Whats a Purity error ?

[dancewav]

is it a watermark type effect on a screen , if so is there a fix ??

[technospark]

hi what is the sets make and model no?
tec

[DRGL]

purity issues usually show on on red screens-a good test screen is the BBC full red screens they show between programms (dunno if they still have them?) it will show up as non uniform patches of colour where it should be all the same shade of red. as seen here :-

[dancewav]

I have the dreaded samsung 409 and what I have noticed when displaying dark colours is two sets of what I would call Watermarks , almost like tire marks or tread marks on the screen , I just dont know what the things are called , i want to know so I can google to see if anyone else has them.

they are colourless , simply like tread marks on the screen most noticable when upscaling from DVD via 1080i , when set to 576 it virtually goes, I thought it was just through the hdmi it was happening but last sunday I noticed them on dark scenes on lord of the rings from channel 4.

tread \ tire marks like watermarks , have they a name ??

[contrex]

Sounds a bit like moiré patterning maybe? (Often spelled moire in English speaking countries) Pronounced mwah-ray. Like when you look through 2 pieces of gauze or fine mesh, you see a pattern which changes as you move the pieces. If this is what you are seeing, there is probably a service menu setting you can alter, but you'll need to contact a Samsung expert for details. Maybe there's one on here?

[dancewav]

thanks , i thinks thats exactly it , nice one , now if there was a secret fix in the secret menu, secretly i'd be very happy

[zircon3035]

Moire is usually caused by optical interference between the scan lines of the image and the cross-ties in the c.r.t. shadow mask. You can sometimes change it (make it better ...or worse) by slightly changing the vertical scan size of the picture. If this does help, check that you haven't made the 'normal' picture worse. I don't know how to adjust this model however.

HTH,

Ian

[clownface]

purity is a bastard, im sorry mate but it cant be fixed.
the best thing you can do is complain to the company you bought it from

[red16v]

Originally Posted by zircon3035

Moire is usually caused by optical interference between the scan lines of the image and the cross-ties in the c.r.t. shadow mask. You can sometimes change it (make it better ...or worse) by slightly changing the vertical scan size of the picture. If this does help, check that you haven't made the 'normal' picture worse. I don't know how to adjust this model however.

HTH,

Ian

Nearly right, in fact moire is caused by interference between the horizontal scanning lines and the slots (in a PIL tube) or holes (in a shadowmask). Altering the vertical size is certainly one thing to try, slightly de-focussing the set is another - although this is unlikely to be a control available to a viewer. Regards, yt.

[red16v]

Originally Posted by clownface

purity is a bastard, im sorry mate but it cant be fixed.
the best thing you can do is complain to the company you bought it from

Of course it can be 'fixed' or adjusted to be correct, although it is not a viewers control. Regards, yt.

[zircon3035]

Moire could be another 'inherent' problem with the Samsung c.r.t.s. As the effect depends on the scan structure of the picture and the pitch of the the shadow mask, shadow mask design has historically been optimised for 625 line systems in Europe. That's why moire was usually more noticable when playing back 525 line sources. (In the US, pitch was optimised for 525 lines)

For what scan rate it the Samsung c.r.t. optimised? It probably won't be one of the HD resolutions as this would require the shadow mask and phosphor pitch to be finer and even more expensive.

This was another advantage of the Sony Trinitron c.r.t.; no horizontal (well only 2) cross ties in the shadow mask and no moire.