how does screen size effect the DLP rainbow?

[henry1234]

A while back I demoe'd some DLP 720p projectors.

The store, in my opinion, was trying to project an image too large.

I was badly affected by the rainbows and ruled out DLP fullstop and started looking at LCD.

A lot of the rainbow effect was generated as I looked around at the action on the screen, which being very large meant my eyes where darting around as different parts of the film caught my attention.

I am now tempted again by single chip DLP.

Does the effect reduce considerable if I where to have a smaller screen, maybe 60inch diagonal from aroound 9/10ft away?

[coldmachine]

Are you sure you were seeing RBE. It may have been CA.

[henry1234]

what is CA?

[coldmachine]

Chromatic Abberation.

[henry1234]

no it was rainbow, i think

the highlights left a trial of red/green/blue for a split second, but it just kept happeniing.

it would be o.k for about 5 seconds then would appear again usually in a low light scene with highlights.

[coldmachine]

Sounds like RBE. If you were viewing a budget 720 machine zoomed too large and with a slower color wheel, its a fair bet.

The size of the rainbow, if that is what it was, will reduce with screensize. Wheels are faster now too and the latest engines render RBE all but gone. Some still claim to see them.

[Liam @ Prog AV]

What models were you viewing? Our local 7oaks still has a Sharp XV-Z91 on demo (4 years old 480p machine!).

[henry1234]

It was 7oaks.

I viewed the in76 and then when I complained of the RBE they took me to another room to show me the optima h70 which wasn't any better.

The screen was way too big and after I said that I thought the image wasn't very good the guy realised the PJ was out of focus.

It wasn't bad after that but it I didn't like all the green twinking & noise on dark scene's and the rainbows drove me mad.

They seemed to think I would be so overcome with the shear size of the image I was going to hand over my cash.

I said I might have too-high expectations and I should wait until I could afford something like the JVC D-ILA or Sony Pearl

The salesman looked at me like I was crazy and said he hadn't heard of JVC making a projector and I should steer clear of JVC and Sony as they where not specialist projector manufactures.

Now my budget has gone down instead of up since my wife discovered the benefit of overpaying on the mortage

[coldmachine]

I dont know 7oaks, as i'm from US.

From your description it seems like they are utterly clueless, dishonest and not worth a cent of your money.

[gazbarber]

I can say when i demo'ed my current projector i wasn't too impressed with the setup and i think the screen was too big, although i didn't see any rainbows, i saw a huge raft of noise in the picture, lack of contrast and black levels. Indeed i didn't think it looked any better than the one i was upgrading from.

Happily when I got home and pluged into my system with a few minutes tweeking the image was completly different, noise is pretty much abscent and the image is far shaper and moew detailed.

The room they had was totaly blacked out and they were using a proper screen and a pansonic blue ray player. They were playing a blue ray through component so it was only 576p (aparently their hdmi cable was 'broke').

I'm using a 7 year old sony DVP725 dvd player at 576i, on a cheapo screen from ebuyer with component cables from lidl. So either the screen was too big, the projector wasn't calibrated properly or at all, or somehow the mix of demo components just didn't play well together.

So just because they are a hifi shop don't assume they know what their doing (especialy if the member of staff is more hifi than av), and they will often be biased towards whatever product they have in or are trying to box shift.

Sevenoaks have a snobery about anything not DLP as thats all they sell, I know the people in the Newcastle branch are friendly and swiched on, but as its a fancise its different from shop to shop.

As for RBE well i've seen it a good few times and its especialy apparent on black and white material, but i have gotten used to it and i've never had a friend/viewer complain about it (when i haven't told them to look for it with the old wobble head test), but somepeople are just more affected by it, although if you look for it your likely to find it. My Yamaha dpx 830 doesn't seem to throw rainbows anywhere near what my old infocus x1 used to (infact only 2 times in a few months of heavy movie watching since i've had it come to mind), so some models will just be better than others.

As you were looking at the in76 before you might be able to streach towards one of the new mitz LCD units as they are ment to be fab, and black level the big bug bearer of LCD is no longer a problem apparently.

[henry1234]

in their defence they did allocate their time to me for free.

so can I assume I may see less rainbow if I view a smaller screen and maybe a better picture if I set it up myself?

[henry1234]

my budgets gone way down with the house move.

I was originally on £1000-£1400.

Now I am looking at £600 to £800max

I don't mind 2nd hand too much but requirments are:

accept 1080p/24 and display at 48hz or 72hz
very quiet
auto iris must be silent and not noticeable
doesn't need to be a light cannon as it will only need to project 60-70inch diagonal from about 9ft away always at night
contrast ratio important (I sold my beloved crt projector before the move)
come with the moon on a stick

[Avi]

Originally Posted by henry1234

in their defence they did allocate their time to me for free.

so can I assume I may see less rainbow if I view a smaller screen and maybe a better picture if I set it up myself?

I don't think the raindows are due to screen size per se. IMO they may be exaggerated by eye movement but they also appear to be related to high contrast and/or movement of bright high contrast parts of the image. Also the brightness of the projector and type/speed of colour wheel appear have an affect.

I recently bought a new PJ and I'm having problems with the multi colour flashes.

AVI

[henry1234]

multi colour flashes

thats a very good way to describe the problem I had.

maybe with a reduced screen size the flashes would be sharper and brighter? therefore making the problem worse

infact I felt a little phased out after the 30 minutes of demo

If it doesn't effect your set-up too much, can you try zooming the image smaller onto your screen (just for a test) and re-focusing just to see if the effect gets worse/better/no-change

[Avi]

Originally Posted by henry1234

If it doesn't effect your set-up too much, can you try zooming the image smaller onto your screen (just for a test) and re-focusing just to see if the effect gets worse/better/no-change

Makes no difference as far as I can tell.

AVI