Analysis of the Samsung Galaxy Tab 2 Screen’s Color Gamut

Samsung Galaxy Tab 2 Gamut vs sRGB

The illustration above shows the color gamut of the seven inch Samsung Galaxy Tab 2, compared to sRGB. This gamut looks quite familiar to anyone who has analyzed the gamut of laptop computers and tablets over the last few years. It can best be described as “small and twisted.” This refers to the fact that the corners of its gamut triangle are not as far from the center of the triangle as the sRGB corners (called primaries), and as well as the fact that the corners are not aligned with the sRGB primaries. The result of this is that colors tend to be the wrong hue when viewed on such as device, and that colors on the device will be undersaturated as well.

Many laptops have similarly small and twisted gamuts. Apple MacBooks had such a gamut until the quite recently. And iPads had such a gamut as well, in the first and second generation iPads. However the iPad 3 moved to a gamut very close to sRGB; as did the Retina display MacBook Pro (see assorted articles on this blog describing these devices).

Gamuts don’t always increase over time: the most recent pre-Retina MacBooks had a gamut somewhat larger than sRGB; normalizing the Retina MBP gamut actually involved reducing the gamut. Similarly the gamut of the first Samsung Galaxy Tab was a bit larger than the gamut of the v2 device, though still sub-sRGB, and still twisted.

The illustration below shows the gamut of the iPad 1 or 2 (they contained the same screen and had the same gamut), which careful comparison will show to be a bit larger than the Galaxy Tab 2, as well as less twisted. But the iPad 3 screen is more interesting, being nearly a perfect sRGB gamut size.

iPad2 gamut over iPad3 gamut

There are multiple advantages to a gamut closely replicating sRGB. It means that even non-color managed applications will show sRGB images correctly, including most web images, where sRGB is the standard, and much video, where the color definitions are similar to sRGB. It also means that variation between various devices, such as your iPad 3, and your MacBook Pro, will be minimized as well.

sRGB gamut over iPad3 gamut

So while Android tablets may be making progress in some areas, its clear that the color gamut of even the flagship devices is not yet up to the standards of the latest iPads. The next tablet of interest to measure will be the Google Nexus; and following that, the Microsoft Surface tablet. When these devices become available, I will attempt to publish articles covering them. The varying, sub-sRGB gamuts of Android tablets means that calibration of these devices will be required to produce consistent and accurate color on them. Datacolor plans to produce an Android version of SpyderGallery, which would help considerably with this issue.

Credits: C. David Tobie, Copyright 2012.   Website: CDTobie.com   Return to Blog’s Main Page

Datacolor Spyder Blog Goes Live

Datacolor’s long awaited Photography and Digital Imaging Blog has finally gone live. There are great photography and color management articles by a number of Datacolor’s world-class Friends with Vision, as well as some of my own work. Thanks to everyone involved in this effort!

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Credits: C. David Tobie, Copyright 2012. Website: CDTobie.com Return to Blog’s Main Page

Top Search Terms Today; In a Nutshell: Retina Display Capabilities

In reviewing the incoming search terms on my blog site today, there is a very clear theme, as the first several term sets show.

Today’s Top Search Terms

Do you see a theme developing here? Clearly there are a lot of people looking for information about the gamut and Photoshop compatibility of the new Retina display MacBook Pro…

Credits: C. David Tobie, Copyright 2012. Website: CDTobie.com Return to Blog’s Main Page

Retina Display MacBook Pro for Calibration and Photography

I have been asked to put together an overview of my observations on the Retina Display MacBook Pro, as related to photography, and specifically to display calibration. The material below draws on my previous analysis, plus further information about calibration of the Retina display.

Resolution

The Retina resolution of the new display is certainly its top feature, and in use this is the first thing you notice about the display. While Adobe has not yet released an update to Photoshop to take advantage of this higher resolution, they did demo an unreleased version at the WWDC keynote where the Retina MBP was announced, so we should be able to take advantage of this resolution soon; at least in Photoshop CS6; no guarantees about CS5 and earlier. In the meantime, the sharper text is a joy to behold, and will reduce eyestrain, even if it has no direct effect on photography or video work.

