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Author Topic: Lighting Prints with Solux Bulbs  (Read 6360 times)
Light Seeker
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« Reply #20 on: August 23, 2011, 04:46:42 PM »
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Above my working desk, I have three MR-16 bulbs, which I am rather sure are 50-watt and approx. 40-degree spread.  They are 30" apart and 4ft3in. straight above the desk (zero angle for photometrics). Also, I have both diffusers and eggcrate baffles over the bulbs. I decided on the spacing after consultation by phone with the people at Tech Lighting (whom you may want to call), and get rather even illumination on the desk.  The chart at the back of their (several years old) catalog, indicates that with that configuration I should be getting a little less than 125 footcandles.  The desk is nicely lit, and certainly not overlit.

Barbara. . .  this sounds very similar to my situation in many respects, and what I'm looking at doing. Solux makes a Plano Plano diffuser and the rep told me to assume loosing ~1/2 of the light with it. He also cautioned that the published bulb specs were ideal, and when I suggested assuming 80% would be realized he agreed. If I map those two parameters onto your situation it suggests you might be getting ~50fc at your desk. That seems to align with your comment that the desk is "nicely lite, and certainly not overlit".

Terry.
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BarbaraArmstrong
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« Reply #21 on: August 23, 2011, 05:33:12 PM »
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Terry, interesting point about the diffusers.  Also, I have a dimmer on the set-up at the wall switch, so don't have to leave it at full output.  As I think about the kind of lighting calculations you're doing, I would say to bear in mind that as you get to the edge of the beam spread for any bulb, you've already lost half the light.  If you want even illumination, you need to have your overlap at that point, or near it.  And you can be surprised how many of these little lights you need to cover an area.  Please tell us how your lighting plan works out.
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Light Seeker
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« Reply #22 on: August 23, 2011, 09:47:10 PM »
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I have learned a great deal from this thread, and through the subsequent research I've done. Thanks to everyone for your thoughts, suggestions and recommended reading. This has been fascinating!

I am planning to order track lighting with one Solux 3500K, 50W, 36 degree MR 16 bulb for each 2.5' section of my display. I would like to light approximately 5' of the 7' panel vertically, with the top 1/2 or so being the most important. The booth is 7.5' wide by 5' deep.

My light bar sits 15" above the top of the booth and I plan to set it so the track lighting is 36" away. If I shine the bulb at a point 21" down from the top of the panel (36" vertically down from the track lighting) the light will be 51" away from the print, and it will be shining at a 45 degree angle. When I look at a generic photometrics chart, take into account differences from the Solux bulb, and factor in bulb/transformer inefficiencies, I get a light level of ~70fc and a beam spread of ~2.7' across by ~4.4' vertically. If I diffuse the bulb the light level goes down to ~35fc.

The purpose of the booth, at least for this event, is to sell artwork. The space I will be in is lit by florescent tubes and I will have no control over ambient light levels.

Will 70fc be enough? It still (easily) falls into the acceptable range identified by the Kruithof curve for 3500K lighting. While diffused light might be nice, I don't think that 35fc will be bright enough.

Any last comments or suggestions before I pull the trigger?

It will of course be interesting to see how this actually works out in real life. My concern now is to prove out my basic approach, and to make sure I'm in the ballpark before I move forward.

Thanks all.

Terry.
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Rob Reiter
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« Reply #23 on: August 23, 2011, 11:03:37 PM »
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I've been using their 3500K bulbs in our gallery and amy very pleased. Solux has a "white paper" on why that temperature is the best for viewing prints and I agree. The higher temp bulbs just look blue. I don't feel the 3500K light is too warm at all. It's "just right."
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Ernst Dinkla
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« Reply #24 on: August 24, 2011, 02:31:41 AM »
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Will 70fc be enough? It still (easily) falls into the acceptable range identified by the Kruithof curve for 3500K lighting. While diffused light might be nice, I don't think that 35fc will be bright enough.

Terry.

Wilhelm calls 450 Lux (40 FC approx) a standard (average) display condition. For fade prone art the local museum here uses 50 Lux (4.4 FC approx) at 3000K. Aardenburg Imaging mentions several standards but for color evaluation a value between 500 and 2000 Lux (D50 illumination, so cooler) is required.  70 FC (800 Lux approx) should be fine for 3500K.

met vriendelijke groeten, Ernst

New: Spectral plots of +250 inkjet papers:

