Help a newbie...rainbow effect with a CRT?

[Nebby]

Hi All

I've just begun to dip my toes into the wonderful world of CRT!

I've recently purchased a second hand Seleco 320...

While I have the option of paying for a professional install, I am keen to learn more about this new 'toy', and have had a crack at setting things up myself.

After a few nights spent tweaking under dimmed lights, I'd say I'm within touching distance of a nice picture. However...

The CRT is currently connected to a DVD player (Pioneer DV-353)by SVHS cable (will switch to component video output soon). When watching a movie (I've tested a few), I seem to be experiencing what I can only liken to a 'rainbow effect' if I happen to glance away from the screen. This sometimes occurs if the action involves fast movement.

I've experienced the 'rainbow effect' before when looking at a dlp projector, but was under the impression that I shouldn't experience the condition with a CRT. This leads me to believe that I've gone wrong somewhere during set-up, although I've started from scratch two or three times now, just in case I' missed something along the way.

While I'm happy to pay for the professional install, I can't stand being beaten! Given my lack of CRT experience, if the above suggests a particular problem or setting I need to look at, I'd be most grateful for any help / advice.

Cheers

[mrxfilms]

Don't panic, i think you'll find this is normal. I run a Barco 7LT froma Denon 2900 and expereince the same. The PJ was professionally installed. You may find that you are particularly sensitive to the effect. I found that DLP gave me a headache and was very distracting, whereas with CRT it is only on light against black, and in fairness you do have to exagerate your eye movement dramatically to see it. Sit back, relax and enjoy the world's best projectors.... CRT

[Nebby]

Hi mrxfilms

Thanks for the reply and encouragement. I guess I'll keep tweaking...it's all part of the fun, I guess...and experimenting with "Y/C delay", "blue stretch", "peaking", "comb filter" and so on.

Do you think there's some kind of conspiracy going on with av equipment manufacturers? The manual that came with the Seleco is a classic...it shows you how to adjust the settings outlined above, but then fails to explain what effect any adjustment will have on the picture!!!

Do you know of any glossary's that I might find on-line, that explain these dark arts?

Nebby

[cessquill]

I've got a fair amount of information with just google searches. My manual is the same. Yes, I'm aware how to turn things up and down - all the settings adjust exactly the same. I want to know what they do.

Some of the Italian-English translation in mine means that when they do try to explain, it just sounds like rubbish.

[mrxfilms]

Hello Nebby,
There is a web site called crtprojectors.co.uk who have bags of info on CRT's. They have a slight bias towards Barco but plenty of info on others. When i first decide to go the way of CRT 2 years ago, this site provided a good grounding of info. Print the FAQ section out and you will have plenty of toilet reading.
Regards
Pete B

[LV426]

Some 'experts' initially deny that CRT rainbows are possible. Indeed, a few years ago at 'The Event' I saw this effect, commented on it, and it was dismissed as imagination by the expert presenter.

Yet there they are. Others have seen them too (although very few people have 'fast' enough vision).

I can only assume that the the coloured tubes are not energised concurrently, but consecutively, and, coupled with the intermittent nature inherent (ie unavoidably flickering) of any CRT presentation, this does indeed produce, effectively, the same thing as 1-chip DLPs do.

To reduce (but never remove) it for a CRT you need to use an external scaler to ramp up the refresh rate as high as the projector will take.

[Nebby]

Hi Pete

Just had a quick look at the site you suggested...looks like I've got plenty of reading material!

Thanks for the help

[Nebby]

And thanks to you too Nigel...although I have to admit, being such a newbie I only understood the last paragraph of your post (I tend to pick up on things that involve spending money!) and, of course, your sign-off reference to one of the greatest movies ever made!

[Jeff]

Originally posted by nigel

To reduce (but never remove) it for a CRT you need to use an external scaler to ramp up the refresh rate as high as the projector will take.

This has a serious impact on picture quality, if you see rainbows on CRTs and flicker bothers you a lot then I would suggest that CRT isn't a solution for you.

Despite the fact that I see rainbows on even the best single chip DLP projectors and 50Hz bothers me on large(28"+) CRT TV's, I run my CRT projector at 48Hz for NTSC film and 50Hz for PAL and enjoy the experience greatly.

Each to his own as they say.

[chrisgeary]

yes i can detect a slight rainbow effect with my 801s, but i have to rapidly move my eye from left to right to get it (a thoroughly unnatural experience - even after a bottle of wine!) - just moving your eye from the left of the screen to the right isnt enough - so i never notice it! if you haven't seen an LCD or DLP projector, you should.. you only have move a millimeter and the rainbow effect strikes!

[LV426]

Originally posted by chrisgeary
if you haven't seen an LCD or DLP projector, you should.. you only have move a millimeter and the rainbow effect strikes!

Do you mean that BOTH DLPs AND LCDs have rainbows?

If yes - you are seriously misguided. Although they aren't without their other shortcomings - LCDs do not, and never have, suffered form any rainbow or any other temporal artefact. They all produce a constant, unflickering image (assuming, of course, that they are working correctly).

[chrisgeary]

yeah i have seen LCDs produce the rainbow effect. i have a friend who has a compaq jobby.. its very noticeable. no its not DLP ;o)

[Jeff]

Nigel, see what you've started. Rainbows on LCOS anyone?

[LV426]

I started it?

I'm sorry chrisgeary. With some (only some) knowledge about how these things work I seriously doubt that what you saw was anything other than the product of a deranged mind. In any case, if true in the specific case, it's probably unique; certainly very very rare for an LCD to produce any kind of temporal artefact. Really - they just can't.

[Jeff]

Originally posted by nigel
Really - they just can't.

Isn't this what was said when you claimed to see rainbows with CRTs?