Luminous Landscape Forum

Raw & Post Processing, Printing => Colour Management => Topic started by: denalilap on April 03, 2019, 11:12:45 pm

Title: Which color temp lights to use to view prints.
Post by: denalilap on April 03, 2019, 11:12:45 pm
I’ve been trying to improve the match between my monitor and the prints. I have a Benq sw2700pt (calibrated using i1display pro, pallete master, followed by DisplayCal). I’ve been viewing prints using an Ott light, with unsatisfying results. I recently installed track lights to illuminate photos on wall. I looked at prints under Solux 3500k lights and the match is exceedingly better. Still not all the way there but much better.

The above prompted me to go back to the Solux site and read:

The Guggenheim Museum uses SoLux 4700K for critical color work on art. Most photographers choose SoLux 4700K and 5000K light for critical color proofing, however, other well respected photographers like John Paul Caponigro recommend using SoLux 3500K for proofing, the light many galleries use to exhibit. Therefore, we now offer the full range of SoLux in our light kits.

Thus, my question... which color temp bulbs should one get and which temp for a given purpose.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 11:06:42 am
Short answer; doesn't matter. The numbers define a large range of possible colors. Pick a Solux you visually prefer and yes many agree with JP by going a lot lower than CCT 5000K.
Title: Re: Which color temp lights to use to view prints.
Post by: faberryman on April 04, 2019, 11:13:01 am
Short answer; doesn't matter. The numbers define a large range of possible colors. Pick a Solux you visually prefer and yes many agree with JP by going a lot lower than CCT 5000K.
You really don't have any control over what the lighting will be in galleries and other venues. So get the 3500 or the 5000 and work on consistency of you prints.
Title: Re: Which color temp lights to use to view prints.
Post by: nemophoto on April 04, 2019, 12:27:10 pm
I use a JUST Normlicht lightbox for viewing prints. I believe it's 5000K (been a while since I looked at the specs). To a degree, Andrew is correct, it doesn't matter, though I find for me it does serve a purpose. I at least know if the color balance is correct in a controlled situation. A while back I had a client who was getting crap pre-press from a pre-press house. Highlights were blown, color was off, etc. They tried to blame me (of course). I printed match prints for a while and FedEx'd them off with each job. I said that if your proofs don't match these, then your pre-press house is screwing you. Eight years later, I still shoot for the client, do the digital imaging and the pre-press house is history.

The moral of the story is, a calibrated lightbox is good to have when you are dealing with color critical issues and for your own peace of mind. Once it's out of your hands, anything is possible.
Title: Re: Which color temp lights to use to view prints.
Post by: denalilap on April 04, 2019, 12:41:10 pm
My question was too vague... What I really should have asked is:

If you were calibrating your monitor to D50 (for example) which light temp would give  you the best match to what’s on the monitor. Same for D65.
Title: Re: Which color temp lights to use to view prints.
Post by: rasworth on April 04, 2019, 02:40:07 pm
denalilap,

IMO it doesn't pay to become overly concerned with numbers/specs, rather one should pay attention to the process, and here is my recommendation:

1. Set up a viewing environment, good illuminants (Solux qualifies), and reasonably bright.

2. Print a reference image thru a properly color managed system, on your printer.  I use PrinterEvaluationImage_V002_ProPhoto.tif.

3. Now the hard part.  Your system display should be in a somewhat dim (not dark) environment, with the print viewing illumination nearby but not shining on the screen.  Calibrate and profile your display until you achieve a reasonable visual match between it and the print, with the evaluation image loaded into Photoshop in soft proof mode thru the same printer profile used to produce the reference image.  Concentrate mostly on brightness and tone, you'll drive yourself nuts trying to exactly match all colors.

That's it, other than perhaps reading Andrew Rodney's tutorial on such.

Or you can obsess over degrees Kelvin, illuminant brand, etc.  Nothing wrong with paying attention to the details, but remember the goal - produce an image on your display that will enable to you create a good print on the first pass (ok, I confess, sometimes I re-print).

