Calibrate Pocket LCD using 2nd camera AWB reading?

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Peter J. DeCrescenzo

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Calibrate Pocket LCD using 2nd camera AWB reading?

PostSat May 08, 2021 2:09 am

I have a really stupid question, but I'm going to ask it anyway, and ask it badly, too. :-)

I know you're supposed to use your eyeballs to "calibrate" a Pocket camera's LCD using the new feature in firmware 7.3, but this seems relatively arbitrary. My question is, could a 2nd camera aid in the calibration process? In other words, use the 2nd camera's AWB feature to help calibrate the 1st camera's LCD?

Here's the set up:

- Let's say you have 2 Pocket cameras; let's call them Pocket #1 and Pocket #2.
- On Pocket #1, display firmware 7.3's LCD calibration gray & white targets.
- Aim Pocket #2 at Pocket #1's LCD, and expose the image normally. Make sure the room is dark to prevent stray light from reflecting off the LCD. Pocket #1's LCD should be the only light source.
- Use Pocket #2's "AWB" to get the white balance value (Kelvin) and Tint value of Pocket #1's LCD.
- Let's say Pocket #2 says Pocket #1's LCD is 5160K with a Tint of 40.

So again, MY QUESTION:

You can use the controls on Pocket #1 LCD to adjust its LCD Temp and LCD Tint -- to what exactly? Is a Pocket LCD monitor "nominally" a 5600K screen or a 6500K screen or what?

You can adjust Pocket #1 LCD calibration controls a bit, and then check its WB using Pocket #2 again, and repeat until Pocket #2 says Pocket #1 LCD is 5600K? Or 5000K or what? With a Tint of what?

As I said, this may be a really stupid question, but I'm curious if something like this might result in a more accurately calibrated LCD instead of simply eyeballing it. Comments welcome.
Last edited by Peter J. DeCrescenzo on Wed May 12, 2021 4:29 pm, edited 1 time in total.
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WahWay

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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 7:34 am

For me matching how the screen WB of one camera with another is not that important. I prefer the screen WB to be closer to what is actually being recorded.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 9:13 am

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Last edited by Tom Roper on Sat May 08, 2021 4:24 pm, edited 1 time in total.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 10:57 am

Short answer to Peter’s question is no. Those kelvin numbers are relative to the sensor, not absolute. Same is true for any camera, even an Alexa. All the auto white balance does is adjust the relative temp + tint numbers so that RGB levels balance for the measured patch. It’s not actually working like a color probe. If pointed at a display and triggered, the kelvin that it hits is not an absolute indicator of how close that display is to the D65 standard white point for REC709 (which BTW is 6500 Kelvin not 5600 Kelvin)

The best way to use the new calibration function is to simply adjust it by eye until it looks balanced to you. If you have another display you trust, put a gray card up on that and eyeball it for comparison while you make the adjustment on the pocket LCD.

While you could obtain a probe to measure the LCD to try and hit D65 as exact as possible, since no camera LCD is even close to a true reference grade monitor IMHO you’d be wasting your time. The new adjustment option is there to get the white point of the LCD in the ballpark. And truly that’s all that’s needed since no one shoots in a reference lighting environment anyway.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 11:04 am

The trick is establishing a 6500K reference. If you have a grading monitor, white balance the camera to that screen and it can serve as the 6500K source. Another way to set it up would be using a 6500K RGB fixture. Once the "probe" is setup, then you can white balace the screen under that reference.

When color correcting LED or Projection to appear white on camera it's a similar process going the other direction.

Good Luck
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 1:12 pm

Which white balance card do you recommend for using with bmpcc cameras. which do you use?
I've read a lot of positive reviews and recommendations regarding https://bhpho.to/3bezCxX
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 4:00 pm

Jamie LeJeune wrote:Those kelvin numbers are relative to the sensor, not absolute...All the auto white balance does is adjust the relative temp + tint numbers so that RGB levels balance for the measured patch. It’s not actually working like a color probe.

Jamie LeJeune wrote:If pointed at a display and triggered, the kelvin that it hits is not an absolute indicator of how close that display is to the D65 standard white point


The kelvin displayed is the temperature of the light. WB is an adjustment of RGB sensor gains.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 5:02 pm

Peter is actually right. He's just asking for the temperature of white. It's 6500K. The display could get a 1 point calibration from a colorimeter or spectrophotometer just like any other. Using a 2nd camera for this of course would not be ideal, but neither is using your eyeballs, which is his point.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 5:58 pm

Tom Roper wrote: The kelvin displayed is the temperature of the light.

