JVC DLA-RS520 AVS Discussions Review

[AVSMike]

I think he's looking to get as much contrast as possible. Using less zoom will allow for the potential of more native contrast. Unless he's needs all the brightness he can get, there's no reason he can't move the projector back further to gain more contrast.

His screen is 165" diagonal and 1.1 gain. The gain is manufacturer's spec, so it may actually be 1.0 gain.

[Dylan Seeger]

Indeed I am but of course I will find a balance where I still get the brightness that I want.
Can you tell me how to measure contrast hopefully with my Sekonic 858D meter?
I want to make sure my changes are really making some progress lol

The general rule of thumb is to measure contrast from the lens and brightness at the screen. For contrast what I tend to tell people is to place their meter as close to the lens as possible before it maxes out the meter's measuring capability. Usually this is somewhere between 4 and 12 inches away from the lens but will depend on the meter and how bright the projector you're measuring is. I tell people to get as close to the projector when measuring contrast because most meters become less accurate with less light given to it for measurement. And on these JVCs the level of black is dark enough where cheaper meters won't measure accurately. So the rule of thumb here is to give the meter the most light possible to get the most accurate measurement possible and this means the meter needs to be as close to the lens as possible. Anyone posting contrast measurements taken at the screen should normally be ignored as they won't be particularly accurate unless you have a crazy expensive meter (ones costing 5-figures) but even then more accurate results can still be had at the lens.

You'll need a tripod for measuring contrast. The meter CANNOT move at all when taking these measurements. If you move the meter the numbers you measure will not be usable to calculate a contrast ratio. Again, place the meter as close to the projector as your meter allows before it trips out/maxes out the meter's measuring capability. Also try and place the meter in the center of the projected image's light beam. You can use the shadow cast on your screen by the meter being in the light path as a frame of reference on where the meter is in relation to the projected image.

You'll need a test pattern suite to take these measurements. You want to be sure brightness and contrast settings in the menu system are set appropriately. This is where a test pattern suite comes in handy as it will have the appropriate test pattern videos to use to set these. The out of the box default setting of '0' for both on the JVC is usually correct or close to correct so it shouldn't need too much adjustment. Once brightness and contrast is set properly all you need to do is pull up a full field 100 IRE test pattern and measure. Write down your result. Then pull up the full field 0 IRE test pattern and measure. Record this number. Then all you need to do is divide the two numbers you just got and you have your on/off contrast ratio. Changing the lamp setting (high/low), iris setting (manual positions and enabling the dynamic iris) and the amount of zoom used will alter how much contrast and lumens you'll get from the projector.

Measuring lumen output is easier. Pull up the full field 100 IRE test pattern. Then all you need to do is take your meter up to your screen, position it with the sensor facing the projector (not the screen) in the middle of the image with the meter touching the screen and record the number. To calculate lumens you need to figure out the square footage of your screen.  With both the lux measurement and screen square footage number there is a formula you can use that I forget off the top of my head but you can use this site as a cheat sheet. Just plug in the numbers and it will spit out a lumen figure for you.

https://www.rapidtables.com/calc/light/lux-to-lumen-calculator.html

Some meters have a "ftL" mode and if yours does then that's even easier to figure out lumens. Just multiply the ftL number on the meter by your screen's square footage.

[jbn008]

to convert LUX to FL you just divide lux by 10.76 and multiply by your screens' gain correct?

example:
172.16 (lux) / 10.76 x 1.0 (gain) = 16ft

I'm asking because i've always used this method, but now i want to make sure my calculations are correct.

thanks

[Dylan Seeger]

to convert LUX to FL you just divide lux by 10.76 and multiply by your screens' gain correct?

example:
172.16 (lux) / 10.76 x 1.0 (gain) = 16ft

I'm asking because i've always used this method, but now i want to make sure my calculations are correct.

thanks

From memory that sounds correct. To be honest, I've been using that cheat sheet website for a while now. I usually have a bunch of numbers written down so being able to just plug new ones in to give me lumens is very helpful and makes things easier.

[jbn008]

thanks Dylan.  I need to get a cheat sheet myself

[Hifiaudio2]

Thanks for the review... I learned a bit about some features of this projector and I have owned it for months, lol. 

Question about the calibrating...  I want to properly calibrate for the P3 colorspace for UHD rips that have had the HDR taken out of them, but I "believe"  the Rec2020 colorspace should still be present...  what is the proper way to calibrate an input for that?  Select User2 (since user1 profile is for Rec709), and then select Rec 2020, and the tell Calman (which I need to purchase support for so I can upgrade to a recent version) to calibrate P3?   Its been a long time since I broke out any calibration gear, and never for this projector, although I have been asking a few questions on AVS lately... not completely comfortable yet...

Also -  is there a way I can "know"  the file is outputting rec2020?  This is being played on an NVIDIA shield.

[Dylan Seeger]

A few things to note. There is no way to accurately convert HDR to SDR and keep the REC2020 color space information in tact so it would look like the original HDR version. So I would say that if all the P3/REC2020 content you're watching is in this form (an SDR conversion), it almost seems like a waste of time calibrating as the color wouldn't be correct anyways, or at least reflect how it was mastered. As far as using your Shield goes, it shouldn't be converting color points. So if the video was encoded for REC2020 that's how you should be playing it back on your projector. Media players typically have an info screen to tell you what the content you're playing back is. Though, with the rips you're downloading, there's usually an NFO file that comes with the movie file and it should tell you. It's hit or miss, some truncate the colors down to REC709 and others try and keep greater than REC709 color, even if it's not completely accurate to the source.

As far as calibration goes, you definitely need the P3 color filter in place. So if you do use a User profile to calibrate, be sure that you choose the REC2020 color profile as that will ensure the P3 filter is in the light path. You actually want to calibrate for REC2020, not P3. In my review, the calibration report shows how accurate the RS520 is at P3 colors within a REC2020 triangle.