What's yer Kelvin?

MurrayMinchin

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Hi there,

When evaluating prints, what degree Kelvin light do you use?

Bonus points for CRI and R numbers.

Super-duper bonus points for wattage/distance/angle.

I've seen everything from 2,700K (Sotheby's) to 5,300K (lighting supplier).

Thanks in advance.
 

lantau

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In my Darkroom I have a lamp for viewing prints, which is using a 6500K CFL. It is a bit cold, but I like it for that purpose.

At home I have a room with a 5000K, 14W LED light and I hold prints (RA4 and b/w) close (30-50cm) to it for evaluation. Prints look very good in that light, when they look good.

With my spectrophotometer I'm measuring it a just over 5000K and a CRI of 96 (the light claims 95). I'm attaching a screenshot with the data, the spectrum and the whitepoint plotted in colourspace.

 
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MurrayMinchin

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Hey, thanks a bunch for that.

I'm using a ceiling fan with two 5000K 10W LED lights which are not directly pointed at the prints and 1.2 metres away. They are are also partially diffused by 'slightly warmish' frosted glass lamp shades. Not sure of their CRI or R#'s. To complicate things further, there is a large window nearby.

I vaguely remember taking a reading of a white piece of paper with a Pentax digital spot meter a decade or more ago (at nighttime) and it matched our local museums gallery lighting for intensity.

It's a complex game, especially if you don't know what lighting a print might experience in different display spaces. I read an article from one photographer who settled on 4000K because then his prints would be somewhere in the middle.

Thanks again.
 
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Luckless

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There are bank selector switches that would allow you to flip through a few different bulbs if you wanted to get creative and like basic wiring.

Most of my bulbs I have are 2700k, and I'll likely use those and a pick up a high CRI daylight bulb for my references as I get printing more this year.
 

gone

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That's a good question. I have no idea since essentially abandoning any sort of critical assessment w/ artificial light. Now I make 2 different exposures using 1 negative, keep notes, label the prints, and take them into the living room the next day in order to judge them in north light.

It sounds wasteful, but it's not necessary w/ every negative, and I like having the 2 different prints to look at side by side. That aspect has saved me time and paper. What looked one way in the darkroom often looks different in another room, so I go w/ the natural light as a base.
 

Philippe-Georges

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In the beginning, I had a rather expensive JustLight setup which accorded to a whole bunch of ISO standards. Then I realised that, with the exception of a few and rare professionals like scanners, chromistes and printers, nobody, literally nobody viewed my prints in a so called calibrated environment, not the publishers nor the editors, co-authors, writers, reviewers, gallerists, collectors, buyers, simply nobody!
Disappointed as I was, I installed an ordinary LED (kitchen-) light in my darkroom so I could view my prints in nearly the same circumstances as all the 'others' did...
 

cramej

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Alan Edward Klein said:
Isn't that why artists set up their spaces with windows facing north where they paint using north light? Isn't the Kelvin at around 5000?
Click to expand...

If I remember correctly, light from an open clear sky, no direct sun, is closer to 10000k. Direct sun daylight, 6500k or so. It's the quality of light from north windows. At least in the northern hemisphere, you mostly don't get direct sun streaming across the room.
 

benjiboy

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Alan Edward Klein said:
Isn't that why artists set up their spaces with windows facing north where they paint using north light? Isn't the Kelvin at around 5000?
Click to expand...
Daylight Alan is about 5,600 Kelvin at noon, and more or less depending on the time of day.
 
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Nicholas Lindan

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The proper inspection light is the light that will illuminate the photograph when it is viewed. So it changes: incandescent, CFL & fluorescent (daylight, white, warm white...), and LED and there is no one 'right' light.

More important than the color temperature of the inspection light is the intensity. To state the obvious, a photo that will be hung in a dark corner of a room needs to be printed lighter than the same photo hung in a company lobby. LEDs are nice in that you can vary the intensity without changing the color temperature.

If you have a gallery showing/selling your work you might want to use the same lighting type and intensity the gallery uses. Take an incident light meter reading at the gallery wall and match that for selecting/adjusting your inspection light.

All that said, I use an incandescent lamp in a photo reflector mounted by the fixer/holding trays. Which, I guess, matches nothing - so I am safe from being tempted to fiddle with it.
 
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Philippe-Georges

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This matches with what I was trying to say, till a certain extend although...
 
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MurrayMinchin

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When I printed selenium toned fibre based B&W silver gelatin prints with a Glycin developer, they came alive with a tungsten + north window light combination. Some sort of magic occurred.

Now that I'm playing with color pigment prints, the viewing light has a different but substantial effect. Reading through museum guidelines it appears our brain can adjust within the temperature range considered normal, but they recommend not changing light temperature between separate galleries because it takes the human brain several minutes to adjust to the new 'white'. This makes me think 4000K might be about right, because it's kind of in the middle.

Nicholas makes a good point about intensity. I pin them so they hang vertically, as what angle you hold them to the light also seems to make a difference.

In the darkroom (for Kallitype's before & during developing) it's recommended that a 25W incandescent bulb from at least 3 feet away is used, right? Once developed and dried it would come upstairs to the area where the digital stuff gets inspected. In the future I might try pigment over Kallitypes, so I'm looking for an all in one solution.

Doorbell just rang...24"x50' roll of Epson Hot Press Natural just got delivered...gotta go!

Thanks a bunch!!
 

MattKing

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FWIW, it is a good idea to standardize on something and then put matching bulbs in more than one location.
Because one doesn't limit themselves to examining prints in a single location.
It may be good to have one of those bulbs in a portable light - for when you venture out in the world!
 

jtk

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When printing (inkjet of course) I allow about 15 minutes after test print to evaluate...because changes occur during that period (a little evaporation). Then I look at my test print under a variety of household lights and "window light" during the day (it does change). Then I make my decision.

Galleries are not consistent, one to the next. It's unfortunate that some light prints with spots...better for them to use a common household type of light.
 
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