What’s That Green Trail On My Plasma?
By Vincent Teoh • Sunday, 1 April 2007, 10:02 pm GMT
When talking about plasma TV, the 2 top concerns for potential buyers are plasma screen burn and excessive glass reflection. While the former can be prevented through judicious use and the latter via ambient light control, there is one other little-known flaw that is inherent in the plasma display technology – phosphor trails. Have a look at this video of a Panasonic TH42PH9 commercial plasma panel (click Play button to start… IE users may need to enable Active X):
Pay close attention to the white bars. As they move faster and faster across the screen, you’ll notice that there are green/ yellow trails behind the white bars, and – to a lesser extent – blue/ purple fringing at the front. These are phosphor trails, also known as “phosphor lag“, “comet trails“, “green tinge“, “yellow smear” or “plainbow” on the forums.
Why Does This Happen?
Different chemical elements are used in the production of individual red, green and blue phosphor coating in plasma cells. The difference in chemical properties results in a variation in the excitation and decay time: blue is the fastest; green, the slowest; and red in between. Consider the following illustration of a moving white bar which requires equal mixing of red, green, blue (RGB):
Which explains the blue and magenta fringing at the front of the moving bar, and the yellowish green trail. Because the human eye is least sensitive to blue intensity, people usually only notice the green/ yellow trails when a bright image moves quickly across a dark background. The faster the movement, or the higher the contrast is, the more apparent the phosphor trails become.
What Are You On About? There’s No Trail On My Plasma!
The good news is that 99% of plasma TV owners do not see the problem 99% of the time. However, some people who are “cursed” with sensitive eyes (these people usually notice flicker even when the refresh rate on their computer monitor is set at 75Hz) can’t help but notice the phosphor trails. The aim of this article is to make you – if you’re considering buying a plasma TV – aware that such a problem exists, and that you should make sure you’re not susceptible to it before committing yourself.
I’m Worried… Should I Still Buy A Plasma TV?
Despite this shortcoming, plasma flat panel remains one of the most affordable display devices available on the market capable of deep blacks and realistic colour reproduction… and you may not even be susceptible to phosphor trails. Just bring a copy of “Sin City” (a predominantly black-and-white film with fast pans that is notorious for bringing out the worst of phosphor trails) to demo on one of your friend’s plasma TV with the lights down… if you don’t see trails then you should be fine.
Ok, I See Them. How Do I Make Them Go Away?
As difference in phosphor excitation and decay intervals is inherent in the plasma display technology, if you’re one of the unlucky ones who see phosphor trails, you can only try to alleviate the problem by:
- lowering the contrast (white level) on your plasma TV
- using suitable ambient lighting to slightly reduce on-screen contrast (that’s why phosphor trail tends not to rear its ugly head in brightly-lit stores)
- waiting for the luminosity of the phosphors to reduce naturally through normal use
- sitting further away from the plasma screen
- avoiding black-and-white movies
If only 1% (ish) of people can see the trails, is the same true of the trails in the above videos, or should almost everyone be able to see them?
The trails in these videos should be visible to all, as they have been shot under circumstances which bring out the worst of trails.
I see it in ordinary TV broadcasts to component HD VGA Films. It is most clear during Sin City. For me the film is black white green and yellow…
Yeah, I was going to get a PDP-508XD for myself, but thanks to this issue, which unfortunately I see, I’m going to go with the 46×3500 from Sony. (LCD)
I’ve just bought the supposedly best plasma screen TV in the world, one of the Pioneer Kuro’s (42 inch)
Out of the box; straight away two dead pixels. But worse still “Plasma trails”. Me, my brother, a friend and my wife all can see them (mostly in high contrast scenes on DVD such as a white bar or highlight on black going across the screen (SIN CITY especially 4 mins in when Bruce is driving along with streetlights going by is a very good way to show it.) Like a prism effect of green and blue flashes/vertical bars, you see them when your eye darts across the scene from side to side or corner to corner, mostly in your periferal vision. It actually starts to give you eye strain. I don’t believe it’s just 1% of people affected. As it is I’m returning my Pioneer incase it’s a one off.
All that said, a little adjustment and I can confirm the picture is fantastic, especially with standard DVD and Freeview. The processing is second to none. Put it on Movie mode like the review says, it’s the best. Hope my next one is pixel perfect and without Plasma trails.
If anyone has any experience of plasma trails disappearing over hours of use, please add a response here to reassure other plasma users, the growing “1%”!
I am sensitive to them too and I own a 508XD. It does seem to get a bit better over time as the panel ages and I’ve also sort of gotten used to it. I sometimes still see them at night with black and white images.
You’ve got to realize though that no display technology is perfect. Even with this shortcoming, IMO this TV and its technology is still lightyears ahead of other ones and I am thoroughly enjoying it everyday..
S.
[...] Opprinnelig skrevet av Joey1313 J Jeg opplever også en slags "trail" av grønt bak objekter i bevegelse av og til. Det likner litt på "regnbue effekten" på DLP projektorer, bare grønnaktig altså. Jeg vet ikke om dette vil gi seg med tiden, og på nåværende vet jeg heller ikke hvor mye mer jeg kan få ut av TV’en med å kalibrere den. Dette du beskriver her høres mest sannsynligvis ut som "phospor trails" som plasma-TVer dessverre sliter med. Samtidig er det visstnok svært varierende fra person til person om man ser dette fenomenet. Har lest antydninger om at omtrentlig 10% ser dette tydelig. Om det er noen sammenheng mellom at man er ekstra sensitiv for dette fenomenet hvis man er sensitiv for regnbueffektene fra DLP-projektorer har jeg ikke klart å finne noe bakgrunnsstoff om. Selv ser jeg dessverre nevnte ‘phosphor trails’, og jeg ser regnbueeffekten på DLP-projektorer. OM phosphor trails: What’s That Green Trail On My Plasma? [...]