Question JVC X35 Calibration tips

Andy360

Active Member
I'm looking for advice on calibrating my JVC X35, specifically the gamma and white balance. I'm using Chromapure with the Xrite ipro meter. I bought the projector 2nd hand a few years ago and calibrated it on the original bulb with the same kit and using Curte Plames excellent Chromapure for dummies guide and the Cromapure manual. I got results I was happy with at the time - a big improvement on White balance along with correction of the infamous JVC gamma droop.

Last week I replaced the lamp so I'm starting again with a calibration. I want to improve my skills this time round and I have the time with the lockdown...

I went about researching some more on calibrating these projectors and then went down the rabbit hole so to speak. Various bits of advice that sounded good at the time often conflict and have made hitting the targets really difficult. So here we go in summary is what i've read and perhaps misunderstood and hopefully some folks here can chip in and clear some of this up?

1. Try not to adjust red, use green and blue to correct RGB

2. Don't adjust green, use Red and Blue to adjust RGB

3. Never use all 3 gain controls as this as it destroys contrast.

3. Don't make positive adjustments to any of the offsets as it raises black level.

4. Get a good RGB @ 30/90 or 20/80 make small adjustments in the gamma RGB at specific IRE levels that need improving.

5. RGB adjustments in the gamma can cause banding

5. Don't worry too much above 80 IRE most content is below that level.

6. Colour space standard or off?

So which of the above are generally good advice then?

My X35 is in a dedicated black velvet treated bat cave projecting onto 102" fixed screen :)
 
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Andy360

Active Member
Ok maybe I'm posing too many questions..

The main points I'd love to hear opinions on are:

1. Does raising offset into positive numbers cause an increase in black level (would seem to make sense if it did to me)? If so then lets say for instance red is +6 and Green is -3 and Blue is -3 does that cancel out the raised black level?

2. Does using all 3 Gain settings harm contrast?

3. Should either Green or Red adjustments to be avoided in Gain/offset - I've heard that green is best left alone if possible but I've also heard that about red too. It clearly can't be both!!

Any advice from more experienced members here very gratefully received.
 
First you need to measure from the lens, 2-3ft away with the difusor on, set the offset to 0, and dont touch them, if they need adjustment its to correct your gamma curve out of black, and they go together, like -1 -1 -1 or the other way, du the X35 have the multipoint gama calibration in the projector menu?

Using the offset to calibrate grayscale make it much worse and you create ringing out of black. That goes for all JVC projectors from X3 and forward.
 
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Andy360

Active Member
Thanks @Stridsvognen

The x35 has the exact same controls as x30/ x3 generation I believe. The gamma is multi point rgb and luminance. X35 lacks cms.
I have always pointed my meter at the screen. I take it to the Lens is only for low IRE values up to say 20 or should I take reading up to 100?

Adjusting the gamma curve is it ok to use the luminance rather than separate rgb If they are all moving to the same value? Can I fine tune rgb in the gamma menu? I take it the higher ire I can use gain controls?
 
Thanks @Stridsvognen

The x35 has the exact same controls as x30/ x3 generation I believe. The gamma is multi point rgb and luminance. X35 lacks cms.
I have always pointed my meter at the screen. I take it to the Lens is only for low IRE values up to say 20 or should I take reading up to 100?

Adjusting the gamma curve is it ok to use the luminance rather than separate rgb If they are all moving to the same value? Can I fine tune rgb in the gamma menu? I take it the higher ire I can use gain controls?
Try start with natural picture mode, color temp custom1. Gamma custom1.
All towards the lens balance 100% IRE, start with the 6500 if you need to lower red and green try 7000 and so on, if its like the X3 you can enter the service menu and set the gain of each color temp preset.
up, down, right, left, enter. press it fast.

Select 2.4 gamma, now make a 21 point grayscale / gamma reading, measure the 1-2-3-4-5% IRE gamma, and 96-97-98-99-100% IRE gamma.

Measure on off contrast, remeasure with -3 on all offset, and with +3 on all offset, if you get higher contrast with -3 its elevating black if you get the same contrast on all, your clipping the low level, we will also see that in the 1-2-3-4-5% IRE gamma curve.

With the Xrite i1Display pro you read faster and more acurate out of the lens, when finished you can measure from the screen and tweak the gain to make the grayscale track to the screen.

Remember to heat up the projector minimum 30 min before measuring.
 

Andy360

Active Member
@Stridsvognen

That’s great I’ll give all that a try. Do you adjust white balance at each ire value only from within the gamma control?

Thanks again fo sharing your knowledge here.
 
Yes you adjust the white balance with the gamma control from 5-95% IRE, ill recommend you do a rough gamma correction first using the white gamma adjustment, and then continue to the colors, try if you have a feature like grayscale with gamma to measure in your software.

