# How do UHP lamps age?

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Hello,

According to this article Link and other info, the estimated used hours of a lamp in a projector's specifications is until it reaches 50% of it's original brightness.
It also claims that lamps will loose 20% of their brightness in a the first several hundred hours, and in a linear way after that.

How would the estimated brightness of an UHP lamp be calculated?

Example:
Lamp is rated at 3500h Normal, 5000 Eco, 7000h SmartEco.
Total lamp hours on all modes is 3300h, but estimated 4400h on SmartEco scale, by manufacturer's formula regarding lamp brightness decrease on all 3 modes.

If it looses 20% of it's brightness in the first few hundred hours (let's say 500), then will it have a linear brightness decrease after that?
Does it matter in what modes it was used? If used in Normal, could it loose it's 20% in 200h rather than, 500h if used in SmartEco?

Would the calculation be made with 80% brightness and 3000h left (for Normal mode), or 80% with 6500h (SmartEco)?
Does it matter in which mode it will be continued to be used?
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These are all general estimates. It's true that UHP lamps can lose up to 25% of their initial lumens in the first ~500 hours of use. The greatest lumen loss is in the first hour of use with lumen loss gradually slowing down over the life of the lamp. Lumen loss is never really linear though it gets closer to linear as it continues to age. Think of lumen loss as a curve that starts steeply and gradually becomes shallower. Lumen loss is also affected by lamp power settings. Manufacturer specs for lamp life in all different lamp power modes are estimates based on rough averages. No two lamps age exactly the same. You can't really accurately calculate how many lumens any given lamp will be producing at any given time. The only way to know for sure would be to measure with a calibrated instrument. Are you trying to calculate a specific lumen output for a specific need you have or are you just trying to understand the general performance of UHP lamps?
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These are all general estimates. It's true that UHP lamps can lose up to 25% of their initial lumens in the first ~500 hours of use. The greatest lumen loss is in the first hour of use with lumen loss gradually slowing down over the life of the lamp. Lumen loss is never really linear though it gets closer to linear as it continues to age. Think of lumen loss as a curve that starts steeply and gradually becomes shallower. Lumen loss is also affected by lamp power settings. Manufacturer specs for lamp life in all different lamp power modes are estimates based on rough averages. No two lamps age exactly the same. You can't really accurately calculate how many lumens any given lamp will be producing at any given time. The only way to know for sure would be to measure with a calibrated instrument. Are you trying to calculate a specific lumen output for a specific need you have or are you just trying to understand the general performance of UHP lamps?
Trying to find out the lumen output for my current projector to input in madvr's HDR>SDR box.

@NxNW took some measurements on the same unit type, with almost widest lens (x1.28 zoom), Cinema, Full Lamp, BC off, 1850 (SmartEco) spent hours, on an 0.85/0.9(?) grey screen (120" 16:9) , with calibrated(?) settings and got 60.560 nits.
Measurements from reviews with the same settings give 1160 ANSI lumens (minus the screen).
Did some calculations with the lamp loosing 20% of life in the first 500 hours, and then linearly loosing brightness, got 68.9 nits (on a 1.0 gain screen) at 1850h.

I'm not sure how the screen fits into this. If the projector hasn't been calibrated for the drop from the negative gain screen, then the value of 60.560 nits would have to be adjusted.
But if it was calibrated, than the value is the same that a 1.0 gain screen would reflect?
What calibration is necessary for a negative gain screen to be equal to an 1.0, a 16-235 greyscale pattern?
Not sure how the screen fits into this as the projector produces the same lumens regardless of what the screen gain is. If you need to include screen gain you would multiply lumens times screen gain, so for example 800 lumens on a 0.8 gain screen would be the equivalent of 640 lumens on a 1.0 gain screen. Whatever you input into madvr is just going to be a rough estimate if you don't have a way to measure actual lumens so just make your best guess based on all the data you've read to date.
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Not sure how the screen fits into this as the projector produces the same lumens regardless of what the screen gain is. If you need to include screen gain you would multiply lumens times screen gain, so for example 800 lumens on a 0.8 gain screen would be the equivalent of 640 lumens on a 1.0 gain screen. Whatever you input into madvr is just going to be a rough estimate if you don't have a way to measure actual lumens so just make your best guess based on all the data you've read to date.
The nits value was measured off the screen, and the screen is negative gain. Don't have the light coming from the projector value.
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