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
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BarbaraArmstrong
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« Reply #25 on: August 24, 2011, 03:14:34 AM »
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Terry, you may need to talk with a lighting designer to give you a good reliable answer to your question.  But let me give you a comparison that makes me think your planned lighting should work.  I have a 35-watt MR-16 (not Solux) 3ft9in above and 3ft9in out from a print that is 31in. square and that is sufficient to give it a nice soft lighting.  Your 50-watt will provide that much more light, and from a closer distance.  If you do a Google or Bing search for "recommended footcandles" you will see some interesting examples of recommended light levels.  Try this site:  http://www.mts.net/~william5/library/illum.htm#6.) where you will also see the paragraph on "When to Break the Rules", which says that "for applications involving merchandising, advertising, decorative, artistic applications...it may be necessary to provide..higher than recommended lighting levels to achieve proper impact."  I think you will want your lighting to be at a higher level than the overall surrounding lighting, so that is another element.
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BarbaraArmstrong
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« Reply #26 on: August 24, 2011, 03:19:54 AM »
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Forgot to mention, my 35-watt bulb also has a diffuser and an eggcrate louver over it, further reducing the light.  I do think a 50-watt for each of your panels should be fine.  If in addition to that (reducing the light), you want to consider adding a diffuser, make sure the fixture into which you are mounting the bulb can take it (that is, make sure it has the capacity for a filter).
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Light Seeker
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« Reply #27 on: August 24, 2011, 02:37:45 PM »
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Order placed. I will put ArgyllCMS onto my laptop, measure the light levels I actually get when I set this up, and report back. It will be interesting to see how close theory and reality align.

Ernst, thank you for your perspective on light levels. That was reassuring.

Barbara, your real-life example was very helpful and also reassuring. I did order diffusers so I have choices. The fixtures have what's required to mount then. Should the diffusers lower the booth lighting too much I'll eventually use them when lighting my studio.

I also ordered two 5000K bulbs for colour proofing and for comparison, along with some 3500K PAR bulbs to try out.

If anyone is interested, here is a link to the Color Proofing Kit I've ordered. . . . .

https://www.solux.net/cgi-bin/tlistore/colorproofkit.html

Terry.
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MHMG
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« Reply #28 on: August 24, 2011, 04:40:05 PM »
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For confirmation, there are many low cost Lux meters on the market today. For example, go to http://www.amazon.com/ and enter "lux meter" in the search field. There are some lux meters at astoundingly low prices (less than $30).  While the low cost meters may not be super accurate (my research grade lux meter cost over $2000), they should be close enough to help you confirm that your lighting method is producing a reasonable level of illumination at the print surface.

As Ernst noted, critical color evaluation takes a minimum of about 500 lux at the print surface, although many museums will light fragile works of art as low as 50 lux.  For middle-aged and senior-aged eyes, 50 lux is a serious challenge in terms of experiencing decent color fidelity in the art work, but at 500-2000 lux, you get where you need to go in terms of high quality gallery lighting.

Another thing you will learn with a lux meter is just how tricky it is to evenly illuminate a large piece corner to center to corner. Some people, however, will conclude that a little fall off (e.g, one "stop" or about 50% of the max center illumination level) in the corners actually helps to draw you into the main subject matter of the artwork.

cheers,
Mark
http://www.aardenburg-imaging.com
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Light Seeker
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« Reply #29 on: August 24, 2011, 06:10:36 PM »
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For confirmation, there are many low cost Lux meters on the market today. For example, go to http://www.amazon.com/ and enter "lux meter" in the search field. There are some lux meters at astoundingly low prices (less than $30).

I have a Sekonic flash meter (L-358) that I tried the other night but I didn't spend much time to work out what it can do in terms of measuring ambient light. It turns out that with one dip switch change it will display EV values. The manual has a table to convert EV to Lux so if I get that into my iPhone I can measure light levels anywhere. I can retract the ambient dome and use it measure flat surface light levels and also light fall off. It will take two ambient readings and show me the delta between them.

I am looking forward to working with the lights and building my understanding about lighting artwork.

Thanks Mark.

Terry.
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cybis
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« Reply #30 on: August 27, 2011, 02:14:50 PM »
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How does one measures illuminance and color temperature with an Eye-One Pro? i1Profiler doesn't seem to provide that information.
I've just started experimenting with Argyll's spotread with the following flags:

Code:
spotread -v -S -a -T -H

This is giving me a Lux and a CCT reading. How reliable are those readings? Am I on the right track?
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Ernst Dinkla
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« Reply #31 on: August 27, 2011, 04:40:51 PM »
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How does one measures illuminance and color temperature with an Eye-One Pro? i1Profiler doesn't seem to provide that information.
I've just started experimenting with Argyll's spotread with the following flags:

Code:
spotread -v -S -a -T -H

This is giving me a Lux and a CCT reading. How reliable are those readings? Am I on the right track?

Gretag Macbeth's i1Share
ArgyllCMS Illumread


met vriendelijke groeten, Ernst

New: Spectral plots of +250 inkjet papers:
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

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cybis
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« Reply #32 on: August 27, 2011, 05:50:26 PM »
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Gretag Macbeth's i1Share
ArgyllCMS Illumread

Thanks Ernst! i1Share did the trick.

