Originally Posted by Light Illusion
Please note that the laser pointer in the Discus is offset from the centre of the measurement spot, with a parallax offset of something like 3cm.
And when comparing FOV spot sizes the manufacturer data is 'generic', as all probes have 'soft' edges to the measurement spot.
The only way to really 'verify' spot size (and position) is to use slow (manual) wipe of a wide white stripe on black.
As soon as the white stripe enters the spot measurement area the probe reading will start to increase above 'black'.
That process will have to be performed for left/right/top/bottom.
Obviously, the 'reading speed' of the probe will define the speed at which the white stripe can be moved.
Yes, we know all that, the 3cm off centre is even mentioned in Daryll's document. We're not sending a rocket to the moon, we're measuring patterns for a home-cinema set-up.
It's just that the data used by myself and others for years without issues was questioned by some.
You have provided useful data for the Discus, but without comparable data for the i1pro2 it doesn't really help, as we don't know exactly what you are measuring.
The whole point of Darryl's table was to provide data that was comparable, precisely because in most cases the manufacturers' data isn't.
I haven't experienced any issues following Darryl's measurements, training a Discus to an i1pro2 with half a dozen JVC projectors over close to a decade.
So until a reliable source (you would be one) provides an alternate set of data for at least the two meters discussed here (Discus and i1pro2), there is no way to compare.
I have zero motivation to take any of these measurements, given that I get excellent results with the values I have already suggested (2ft for i1pro2, 1ft for Discus or 3ft for i1pro2 and 2ft for Discus, or both Discus and i1pro2 at the same distance, provided the pattern is large enough, which should be the case with the meters at 1-2 ft, aimed the way I suggested, with 100% size patterns). Here, all of these provide repeatable, accurate results.
So if you can't provide the other half of the information, there is no point in questioning the data already available, or the methodology.
The day an alternate set of values is published, I'll happily compare results.
In the meantime, I'll keep doing what I've done for many, many years