent trip to a different store looking at a 56 i did notice to my horror some significant dithering. question for those of you out there with these sets: is the dithering an issue on all inputs or does it go away/dramatically reduce when dvi connected? i don't want to walk away from what may be a great set based on a lousy feed/connection at the store.

thanks for your help!
 

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Dithering is part of the design of single-chip DLP, but I think the source signal does have something to do with it.


Here's an old post from MrWigggles that discusses the causes of temporal dithering (dithering over time) artifacts:

Quote:
Originally posted by MrWigggles
Getting to the Samsung, the Samsung does have the worst temporal dithering I've seen in an HD-2. It can be described as mosquito type noise that pops up when there is fast movement on the screen espically in high contrast situations.


But the cause of temporal dithering comes from a few things other than simply the DLP. Here is an aproximate run down of percentage-wise what makes the problem noticeable.


1. MPEG artifacts : 10%


MPEG breaks up during fast motion.


2. Film grain : 5%


Speckles of film grain in the source material doesn't help


3. Brightness : 15%


The Samsung are a bright display especially the 61".


4. The gamma is too high : 10%


I don't know how prevelant this is but on my friend's 507 set, the DVD input was measuring a gamma of 3.0 which means the image was very contrasty and percentage wise darker than it needs to be (for instance, with a gamma of 3.0 mid-gray is 12.5% the intensity of full white compared to a gamma of 2.2 where mid-gray is 22% of full-white). Even with DVI the gamma was still 2.55 which is still too strong IMO, but temporal dithering was less noticeable.


5. Poor imput filtering on the Samsung: 5%


Everyone whines about analog filters but they do serve a purpose. Hard edges and ringing with a lot of input signal causes inaccurate sampling when the input signal is changing rapidly. The filters are too mild on the Samsung.


6. Poorly set-up displays: 5%


All of the 507's I've seen in stores have had serious set-up issues. The biggest one is brightness being set too low. This causes the blacks in the image to be clipped and the overall image to be darker than it should be (percentage-wise versus full-white that is)


7. Inherent dithering in the HD-2 chipset: 30%


Dithering is there but not nearly as bad on other projectors that use the chipset. The Seleco has almost no temporal dithering that I could detect and that is because it does 1 through 6 so much differently.


8. Samsung's implementation of the HD-2: 20%


I'm not completely convinced Samsung is doing everything correctly in there electrical/firmware design. For instance, I can freeze the image on completely uniform fields and there will be speckles on the screen probably mainly due to round off error in all of the processing stages used in the 507. DVI input produces a better input for this reason. I think Samsung has set their firmware up better with some of the more recent 507's but still have a ways to go IMO.



Some of these things are fixable while some of these are not. And I know I'm being confusing on the brightness issue. A darker image due to less light out of the display will help reduce the appearance of the artifacts of the display and the source.


But simply reducing brightness setting or raising the gamma will only make things worse. This is because by reducing the brightness settings only makes the image darker and thus the duty cycle of the mirror is reduced and this is what causes dithering the most.


I hope this helps. I could go on and on...


-Mr. Wigggles
 

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It is sometimes hard to get the right idea conveyed through a post, but depending on which phenomena you are experiencing (or both), they might be able to be helped. Mosquito noise, often confused with dithering, can be significantly reduced in a calibration, as well as adjusting the gamma. The old 2.2 Gamma correction commonly used in CRT's doesn't always cut it. I am finding that these set's look really good at around 2.5, and many other tech's across the country are doing the same now. The dithering artifacts can be confused with a poor source, but at some point, are still part of the technology.
 

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So what's a good scene from a movie to see the dithering problem? I'm about to pull the trigger on a 567, and I haven't really noticed ther dithering probelm. The store had "Driven" playing through pioneer DVD. Should I check the firmware, will that make a difference?
 

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Discussion Starter · #7 ·
i saw the most dithering on a hd cable feed that granted was probably split *many* times. dark scenes with fast motion seemed to cause the most trouble. i didn't have a lot of time so didn't get a chance to see a dvd feed.
 

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I am thinking of buying a 567 as well. Yesterday I went to the Tweeter in Dallas and took Gladiator and The Matrix DVDs with me. The salesman hooked up a low-end progressive DVD player via component cables and we tried out both DVDs. The opening battle scene in Gladiator looked great. I could not find any instances of dithering and I have heard many people use this scene as an example of dithering. The Matrix looked very very good as well.
 

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I looked at the 567 at the Tweeters on the Dallas Tollway on Monday. I just watched some Discovery HD content, but didn't notice any dithering whatsoever -- not even on scenes where the camera was panning over grass. Note that on previous Sammy views a lot of dithering has always been apparent to me. I think they have been doing some improvements in this area. With the sales they are showing you would expect that to be the case. I would like to go back and see some actual D* SD like ESPN. On the Optoma DLP (down the road at StarPower) this looked extremly grainy, a far cry from my current Tosh LCoS. I would have to say that such typical SD quality is a major concern for me -- or at least it will be until the HD-TiVo shows up.
 

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Discussion Starter · #10 ·
the sd feeds i've seen are ok at best. granted in a showroom you can't expect much - sets not adjusted, low quality feed etc. the sammy is not a tv to buy if you're interested in *top* quality sd. many people seem fine with it once they have it home and tweaked a little.

my concern is that even with an hd feed and or dvd, dithering would still be a significant issue. i'm willing to put up with some artifacts given the size, weight, price combination but don't want to build my home theatre around this thing and then be let down by its pq.

i will use comcast cable which means component connection - dvi is apparently coming at some point but not yet available from what i've heard. that said my hd connection won't be optimized. a dvi dvd would also need to be added to the shopping list to ensure peak performance.

since i have yet to see a dvi feed, in your experience does dvi equal little/no dithering or does it simply pump up color depth etc.?
 

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I've seen it... considering you're going from analog to digital, it's probably just eliminating most of the noise. Someone pointed out on here that they thought the samsung wasn't doing enough filtering on the component video inputs. I recently saw the sim2, which uses the same DMD, and it had virtually no noise on component.
 
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