Richard Southworth

Added by edit - I have my monitor calibrated to D50 chromaticity, and very dim, 50 L.  This isn't supposed to work but I'm weird.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 02:41:04 pm
Definitely SoLux 4700K or 5000K; adjust your calibration color temp and brightness to get the best match.
Nope; Definitely NOT!  First of all, the two (CCT 4700K and 5000K) are the same, the 5000K runs hotter and dies sooner, just so you end up with a silly number. Next, as you've been told in the past (https://www.photo.net/discuss/threads/major-update-of-my-article-on-digital-darkroom-lighting.481118/#post-5081566), the numbers are both meaningless, define a range of possible colors are more often than not, don't look as appealing as lower values.
The OP should contact Solux and ask, as my clients like Art Wolfe did, if they would ship several differing bulb values, then after actually examining the illuminant, pick which they desire. Like JP, Art vastly preferred the CCT 3500K bulbs and selected them for his entire gallery in Seattle (https://blog.photoshelter.com/2009/03/visit-art-wolfe-if-youre-in-se/).
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 02:44:20 pm
My question was too vague... What I really should have asked is:

If you were calibrating your monitor to D50 (for example) which light temp would give  you the best match to what’s on the monitor. Same for D65.
The only object that actually produces D50 is 93 million miles from any display.  ;)
These Standard Illuminants were produced from hundreds of actual measurements around the world, then averaged.
To answer your question, the real need to match a display to an illuminant is for viewing the print next to the display when soft proofing as outlined in my video below. Now you can use the same Solux system that you'll light the prints elsewhere or maybe you will not; doesn't matter. Your eyes adapt to the illuminant. Assuming it's a half decent Light source. You'll adjust the WP of the display calibration to produce a visual match. So it doesn't matter if the Solux bulbs are CCT 3500 or 4700 (and do not even think about wasting your money on those labelled 5000K).


See:

Why are my prints too dark?
A video update to a written piece on subject from 2013

In this 24 minute video, I'll cover:
Are your prints really too dark?
Display calibration and WYSIWYG
Proper print viewing conditions
Trouble shooting to get a match
Avoiding kludges that don't solve the problem

High resolution: http://digitaldog.net/files/Why_are_my_prints_too_dark.mp4
Low resolution: https://youtu.be/iS6sjZmxjY4
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 02:44:51 pm
denalilap,

IMO it doesn't pay to become overly concerned with numbers/specs, rather one should pay attention to the process, and here is my recommendation:

1. Set up a viewing environment, good illuminants (Solux qualifies), and reasonably bright.

2. Print a reference image thru a properly color managed system, on your printer.  I use PrinterEvaluationImage_V002_ProPhoto.tif.

3. Now the hard part.  Your system display should be in a somewhat dim (not dark) environment, with the print viewing illumination nearby but not shining on the screen.  Calibrate and profile your display until you achieve a reasonable visual match between it and the print, with the evaluation image loaded into Photoshop in soft proof mode thru the same printer profile used to produce the reference image.  Concentrate mostly on brightness and tone, you'll drive yourself nuts trying to exactly match all colors.

That's it, other than perhaps reading Andrew Rodney's tutorial on such.

Or you can obsess over degrees Kelvin, illuminant brand, etc.  Nothing wrong with paying attention to the details, but remember the goal - produce an image on your display that will enable to you create a good print on the first pass (ok, I confess, sometimes I re-print).

Richard Southworth
+1
Title: Re: Which color temp lights to use to view prints.
Post by: denalilap on April 04, 2019, 02:58:37 pm
Thanks for all the responses. The difference in viewing between the Ott and the Solux is what got me thinking about the temp of the illumination. I’ll stick with the Solux (since I like the way it illuminates my office) and go back to tweaking the calibration for a better match.

Thanks
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 03:07:32 pm
What happens after that under different lighting conditions is way, way less critical thanks to a phenomenon called "Color Constancy" or "discounting the illuminant"; this is very well explained in Real World Color Management by Fraser, Murphy and Bunting, a book I cannot recommend enough.
It is of course well explained and dismisses what you wrote, the opposite of what I did in terms of the numbers:
page 48
A final point about color consistency and color management:color constancy presents and argument that the color temperature of lighting isn't as important as some people (Franz?) think. it's still is important but not at the expense of everything else. For example, when calibrating your monitor, to a D50 or D65 white point. Many people choose D50 in order to match the exact white point color of viewing environments which is usually a D50 lighting booth. But we, alone with many other practitioners recommend D65 because we think you'll be happier looking at a bright D65 monitor rather than a dingy yellow D50 one, even if D50 is colorimetrically closer to D50 lighting.