In theory, yes. But in practice each sensor will report different numbers under identical light + gray card. You could line up a dozen cameras and they would all be somewhat different. A camera sensor isn’t like a calibrated probe.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 8:03 pm

Jamie LeJeune wrote:
Tom Roper wrote: The kelvin displayed is the temperature of the light.

In theory, yes. But in practice each sensor will report different numbers under identical light + gray card. You could line up a dozen cameras and they would all be somewhat different. A camera sensor isn’t like a calibrated probe.


The sensor is usually less to blame. For the same camera, if you point the lens directly at the light source, you will usually get a similar number.
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Peter J. DeCrescenzo

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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSat May 08, 2021 8:13 pm

Thanks everyone for the informative replies.

I'll have access to another (2nd) Pocket 4K in a few days to try a few LCD calibration experiments.

On a related note, the Pocket's built-in preset WB settings (Daylight, Tungsten, Fluorescent, Daylight Shade, and Cloudy) have Tint values ranging from 0-15. IOW, clustered near the "middle" of possible Tint values, which can range from -50 to +50.

If I use the 2nd Pocket cam's AWB (as a "probe") to adjust my Pocket 4K's LCD to 6500K, and give it a Tint value between 0-15, I'm curious to see if the calibration targets on my Pocket LCD looks good to my eye.

Good shooting all.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostSun May 09, 2021 2:39 am

Tom Roper wrote:The sensor is usually less to blame. For the same camera, if you point the lens directly at the light source, you will usually get a similar number.
I often shoot with more than one Pocket camera and have had up to 6 Pocket cameras on set at one time before. There is always quite a range in values for temp + tint under the same light. Enough of a range that IMHO simply adjusting it by eye is going to deliver a more reliable result than trying to use the Pocket camera AWB (or any camera for that matter) as a probe.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostMon May 10, 2021 12:36 am

Tom Roper wrote:The kelvin displayed is the temperature of the light.

Approximately. The Pocket cameras are calibrated to reduce variation in the numbers you would get, but you may still get some variation.
Tom Roper wrote:WB is an adjustment of RGB sensor gains.

It also changes the 3x3 matrix used to transform from sensor to your output space. So the channel mixing varies with white balance also, not just the RGB gains.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostMon May 10, 2021 11:42 am

There may be a confusion here.
The sensor's white balance is one thing, while the LCD's white balance is an entirely different thing.
In order to get good and accurate results in post-production, including max. dynamic range for any given shooting ISO setting, it's very useful and important to have a proper white balance of the camera's sensor.
The best way to do it is with good and accurate grey (or white) card, like the X-Rite Colorchecker Passport Video. In the camera one should perform Auto White balance with the grey (or white) card, with the same lens used for shooting and under the same lighting used in the shooting. When shooting in ProRes, it's important to perform the auto white balance before the shooting. When shooting in BRAW, it can be done also after the shooting. Whenever the lighting condition change, auto white balance should be done again.
When shooting with more than one camera, the auto white balance should be done in each one of the cameras.
The LCD's white balance is entirely different issue. It has no influence on recorded file, only on the viewing. Once the camera, or cameras, were auto white balanced, the LCD's white balance should be done by the eye, or by viewing impression, for the comfort of the cinematographer and/or the director.
However, setting the camera's sensor white balance for satisfactory LCD viewing colors is a wrong approach.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostMon May 10, 2021 2:56 pm

Joshua_G wrote:There may be a confusion here.
The sensor's white balance is one thing, while the LCD's white balance is an entirely different thing.
In order to get good and accurate results in post-production, including max. dynamic range for any given shooting ISO setting, it's very useful and important to have a proper white balance of the camera's sensor.
The best way to do it is with good and accurate grey (or white) card, like the X-Rite Colorchecker Passport Video. In the camera one should perform Auto White balance with the grey (or white) card, with the same lens used for shooting and under the same lighting used in the shooting. When shooting in ProRes, it's important to perform the auto white balance before the shooting. When shooting in BRAW, it can be done also after the shooting. Whenever the lighting condition change, auto white balance should be done again.
When shooting with more than one camera, the auto white balance should be done in each one of the cameras.
The LCD's white balance is entirely different issue. It has no influence on recorded file, only on the viewing. Once the camera, or cameras, were auto white balanced, the LCD's white balance should be done by the eye, or by viewing impression, for the comfort of the cinematographer and/or the director.
However, setting the camera's sensor white balance for satisfactory LCD viewing colors is a wrong approach.


