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 > > > > > ------------------------------ > > To unsubscribe from the MUSEUM-L list, click the following link: > http://home.ease.lsoft.com/scripts/wa-HOME.exe?SUBED1=MUSEUM-L&A=1 > ========================================================= Important Subscriber Information: The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes). If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).