Paul Verizzo
Print Addict
- Joined
- Apr 16, 2011
- Messages
- 427
- Reaction score
- 88
- Points
- 173
- Location
- Sarasota, FL, USA
- Printer Model
- Canon ip4500, 9000 MK II, PRO-
OK, granted, this is my "Amateur Scientist" research and view of things. Not yours? Always willing to see if I've something wrong. And, I'm sure some of you already know this, but I didn't, and I've not seen reference to what follows.
The summarized version of the varying standards of lux is handily summarized in Table II of Aardenburg's "Converting Megalux-hours of Light Exposure to estimated “Years on Display” " It's one of those (printer/ink/paper) informational earthquakes "hidden in plain sight." Sort of aware of this for years, but just in my mental background. Folks bandy those "X Years" numbers around like they are from on high.
The bottom line is simply this: Kodak, Wilhelm, and Aardenburg all use different lux levels to arrive at their conclusions! Yet, the average person or of even well informed, will seldom know this when comparing paper/ink X to paper/ink Y. To wit:
Kodak uses 120 lux, 12 hours per day
Wilhelm uses 450 lux, 12 hours per day
Aardenburg uses megalux/hours, then uses 228 lux for 12 hours per day to obtain a "years" equivalency.
Quite a range. So what's realistic?
I took my incident light meter which can give a photographic EV (Exposure Value) reading, and using an online chart from Wikipedia, converted my readings to Lux. This morning: cloudless, bright, low winter morning Florida sunlight. EV of 14 through the SE window and screen, that's 41,000 lux. Yet, Aardenburg claims such a situation should be only 10,000 lux. That's a bit more than margin of error or meter variance.
Inches to the side of the sunbeam, down to EV 6.5, about 240 lux. Step back five feet, still a well illuminated interior, and it's now EV 3.5, about 30 lux. With the afternoon SW sun blasting into the Florida room later (there's actually less light in the summertime due to roof overhang), EV 9, about 120 lux, in the indirect light against a wall. I think that this is as bright as most homes will ever see in "indirect sunlight."
To the eye, the second and third readings above are visually the same, yet have an 8:1 ratio!
Lesson 1: (I think.) That "indirect indoors" can cover a LOT of lux and lifespan difference! From 30 to 120 may be typical, still 4:1. Moving a print to a slightly different location can hugely change its fading rate.
Lesson 2: Not unreasonable to take Wilhelm's ratings and multiply them by a factor of 10 for a less than real bright indoor setting. If they say ten years at 450 lux, it's one hundred using 45 lux as an indoor realistic number. Major caveat: This is for UV only, gas fading will take place regardless unless coated or otherwise protected.
Lesson 3: This is a cousin to my "Perfection is the enemy of good enought," and "Subjectivity trumps objectivity." "The more you try to nail things down with more data, the more likely the mole will pop up again, the one you thought you whacked."
Confounders that I've thought of:
1. All the settings are for 12 hours a day. Well, the sun doesn't just instantly pop up to full strength, nor does the opposite at sundown. Most offices don't have the lights on 12 hours a day. A given "bright indoors indirect" setting may only see four hours at increased lux levels, other hours tapering to less.
2. How do the daylight flourescents that "they" use compare to natural daylight? My review of histograms of sunlight and daylight sources show that they are not even close, the fluorescents having much more UV in them. That's without even taking into account ordinary window glass cuts out most of the UVB spectrum.
The summarized version of the varying standards of lux is handily summarized in Table II of Aardenburg's "Converting Megalux-hours of Light Exposure to estimated “Years on Display” " It's one of those (printer/ink/paper) informational earthquakes "hidden in plain sight." Sort of aware of this for years, but just in my mental background. Folks bandy those "X Years" numbers around like they are from on high.
The bottom line is simply this: Kodak, Wilhelm, and Aardenburg all use different lux levels to arrive at their conclusions! Yet, the average person or of even well informed, will seldom know this when comparing paper/ink X to paper/ink Y. To wit:
Kodak uses 120 lux, 12 hours per day
Wilhelm uses 450 lux, 12 hours per day
Aardenburg uses megalux/hours, then uses 228 lux for 12 hours per day to obtain a "years" equivalency.
Quite a range. So what's realistic?
I took my incident light meter which can give a photographic EV (Exposure Value) reading, and using an online chart from Wikipedia, converted my readings to Lux. This morning: cloudless, bright, low winter morning Florida sunlight. EV of 14 through the SE window and screen, that's 41,000 lux. Yet, Aardenburg claims such a situation should be only 10,000 lux. That's a bit more than margin of error or meter variance.
Inches to the side of the sunbeam, down to EV 6.5, about 240 lux. Step back five feet, still a well illuminated interior, and it's now EV 3.5, about 30 lux. With the afternoon SW sun blasting into the Florida room later (there's actually less light in the summertime due to roof overhang), EV 9, about 120 lux, in the indirect light against a wall. I think that this is as bright as most homes will ever see in "indirect sunlight."
To the eye, the second and third readings above are visually the same, yet have an 8:1 ratio!
Lesson 1: (I think.) That "indirect indoors" can cover a LOT of lux and lifespan difference! From 30 to 120 may be typical, still 4:1. Moving a print to a slightly different location can hugely change its fading rate.
Lesson 2: Not unreasonable to take Wilhelm's ratings and multiply them by a factor of 10 for a less than real bright indoor setting. If they say ten years at 450 lux, it's one hundred using 45 lux as an indoor realistic number. Major caveat: This is for UV only, gas fading will take place regardless unless coated or otherwise protected.
Lesson 3: This is a cousin to my "Perfection is the enemy of good enought," and "Subjectivity trumps objectivity." "The more you try to nail things down with more data, the more likely the mole will pop up again, the one you thought you whacked."
Confounders that I've thought of:
1. All the settings are for 12 hours a day. Well, the sun doesn't just instantly pop up to full strength, nor does the opposite at sundown. Most offices don't have the lights on 12 hours a day. A given "bright indoors indirect" setting may only see four hours at increased lux levels, other hours tapering to less.
2. How do the daylight flourescents that "they" use compare to natural daylight? My review of histograms of sunlight and daylight sources show that they are not even close, the fluorescents having much more UV in them. That's without even taking into account ordinary window glass cuts out most of the UVB spectrum.