Now this is important:
Matching brightness levels between two viewing environments may be as important as, or even more important than matching the color temperature - color constancy does a lot to adapt to slight differences in color temperature.


Adapt to the illuminant; as I outlined! Ignore the numbers because someone incorrectly believes this large range of values is closer to something else (it's not). Again, this fine book dismisses so much of what you wrote a few years ago about Solux over on PhotoNet. URL of that silliness provided earlier. And what you wrote today.  :-\
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 03:10:48 pm
Thanks for all the responses. The difference in viewing between the Ott and the Solux is what got me thinking about the temp of the illumination. I’ll stick with the Solux (since I like the way it illuminates my office) and go back to tweaking the calibration for a better match.

Thanks
The Ott light sucks like so many illuminants once you examine it's spectrum. Which is really important and something that requires special software and hardware.
http://digitaldog.net/files/15TheRightLightpart1.pdf
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 03:53:32 pm
Blah, blah, blah...
There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.” -Søren Kierkega\
We both agree that Bruce and Chris's book is excellent, but only one of us, as illustrated, understands it.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 03:58:01 pm
The 5000K runs hotter, has a higher color temp and lasts not as long, but lasts for years in my setup.
Got actual proof? Didn't think so. And why pay for a bulb that burn's out faster just for a number that's meaningless? No reason.

Quote
Not a silly number as I prefer the results with the 5000K over the 4700K.
Got any proof other's should? Didn't think so.

Quote
If lower values look more appealing all by themselves is an issue of personal taste/preference.

As multiple people have reported.
Quote
The OP clearly stated that he wants to match the monitor to the print viewed in the digital darkroom and in my experience the 4700K or 5000K give a way better match than lower values; 3500K for instance forces me to lower the color temp of the monitor so much that I end up with a dingy yellow looking monitor.
Utter nonsense. As other's have reported. Myself, Art Wolfe, JP; no such issues.
Quote
What lighting to use for displaying your prints for others to see is a totally different issue and is very subjective; Guggenheim likes 4700K, Wolfe and Caponigro like 3500K.
And you stated, incorrectly again I'll add:

Definitely SoLux 4700K or 5000K; adjust your calibration color temp and brightness to get the best match.
No, it's not definitely; you've now changed your tune that it's subjective and that different people definitely do NOT want CCT 4700K or 5000K.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 04:26:06 pm
Blah, blah, blah...
Your sad and repetitive answer to facts.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 04, 2019, 08:33:20 pm
More facts.

Mark D. Fairchild's Color Appearance Models, page 29
Color constancy refers to the everyday perception that the colors of objects remain unchanged across significant changes in illumination color and luminance level. Color constancy is served by the mechanisms of chromatic adaptation and memory color and can easily be shown to be very poor when careful observations are made.
Discounting the illuminant refers to an observer's ability to automatically interpert the illumination conditions and perceive the colors of objects after discounting the influences of illumination color.

Page 156:
6.12 Color Constancy?
Color constancy is another phenomenon that is often discussed. Typically color constancy is defined as the apparent invariance in the color appearance of objects upon changes in illumination. This definition is somewhat misleading. The main reason for this is because color constancy does not exist in humans! The data presented in the previous sections of this chapter and the discussion of chromatic adaptation in Chapter 8 should make this point abundantly clear.
Title: Re: Which color temp lights to use to view prints.
Post by: Alan Klein on April 04, 2019, 10:45:46 pm
The 5000K runs hotter, has a higher color temp and lasts not as long, but lasts for years in my setup. Not a silly number as I prefer the results with the 5000K over the 4700K. If lower values look more appealing all by themselves is an issue of personal taste/preference. The OP clearly stated that he wants to match the monitor to the print viewed in the digital darkroom and in my experience the 4700K or 5000K give a way better match than lower values; 3500K for instance forces me to lower the color temp of the monitor so much that I end up with a dingy yellow looking monitor.

What lighting to use for displaying your prints for others to see is a totally different issue and is very subjective; Guggenheim likes 4700K, Wolfe and Caponigro like 3500K.

