Monitor Brightness & Room Lighting Levels.
I had promised myself I was going to do a video review of my latest purchase – the Lee SW150Mk2 system and Big and Little Stopper filters I’ve just spent a Kings ransom on for my Nikon 14-24mm and D800E:
But I think that’ll have to wait while I address a question that keeps cropping up lately. What’s the question?
Well, that’s the tricky bit because it comes in many guises. But they all boil down to “what monitor brightness or luminance level should I calibrate to?”
Monitor brightness is as critical as monitor colour when it comes to calibration. If you look at previous articles on this blog you’ll see that I always quote the same calibration values, those being:
White Point: D65 – that figure takes care of colour.
Gamma: 2.2 – that value covers monitor contrast.
Luminance: 120 cdm2 (candelas per square meter) – that takes care of brightness.
However, when you’ve been around all this photography nonsense as long as I have you can overlook the possibility that people might not see things as being quite so blindingly obvious as you do.
And one of those ‘omissions on my part’ has been to do with monitor brightness settings COMBINED with working lighting levels in ‘the digital darkroom’. So I suppose I’d better correct that failing on my part now.
What does a Monitor Profile Do for your image processing?
A correctly calibrated monitor and its .icc profile do a really simple but very mission-critical job.
If we open a new document in Photoshop and fill it with flat 255 white we need to see that it’s white. If we hold an ND filter in front of our eye then the image won’t look white, it’ll look grey.
If we hold a blue filter in front of our eye the image will not look white – it’ll look blue.
That white image doesn’t exist ‘inside the monitor’ – it’s on our computer! It only gets displayed on the monitor because of the graphics output device in our machine.
So, if you like, we’re on the outside looking in; and we are looking through a window on to our white image. The colour and brightness level in our white image are correct on the inside of the system – our computer – but the viewing window or monitor might be too bright or too dark, and/or might be exhibiting a colour tint or cast.
Unless our monitor is a totally ‘clean window’ in terms of colour neutrality, then our image colour will not be displayed correctly.
And if the monitor is not running at the correct brightness then the colours and tones in our images will appear to be either too dark or too bright. Please note the word ‘appear’…
Let’s get a bit fancy and make a greyscale in Photoshop:
Look at the distance between Lab 50 & Lab 95 on the three greyscales above – the biggest ‘span’ is the correctly calibrated monitor. In both the ‘too bright & contrasty’ and the ‘too dark low contrast’ calibration, that valuable tonal range is compressed.
In reality the colours and tones in, say an unprocessed RAW file on one of our hard drives, are what they are. But if our monitor isn’t calibrated correctly, what we ‘see’ on our monitor IS NOT REALITY.
Reality is what we need – the colours and tones in our images need to be faithfully reproduced on our monitor.
And so basically a monitor profile ensures that we see our images correctly in terms of colour and brightness; it ensures that we look at our images through a clean window that displays 100% of the luminance being sent to it – not 95% and not 120% – and that all our primary colours are being displayed with 100% fidelity.
In a nutshell, on an uncalibrated monitor, an image might look like crap, when in reality it isn’t. The shit really starts to fly when you start making adjustments in an uncalibrated workspace – what you see becomes even further removed from reality.
“My prints come out too dark Andy – why?”
Because your monitor is too bright – CALIBRATE it!
“My pics look great on my screen, but everyone on Nature Photographers Network keeps telling me they’ve got too much contrast and they need a levels adjustment. One guy even reprocessed one – everyone thought his version was better, but frankly it looked like crap to me – why is this happening Andy?
“Because your monitor brightness is too low but your gamma is too high – CALIBRATE it! If you want your images to look like mine then you’ve got to do ALL the things I do, not just some of ’em – do you think I do all this shit for fun??????????……………grrrrrrr….
But there’s a potential problem; just because your monitor is calibrated to perfection, that does NOT mean that everything will be golden from this point on
Monitor Viewing Conditions
So we’re outside taking a picture on a bright sunny day, but we can’t see the image on the back of the camera because there’s too much daylight, and we have to dive under a coat with our camera to see what’s going on.
But if we review that same image on the camera in the dark then it looks epic.
Now you have all experienced that…….
The monitor on the back of your camera has a set brightness level – if we view the screen in a high level of ambient light the image looks pale, washed out and in a general state of ultra low contrast. Turn the ambient light down and the image on the camera screen becomes more vivid and the contrast increases.
But the image hasn’t changed, and neither has the camera monitor.
What HAS changed is your PERCEPTION of the colour and luminance values contained within the image itself.
Now come on kids – join the dots will you!
It does not matter how well your monitor is calibrated, if your monitor viewing conditions are not within specification.
Just like with your camera monitor, if there is too much ambient light in your working environment then your precisely calibrated monitor brightness and gamma will fail to give you a correct visualization or ‘perception’ of your image.
And the problems don’t end there either; coloured walls and ceilings reflect that colour onto the surface of your monitor, as does that stupid luminous green shirt you’re wearing – yes, I can see you! And if you are processing on an iMac then THAT problem just got 10 times worse because of the glossy screen!
Nope – bead-blasting your 27 inches of Apple goodness is not the answer!
Right, now comes the serious stuff, so READ, INGEST and ACT.
ISO Standard 3664:2009 is the puppy we need to work to (sort of) – you can actually go and purchase this publication HERE should you feel inclined to dump 138 CHF on 34 pages of light bedtime reading.
There are actually two ISO standards that are relevant to us as image makers; ISO 12646:2015(draft) being the other.
