Re: UV cut or not for i1 Photo Pro
Re: UV cut or not for i1 Photo Pro
- Subject: Re: UV cut or not for i1 Photo Pro
- From: Robin Myers <email@hidden>
- Date: Sat, 23 Apr 2011 10:39:06 -0700
By "UV enabled" I believe Mr. Dinkla was referring to an instrument without a UV cut filter, so it is enabling measurement of UV wavelengths. In which case he correct in his assertion that it measures a wider spectral range.
The UV Cut filter employed in the i1Pro removes all illumination below 400 nm. Without illumination there should be no reported data in this region. So the actual range for the i1Pro UV (this is X-Rite's nomenclature for an i1Pro with a UV-cut filter installed) is 400-730 nm in reflectance measurement mode.
However, X-Rite, for some unknown reason, creates and reports extrapolated data in the 380-400 nm region. At best this leads to false interpolations of data in this region, at worst it creates highly erroneous data which causes problems further along. I have measured papers with FWA additives that sometimes cause their interpolation algorithm to produce values in excess of 200% reflectance in the 380-400 nm region.
I have a more thorough report on this issue in my Chromaxion newsletter available at http://rmimaging.com/information/Chromaxion_Issue_1.pdf.
To remove issues with bad extrapolation data in my SpectraShop program, I set the data to 0% reflectance in this range for the i1Pro UV and the Spectrolino when used with the UV Cut filter.
Robin Myers
On Apr 23, 2011, at 9:55 AM, Roger Breton wrote:
> Ernst,
>
> You wrote:
>
> ... but UV enabled spectrometers are preferred as they in general measure a
> wider range of wavelengths.
>
> I don't want to cite you out of context but surely you must not mean that
> "UV-cut" measure over a larger spectral range than non-UVcut instruments?
> Assume two EyePros, one with UV-cuter filter and one without UV-cut filter,
> don't they both measure over the same spectral range, from 380nm to 730nm?
>
> Roger
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