Re: Spectrometers for graphic arts and UV.
Re: Spectrometers for graphic arts and UV.
- Subject: Re: Spectrometers for graphic arts and UV.
- From: robin--- via colorsync-users <email@hidden>
- Date: Thu, 12 Dec 2024 00:41:33 -0800
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Hello Peter,
> On Dec 11, 2024, at 22:16, Peter Miles via colorsync-users
> <email@hidden <mailto:email@hidden>>
> wrote:
>
> Hi List members.
> I have been wondering why the spectrometers that we use in colour management
> have not begun to include some UV measurement, given ISO3664:2009 requires
> lighting with specified amounts of it. Or in the case of the upcoming P3/P4
> viewing condition, its absence.
>
> I use ours (XRite) to measure CRI/TM-30 of room lighting, and to check light
> modifiers used in our photo studio as they age, and that’s great. But I
> can’t use it for to check if lighting is ISO 3664 compliant. And that seems
> strange, given these spectrometers target market.
I think the folks that made ISO 3664 were expecting that if they defined the
standard then the manufacturers would produce instruments to match. There are
two things the spectrometer must do to pass ISO 3664. First, for emissive
measurements it must sample in 5 nm or smaller bands. Second, it must measure
from 300 nm to 780 nm. The standard does note that few instruments existed at
that time which met those requirements. Unfortunately it is true that few
instruments still exist that meet these criteria. As it happens, the
Konica-Minolta FD-7 and the MYIRO-1 provide 5 nm sampling from 360-730 nm.
These are the only two ones I know that can almost pass the reflective
measurement requirements of ISO 3664. I think they felt that measuring down to
360 nm would be enough. It does include the 365 emission peak from mercury lamp
illuminators. Neither of these two instruments measures to 780 nm.
The instruments I know that have the range to measure from 300-780 nm at less
than 5 nm are all fiber optic instruments. They have the range but they lack
good optical illumination for reflective samples. Some do have a 45x:0
measurement device, but that is not as good as 45c:0 or 45a:0 measurement
optics. These instruments are designed more for chemical analysis, not
calibrated to provide spectral reflectance factors like the graphic arts
instruments. Instead they provide counts and the user is expected to convert
counts into reflectance/transmittance factors.
So this is a case where the standards guys made a standard that for practical
purposes cannot be fully achieved by off-the-shelf instruments.
>
> Would adding UV sensitivity make spectrometers too expensive for not enough
> added value? Or are there other cans of other worms that make it not
> practical?
Perhaps there was not enough of a perceived market to make ISO 3664
instruments, especially when the ones currently offered meet the requirements
for most of the market. How many clients ask for ISO 3664 measurement and
reporting?
Notice that it is only in the last few years that instruments have appeared
that have M0, M1 and M2 measurement modes (ISO 13655). And fewer still that
have an M3 mode. X-Rite could not get the M3 mode to work on the i1Pro3 (4.5 mm
aperture) so only the i1Pro3 Plus (8 mm aperture) has an M3 filter. Neither the
FD-7 or MYIRO-1 offer M3 measurement. The X-Rite eXact does have all four
measurement modes (M0, M1, M2, M3) but it does not measure light sources.
It seems there is not one instrument that does everything required for all the
standards used in the graphic arts market. If I have missed one that does,
please let me know.
Best regards,
Robin Myers
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