Re: B+W 77mm UV/IR Cut (486M) MRC Filter
Re: B+W 77mm UV/IR Cut (486M) MRC Filter
- Subject: Re: B+W 77mm UV/IR Cut (486M) MRC Filter
- From: Ben Goren <email@hidden>
- Date: Sun, 26 May 2013 11:01:15 -0700
On May 26, 2013, at 10:23 AM, Robin Myers <email@hidden> wrote:
> UV light should always be filtered out at the source not just to control fluorescence, but more importantly to eliminate damage to the subject. UV is high energy light that breaks molecular bonds, altering the artwork. It can easily fade more fugitive colors, degrade optical brighteners, can cause chemical changes, and much more.
Without disputing any of that, outside perhaps of very rare instances in preservation of very fragile objects, I don't see it being a practical concern in reproduction work. If the work is carried uncovered from the parking lot, it's going to get more UV exposure than in the imaging process. Unless a minute or two of direct exposure to the Sun is going to damage the work, nothing you'll reasonably do to it in the studio will, either.
(Of course, there are unreasonable and even stupid things you could do in the studio, like set a hot lamp inches away from the art and leave it on while you go to lunch....)
Where the UV content of the light becomes a concern for damaging art is in display conditions. If there's nothing fluorescent in the art, you don't want any UV light on it to prevent just the type of damage you describe.
But, if there *are* fluorescent pigments in the art, and especially if the fluorescent pigments are a prominent feature of the art...well, you'll want to display the art under light with plenty of UV in it in order to best showcase it, but you'll also want to consider ways of limiting the exposure. For example, you could significantly dim the ambient conditions and use a directional UV-rich source to illuminate the art (which won't have to be as absolutely bright), and you can only turn on the UV-rich light when the work is actively being viewed. But you also have to acknowledge that the work has a limited lifespan, no matter what you do, and that all you can do is prolong its life.
> There are also big issues with flash units in their exposure and color variability. It is more by luck than design that some may be acceptable for fine art imaging, most are not, and I do not recommend their use.
That's one reason why I recommend the Einsteins. Their color and output constancy was *exactly* the driving factor in their design. They offer two modes: a ``constant color'' mode and an ``action'' mode. In constant color mode, the color temperature is held constant at 5600K +/- 50K over the entire power range. Even in action mode, the color temperature only varies from 5600K to 6300K over the range.
And, in practice, I can't spot any deficiencies in their operation. Not only are they extremely stable, they're extremely consistent between units (no more than 1/10 stop variation, and that may well be due to light placement / aiming). They're also very linear; if I set up the lights in a copy stand configuration and adjust them all by 1/10 stop, the resulting exposure changes by 1/10 stop.
Cheers,
b&
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