Never calibrated a X35 but the older ones the gamma points dont adjust exact the value they should, so you need to fiddle with it a bit.
 
Just spend a few hours playing with the old X3, and this is the absolute best i can get out of it, a single touch on the offset will make the out of black ringing worse, look the out of black graph, its 1-20% IRE measured in 1% steps ilustrating what goes on in between the correction points, if you dont have focus on that you can make a total mess of it, there is so much you wont see in a 10 point grayscale/ gamma tracking. So getting that good gives you more/ better bit resolution wich is very visible.
JVC X3.jpg
JVC X3 out of black.jpg
 

Andy360

Active Member
Thanks @Stridsvognen

I've spent a few evenings sitting in the dark with my x35, laptop and i1dpro pointing back to the lens as recommended. This is what I have so far....

I set the white balance at 100% in the JVC service menu. 7k got me to D65 with delta errors of less than 0.5. Much, much better than previous attempts from the screen using the standard RGB gains.

Next contrast measurements to check for black clipping. This step is a game changer. I'm pretty confident I'm not clipping black with brightness set to zero now. Offsets are all set to 0 having checked -3 and plus 3 to confirm black is not raised or clipped. Great tip thanks.

Contrast measures 34,000:1 at 13FL (double checked at the screen with a lux meter) with iris at -11. I give up some lumens because I use a Navitar Screen star 0.65 wide converter lens to shorten throw and get 102" in my small bat cave :)

Gamma is averaging 2.37 with delta errors in the grey scale less than 1 at most points and 1.5 overall.
Chroma Pure 3 standard greyscale options are 12 point gamma at 10% steps or 21 point 5% so not clear how to read the low IRE 1, 2, 3, 4%. I have calibrated RGB and gamma at 5, 10, 15, 20 through to 95%. Perhaps if I download HCFR software I can calibrate below 5% IRE? Are you using Calman?

I found 10% very, very hard to tame! RGB 1 notch of change effects red quite severely here. Otherwise grey scale has delta errors of less that 1 with a mean of 1.5. 100% white has some small errors now. I might try going back to the service menu, but expect this will create errors elsewhere.

Gamma is not tracking perfectly in the mid range which is partly a trade off with setting the white balance at those points. I need to put some more time in but might just watch some movies until the lamp hits 100hr mark. I'm sure I can get more performance out of this machine, mostly I'd like to improve near black calibration, however this is still by far the best picture I've experienced so far. Skin tones, contrast, clarity, shadow detail all looking lovely. Many thanks for your help @Stridsvognen.



Gamma before and after. Check out the droop in the before!

gamma.JPG

Capture.JPG


rgb2.JPG
rgb.JPG
 
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Andy360

Active Member
Just noticed you are using HCFR. I will download it and attempt the low IRE calibration you have posted.
 
There is a few tricks setting up HCFR that will help you when adjusting. You should be able to tame it a bit better, not sure why you have better white balance before than after, is it possible that is drift from heatup? if you can handle the fan noise run it in high altitude mode, ill also highly recommend you open up the projector and clean the lamp blower, it could be blocked with dust.
 

Andy360

Active Member
The before reading was taken straight after setting white in service menu. I think the change must be because of adjusting the RGB in the gamma across the greyscale. It’s still respectably well below a delta error of 3 but I might dip back into the service menu and realign.

I have to run in low lamp as the projector is on a shelf right over my head so a bit noise sensitive.

I plan to write up a thread on my room (a small basement) as it was quite a challenge, obviously It’s treated with black velvet and paint throughout and has a fixed screen with masking. The ceiling is low, room only 11ft long so throw is very short! I was lucky to pickup a Navitar lens very cheaply otherwise I’d only have an 80inch diag image. As it is I have 102” diagonal 16:9 from less than 9ft throw. Allowed me to upgrade from a Benq w1070 (Via Sony 40es) without reducing screen size 😊 Other benefit is I’m near mid zoom on the JVC so better contrast/optical performance. Other than being a pain to setup no negatives, lens is a massive, heavy lump though! Navitar make lenses for NASA so the optics are great.
 
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You dont really gain contrast by changing zoom, if you look at it with a specifik lightoutput target on screen, longest and shortest trow will measure pretty much the same contrast if you set the iris to keep the same lightoutput.
Personally i find de3 to be way to rough, if it was a completly straight linear error, where the colors did not shift or cross, then ok, but as your fighting shifting colors you can say that you can have a 20%IRE with de3 with 5% to much blue and a 25% with 5% to much red, that introduces color banding, and god knows whats going on in between these 2 points that you did not measure.
These JVC projectors have the capabilities to calibrate extremely nice if your willing to spende the time, and when done right you will get a image that you cant pay any pro calibrator to make.
The 100% balance ill recomend you select the 6500K and set it in the service menu so that it has 5% to much green and blue, then select the 6500K color temp, and adjust green and blue gain down to get a perfect match, now you have a bit of space to readjust as it change, and going forward all you need to adjust is likely the gain to balance the 100% IRE.
 