You're misunderstanding. He's trying to use the second camera as a field monitor probe to help calibrate the screen more accurately.

It's definitely not the best method, but I'd be interested to see how close it can get to a properly calibrated display.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostMon May 10, 2021 8:21 pm

RyLo2797 wrote: You're misunderstanding. He's trying to use the second camera as a field monitor probe to help calibrate the screen more accurately.

Even so, I fail to see how it may be useful, since on each of the BMPCC cameras with Camera 7.3 update, the LCD's white balance is changeable by the user, independent of the sensor's white balance.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostTue May 11, 2021 11:50 am

Joshua_G wrote:
RyLo2797 wrote: You're misunderstanding. He's trying to use the second camera as a field monitor probe to help calibrate the screen more accurately.

Even so, I fail to see how it may be useful, since on each of the BMPCC cameras with Camera 7.3 update, the LCD's white balance is changeable by the user, independent of the sensor's white balance.


That's what he's doing. He's using the other camera to try and give him a better way to find the right setting than by eye.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostTue May 11, 2021 5:08 pm

Joshua_G wrote:I fail to see how it may be useful, since on each of the BMPCC cameras with Camera 7.3 update, the LCD's white balance is changeable by the user, independent of the sensor's white balance.


The experiment would work like this:

1.) Bring up the calibration screen on Cam #1.
2.) Point Cam #2 at Cam 1's calibration screen and perform AWB on #2.
3.) Read WB result from #2.
4.) Adjust temp and tint sliders on #1 by some amount and repeat test until readout from #2 is 6500K Tint 0.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostTue May 11, 2021 11:09 pm

(Thanks, Tom. Your short step-by-step is exactly what I'll being doing.)

Fun with Kelvins:

I won't have access to a 2nd Pocket cam for a few more days.

As many of you know, different model/make lenses have different color characteristics. Among other things, when you switch among lenses, the color temperature of the light reaching a camera's sensor will change. For example, 3 of my lenses are hundreds of Kelvin apart, cooler or warmer compared to the others.

If I want to use a 2nd Pocket 4K camera's sensor to measure the Kelvin color temp of the my Pocket 4K camera's built-in LCD, I don't want a lens to affect the measurement. For example, when I look at my cam's LCD I don't normally look at it through a lens. Instead I view it with my naked eyeballs.

To demonstrate this, I did a test using my Pocket 4K and Olympus 12-40mm f2.8 lens to measure the AWB Kelvin value of a continuous, non-varying light source (the only light source in the room). Note: The light source was NOT a Pocket camera LCD! In this example, the camera reported an AWB Kelvin value of 5450K and Tint 21. Then I removed the lens, leaving the bare sensor exposed to the air, and then measured the light source again. Now the AWB Kelvin was 6150K and Tint 19. A 700K difference!

So, when I later measure the color temp of my camera's LCD using a 2nd camera, for best results I'll do it without a lens mounted on the 2nd camera. Stay tuned.

Note 1: To properly expose the bare sensor, I used the camera's Shutter Angle, ISO, and/or frame rate so the Histogram peaked about mid-way. I also set these values to many different combinations to confirm they have no effect on AWB Kelvin/Tint results.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 11:49 am

RyLo2797 wrote:
Joshua_G wrote:
RyLo2797 wrote: You're misunderstanding. He's trying to use the second camera as a field monitor probe to help calibrate the screen more accurately.

Even so, I fail to see how it may be useful, since on each of the BMPCC cameras with Camera 7.3 update, the LCD's white balance is changeable by the user, independent of the sensor's white balance.


That's what he's doing. He's using the other camera to try and give him a better way to find the right setting than by eye.

That's utterly futile. In both camera 1 and camera 2, the screen white balance is user defined, adjusted by the eye only (on top of the display LUT chosen). If there may be inaccuracy in the LCD of camera 1, the inaccuracy will be doubled in camera 2.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 11:57 am

Tom Roper wrote:The experiment would work like this:
1.) Bring up the calibration screen on Cam #1.