It seems to me that 3500 is liked better by people.  It's why I lit my home in warmer light with lower Kelvin values.  4700 or 5000 is just too cold.  While 3500 may not bring out "exact" color in prints, people are just happier in a warmer environment. People adjust to any color shifts brought on by a change in Kelvin.   

So if you're selling something like pictures in a gallery, you want prospective clients to feel comfortable, warm and cozy and not let them think they're in a medical clinic or workshop. 
Title: Re: Which color temp lights to use to view prints.
Post by: Doug Gray on April 04, 2019, 11:46:01 pm
It seems to me that 3500 is liked better by people.  It's why I lit my home in warmer light with lower Kelvin values.  4700 or 5000 is just too cold.  While 3500 may not bring out "exact" color in prints, people are just happier in a warmer environment. People adjust to any color shifts brought on by a change in Kelvin.   

So if you're selling something like pictures in a gallery, you want prospective clients to feel comfortable, warm and cozy and not let them think they're in a medical clinic or workshop.

Yeah, me too.

But it sucks for comparing prints to a monitor. For that matter, ever try profiling your monitor to 3500K? It looks pretty horrible! Yet lighting a room at 3500K or even 2800K is pleasing. Why, one might ask?

The effect is beyond adaptation. It is, to a large degree, psychological. We get accustomed throughout our life to expect certain "whites' and "colors" to be certain ways. We all have grown up looking at monitors/TVs that are set to 5500K to 7500K. And when we look out the window we see the same, higher CCT level view. But scenes from the window just look brighter, not so much bluer. Even when our homes are illuminated with 2800K.

If you have a white sheet of paper on your desk and measure it's color in CIE XYZ and duplicate that exact same color and size of paper on your monitor it will not look the same as the one on your desk. The monitor's image will look like a yellowish brown and very different than the paper on your desk.

But if you pick up the paper and bring it close to the monitor, there is a sudden, freaky, shift when it gets within a few inches of the monitor and suddenly the colors will blend. Every time I do that experiment or show it to others, it is just mind boggling.

This phenomena is also described in the Wiley book: "Color Appearance Models" in Chapter 8.3

Perception of color is highly complex combination of adaptation based on the brightest surrounding light colors, as well as "known" colors, such as a white sheet of paper. And other knowns such as our expectations of what white looks like on a monitor.

There are ways of suppressing this. For instance camouflaging the monitor such that it isn't apparent we are seeing a screen and setting the light levels to be the same as what room surface reflecting light would produce.

Title: Re: Which color temp lights to use to view prints.
Post by: Rand47 on April 05, 2019, 10:30:03 am
This is kind of an “aside” to this conversation.  I have a little Fiilex V70 lamp that cycles 3000, 4000, 5000 and 6500k light.  I have both a GTI booth at 5000k and a gray magnetic 4x8’ wall illuminated at 4700k Solux track lights, for my print evaluation use.  Once I have a final print made, I’ll often show someone what it looks like at 3000, 4000, 5000, and 6500k, and at differing luminance, just as an “education” bit to illustrate to them that “where and under what lighting” they display the print will make a significant difference in how it looks. 

