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The downside is ambient light getting into your sensor from the room, which can be reflected light bouncing off the walls in a darkened room. Hence the light measurement guidelines instruct use of cone frustums to eliminate ambient light noise. Which brings us back to the real world of our reality, for what ever that is(another discussion), where it isn't practical for the average person to control all artifacts and you are left with placing the sensing device at a distance that eliminates any ambient light and allow longer duration readings.
Nice post, full of understanging on the matter.
I use different lenght cone frustums for meter profiling and then I use the longer one for calibration. That way solved any problem related to ambient light, photons and small area reading.
 

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There's no learning or progress if you regard every opinion as "equally valid", and not open to discussion or criticism.

Many people seem to waste their time pursuing irrelevancies, simply because they don't understand how things actually work. It's all black magic voodoo, and they feel compelled to make cryptic offerings to the gods to ensure success.

Add some science and understanding, and the voodoo can be banished.
I agree with you, but if you stop progress by saying "that is useless, contact mode is the way for HT calibration" you are adding nothing else than your "religion" to a scientific discussion. I don't regard as equal every option but I tried them all and concluded that contact mode is not the best way, it is just the easy way to get a (wrong) result.
 

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Discussion Starter #23
I use different lenght cone frustums for meter profiling and then I use the longer one for calibration. That way solved any problem related to ambient light, photons and small area reading.
Interesting! Could you please share images of the cone frustum for both i1D3 and i1Pro 2? I suppose these are DIY stuff.
 

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Right now they're a couple of fastfood big cup coated with adhesive tape and wool socks and cutted at 136 mm and 178 mm, but I'm developing something specifically made for xrite probes. Stay tuned.
 
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Right now they're a couple of fastfood big cup coated with adhesive tape and wool socks and cutted at 136 mm and 178 mm, but I'm developing something specifically made for xrite probes. Stay tuned.
Excuse me, I have a X-Rite I1Pro, rev D. Shoudn't I use it directly in contact with my oled tv screen?? In the I1Pro box there is a specific tool to make the instrument in touch with the screen.
Do you think it is better to keep the I1Pro on a tripod like if I am calibrating a projector? Why?
 

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Hi,
That tool has been projected for PC monitors (smaller display, increased ppi). However, especially the i1 Pro 1/2 in contact it reads a very small area, so the more the probe is far from the panel, the more pixels it reads, the more accurate the calibration / profile is. On the other hand, the probe placed at a distance from the screen reads ambient light (from windows, etc ...) direct or reflected by the panel, that light modifies meter readings. Some prefer to have these environmental readings. Personally I do not like this kind of interference (that, inter alia, it changes with time/weather), so I prefer to avoid that by covering the probe and the part of the panel object of detection with the object of which we spoke before. What I practice is better described in the IDMS display measurement and metrology standard publication which is the actual reference.

Among other things, some time ago a professional calibrator (I do not remember who and when) has reported his data on the use of i1 Pro at various distances comparing them with those of a Jeti spectrometer (one of the best brands on the market). Well, at a certain distance from the display (if I remember correctly about 1 meter) the i1 Pro had readings similar to those of a Jeti.

Furthermore, in contact mode, your meter is going to get heat from the panel modifying its behavior. Contact mode is easy and comfortable but, as almost all the easy ways, it's not the best mode.

I hope this helps.
 
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Excuse me, I have a X-Rite I1Pro, rev D. Shoudn't I use it directly in contact with my oled tv screen?? In the I1Pro box there is a specific tool to make the instrument in touch with the screen.
Do you think it is better to keep the I1Pro on a tripod like if I am calibrating a projector? Why?
Hi,

EBU TECH.3325 Publication (Methods for the Measurement of the performance of Studio Monitors) recommends the distance measuring geometry rather than the contact method.

You can see a lot of more info there: https://www.avsforum.com/forum/139-...ion-resources-documentation.html#post55447708

Even if you want to use contact mode using the display holder, the length of the counter weight is not enough for OLED displays 55/65/77 inch.

 

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Hi, here the JETI 1501 target measures ~67 mm at 6 feet distance to my flatscreen.

Is this accurate or is the actual measuring diameter smaller than the aiming circle is showing? Thanks for help.
 

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Hi, here the JETI 1501 target measures ~67 mm at 6 feet distance to my flatscreen.

Is this accurate or is the actual measuring diameter smaller than the aiming circle is showing? Thanks for help.
The measuring area is within the red circle.

It will be true for all measuring distances.

So you can be sure that you measure correctly without dealing with geometrical calculations.

The homogeneity of the device sensitivity inside the measuring area as well as the influence of light outside the measuring area on the result are important parameters.

The optical system of JETI ensures, that there is a plateau shape of the local sensitivity.