Andy360

Active Member
That makes sense leaving a small error in the service menu I can correct with gain later👍. I’m going to have another go at this but might put some more hours on the lamp first - less than 40hrs on a new diamond lamp. Willing to put the time in to get the best performance, I generally obsess about this kind of stuff so expect many more hours lie ahead for me 😂
 

Andy360

Active Member
I take it I should aim for linear errors in RGB and avoid the lines from crossing as a first step?

I take your point about the zoom and contrast although I was led to believe that these projectors didnt give there best fully zoomed out. Generally speaking a lenses performance is compromised at the extremes of the zoom range, unless they are huge lumps of glass like the best cine and high end photography lenses.
 
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Mine is basically as close to the screen as possible, and i dont really see much difference changing zoom, so its not something i would worry about.
If you aim for linear error its a good start, it might not be possible. if there is any color that is least anoying its blue, so to much blue is better than to much red, and green is the worse, so if you need to do a compromise chose it in that order. The 0-20% ire was to ilustrate that there is more between the measurements than you think, and perfect is a ilution, your already off having a probe that is not profiled for the projector, however that error will be compleetly linear, what you can do is do a calibration where gamma is spot on, and colors tracks as linear as possible, thats still better than a pro calibration with a profiled Klein K10A where its balanced to 20 and 80% IRE using the gain and offset, and beeing below de3, as those dont take any concideration to the amount of ringing you create in the JVC using the offset, and finding a calibrator that is willing to fiddle 4-8 hours tweaking your multipoint gamma adjustments is not going to happen.
 
Tested the heatup drit on the X3, and checking it hits the calibration again/ repetability.

Cold
Cold.jpg


15min
15min.jpg


30min
30min.jpg


60min
60min.jpg
 

Andy360

Active Member
Mine is basically as close to the screen as possible, and i dont really see much difference changing zoom, so its not something i would worry about.
If you aim for linear error its a good start, it might not be possible. if there is any color that is least anoying its blue, so to much blue is better than to much red, and green is the worse, so if you need to do a compromise chose it in that order. The 0-20% ire was to ilustrate that there is more between the measurements than you think, and perfect is a ilution, your already off having a probe that is not profiled for the projector, however that error will be compleetly linear, what you can do is do a calibration where gamma is spot on, and colors tracks as linear as possible, thats still better than a pro calibration with a profiled Klein K10A where its balanced to 20 and 80% IRE using the gain and offset, and beeing below de3, as those dont take any concideration to the amount of ringing you create in the JVC using the offset, and finding a calibrator that is willing to fiddle 4-8 hours tweaking your multipoint gamma adjustments is not going to happen.

That’s great info and its what I will shoot for from here out. Makes much more sense to me than the simple all be it fast 2 point grey scale approach. I also suspected the offset controls might compromise picture quality by introducing banding or raising the black floor, so glad you confirmed all that 👍
 

JamesBaby

Well-known Member
Reading the comments about not using the offset controls. Can someone explain how best to lower a large Blue push without using these controls.

For example I have Green ruler flat across the line, and Red is easy enough to sort. However Blue is so high that when trying to use the 10 Point Gamma controls I'm requiring huge adjustment that throws others things out. What am I doing wrong?
 
Reading the comments about not using the offset controls. Can someone explain how best to lower a large Blue push without using these controls.

For example I have Green ruler flat across the line, and Red is easy enough to sort. However Blue is so high that when trying to use the 10 Point Gamma controls I'm requiring huge adjustment that throws others things out. What am I doing wrong?
First you balance the 100% IRE adjusting the gain, and never lower red leave that to 0. when thats done you can correct the multipoint gama, to do that you need to measure with a probe direct from the lens, as you will then have a very acurate low end reading, if your using something like a Xrite I1display pro.
If you dont have a probe, you cant really adjust the multipoint gamma, also expect you have a significant gama drop if its on its defoult gamma settings.
 

Andy360

Active Member
Earlier in the thread it was recommended to go into the service menu and set the white balance (ie 6500k) with a 100% IRE white pattern. This gave me a really good starting point.

After that work your way through the 10 point gamma. If the blue is maxed out you can always add red to reduce the blue push but then most likely you will then need to adjust green too. It's time consuming the way the RGB interact and mess with each other but I got there in the end. I'm guessing the problem spot is in the lowest gamma points? It's where I ran into difficulty. In the end it's worth the effort and you'll get the very best black level and contrast these machines are capable of.
 
If you guys really want to go hardcore HCFR have a out of black reading where you can set the range so you measure 0-20% IRE with 1% steps, if you do that measuring about 60cm from the lens you will see if you have created some odd banding isues, as a lot goes on in between the normal 5 or 10% measuring steps.
 

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