The first step can be done only by the eye (on top of the chosen display LUT).
Would there be any inaccuracy in setting the display white balance of Cam #1, no matter what the other steps may be, the inaccuracy will be doubled in the display of Cam #2.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 12:18 pm

I really don't get why you insist of making the issue of the screen white balance so complicated and convoluted.
Peter J. DeCrescenzo wrote:As many of you know, different model/make lenses have different color characteristics. Among other things, when you switch among lenses, the color temperature of the light reaching a camera's sensor will change. For example, 3 of my lenses are hundreds of Kelvin apart, cooler or warmer compared to the others.
The one and only way to set the sensor white balance is to use auto white balance in the camera, having accurately calibrated grey (or white) card as the target.
When different lenses have different color cast, the auto white balance should be done each time the lens is being changed (as well as each time the lighting of the scene changes),

Peter J. DeCrescenzo wrote:If I want to use a 2nd Pocket 4K camera's sensor to measure the Kelvin color temp of the my Pocket 4K camera's built-in LCD, I don't want a lens to affect the measurement. For example, when I look at my cam's LCD I don't normally look at it through a lens. Instead I view it with my naked eyeballs.
Setting the sensor white balance without a lens is completely wrong.
During my 20 years of experience in digital photography and cinematography, including constant participation in relevant forums, I never encountered such procedure.
On top of that, no matter what way you perform the auto white balance in the camera, or camera 1, that auto white balance affects only the sensor. The screen white balance is being set separately, manually, by the eye. Thus, even if the sensor is correctly and accurately white balance, there is guaranty that the screen will also be accurate.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 3:13 pm

To make my replies short, concise and to the point.
The sensor white balance and the display white are completely independent of one another.
Whatever method one may use to calibrate the sensor white balance - suppose the sensor white balance is calibrated correctly and accurately - it doesn't guaranty that the display white balance is also calibrated. Since the display white balance is user defined and separate from the sensor white balance, the sensor white balance means nothing, when it comes to the display white balance (and vice versa).
In any case, there is no way I know of to set the display white balance accurately, save, perhaps, using good and accurate color temperature meter.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 3:54 pm

Hi Joshua G.,

You appear to misunderstand the EXPERIMENT Tom & I are discussing. Tom's concise step-by-step description sums it up nicely here:
viewtopic.php?p=758942#p758942

In my most recent post ...
viewtopic.php?p=759050#p759050

... I added a detail: Because a lens affects the AWB reading obtained by a camera (any camera, any lens), when I use a 2nd camera as a "color temperature meter" to help calibrate my Pocket camera's LCD screen (and ONLY in this situation), I'll remove the 2nd camera's lens to get a more-accurate result.

Again, this is an EXPERIMENT. It may or not be a waste of time or a bad idea, but I'm going to try it anyway. Like you, I've been pointing cameras at things for decades. I've learned a lot, but there's plenty more I have yet to learn. I occasionally learn new things by using my cameras in odd ways. If this EXPERIMENT proves to be a waste of time, I'll be the first to say so.

Meanwhile, I just did a quick sanity check, and as expected, a Pocket camera LCD display LUT has no effect on how the firmware 7.3 calibration screen is displayed. Obviously a Pocket LCD display LUT definitely does affect how video images are displayed on the camera's LCD (when enabled in the Monitor menu).

The point of all this is to see if a 2nd camera can be helpful (or not) when calibrating a Pocket camera's LCD screen displaying the firmware 7.3 LCD calibration menu item. The way to find out is to try it.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 4:15 pm

Today I measured the color temperature of the screen of my PCC4k, firmware 6.9.6.

To do that I made a white balance on a graycard showing fullscreen.
The measurement with my spectrophotometer (x-rite colormunki photo) together with ArgyllPro Software resulted in 6450 K :D
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 4:23 pm

Use generated graphics to eliminate a variable. 100% generated white leaves no room for error or interpretation and will yield a more accurate result every time.

Good Luck
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 4:25 pm

Frank2021 wrote:Today I measured the color temperature of the screen of my PCC4k, firmware 6.9.6. To do that I made a white balance on a graycard showing fullscreen. The measurement with my spectrophotometer (x-rite colormunki photo) together with ArgyllPro Software resulted in 6450 K :D


Awesome. :D
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 5:14 pm

Howard Roll wrote:Use generated graphics to eliminate a variable. 100% generated white leaves no room for error or interpretation and will yield a more accurate result every time.

