[Pecker]

Hi, I've come looking for a little expert opinion.

Lamps on projectors and ISF calibration. Does anyone want to offer an opinion on the impact the lamp has, as opposed to the rest of the machine.

So, for example:

- When a lamp ages, does it need a new calibration? If so, how long before it's so far out before this is needed?

- If you were to calibrate your projector then replace your lamp, would you need to totally re-calibrate, or is a lamp a lamp, and they all output a pretty constant standard of white light from one lamp to the next?

Cheers.

Steve W

[Pecker]

25 views and no answers? Surely this is extremely important.

If one has to spend £200 on an ISF calibration, you can weigh up if that's worth it.

Do you have to get the calibrator back in every thousand hours? Every 500? Every 100? Not even when you change lamps?

Surely, someone must know!

If I watch around a film a week, that's about 100 hours a year. So if I have to re-calibrate every 100 hours, that's £200 a year (£4 a week).

If I only have to re-calibrate every time I get a new lamp, then on a 2,000 hour cycle that's once every 20 years, or 20p per week.

In the real world, that's a big difference. I thought someone could answer that.

Steve W

[dwhite]

Originally Posted by Pecker

25 views and no answers? Surely this is extremely important.

I'm afraid that's the way of this particular sub-forum, lots of view but very few posts. Just did a quick calc and for the first page view in this forum there is approximately 9000 views and only 100 replies, so that's an average of 90 views per reply. You might have to wait a bit longer before anybody replies.

Also some of those views are of course the moderators as they have to read every post, whether they intend to reply or not.

[Neil Davidson]

Mercury lamps (what almost all consumer PJs use) have a spectral characteristic that changes quite markedly from new to about 100 hours. More changes occur after this but they are much less pronounced and after about 200 hours the lamp becomes quite stable just dimming with age.

All things being equal, changing a lamp in a calibrated projector and then waiting 200 hours should result in a very very similar image - of course all things are very rarely equal...

Probably the biggest weakness of LCD and DiLA technologies is that the light has to pass through the panel rather than be reflected off it like DLP. This creates heat - lot's of heat and this causes the characteristics of the panel to change considerably over time. In 3 chip DLP this is obviously a non issue. In 1 chip DLP the filter elements in the colour wheel fly in and out of the light path so quickly that there is no chance for heat to build up meaning the filters hardly alter over the lifetime of the projector.

It would be interesting to see if the readings of some of the HD750 owners have varied during the current heatwave. I am not sure that the change in ambient will have an impact but could be interesting anecdotal data for the future.

[Pecker]

Strangely enough someone has just started a thread on the heatwave damaging projectors in the projector forum.

Neil, in my school we have cheap LCD data projectors in every room. Most staff put them on at maybe 8:30am and leave them on until c.3:30 every day. It's a common sight to walk round school and see an image where the LCD has clearly 'gone' has a greenish or purpleish cloud around it.

When DLP first started to take off I remember Texas Instruments running a DLP projector and LCD projector constantly, and after a few days (I think) the LCD panels went. LCD manufacturers cried fowl, saying they were only usualy used for a few hours at a time.

Where does that take us?

On the one hand, it really doesn't matter how good the 750 is, if the colour is going to deteriorate over time with the heat. Even if it gives the best picture on the market for under £20k, it's pretty worthless if it will only do that in the early, 'unheated' life of the panels.

On the other hand we have plenty of people at this forum and AVS with LCD projectors who live in warmer climes - I think our 'heatwave' would be called a 'chilly spell' in California - and I haven't heard of any problems from there.

If these problems were going to manifest themselves, surely we'd have heard about them from the states by now.

Thanks for the comments on the lamps. It'd be interesting to know if anyone has had any experience with this.

The reason I asked here is that I thought some of our resident ISF calibraters would have been called back to a client's house to re-calibrate after a lamp change, and I wondered what they'd found.

Steve W

[Neil Davidson]

Originally Posted by Pecker

On the one hand, it really doesn't matter how good the 750 is, if the colour is going to deteriorate over time with the heat. Even if it gives the best picture on the market for under £20k, it's pretty worthless if it will only do that in the early, 'unheated' life of the panels.

I think it is too early to write off the 750 on this basis alone. Since this is a relatively new model we have no data to indicate the extent of how the panels vary over time. Remember a home cinema projector is a very different beast to a business projector, typically with a load less light hitting the panels for a start. I don't expect we will see any gross errors of the type typical in business projectors.

Originally Posted by Pecker

On the other hand we have plenty of people at this forum and AVS with LCD projectors who live in warmer climes - I think our 'heatwave' would be called a 'chilly spell' in California - and I haven't heard of any problems from there.

If these problems were going to manifest themselves, surely we'd have heard about them from the states by now.

Indeed this was mere speculation. I thought it could be a bit of fun for the 750 owners, some of whom must surely have the colorimeter on permanent setup in their living rooms

Originally Posted by Pecker

Thanks for the comments on the lamps. It'd be interesting to know if anyone has had any experience with this.

The reason I asked here is that I thought some of our resident ISF calibraters would have been called back to a client's house to re-calibrate after a lamp change, and I wondered what they'd found.

Steve W

LOL - do you think I just make this sh*t up! I can assure this is based on my own experience of running a calibration business and subsequently selling high end projectors!

[Pecker]

Originally Posted by Neil Davidson

LOL - do you think I just make this sh*t up! I can assure this is based on my own experience of running a calibration business and subsequently selling high end projectors!

No, you misunderstand.

What I meant was, have any ISF calibrators been to a client's house where they've previously calibrated their kit, and have been asked to look at it again after a lamp replacement. And if so, did they find they had to change the settings much because the light from the lamp was 'different'?

I wasn't having a go at you Neil, just wondering if anyone had done this. So far, none of the replies (including your own excellent ones) have said that they have, or what they've found.

Sorry if you misunderstood.

Steve W