Video is certainly the second area where the Retina display will excel, and versions of the more popular video editing tools for the Mac should be forthcoming to utilize this display to its fullest. The image below shows a standard resolution app on the left (current version of Photoshop CS6) versus a Retina resolution app (Apple’s Preview Utility). Click on the image to see full size, for comparison of what Retina resolution can add to an image.

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Color Gamut 

Earlier MacBooks and other Apple laptops had a sub-sRGB color space that was not only smaller, but twisted in a way that offset the primary colors from their ideal hues. While this issue had been improved substantially in the more recent MacBook Pro models, the Retina display now offers a very close replication of sRGB on screen. This offers a number of advantages; not just over smaller gamut displays, but to a lesser degree over wide gamut displays as well. In addition to increasing the gamut from earlier devices, emulating sRGB in hardware means that non-color managed applications, browsers, and video players will show more reasonable color even without the ability to use a profile.

Retina Display Gamut

Earlier Unibody MacBook Pro Gamut

Reflectance 

The gloss screen on recent Apple displays has been an issue for some people, especially for mobile use, where uncontrolled lighting may mean distracting reflections on screen. While a matte surface helps spread such reflections around and remove their sharp edges, it reduces the contrast of the scene in the process. The Retina display uses low reflectance glass, plus one less layer of glass than earlier MacBook screens, reducing this issue without resorting to a matte surface. The image below shows the reduced reflectance of the Retina display on the left, compared to an older Unibody MBP screen on the right. Again, clicking on the image can provide a more detailed view of the image. Note the second reflection in the Unibody screen, caused by the extra layer of glass.

Retina Versus Unibody Reflectance

Viewing Angle 

Many laptops reduce energy usage and extend battery life by focussing most of their light output in a narrow cone in front of the screen, amplifying the brightness for viewers directly in front of the display. This technique has its drawbacks, however, and means that users can never quite trust the brightness and shadow detail of an image on a laptop display. Are the shadows in the image file actually as seen, or are they a bit more open, or a bit more clogged, as seen when your head is a bit higher or lower in relation to the screen. And are colors exactly as seen on screen? Even to a second viewer, who is reviewing your images with you, and is a bit to your left or right.

The answer to this conundrum is to use a proper IPS screen which shows similar color and brightness at a wide range of viewing angles. The flip side of this coin is increased battery drain to display this wide, even view of the screen. In addition to the increased pixel count of the Retina screen, these two factors (resolution, viewing angle) are the top two reasons the computer uses more juice. Apple’s solution to this is to build a series of custom sized battery cells into the ultra-thin body to provide for the higher energy uses of this amazing display. This produces the highest quality screen I have ever seen on a laptop; but the high drain, custom batteries will not be inexpensive to replace, when the time comes.

Brightness 

The Retina display can produce luminance levels as high as 280 candelas per meter squared. This is not the brightest display on the market, but it is still bright enough for all reasonable uses. The display dimming controls allow a full range of dimming of this screen for use in low light, color managed conditions as well, plus the bonus of an “off” setting at the bottom of the dimming scale, to turn the screen’s backlight completely off, for conditions such as a long, overnight session of moving files to another drive. This range of brightness is valuable for color managed use and calibration, where adjusting the display to an appropriate brightness for the ambient light level is important.

Device Type Category 

The best of current display calibration systems, including the Spyder4 devices, characterizes devices based on display type. The Retina display fits nicely into the Standard Gamut, White LED backlight category. At this time, the Retina display MBP is newer than the latest release of Spyder4 software, so until the next Spyder4 software update, when you calibrate a Retina display MBP, the Spyder’s New Display wizard will ask you to choose a gamut and backlight type for the display (after the next update, this will be done automatically, and invisibly). The choices noted above (Standard Gamut, White LED Backlight) are correct.  Fitting well into this category improves the accuracy of calibration on this display.

Calibration 

Display calibration includes user control adjustments, which are not really relevant for laptops, where the brightness must be changed for use in different environments, with different levels of ambient light; and video LUT adjustments, which gray balance the display and set an appropriate tone response curve (gamma, in simplest terms) for all applications on the device, at a global level. The Retina display is a good citizen, allowing accurate readings of colors for gray balancing, and accurate readings of luminance for tone response mapping. So calibration is very effective on the Retina display, and the resulting “Before and After” demo in the Spyder4 software will show that the uncalibrated state is not bad, but that the calibrated state is indeed better, both in terms of white balance, and densities in images.