I couldn't get illumread to give me an illuminance reading. All I can see is to use specplot with illumread, but that only gives me the CCT, no Lux.
spotread -a gives a Lux reading but the documentation seems to indicate '-a' works only with an Eye-One Display 2.
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Light Seeker
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« Reply #33 on: August 27, 2011, 09:52:27 PM »
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spotread -a gives a Lux reading but the documentation seems to indicate '-a' works only with an Eye-One Display 2.

I've been using spotread -v -a to measure light levels using my Colormunki. I compared those results with readings from my Sekonic flash meter and allowing for a reasonable margin of error, they are the same.

Terry.
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cybis
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« Reply #34 on: August 28, 2011, 12:06:04 AM »
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I've been using spotread -v -a to measure light levels using my Colormunki. I compared those results with readings from my Sekonic flash meter and allowing for a reasonable margin of error, they are the same.

Excellent! I also compared i1share to spotread -a and the results are identical using an i1pro.

One more question, the sensor should be oriented square with the artwork, not toward the light source, correct?
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Light Seeker
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« Reply #35 on: September 02, 2011, 07:35:45 PM »
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My lights arrived and I wanted to report on how things worked out.

I set up a corner section of my booth and hung 3 canvas prints. A 20"x24" print was hung 2" from the top. A 20"x28" print was hung 20" from the bottom and a 14"x20" print was positioned in between these two. They were all in landscape orientation, and the three prints comfortably filled most of the 2.5'x7' section. More specifically, I had planned to use ~5' of the vertical, and that is how I positioned the prints.

I took measurements on all four sides of each print (midway on the side) and in the centre. The ambient light level in the room was 184 lux. The brightest point was the bottom of the top print without diffusion and the center of the top print with diffusion. It measured 905 lux without diffusion and 520 with diffusion. I had estimated that I would get 753 lux (70 fc) without diffusion and 377 lux (35 fc) with diffusion. I've done better, and the difference seems to be the 20% reduction I applied to account for inefficiencies. That factor was not required, and removing it virtually brings the numbers into alignment (theoretical versus measured). That's cool.

Shifting to light coverage now. Without diffusion the light levels across the top print varied by 1.6 EV. The second print varied by 0.7 EV and third by 1.1 EV. Note that the second print was smaller and yes, I realize it would have been more balanced to have used sample points spread evenly across the panel. However, I wanted to test a real-world scenario.

With diffusion the light levels across the top print varied by 0.6 EV. The second print varied by 0.8 EV. The third print varied by 0.8 EV.

I much preferred the diffused lighting. It was more even and more pleasant to look at. Giving up some light level was well worth it. In fact, the prints looked "just right". Not too bright and not too dark, almost as if they weren't even lit. You could of course see the difference when switching the lights off and on, and the kind of "pop" they added. Conversely, with no diffusion you knew they were lit, as the light was harsher and you could see the brighter area where the bulb was aimed.

I did one last experiment. I turned off the overhead florescent lights to see how the prints would look when the ambient light was significantly reduced. This was a boardroom with windows on one side, and it became noticeably dim but not dark. Unfortunately I didn't think to measure the ambient light. In this light the prints looked somewhat under-lit. This is of course subjective, and without the a-b comparison, and with some time for my eyes to adjust, I might have formed a different opinion. The room was likely close to subdued museum lighting. However, I want the prints to have an impact (i.e. marketing) and the first environment I will be in has an ambient light level of only 50 lux. So, I will be adding some fixtures to increase the overall level. The way my light bars are positioned allows me to mount fixtures further away to get the wider coverage I need for this.

I am very pleased with how things turned out. The methodology used to integrate two sets of data, and the general math behind all of this, worked well. Most importantly, the prints look great under these lights.

Thank you again to everyone who helped me work through this. I hope this information is useful to someone else down the road.

Terry.

<snip>

I am planning to order track lighting with one Solux 3500K, 50W, 36 degree MR 16 bulb for each 2.5' section of my display. I would like to light approximately 5' of the 7' panel vertically, with the top 1/2 or so being the most important. The booth is 7.5' wide by 5' deep.

My light bar sits 15" above the top of the booth and I plan to set it so the track lighting is 36" away. If I shine the bulb at a point 21" down from the top of the panel (36" vertically down from the track lighting) the light will be 51" away from the print, and it will be shining at a 45 degree angle. When I look at a generic photometrics chart, take into account differences from the Solux bulb, and factor in bulb/transformer inefficiencies, I get a light level of ~70fc and a beam spread of ~2.7' across by ~4.4' vertically. If I diffuse the bulb the light level goes down to ~35fc.

<snip>

It will of course be interesting to see how this actually works out in real life. My concern now is to prove out my basic approach, and to make sure I'm in the ballpark before I move forward.

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BarbaraArmstrong
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« Reply #36 on: September 02, 2011, 10:37:01 PM »
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Great!
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