Rand

Title: Re: Which color temp lights to use to view prints.
Post by: denalilap on April 05, 2019, 11:43:55 am
OP here, I watched Andrew's video (see his earlier post) and the key take-away is that the monitor color temp and luminance needs to be tweaked to match the print (using a reference image). Must webpages I've seen that explain calibration tend to recommend specific values and never mention that they need to be tweaked. Andrew's video was very helpful.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 05, 2019, 12:23:17 pm
The idea that using a CCT 3500K viewing setup and then trying to match it on a display will always result in muddy yellow is a huge generalization mostly based on the behavior of very old, CRT's where you'd be hard pressed to get more than 100cd/m2 out of em even new.
Or that modern LCD's don't have superior backlight technology well beyond CCFL let alone what was found in CRTs. One advantage of some of the newer GB-R LED technology is more control over setting white point. GB-R LED allows more precise control of whitepoint (vs. CCFL). Some may suggest they flicker and maybe that's why they can't get a good match to their 20th century CRT? :-[
Then there's the idea that you can and should calibrate a display or a lamp to D50 or similar. Measure the results with a Spectrophotometer and show me it matches actual daylight SPD.
Then there's the idea that a bulb labelled 5000K actual produces 5000K on the exact area the lines of correlated color temp state it should exactly lay.
Then there's the idea that once you match your display to it, it's measured WP also exactly lines up with the above.
Then there's the idea that you can't or shouldn’t use a differing CCT light course or even a Fluorescent booth next to the display, get that visual match to the print then hang the prints anywhere you desire with a totally different light such as the CCT 3500K Solux and there's going to be an issue (no, there isn't; our eyes adapt to the illuminant).
What's clearly wrong IMHO, is a blanket statement that CCT 4700K or 5000K Solux bulbs is always the right answer. For display to print matching. There are plenty of Solux customers who will tell you this fact.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 05, 2019, 04:08:05 pm
Apparently, Doug Gray and I didn't get the memo; we both find that matching the monitor to 3500K lighting stinks.
Where did he specifically say that and unlike you, unable to produce a match to a print and specifically what kind of display and bulb?
Maybe with that old CRT you use that presumably doesn't flicker, you're unable to produce a match. But that in no way implies it's not possible; it is. Just not for you it seems.
You of course once again failed to read the OP or the facts:
Quote
other well respected photographers like John Paul Caponigro recommend using SoLux 3500K for proofing,
No, you didn't get or read the memo.....
Title: Re: Which color temp lights to use to view prints.
Post by: Daverich on April 05, 2019, 04:19:17 pm
Apparently, Doug Gray and I didn't get the memo; we both find that matching the monitor to 3500K lighting stinks.

That’s certainly been my experience.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 05, 2019, 04:22:39 pm

Reply #22: "For that matter, ever try profiling your monitor to 3500K? It looks pretty horrible!" It's possible, but it stinks.
I profile to a value that matches the illuminant to the display not some fixed value that doesn't and which defines a large range of possible colors. Maybe that's why for you, it looks horrible. The video referenced that was helpful to the OP might be helpful to you but its fact filled so I doubt that will be the case.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 05, 2019, 06:37:50 pm
That's exactly what I do. When I use 3500K and adjust the monitor I get a match, but the monitor looks grungy and yellowish; when I use 4700K or 5000K I adjust the monitor and get a match, the monitor looks good in both cases, but I prefer the 5000K setup.

Of the 10 people participating in this thread so far, 3 hate the looks of the monitor when matched to 3500K lighting and we don't know if the others have even tried to do that.
And more don't which dismissed your statement "definitely 4700/5000K". For you. Definitely.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 05, 2019, 06:47:36 pm
You don't know if more don't. Critical thinking! Three out of maximum ten don't like it, but according to you it is utter nonsense.
Never said that. The utter nonsense came from your own keyboard starting with "definitely". That isn't correct for everyone. Think about that critically if that's even possible.
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 05, 2019, 07:54:56 pm
Reply #17:
Quote from Frans Waterlander:
"The OP clearly stated that he wants to match the monitor to the print viewed in the digital darkroom and in my experience the 4700K or 5000K give a way better match than lower values; 3500K for instance forces me to lower the color temp of the monitor so much that I end up with a dingy yellow looking monitor."

Reply by digitaldog:
"Utter nonsense. As other's have reported. Myself, Art Wolfe, JP; no such issues."
Yes what you wrote is utter nonsense! I told you in post #35 READ!
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 05, 2019, 11:40:04 pm
??? Reply #35 is mine.
Lost again:
Title: Re: Which color temp lights to use to view prints.
Post by: Doug Gray on April 06, 2019, 12:23:49 am
I don't know what universe or time warp you are in, but in my world reply #35 reads as follows:
---------------------------------------------------------------------------------------------------------------
Reply #17:
Quote from Frans Waterlander:
"The OP clearly stated that he wants to match the monitor to the print viewed in the digital darkroom and in my experience the 4700K or 5000K give a way better match than lower values; 3500K for instance forces me to lower the color temp of the monitor so much that I end up with a dingy yellow looking monitor."

