Luminous Landscape Forum
Raw & Post Processing, Printing => Colour Management => Topic started by: BertWaife on February 07, 2011, 10:23:20 am
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What kind of light meter will measure the K temperature of the ambient light in my studio? Do you have a brand and model to recommend? I need to adjust my lighting and also to measure what the daylight lux and temp I have here.
thanks
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First off, what do you hope to gain by measuring the lighting and coming up with a Kelvin value (which describe a range of colors)?
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I want to know the viewing conditions of my studio. I am printing with an epson 9900 at different times of day. Would like to know what my lights are producing and see if I need to make correction. Also I have sky lights on both North and South sides, and day light is strong, but sometimes I put on the lights. I see that an option is a viewing box. Also I may be looking for some D50 bulbs?
thanks
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One issue is that the proper lighting for working on files and printing is a lot lower than what most people use to view the prints. A viewing box is a good solution, or you can set up some color-corrected lamps over one part of your desk or workspace, and turn them on just when viewing the prints. Some photographers have a place on the wall where they can mount prints, using magnets or thumbtacks, sometimes in another room, with brighter, color corrected lighting. I often carry my print outside, where I can view it under indirect north daylight.
If you have very bright daylight coming into your work space, that might affect your work. If it were me I'd want to block that, at least when working on files and printing.
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I’m not sure how useful a color meter is going to be here based on what you describe. Not sure its even necessary (there is one for sale here on the site: http://www.luminous-landscape.com/forum/index.php?topic=16966.0;topicseen)
Kelvin values provide a range of colors (its not one color). You’ll be better off with a good print viewing station, either one you build from say Solux blubs or one you buy off the shelf, usually using “daylight” Fluorescents (daylight in quotes for good reason). Then controlling the ambient lighting around the display and print viewing area next to the display.
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You'll most likely require a spectrophotometer to measure the light spectrum like an i1Pro (purchase as either a run out i1Basic, i1Xtreme, or the new i1Basic Pro, i1Photo Pro or i1Publish Pro that's due out shortly from X-Rite - which is a better deal). I use my i1Pro with Eye-One Match to measure light sources with the ambient head filter, so you can use it to theoretically build ICC profiles to compensate for different light conditions or measure light source quality in CRI or vs a set spectrum.
Again with Andrew it's best to build/buy some good quality Solux fixtures + lamps initially or spend some money on a good viewing booth (preferably dimmable for better flexibility). Depending on how serious you are the i1Pro or ColorMunki would be a good purchase as well to assist you in colour management jobs.
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For your purpose a digital camera is an excellent colorimeter.
Shoot a graycard in Raw and whitebalance it in either PS or another rawconvertor. Then the raw-convertor will show the colortemperature.
Ton
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For your purpose a digital camera is an excellent colorimeter.
Shoot a graycard in Raw and whitebalance it in either PS or another rawconvertor. Then the raw-convertor will show the colortemperature.
Except every converter will likely produce differing K values and again, even the “correctly” measured K value is a range of colors. The suggestion of using a true Spectrophotometer in something like i1Share is a vastly more accurate and appropriate means of gathering this data.
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Except every converter will likely produce differing K values and again, even the “correctly” measured K value is a range of colors. The suggestion of using a true Spectrophotometer in something like i1Share is a vastly more accurate and appropriate means of gathering this data.
You are completely right if you have to measure a viewing box or precise lightning conditions. But for a general measurement of the ambient light conditions, which are ever changing because of the daylight coming in, I should say a digital camera can do a reasonal job.
Ton
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I use daylight balanced fluorescents in my studio and print room.
Their CRI is similar to my SOFV.
I use one of these (see attachment) to evaluate the CRI of room light.
In a high quality viewing booth you can not see a distinction between the 2 patches.
As the CRI decreases the 2 patches become more distinct as in the photo.
(very handy)
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Found some helpful information about the origination of CRI and how it was established while investigating Alzo Digital's "Daylight" balanced CFL's with a CRI of 91 at 5500K...
http://www.alzodigital.com/online_store/color_render_index_definition.htm
I just got the bulb yesterday and all I had to do to see its color rendering capability was check whether the X-rite CCchart yellow patch turns lemon yellow (inaccurate)...
http://www.libidex.com/latex-colours-sml/4D%20-%20Vibrant%20Lemon%20Yellow.jpg
or cadmium yellow (accurate)...
http://www.utrechtart.com/images/products/fc_cadmium_yellow_107.gif
I get a lemon yellow just as I do with all "Daylight balanced" and/or "neutralish" flourescent lights only not as severe as others.
I do have to say though this bulb renders the most neutral white and gray I've ever seen out of any light but its neutral hue looks more like my 6000K desaturated navy blue calibrated display which is close enough to 5500K. The 5500K CRI 95 100 watt Ottlights look way too blue green next to the Alzo's. So much for reliable CRI ratings.
The Solux rated at 98 CRI will render a warmer buttermilk hue to neutrals which should be expected since it's rated at 4700K but the closest to D50 possible according to scientific measuring instruments.
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Here's exactly how the Alzo renders an X-rite CCchart. Note the yellow and that instense vibrant green just to the upper right of the yellow patch which shows this light's green spike. The cyan patch takes a hit and looks similar to converting to sRGB from ProPhotoRGB. Still pretty good for a CFL.
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Found some helpful information about the origination of CRI and how it was established while investigating Alzo Digital's "Daylight" balanced CFL's with a CRI of 91 at 5500K... The Solux rated at 98 CRI will render a warmer buttermilk hue to neutrals which should be expected since it's rated at 4700K but the closest to D50 possible according to scientific measuring instruments.
I've pretty much given up on CRI as a measurement of quality when it comes to CFL's as they all have spikes in their spectrum from what I've seen online and measured for myself. I purchased some Solux lamps a while ago and measured it with my i1Pro, they come very close to what I expected from them. Given a clip on Solux fixture + bulb when I bought it recently was $50 it's well worth buying.
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I have the Solux task lamp. It does give off a beautiful light and renders the CCchart's colors equally meaning there's no colors that are glowing or over emphasized as in the yellow with the Alzo's and the cyan patch renders with just the right amount of green. Closest to how it looks in direct sunlight.
The Solux draws a lot of energy with comparatively very little light and can get quite hot. I'm currently using it as a space heater clipped to the table right beside me to warm my legs this winter.
This Alzo bulb is a big improvement over the 5000K CRI 90 GE Sunshine fluorescent T8 tubes I've been using as an energy saving, low heat generating ambient light source for my studio. For their small size and standard base that fit most lamps they put out a ton of bright neutral looking light comparatively. I had to get the 4 ft T12 GE tubes and a cumbersome light fixture to get the same amount of light.
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I've pretty much given up on CRI as a measurement of quality when it comes to CFL's as they all have spikes in their spectrum from what I've seen online and measured for myself.
Exactly! CRI is a useful metric for those selling Fluorescent lighting. Not that useful for those that want to evaluate the quality of differing lighting types. Its as much marketing as science.