I'm going to give an example of a procedure to use for brightness measurements. Note that you do not have to follow the exact procedure given here. You can choose any procedure that is convenient for you. But it is important that whatever procedure you use, you must do it exactly the same way for every measurement.
This is necessary so that if there is a change in your measured value, we know that the difference (probably) comes from a change in the brightness from the projector lamp, and not because you changed the procedure.
If anyone has any suggestions or corrections for these procedures, please do not hesitate to post in this thread. I will update this post accordingly.
You will obviously need a light meter (aka luxmeter) to measure the brightness. If you don't have one, check out post #7
If at all possible, please check your lamp and lamp housing before you set up the projector. Record all numbers printed on the lamp or housing (serial number, part number, batch number) and post them in this thread.
If you expect to use your projector less than 100 hours per month, then you should report your data once a month. If you expect to use your projector more than 100 hours per month, then you should report your data every 100 lamp hours. The first measurement should be when you first set up your projector, as close to 0 hours on the lamp as possible.
For each measurement, follow the same procedure, for example:1. Power on the projector and let it warm up for a set amount of time.
I suggest 30 minutes of warm-up time to be safe (it may warm up faster than that), but you can use any amount of time as long as you are consistent in each of your measurements.
While the projector is warming up, double-check the settings to make sure they are the same for each measurement:
2. Display a white field that fills your screen
- Lamp Mode : normal or high
- Lens Aperture Setting
- Lens Memory and Zoom Setting (16:9, 2.35:1, etc.)
- Picture Mode
- 2D (not 3D) Mode
- Calibration: Gamma, Color Temp., Color Space, Contrast, Brightness
Would be a good idea to save all the settings into a memory called something like "lamp measurement" so you can recall them whenever you make another measurement.
The image on your screen should be at the same zoom and focus every time you make a brightness measurement.
Typically you would display a "100 IRE" white field.
It is possible to get the JVC to display a 100 IRE field from the service menu. Enter the service menu by pressing (fairly quickly): up, down, right, left, OK. You may need to try it several times with different timing to get it right. Once the service menu comes up, navigate to Options, to Adjust pattern, then hit the right button several times to get to the white screen.
If you have an HTPC, you can download a .TS video file with a 100 IRE field here:http://www.w6rz.net/http://www.w6rz.net/irefield100.zip
If you are using a blu-ray player as a source, you may already have a calibration disc that can display a white field. If you do not have a calibration disc, you may be able to burn a DVD yourself, for example:http://www.avsforum.com/avs-vb/showt...4#post123732543. Take brightness measurement(s) with your light meter
You should hold the light meter close to your screen (within a few inches) and facing the projector lens. You can use a tripod if you like, or you can just hold the sensor away from your body, making sure that no part of your hand or body is anywhere near the front of the sensor. The idea is for the sensor to have a completely clear field of view towards the projector lens.
The best procedure is to mentally divide your screen into a 3 x 3 grid (like a tic-tac-toe board) and take a light measurement at the center of each of the nine grid squares, then average them together (you can use the attached spreadsheet to compute the average if you like).
A quick and dirty procedure is to just measure the brightness at the center of the screen. If you do this, please at least move the sensor around a bit to find the maximum reading. This is easier if your meter has a MAX or PEAK function, but you can still do it manually by just quickly looking at a few slightly different positions near the center of the screen and recording the maximum.
You can report your measurement here in lux if you like. Or if you prefer, you can convert it to lumens. There is a nice spreadsheet file (from Ron Jones) that I have attached to this post that you can use to convert lux to lumens: you just enter your screen aspect ratio, diagonal size of the screen, and the lux measurement(s), and it computes the lumens. If you use the nine-point measurement technique, the spreadsheet will also take the average for you.4. Report the measurement results
You can post your results in this thread, or PM the results to me. I will maintain a master spreadsheet with everyone's data so that I can analyze the data and post the aggregate results.
Please include the following information with your results:
- Date of measurement
- Model of projector
- Source of white field used (service menu, w6rz, calibration disc, etc.)
- Hours on lamp
- Whether lamp was primarily used in Normal or High Mode (or hours each of normal and high if you know)
- Normal or High Lamp Mode
- Lens Aperture setting
- Warm-up time between powering-on projector and measuring brightness
- Measurement of brightness
If you need suggestions on how to measure the brightness, please post a question in this thread. I imagine you will get responses from people who are more experienced than I am at making those sorts of measurements.
This post has an attachment, a spreadsheet file written by Ron Jones, which can be used to convert your lux measurement to lumens. But it is not necessary to convert your measurement to lumens if you do not want to. A lux measurement can be reported directly, as long as you do not change your screen size between measurements.
Lux to Lumens Calc - v2g.zip 3.9033203125k . file