Good Luck


True but you still need a way to get that graphic into the camera, so we go with the assumption that the calibration screen white and gray patches are neutral, i.e. RGB 255,255,255 and 128,128,128 or similar.

In the usual LCD screen calibration process, series of gray patches light to dark are displayed.
Ex, patch #1 is RGB 255,255,255, #2 128,128,128, #3 56,56,56, #4 28,28,28 etc.

The temp of each is measured using the colorimeter or spectrophotometer. It's called gray scale tracking. You're hoping every patch reads 6500K but if not, the display has multi-point controls to adjust the individual RGB offsets to bring every patch to 6500K. The Pocket LCD calibration screen has two patches, white and gray however the just a 1 point calibration is possible.

That goes back to a point by Joshua that the calibration screen is lutted. If so, then turn off the display lut, but I don't think this much matters for the experiment.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 5:33 pm

Frank2021 wrote:Today I measured the color temperature of the screen of my PCC4k, firmware 6.9.6.

To do that I made a white balance on a graycard showing fullscreen.
The measurement with my spectrophotometer (x-rite colormunki photo) together with ArgyllPro Software resulted in 6450 K :D


This would be the way to go, for doing an end to end calibration of the sensor, 3x3 matrix (Thanks Captain Hook) to the LCD screen, up to the accuracy limit of the AWB in the camera. The AWB would be in agreement with the LCD screen, but not necessarily in the absolute. To get absolute, you would then have to record the patches in BRAW, and check the RGB levels with the eyedropper. You could never correct AWB in camera because there is no adjustment like there is for the LCD screen unless you created a custom lut and loaded it into the camera, maybe. I don't think a lut would work for every circumstance so that is probably academic.

But the main problem for you, is you measured 6450K. Wonderful! But so what? Even if it was 5450 you would have no way to adjust the LCD screen without updating your camera version to 7.3.
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Re: Calibrate Pocket LCD using 2nd camera WB?

PostWed May 12, 2021 6:58 pm

Peter J. DeCrescenzo wrote:Awesome. :D

Good luck.
However, as I wrote few times above, it's utterly futile since there is no possible way to calibrate accurately the display, regardless of whether the sensor is calibrated or not - unless, perhaps, using a color temperature light meter for calibrating the screen.
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Frank2021

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Re: Calibrate Pocket LCD using 2nd camera AWB reading?

PostWed May 12, 2021 9:48 pm

Tom Roper wrote:
This would be the way to go, for doing an end to end calibration of the sensor, 3x3 matrix (Thanks Captain Hook) to the LCD screen, up to the accuracy limit of the AWB in the camera. The AWB would be in agreement with the LCD screen, but not necessarily in the absolute. To get absolute, you would then have to record the patches in BRAW, and check the RGB levels with the eyedropper. You could never correct AWB in camera because there is no adjustment like there is for the LCD screen unless you created a custom lut and loaded it into the camera, maybe. I don't think a lut would work for every circumstance so that is probably academic.

But the main problem for you, is you measured 6450K. Wonderful! But so what? Even if it was 5450 you would have no way to adjust the LCD screen without updating your camera version to 7.3.


May be you have a problem, I do not have one. Surprisingly, the colortemp of the display is good: The white balance of the camera (the camera "believes" that R=G=B) results in aprox. 6500K. There is no need to update to 7.3 which is full of bugs.
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Peter J. DeCrescenzo

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Re: Calibrate Pocket LCD using 2nd camera AWB reading?

PostTue May 18, 2021 6:40 pm

Apologies for the delay. I did a few simple tests using a friend's Pocket 4K camera (I'll refer to it as Pocket-B) together with mine (Pocket-A). If it makes a difference, both cameras were purchased within a few weeks of January 2019.

At the start of testing, Pocket-B had firmware 6.1 installed, and Pocket-A has fw 7.3.

Test #1:

Same make/model lens on both cameras. No filters. Identical settings on both cameras, both in fully manual mode. Let both cams warm up for a few minutes. Aimed both cameras directly at the center of an incandescent bulb (the only light source in the room) so the bulb filled the frame, and adjusted aperture, ISO & shutter identically on both cameras so 2 stops below 100% zebras clipping. Then did an AWB on both cameras. Pocket-A reported 2750K Tint -13, Pocket-B reported 2750K Tint -8. Repeated a couple of times. No change. IOW, these two particular Pocket 4K cameras report nearly identical AWB results when aimed at the same, single, constant light source. Good!