Reply by digitaldog:
"Utter nonsense. As other's have reported. Myself, Art Wolfe, JP; no such issues."
--------------------------------------------------------------------------------------------------------------

Aside from the numbering issue that you apparently have in your neck of the world, you clearly called my statement utter nonsense, so man up and admit it. Two other posters agree with me, so I guess that makes their inputs also utter nonsense.

I've noticed on other threads that some posts references seem off by one. I wonder if there is some problem in the way different browsers render the site?

Here's what post #35 looks like on my browser:
Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 06, 2019, 09:01:21 am
I've noticed on other threads that some posts references seem off by one. I wonder if there is some problem in the way different browsers render the site?

Here's what post #35 looks like on my browser:
Could be but don't let the vortex of confusion from Franz use it to digress from what he wrote and my screen shot shows; another tactic seen from him that doesn't protect him from what he incorrectly writes here.  ;)
Title: Re: Which color temp lights to use to view prints.
Post by: JRSmit on April 06, 2019, 12:13:31 pm
I used to work with Solux4700, but now several years i work with fluorescent tubes of Philips for my print-studio, the ones they make specific for the graphical industry. The main advantage over solux is the even illumination of my observation table. I can now look at a full size print, instead of only a small portion due to the limited area of illumination with Solux 4700.

I also tested a JUST box, but whatever i did, the light of the JUST box was a bit purplish to my eyes. As i did not experienced this with my Philips fluorescent lights, i returned the JUST.
The intensity of my EIZO 248-4K is adjusted so that the print on my observation table w.r.t. lightness appears the same.

Since a year now i also have the white point of the monitor adjusted to visually match with a paper of a known whiteness, without any OBA's, but a close to proper white as possible. I ended up with 5300K for my monitor, yet measured with CT&A the light on my observation table is ~5000K.
Obviously spectrally different, but now i can interact with my customers on the common issue " why is the print too dark" and color differences.
Much to the pleasure of my clients, finally having a clear benchmark. (note i care less about the numbers measured, i care only the visual match)

For papers with different white-point, and no OBA's, i use the softproof in Lightroom or Photoshop if needed to see if it still matches the print.

My experience is also that when the print matches what is shown on my monitor, it will also look fine under lighting conditions one can expect in living rooms or galleries.
With respect to color temp of light and how we as humans perceive this, just look up "Arie Andries Kruithof" , I have added a slide of my workshop presentation, be it in Dutch, but the essence is clear. To this date i have not found research that contradicts this phenomenon. And serious museums do know an use this study.
In simple words it shows the capability of our visual system in perceiving white as white under different lighting conditions. A truly remarkable capability.




Title: Re: Which color temp lights to use to view prints.
Post by: digitaldog on April 06, 2019, 12:58:27 pm
My experience mimic's JRSmit's closely as I use Solux, Just and a GTI booth depending on the needs. With the GTI which we are told is a "D50 viewing booth", CCT 5150K works out to produce a good visual match on my SpectraView using specific software, and instrument along with specific other calibration targets. I like the SOFV-1e not specifically due to the spectrum (it's like all Fluorescent illuminant's, spiky) but because I can set the intensity digitally and I can collaborate with other's using the same booth and display remotely without any ambiguity in how to produce a match IF all the other attributes are specifically defined. It runs cool, unlike Solux. It's consistent in terms of how bright it appears where the Solux varies of course depending on the distance from the print being proofed. It's far more energy efficient. But it's not ideal in other respects. But there's no issue getting a very close print to display match with good ICC print profiles (their soft proof table plays a role) and again, the numbers that work for that match, far more often than not, do not match the numbers of what is 'reported' by a manufacturer for the light source. The same is true with Solux and Just; the numbers claimed are not the numbers measured, the numbers to produce a match to a display more often than not, don't match the calibration targets used for a match. YMMV. No one can or should state (https://forum2.luminous-landscape.com/index.php?topic=129784.msg1102489#msg1102489) what values to use without exact specifications for the booth, it's setting if possible, the display and it's back light technology, the software used for calibration, the instrument used for that calibration and so forth. Someone with the same brand/model of display, booth, colorimeter, and specified settings can match very closely what I see (ambient conditions and the surround play a role too!). Otherwise, take with a large grain of salt anyone who tells you want to set without such specifics. IOW, 'definitely use this' without such specifics is ambiguity, assumption, and just bad advise.
Title: Re: Which color temp lights to use to view prints.
Post by: Doug Gray on April 06, 2019, 01:16:41 pm
I used to work with Solux4700, but now several years i work with fluorescent tubes of Philips for my print-studio, the ones they make specific for the graphical industry. The main advantage over solux is the even illumination of my observation table. I can now look at a full size print, instead of only a small portion due to the limited area of illumination with Solux 4700.

