Hardware vs Software Monitor Calibration

Monitor calibration produces a set of curves, one for each of the three color channels. These curves are responsible for bending and twisting the device’s native color to reach our calibration goal. Where these curves are stored is a main differentiator between regular and so-called “hardware-calibrated” monitors.

Regular monitors depend on the computer’s video chip to store the curves. Hardware-calibrated monitors store the curves inside the monitor’s look-up table (LUT).

MonitorVsVideoLUTs

Above are the calibration curves for my current setup as shown by the ColorEyes Display Pro calibration software. On the left are the curves for my Retina MacBook Pro’s internal display; while on the right are the curves for the EIZO CG241W monitor. Note that this software puts the curves either in the video LUT or in the monitor LUT – but not both. Other packages, such as basICColor Display tend to utilize both for hardware-calibrated monitors.

While the video card stores these curves at 8-bit, my EIZO’s internal curves are at 12-bit. At higher bit depth calibration is more precise and virtually eliminates color banding and seepage. Hardware-calibrated monitors also store the curves permanently (of course until the next calibration).

Calibration software loads the video LUT as part of the calibration process. But what happens if the computer is rebooted or turned off and on again on the next day? Unfortunately video card hardware does not store and automatically re-apply calibration curves on startup. So the question remains: where to store them and who will reload them?

Apple invented a fairly obvious solution to answer this question: embed calibration curves into the display’s ICC profile. This way they could be handled together as a single entity. Because the ICC profile specification does not provide any storage space for calibration data, Apple had created a new profile tag, the infamous video card gamma table (VCGT). To complete their solution ColorSync loads these curves when needed. Calibration packages also support this by embedding newly computed calibration curves into the profiles they create.

Windows 7 and above also sports a video card LUT auto-loading feature, but it isn’t as obvious as on a Mac. I would recommend reading my old post about the topic.

In the next installment of my monitor calibration series I’ll talk about what can one reasonably expect from proper calibration and profiling.

Keeping OS X Display Brightness Unchanged

In the previous installment in my monitor calibration series, I mentioned the need to keep monitor brightness unchanged after calibration – as any change to it invalidates the profile.

But what if I press the brightness control buttons on the Retina MacBook Pro (or on any other MacBook)? Should I immediately re-calibrate and re-profile? Well, there’s a slick trick.

MacBookBrightnessControl2MacBook display brightness is changed by default in whole unit steps using the brightness keys. But holding down Shift + Option while pressing the keys will change it to 1/4 unit steps – the same amount ColorEyes Display Pro (and other software) uses when controlling the display.

What I usually do after calibration and profiling is: increase the brightness by 1/4 unit, take note of the (previous) value, and immediately decrease it back to where the software set it. This way I could return the display to the calibrated state even if I had to change, or accidentally changed its brightness.

Another enemy of keeping the calibration intact is the display dimming preference of OS X – which tells the machine to slightly dim the display while running off of batteries. It might be useful for users not requiring color accuracy and consistency, but turn it off for calibrated displays (by default it’s on).

DisplayDimming2

In the next installment I’ll examine the differences between hardware and software calibration.

Sleepless External Display on a Mac

The original frustrating issue: my other half’s 13″ retina Macbook Pro was unable to put the external display into sleep. Video signal was off, but something kept the display always on (it’s a Samsung SyncMaster 213T – which isn’t a young one, but still a very capable monitor). So I tried a crazy idea: swapped my Mini Displayport to DVI adapter with hers.

And the result was – to my biggest surprise – proper display sleep. I was curious whether it is a faulty adapter or what, so tried the non-sleeping adapter with my EIZO CG241W. The result? Proper sleep behavior again.

The only difference between the two MiniDP to DVI adapters is that mine is almost three years old, while hers is from last December. They look exactly the same, have the exact same part number, etc.

Conclusion: if you encounter display sleep issues, the culprit might be compatibility between your adapter and monitor. Try to get an older Apple adapter or try an aftermarket one.

Retina MacBook Pro – After 2 and a Half Months

The 15″ MacBook Pro with Retina Display is by far the best computer I had ever used, no question about it. And I had used great many – although only a handful made a deep impression (I mean a positive impression, because I came across several that made unforgettable bad impressions). These are heavy words from me. As you might have been noticed I’m really picky on everything I use (just browse the Hall of Shame section for rants about bad design and/or execution).

You can read my initial impressions about the machine here.

During the last months I had used the machine as a desktop for software development (both iOS and OS X) as well as studio work, and lugged it around the country as a field laptop to assist during my photo trips. Most of my first impressions are still valid, and I love the machine even more than I though at first. I would just like to add further observations.

Battery Life

In my initial post I wrote around 5 hours. Since then OS X 10.8.2 came out, which increased battery life substantially. Now I get something between 6 and 8+ hours, depending on the usage pattern (disabling Adobe Flash holds a great contribution to increased battery life, though).

Tethered Shooting

Working Tethered

I started working tethered for landscape shots immediately after receiving the MacBook, and the benefits far outweigh the inconvenience of lugging around a computer. Before the MacBook I had tried to use the Lenovo X200s for tethered work, but was not really satisfied with it and abandoned the idea until the MacBook arrived.

I like several things about this setup.

No time required for image sorting and selection later. I just bring home the keepers. This proved to be a huge time-saver!

I can make the first cut of the final processing in the field, using the same tools I use in the studio. This fits extremely well into my creative process. The high resolution and color-accurate display helps a lot in this. It’s like holding an A4 sized print in front of me. I even stitch panoramas made with the 24mm TS-E lens to check whether everything is good about the shot.

Images are immediately backed up, as the the tethering software saves images to both the memory card in the camera and onto the computer. (Which app? – you might ask. Don’t worry I’ll devote a few posts for that subject later.)

As I wrote in my first impressions piece, the machine fits perfectly into my Lowepro Pro Trekker 400AW. Fully loaded it’s now a back-breaking experience, but if I leave home stuff I don’t need for the shoot, then the full weight is around 15kg, which is bearable. I did several 2-3 hour hikes with the setup without any effects on my back and shoulders (did I mention that the Pro Trekker is a great backpack?).

Other Good Things

The notebook-as-the-desktop was really helpful during the August storms. I routinely power down and disconnect sensitive equipment during thunderstorms, as I saw quite a few over-voltage spikes in the past. But with the MacBook I can continue working during these hours. I really like thunderstorms and they put me in a creative mood, so it’s a big plus!

Last, but not least, no more copying or syncing or Dropboxing files between my desktop and field notebook! No more forgetting to copy something in the hurry before I leave! This saves me lot of time and the peace of mind that comes from the fact that I always have everything I need with me is priceless.

What I miss?

Thunderbolt docks. Matrox’s and Belkin’s solutions are both delayed. Plugging in all those cables (all the connectors of the machine are populated) in the morning really pisses me off. I’ll be first in the line for one of those docks!