Test #2:

Set Pocket-B (still running fw 6.1) LCD at 75% brightness, pressed the Menu button and displayed a menu page containing only shades of gray (no blue highlighted buttons). Note: Remember, firmware 6.1 doesn't have a calibration menu. Removed the lens from Pocket-A, and fitted a black-wrap "snoot" (see attached photo) -- with no air gap between the LCD/snoot/lens mount -- so the sensor only received light from Pocket-B's LCD (no other light in the room). Lens removed from Pocket-A to eliminate the variable of the lens (any lens) affecting results. Let both cams warm up for a few minutes. Adjusted Pocket-A exposure using shutter & ISO (no lens). Then did an AWB on Pocket-A, which reported 6000K Tint 50. Repeated a few times with consistent results.

Note: For these tests, the black wrap snoot is held in place on two MFT extension tubes (see photo). They contain no optics, so don’t affect AWB color results.

Test #3:

Updated firmware on Pocket-B to 7.3. Let both cams warm up. Then repeated Test #2 (same menu page with no blue buttons as the target). This time, AWB results reported by Pocket-A was 6150K Tint 11. IOW, Pocket-B LCD was now slightly closer to "6500K Tint 0" ideal. Theoretically.

Test #4:

Immediately following Test #3, with Pocket-A's sensor still aimed via the black wrap snoot at Pocket-B's LCD: Displayed fw 7.3 LCD calibration targets on Pocket-B. Insured snoot was aimed at gray & white targets, and NOT at the colored temp/tint slider controls, and Pocket-B LCD was the only light source. Let both cams warm up for a few minutes. Adjusted Pocket-A exposure using shutter & ISO (no lens). Slightly adjusted Pocket-B's LCD calibration Temp & Tint sliders, and did an AWB on Pocket-A, until it reported as close to "6500K Tint 0" as possible. Results ranged from 6450K-6550K and Tint 5-25. The attached photo shows the calibration screen, with the Temp slider now directly above "nc" in "Cancel", and Tint just to the right of "Save". :D Meanwhile, Pocket-B LCD looks good to my eye, too. Not perfect, but fine for what it is.

Test #5:

Same as Test #4, except this time switched cameras -- removed the lens from Pocket-B and mounted the snoot on it, and then aimed it at Pocket-A's LCD displaying the LCD calibration targets. Results were identical -- Pocket-B reported AWB results between 6450K-6550K and Tint 5-25. We left the Temp/Tint sliders set as shown in the photo on this cam also. Eyeballing the two LCDs, they now look very close.

===

So, what did I learn?

At least in the case of these two Pocket 4K cameras, they report nearly identical AWB results when aimed at same single light source (when each using same optics, settings, etc.). That doesn't mean the AWB results are accurate, but at least they're consistent.

And, (obviously) not only can you use a 2nd Pocket camera to measure an AWB value for the light emitted by another Pocket camera's LCD, you can (maybe not so obviously) use this together with the firmware 7.3 LCD calibration menu display to set both camera's LCD to display almost identical color temp & tint. Whether this is as accurate as ones eyes depends on your eyes.

Of course, different cameras may produce different results. YMMV. Have fun. Cheers.

P.S.: Extra points: Notice my now half formerly full SmallRig cage in the snoot photo. Weird, huh? :D
snoot on ext tubes.jpeg
snoot on ext tubes.jpeg (279.48 KiB) Viewed 1719 times

extension tubes.jpeg
extension tubes.jpeg (340.24 KiB) Viewed 1719 times

Pocket-A peter.jpg
Pocket-A peter.jpg (279.36 KiB) Viewed 1719 times
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Tom Roper

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Re: Calibrate Pocket LCD using 2nd camera AWB reading?

PostThu May 20, 2021 3:02 am

Well done Peter. The naysayers will find fault in everything but I knew that if you pointed a camera at a light source directly you will get a more accurate reading of the temperature than you would bouncing it off of a card. It is no different than an incident light reading that you take by putting the meter where the subject is and aiming the meter at the camera, the meter sees the same light the camera will see.

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