thanks for all that, Marc. A lot to consider. Kathie Gow Curator, Hatfield Historical Museum hatfieldhistory.weebly.com Oral History Producer wordspicturesstories.com On Fri, Jan 25, 2019 at 2:31 PM Marc A Williams <[log in to unmask]> wrote: > Kathie, > > I probably would order your list as follows. > > 1) No UV - that should be the case for LEDs, but some have had UV in the > past when tested. > 2) Intensity (lux or foot-candles) that is below recommended levels for > objects exhibited. This requires actually holding the fixture in place and > using a light meter placed at the object of most concern. Inexpensive > (less than $20) acceptable accuracy meters are available (or at least were > when I tested them roughly 3-4 years ago and discussed this on MuseumL) if > you do not have one. You are not interested in the total light output, > which generally is listed on the package in lumens, but the actual amount > falling on the objects, which must be measured with the light unit in place. > 3) Color temperature. I would suggest you at least try 3500K compared to > 3000K, which I'm concerned will be too orange. Once again, hold units in > place and make observations/decisions. Do not have them installed first. > 4) CRI ideally of 95+ but if necessary as low as 90. This is last as it > probably will be the hardest to satisfy. Maybe I will be pleasantly > surprised? > > I would not necessarily expect the electrician firm to know the > specifications of the lamps, but you may get lucky. They are going to to > have to ask their supplier, and probably they will have to ask the > manufacturer. You could get the manufacturer and model number and go > directly to the manufacturer yourself. This might be the most efficient > method. > > The other possible complication is being able to have units of different > color temperature (hopefully by the same manufacturer so apples can be > compared to apples) that you can "install" by holding in place to judge > appearance and measure intensity. Hopefully you will have an electrician > that is friendly and helpful. Some may not want to open packages or take > the time to do this. Changing the intensity if it is too high will require > either moving the light source further away from the objects, using less > LED lamps in the fixture, or decreasing the output of the lamps. You may > not have a lot of flexibility in this and may have to get creative. Please > let me know if you have any additional questions. > > Marc > > *From:* Kathie Gow <[log in to unmask]> > *Sent:* Friday, January 25, 2019 12:02 PM > *To:* [log in to unmask] > *Subject:* Re: [MUSEUM-L] best color temperature for new LED lights? > > Thanks Elizabeth and Marc. Marc, I hoped you'd respond, because I know you > know a lot about this stuff, but wow, that is a lot to consider! > > I will take that info to the electrician firm we are dealing with, but > since the town is paying for this replacement from a local firm, our > options may not be as wide as all that. From your thoughtful reply, I am > taking away we should try to get the following conditions met, in this > order? > > --no UV light (I'd thought this was the case for all LEDs!) > --high CRI number (like, MR-16, with 96 or higher), which addresses color > accuracy > --color temp that feels natural for our setting -- there's a wide variety > in museum settings and we think a warmer light will best fit ours (so maybe > we go for around 3000K...) > > Again, no idea how much choice we will actually have with regard to CRI, > for instance, but now I can ask for what we want and see what's available > at what price. > > If anyone else has experience purchasing recent LED fixtures for their > museum space with additional input, would love to hear it. > > Thanks again! > > --Kathie > > Kathie Gow > > Curator, Hatfield Historical Museum hatfieldhistory.weebly.com > > Oral History Producer wordspicturesstories.com > > > On Thu, Jan 24, 2019 at 11:22 AM Marc A Williams <[log in to unmask]> > wrote: > >> Kathie, >> >> Your question actually has more facets than just color temperature. A >> color temperature of 2700K is on the very warm (yellow/orange) side, >> somewhat equivalent to sunlight at sunrise or sunset. "True" daylight is >> considered to be around 5500K, which is definitely on the cooler or bluer >> side, somewhat equivalent to sunlight at high noon. Perhaps more important >> than color temperature is CRI, or color rendering index. This is how >> closely a light source replicates sunlight at that color temperature. >> Ideally, you want a CRI very near 100, which would indicate it replicates >> it almost perfectly. Incandescent lamps (the correct term according to the >> industry for a light source, rather than bulbs) commonly used for lighting >> museums (the MR-16, for example) are available in CRI of 96+. A lamp with >> a CRI of 80 would be considered woefully inadequate. >> >> So, the first thing to ask the manufacturer of the lamp (not the vendor) >> is what is the CRI? Ideally, they also can provide you with a spectral >> curve of the lamp. This shows the light emitted at each wavelength, >> ideally compared to natural sunlight. It also will show if there is any UV >> light present, which there should not be - if there is, that is not the >> lamp you want. LEDs have progressed a lot in the last few years, and >> technically, it should be possible to fine-tune them to be near 100 CRI. >> Whether specific manufacturers have done this is something you will have to >> ascertain. Due to the progression in technology, advice from 2012 such as >> the Getty publication may no longer be relevant. For your application, >> just buying an off-the-shelf fixture made for the general public probably >> will not be ideal. You should look for ones that promote their color >> accuracy on their packages and in their literature. If they are simply >> promoting energy savings and long life, they probably have poor CRIs. But >> this can only be determined with CRI ratings and spectral curves from the >> lamp manufacturers. Complicating this further is the fact that the >> manufacturer of the fixture may or may not be the manufacturer of the LED >> lamps in the fixture. So some sleuthing may be necessary >> >> To answer your question about what color temperature would look best >> (assuming you have found high CRI lamps), the best information I am aware >> of about that was testing done with high CRI MR-16 lamps in an actual >> museum setting. Regular visitors were asked to look at objects illuminated >> with different color temperatures between about 2700K and 5500K. They were >> asked to indicate which lamp produced the most "natural" colors. Thus, >> this was clearly subjective, but also real-world for museum viewing. The >> color temperature that was found the most natural was 3500K. It can be >> assumed that this would translate to LEDs that also are of high CRIs. >> >> Many other factors influence perceived color, including the color >> temperature and CRI of nearby lighting. A 3500K display case in a room >> filled with 5500K overall lighting may appear too yellow/orange, for >> example. Also remember that light intensity on the objects in the case is >> important even if it is LED lighting. Select fixtures or combinations of >> lamps that keeps the light levels in the desired range for the types of >> objects within the case. >> >> Marc >> >> American Conservation Consortium, Ltd. >> 4 Rockville Road >> Broad Brook, CT 06016 >> [log in to unmask] >> >> *From:* Kathie Gow <[log in to unmask]> >> *Sent:* Wednesday, January 23, 2019 4:48 PM >> *To:* [log in to unmask] >> *Subject:* [MUSEUM-L] best color temperature for new LED lights? >> >> Hi Listers. We are replacing our 8-foot-long fluorescent tube light >> fixtures in two large display cases (due to a smelly blown-out ballast!), >> with new LED fixtures, and I need to decide the color temp of the new >> lights. I am thinking we want warm light, but something that will still >> show whites as white. Would 2700K do the trick? >> >> (We are a small historical society museum with lots of oak and other wood >> cases, whitish walls (that are mostly covered) and some exterior LED >> fixtures that have cooler light... >> >> Happy for all LED lighting tips and things you've learned! >> >> best, >> --Kathie >> >> >> Kathie Gow >> >> Curator, Hatfield Historical Museum hatfieldhistory.weebly.com >> >> Oral History Producer wordspicturesstories.com >> >> ------------------------------ >> >> 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 >> >> ------------------------------ >> >> 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 >> > > ------------------------------ > > 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 > > ------------------------------ > > 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/ . 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