There exist special parameter values, defined by CIE, to characterize deviations from an ideal behavior.

The most important of them with regard to the directional sensitivity of a device are f2(g) and f2(u).

f2(g) is called uniformity error and f2(u) "influence of surrounding field" error.

f2(g) will be calculated by the ratio of the smallest sensitivity within 90% of the measurement field to the maximum sensitivity in the same field.

f2(u) will be calculated using the signal outside the measuring field compared to the inside signal. Both values will be measured using special apertures.

The values for JETI are very low, resulting in class A for a luminance meter.
 

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Ted, thank you for going into this level detail. Is the available StrayLight protection tube for bright room measurements or contact mode, or what?
 

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Ted, thank you for going into this level detail. Is the available StrayLight protection tube for bright room measurements or contact mode, or what?

Its for contact measurements, to protect from surround light. Its 16cm long.
 

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How's the spot size at that range? Too small to match with the Klein? The Klein is far more easy to set up in contact mode. If I can do that with the JETI and get equal results, I like it.
 

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How can I figure out the spot size with the i1D3 meter? No angles, just direct line of site to the display? I know you have charts, but is there a simple formula to use with this meter?
 

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How's the spot size at that range? Too small to match with the Klein? The Klein is far more easy to set up in contact mode. If I can do that with the JETI and get equal results, I like it.
JETI has 5mm with Stay Light Protector.

Klein has 43mm without any accessory attached.
 

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How can I figure out the spot size with the i1D3 meter? No angles, just direct line of site to the display? I know you have charts, but is there a simple formula to use with this meter?
According to X-Rite, its 24mm in contact measurement, for full specs see there.
 

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(An old thread, I know, but it seemed like maybe the best place to post this.)

I've seen it oft stated that placing the i1Dx/C6 at 136mm from the screen will result in a 25mm diameter read area. I gather this is obtained by using the C6 FWHM (rather than the TLT) and equation in the SpectraCal article. But DarrellB states above that the equation breaks down below 12 inches, and that the i1Dx/C6 read area might be as much as 24mm in contact mode (I haven't seen if anyone has really confirmed that). Omarank suggests above that, if that's the case, the correct i1Dx/C6 placement might be as little as 5mm from the screen.

I have a neighbor who has kindly been doing 3D modeling and printing of parts for me to try to make Stray Light Elimination Tubes for my C6 HDR2000 and i1Pro 3, with of course the desire to end up with the same read area for both meters. We've been working on the C6 first, design based on the top picture in Figure 8 in the NIST SLET paper. With the current prototype, I have a 60mm inside diameter cylinder, and the two frustums have 30mm diameter openings. Total length with felt rings is 136mm. The inside frustum 30mm opening is distance 63.5mm from the face of the C6.

If the final read area is indeed only 25mm at 136mm, the 30mm frustum opening and 60mm cylinder should not cause problems. Yet when I take measurements, I see a very measurable drop in luminance. For example, measuring a 100% White 100% Window SDR pattern, I measure ~108 nits in contact mode, ~108 nits with the C6 at 136mm with no SLET attached, but only ~88 nits with the SLET attached. If I use this exact same prototype with the i1Pro 3 (which has both a smaller FWHM/TLT and I believe a smaller contact mode read area), I do not see a drop in luminance. From this, I conclude that the C6 read area is already exceeding 30mm diameter at 63.5mm distance; by how much, I do not know. If true, that would suggest the read area might even exceed 60mm at 136mm distance, but I haven't tried to examine this yet.

Is there a flaw in my thinking?
 

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Telescopic optics (telescopes, weapons sights, binoculars, microscopes, etc) also produce a significant drop in luminance of the viewed scene, despite the addition of larger tubes and high-tech lens coatings. My guess would be that it has partly to do with the physics of viewing something through a tube.
 

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Telescopic optics (telescopes, weapons sights, binoculars, microscopes, etc) also produce a significant drop in luminance of the viewed scene, despite the addition of larger tubes and high-tech lens coatings. My guess would be that it has partly to do with the physics of viewing something through a tube.
Hmm, I thought refracting telescopes were lossy primarily because of some degree of light absorption and reflection when passing through both the lens and the eyepiece, not because of the tube. A comparable thing isn't happening here, unless you're thinking absorption/reflection due to the cylinder walls is that significant. But in that case I would expect similar loss for both meters, and I'm not seeing that. I'm also seeing similar results with both shiny black interior surfaces and surfaces painted with black paint (Stuart Semple's Black 3.0) that claims to absorb up to 99% of visible light. I realize now I forgot to include that I've also tried C6 measurements with the inside frustum removed, and I don't see the same drop in luminance. So the tube itself doesn't seem to be the primary cause.
 

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Good points. Yes, I was thinking absorption/reflection within the tube more so than loss through the glass elements.
 
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