12646 pertains to digital image processing where screens are to be compared to prints side by side (that does not necessarily refer to ‘desktop printer prints from your Epson 3000’).
3664:2009 applies to digital image processing where screen output is INDEPENDENT of print output.
We work to this standard (for the most part) because we want to process for the web as well as for print.
If we employ a print work flow involving modern soft-proofing and otherwise keep within the bounds of 3664 then we’re pretty much on the dance-floor.
ISO 3664 sets out one or two interesting and highly critical working parameters:
Ambient Light White Point: D50 – that means that the colour temperature of the light in your editing/working environment should be 5000Kelvin (not your monitor) – and in particular this means the light FALLING ON TO YOUR MONITOR from within your room. So room décor has to be colour neutral as well as the light source.
Ambient Light Value in your Editing Area: 32 to 64 Lux or lower. Now this is what shocks so many of you guys – lower than 32 lux is basically processing in the dark!
Ambient Light Glare Permissible: 0 – this means NO REFLECTIONS on your monitor and NO light from windows or other light sources falling directly on the monitor.
Monitor White Point – D65 (under 3664) and D50 (under 12646) – we go with D65.
Monitor Luminance – 75 to 100 cdm2 (under 3664) and 80 to 120 cdm2 (under 12646 – here we begin to deviate from 3664.
We appear to be dealing with mixed reference units, but 1 Lux = 1 cdm2 or 1 candela per square metre.
The way Monitor Brightness or Luminance relates to ambient light levels is perhaps a little counter-intuitive for some folk. Basically the LOWER your editing area Lux value the LOWER your Monitor Brightness or luminance needs to be.
Now comes the point in the story where common sense gets mixed with experience, and the outcome can be proved by looking at displayed images and prints; aesthetics as opposed numbers.
Like all serious photographers I process my own images on a wide-gamut monitor, and I print on a wide-gamut printer.
Wide gamut monitors display pretty much 90% to100% of the AdobeRGB1998 colour space.
What we might refer to as Standard Gamut monitors display something a little larger than the sRGB colour space, which as we know is considerably smaller than AdobeRGB1998.
Find all the gory details about monitors on this great resource site – TFT Central.
At workshops I process on a 27 inch non-Retina iMac – this is to all intents and purposes a ‘standard gamut’ monitor.
I calibrate my monitors with a ColorMunki Photo – which is a spectrophotometer. Spectro’s have a tendency to be slow, and slightly problematic in the very darkest tones and exhibit something of a low contrast reaction to ‘blacks’ below around Lab 6.3 (RGB 20,20,20).
If you own a ColorMunki Display or i1Dispaly you do NOT own a spectro, you own a colorimeter! A very different beast in the way it works, but from a colour point of view they give the same results as a spectro of the same standard – plus, for the most part, they work faster.
However, from a monitor brightness standpoint, they differ from spectros in their slightly better response to those ultra-dark tones.
So from a spectrophotometer standpoint I prefer to calibrate to ISO 12646 standard of 120cdm2 and control my room lighting to around 35-40 Lux.
Just so that you understand just how ‘nit-picking’ these standards are, the difference between 80cdm2 and 120 cdm2 is just 1/2 or 1/3rd of a stop Ev in camera exposure terms, depending on which way you look at it!
However, to put this monitor brightness standard into context, my 27 inch iMac came from Apple running at 290 cdm2 – and cranked up fully it’ll thump out 340 cdm2.
Most stand-alone monitors you buy, especially those that fall under the ‘standard gamut’ banner, will all be running at massively high monitor brightness levels and will require some severe turning down in the calibration process.
You will find that most monitor tests and reviews are done with calibration to the same figures that I have quoted – D65, 120cdm2 and Gamma 2.2 – in fact this non-standard set up has become so damn common it is now ‘standard’ – despite what the ISO chaps may think.
Using these values, printing out of Lightroom for example, becomes a breeze when using printer profiles created to the ICC v2 standard as long as you ‘soft proof’ the image in a fit and proper manner – that means CAREFULLY, take your time. The one slight shortcoming of the set up is that side by side print/monitor comparisons may look ever so slightly out of kilter because of the D65 monitor white point – 6,500K transmitted white point as opposed to a 5,000K reflective white point. But a shielded print-viewer should bring all that back into balance if such a thing floats your boat.
But the BIG THING you need to take away from the rather long article is the LOW LUX VALUE of you editing/working area ambient illumination.
Both the ColorMunki Photo and i1Pro2 spectrophotometers will measure your ambient light, as will the ColorMunki Display and i1 Display colorimeters, to name but a few.
But if you measure your ambient light and find the device gives you a reading of more than 50-60 lux then DO NOT ask the device to profile for your ambient light; in fact I would not recommend doing this AT ALL, here’s why.
I have a main office light that is colour corrected to 5000K and it chucks out 127 Lux at the monitor. If I select the ‘measure and calibrate to ambient’ option on the ColorMunki Photo it eventually tells me I need a monitor brightness or luminance of 80 cdm2 – the only problem is that it gives me the same figure if I drop the ambient lux value to 100.
Now that smells a tad fishy to me……..
So my advice to anyone is to remove the variables, calibrate to 120 cdm2 and work in a very subdued ambient condition of 35 to 40 Lux. I find it easier to control my low lux working ambient light levels than bugger about with over-complex calibration.
To put a final perspective on this figure there is an interesting page on the Apollo Energytech website which quotes lux levels that comply with the law for different work environments – don’t go to B&Q or Walmart to do a spot of processing, and we’re all going to end up doing hard time at Her Madges Pleasure – law breakers that we are!
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