Great information!

Thanks Doug!

Cheers!
Dave

David Harvey
Senior Conservator & Museum Consultant
Los Angles CA  USA
www.cityofangelsconservation.weebly.com


On Fri, Mar 4, 2016 at 10:36 AM, D NISHIMURA <[log in to unmask]> wrote:

> I did too until I read CIE 157:2004 which made me realize that the studies
> that I’ve read, deal with flashes in isolation. That is to say, without
> consideration of the already existing exhibition lighting.
>
>
>
> They start with the assumption of ISO 100 film shot at f/8. The flash
> delivers and exposure of about 600 lux seconds in 1/1000 of a second.
> Apparently the possibility of biphotonic reactions has been studied and
> dismissed (more than one photon hitting a molecule in such rapid succession
> that there is no time for energy loss between them and their affect is
> additive.)
>
>
>
> So the exposure is roughly 0.17 lux hours.
>
>
>
> For what they define as a medium responsivity object, their recommended
> maximum annual exposure is 150 000 lux hours so a single flash is about on
> millionth of this value. However, if the object is on display fo4 3000
> hours per year. If you’re exposing it to 50 lux with the exhibition
> lighting, then 30 flashes per hour will roughly push you over their
> recommended limit by 10%.
>
>
>
> For high sensitivity materials, they recommend a limit 15000 lux hours per
> year and if you use a very dim lighting of 30 lux for 500 hours of display
> per year then 18 flashes per hour would push you over the limit by 10%,
> which they suggest is very likely for a popular exhibit in a public museum.
>
>
>
> They also point out the distraction for other visitors and the fact that
> flash photography with objects under glass would result in very poor images
> due to reflection.
>
>
>
> Their medium category includes many historic plant colorings emphasizing
> alizarin in particular either as a dye on wool or as a lake pigment on any
> media; the color of most fur and feathers; and most chromogenic photographs
> with “chrome” in the name.
>
>
>
> I know that Kodak used “chrome” in any reversal color including slides
> (Kodachrome and Ektachrome) and other companies seemed to follow suit. They
> also used it for their reversal color paper so chromogenic paper that you
> could directly print from a positive slide.
>
>
>
> Their sensitive category consists of most plant extracts (most historic
> bright dyes and lake pigments on all media), insect extracts including lac
> on all media, most early synthetic dyes, many cheap synthetic colorants,
> most felt tipped markers (including black), pre-20th century tinting dyes
> for paper, and chromogenic prints with “colour” in the name.
>
>
>
> Kodak used “color” for their negative/positive photographs so Kodacolor
> negatives were printed on Ektacolor paper.
>
>
>
> -Doug
>
> Douglas Nishimura
>
> Image Permanence Institute
>
> Rochester institute of Technology
>
>
>
>
>
>
>
> *From:* Museum discussion list [mailto:[log in to unmask]] *On
> Behalf Of *Dan Bartlett
> *Sent:* Thursday, March 03, 2016 2:02 PM
> *To:* [log in to unmask]
> *Subject:* Re: [MUSEUM-L] signage welcoming photography
>
>
>
> I thought the flash question was laid to rest some time ago.
>
> Selfie sticks on the other hand...
>
> db
>
>
>
>
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