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Old 10th January, 2005, 12:43 AM
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Chernobyl Chernobyl is offline
Projector Wizard
Join Date: November 2004
Location: UK
Posts: 594

Originally Posted by Nanoman
Thanks for your replies I will surely make one (at least ) but my tempo will no way be as fast as yours are. When you are living here in Novi Sad (Serbia & Montenegro) every purchase via internet is nightmarish. Phhuu...I remember my quest for my Ibanez RG570 which i bought on ebay from was something like 3 months of spear fighting with banks and automated denial servers

But despite all that, i`m gonna give it a big shot! Did you guys noticed any "laws" when buying a OHP? I mean about singles, doubles, triplets...what`s the difference in our story here? And of course lumens. Is it buying a 2000-3000 lumens ohp a waste of money or could be enough? I presume it`s bad, but what do I know

Guys, thanks for all your info, it means a lot for me. Here I can`t go to check it nowhere and you can also imagine how long a wrong shopping and a replacement for it can last from here. Your are a real and one and only source for me now.

And Yeah, somewhere I have few light bulbs named "True Sunlight" "Bright White" or something like that...the key is that bulbs are colored in (when light is off) transparent dark blue, exact complementary colour from volfran yellow. When that two colors mix, (although when on..bulb looks pretty light marine blue) what you get out of it is a really bright and white light. Just than you realize how a classic bulb is realy yellow These bulbs are actually used in photography and anywhere where the fine control on colors is reqiured. I`m saying all that just in case that bulbs or anything of your equipment again starts to grow yellow, maybe you could use filters of that colour. If it`s interesting, check out phillips, i know they surely are making bulbs of this type.

Sure I`ll be around
[Reminder] Started new bulb today!

Hi Nanoman, it seems you need to purchase right first time, not much room for trying parts.

I will be doing a full writeup soon of the whole process and pitfalls. This isnt in time for you, so I'll pass some on now.
Currently there are lists of things to write up about, so I'll do my best to explain each point.
This is going to be long!

for the OHP, you may want to consider the following properties:

Physical size/type
Doublet or triplet lense system
Cooling stage?
Power /running cost
Low power mode
Ease of Mod-ability (12ā€¯fresnel+ ease of cutting case, quieter/better fan system)
Lamp type (DIY)
UV spectrum / filter
Lamp cost + availability
Lamp life /running cost
Closed lense system?

I'll cover the ones that arent obvious

Physical Size/Type:
There are a few types to consider based on:
price, power, size, weight, bulb life, loudness, definition, looks

Ideally small, light, powerful, long bulb life, quiet is required but unless you have the money you arent going to achieve all and maybe wont achieve all anyway.
Portables are small but limited in power unless you pay up.
Quiet OHPs tend to be low power
Cheap tend to be low definition (singlet lense system)
Powerful OHPs are usually louder
Looks can cost

You found a supplier for the OHP, you need to make sure you get a good supplier bulbs at the right price. It would be a shame if it was too difficult or costly to run.

Doublet or triplet lense system
Triplet lense systems supposedly produce a sharper image than Doublet.

Cooling stage
Some OHPs have a cooling stage mirror to prevent curling of acetate sheets. Some OHPs may be capable of running an LCD with no cooling on the LCD but It seems unlikely. There is a slight loss of light power going through a cooling stage.
Its possible for an OHP to use an IR filter to reduce radiated heat, I dont know of any that do. Best check the Lumens output of the OHP is suitable.

Power/running cost
Its may be wise to work out how much it is going to cost you per month in electricity to run your OHP. The higher the power, the higher the cost.
In the UK, I have worked out its using 3pence (ish) an hour in low power mode
The cost of running the LCD is very cheap as it runs at even lower power without its backlight.

The Power of the lamp doesnt always translate into a standard light power (Lumens). The quality/type of reflector(s), lenses, cooling stage and the lamp type can vary the Lumens for a given power. Lamp type can be ignored unless building your own OHP.
250W systems without any IR filtering seem to hang around 2500 Lumens and 400W about 4000 Lumens.

From all the feedback and reading I have done so far, it seems that 4000 Lumens and higher is desireable. Its not say you couldnt be happy with 2500 Lumens and a top notch screen, it depends what you have acesss to.

Low power mode
Low power mode is handy if you really dont need the brightness so high.
It will save running costs and bulb life.

Some OHPs are designed to be quiet in operation. These are usually lower in power/Lumens.

Ease of Mod-ability
A 15" LCD is 12.1" across but the OHP lit area is generally less, down to 10.5" in one case. The Fresnel lense underneath the OHP glass in most cases is over 12", so it makes sense to try and fit the whole screen on without shrinking it.
The area between the glass and the Fresnel lense is an air route. Cold air is drawn in over them before it enters the OHPs main bay. The route is made by parts of the plastic/metal lid hanging down and block the flow of air down the sides of the fresnel lense. To liberate the full size of the LCD, it may be necessary to cut part of these out or play a safer option.
It may be worth inspecting OHPs to see how easily this mod can be accomplished. If it has a metal lid, do you have the tools to do the job?
Can you remove enough material to match the LCD enough without destroying the air routing?
Do you care

Lamp type (DIY)
If you buy an OHP, it will generally be ready for use, you replace the bulb with a known one.
If wanting to mod your OHP or make your own, you must consider the light spectrum the bulb produces (as well as cost, lamp life, light deterioration with age...). I havent researched this fully yet. Do ask if you need more information.

UV spectrum / filter
Your OHP may produce a lot of UV light. I havent quantified this yet, but it might be necessary to fit a UV filter.
From what I have read so far, UV light degrades the colour pigment in the LCD panel and turns the LCD screen brown over time. I dont know how fast this happens yet or if it needs to be considered. For DIY OHP'ers, it would be wise to choose a bulb with lower UV unless adequate filtering can be achieved while keeping Lumens high enough.

Lamp life /running cost
How long the bulb in your OHP lasts is a prime concern for most.
Changing the bulb often isnt desireable and its likely to cost more too.
I have seen some last as little as 65 hours and some that last 100's
Mine last 180 hrs high power, 270hrs low power from the mfrs spec.
Its worth finding how much it costs per bulb and balancing that with how long they last to get the running cost.

Closed lense system
This is the lense and miror that you adjust up and down.
A closed lense system may be useful if you have a dusty environment.

Phew! Any questions?
2.9m DIY home made LCD PC projector !
Venice 3000+ (1.8GHz) @ 2.7GHz, 1.4V
Stock air cooler
X1800XT clocked to PE

Last edited by Chernobyl; 10th January, 2005 at 01:48 AM.
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