I also tested a JUST box, but whatever i did, the light of the JUST box was a bit purplish to my eyes. As i did not experienced this with my Philips fluorescent lights, i returned the JUST.
The intensity of my EIZO 248-4K is adjusted so that the print on my observation table w.r.t. lightness appears the same.

Since a year now i also have the white point of the monitor adjusted to visually match with a paper of a known whiteness, without any OBA's, but a close to proper white as possible. I ended up with 5300K for my monitor, yet measured with CT&A the light on my observation table is ~5000K.
Obviously spectrally different, but now i can interact with my customers on the common issue " why is the print too dark" and color differences.
Much to the pleasure of my clients, finally having a clear benchmark. (note i care less about the numbers measured, i care only the visual match)

For papers with different white-point, and no OBA's, i use the softproof in Lightroom or Photoshop if needed to see if it still matches the print.

My experience is also that when the print matches what is shown on my monitor, it will also look fine under lighting conditions one can expect in living rooms or galleries.
With respect to color temp of light and how we as humans perceive this, just look up "Arie Andries Kruithof" , I have added a slide of my workshop presentation, be it in Dutch, but the essence is clear. To this date i have not found research that contradicts this phenomenon. And serious museums do know an use this study.
In simple words it shows the capability of our visual system in perceiving white as white under different lighting conditions. A truly remarkable capability.

Good approach!

This is similar to what I do. Basically, I have two approaches. One for all papers w/o OBAs OR Papers that will be viewed with little uV content. But another for papers with OBAs.

My preference is to start with D50. In the first case I initially profile the monitor for D50 and set the luminance to match the view box but slightly higher. Then, using soft proof using a uV cut paper profile with show paper white selected, I carefully adjust the RGB curves so the tint matches the view box. Then I use Bruce Lindbloom's site to calculate the xy coordinate and plug that into the monitor profiling s/w and re-profile the monitor. This now gives a good visual match to the paper white using soft proof and requires no changes at all with different papers/printers. However, this only works with u/v cut spectros and papers w/o OBAs. This is my main approach where I prefer paper w/o OBAs.

The second approach works with anything and is pretty much the same as Andrew describes in his excellent videos. I  deselect show paper white in view proofing and adjust the xy coordinates and luminance to match the specific paper being viewed. This is easier to do and works with OBA papers but has to be done with each paper that has significant differences in L* max, white points, or uV response.

I have done some work using Luminant A (2800K). It takes a bit to get used to the low color  temp and is best done taking efforts to make the viewing box and display look as close as possible to each other.  One thing I did that seemed to work reasonably well is to take a picture of the view box and embed the working image as a layer inside that image. It kind of fools your mind so you don't see the monitor in quite the same way. Adjusting as above provides a reasonable paper white match. However...

Turns out there is another difference that impacts side by side matching at low CTs. The monitor profiling software adapts colors to illuminant based on the Bradford transform. The print, OTOH, doesn't know about transforms so just reflects light based on the characteristics of the CYM ink. There is some divergence as the CT get further from D50. I got some improvement by using I1Profiler's ability to use non D50 spectra when creating profiles. I1P also uses a Bradford transform and produces a somewhat better match.

That said, there aren't many reasons to be hard/soft proofing with low CT illuminants and it's something I've done more out of curiosity than anything else. My preferred operating point is D50 with xy adjusted to match the white of my view box. This typically comes out close to something along the 5000K CCT line when in mode 1 (using show paper white) and a bit higher for most papers that have negative b* when in mode 2. Mostly I stick with mode 1 since I will always used OBA free paper where possible.
Title: Re: Which color temp lights to use to view prints.
Post by: JRSmit on April 06, 2019, 02:28:53 pm
Andrew, you give me too much credit ;-) I followed your videos and explanations, which i thank you for.
It works!