Profiling

The other component of the calibration and profiling process consists of creating an ICC profile describing the current state of your display, its primary colors, its tone response curve or gamma, and other factors. Resolution does not effect color and density measurements, so the main feature of the Retina display is not a problem for profiling. The Retina display, by avoiding problematic technologies or extreme color saturations, allows for very accurate profiling of the display. I will oversee detailed comparisons to a laboratory grade display measurement device next week, but even in advance of that process, I have full confidence that the Retina display is being capable of being very accurately profiled by latest generation profiling tools such as the Spyder4.

Credits: C. David Tobie, Copyright 2012. Website: CDTobie.com Return to Blog’s Main Page

Reduced Reflectance of Retina Display MacBook Pro

When Apple announced the Retina display MacBook Pro, they made a number of claims about its improvements. One of those claims had to do with reduced reflectance, and involved not adding an extra sheet of glass across the entire display screen as in previous MacBook designs. Photographers immediately picked up on this statement, and the greatest complaint against Apple’s glossy screens is the difficulties that reflections cause. A matte surface, which was available on older models, did not eliminate this reflectance, but it spread it around, so that it was not sharp-edges and distracting. Instead of seeing the view out the window is full detail, with a matte screen you just see a big smear of light on the screen, reducing the contrast range in that area.

 

The photo below shows a previous generation of 15 ” Unibody MacBook Pro (hereafter just “Unibody”) and the Retina Display MacBook Pro (hereafter Retina). As you can see, reflections in both screens are still sharp, and not smeared as with a matte screen. On the other hand, there is definitely a lot less reflection in the Retina screen on the left. There is also a double glazed artifact on the Unibody screen, from the extra layer of glass, which causes a second ghost image offset from the main image. This photo was shot in a dimly lit image editing studio; I’ll leave it to you to decide if this reduction in reflectance is sufficient to allow you to move to a gloss screen; but as someone moving from a Unibody MacBook Pro with a gloss screen already, this is all good from my perspective.

Retina Versus Unibody Reflectance

It is quite difficult to quantify this type of reflectance, which is why I led off with a photo. I took many measurements, with differing types of sensors, to attempt to capture this characteristic. The table below lists a small number of them. I will describe the items in detail, to let you determine for yourself which measurements may be meaningful.

Let me start off my noting that to a display colorimeter, as to the eye, a screen with the backlit turned off looks darker than one with the display turned on, and displaying a full screen black field. With a Spyder4, the Retina screen measured 0.001 candelas/meter squared, versus .375 c/m2 in these two states. However, a 45/0 reflective measurement device, in this case SpyderPrint, a lit screen consistently reads darker. I’m going to propose that the nature of the light limiting valves in the screen may be responsible, as no other factors leap to mind. But the variations based on the Off/On nature of a black screen tend to be relatively small, so my conclusions below will not be affected by them.

Is a 45/0 device (where light is emitted at 45 degree angles, and measurement taken at  a zero degree angle, meaning perpendicular to the screen) appropriate for measuring the type of reflectance in question? Probably not, but as no other tool was available, I felt it worthwhile to make the attempt, and see what differences existed using this method.

Measurement Data from Retina Display and others

First we measure a number of black standards. The black trap in the SpyderCube is very black indeed, with an L-star value of .008. A glossy black calibration tile jumps up to 5.1, while the matte black face of a SpyderCube is 12.85, and the matte black patch in a SpyderCheckr is 15.85. All of these are as expected.

A couple of matte finish desktop displays are then measured, including  a high end Eizo. The Eizo scores lower than the Apple Cinema Display, but I suspect that is due to its dimmer max brightness, rather than some other characteristic of the screen.

Now onto the target devices: the Unibody MBP is a bit less reflective than the matte screens, even though its as bright as the Cinema Display. And the Retina display shows only half the reflected light at both on and off conditions of the Unibody model.

Setting the measuring device back half an inch to allow for ambient light to be introduced into the measuring area produced even  lower values with the Unibody MBP, and amazingly black results with the Retina display.

Attempts to create light leakage into the measuring device by placing a bright fluorescent proofing lamp so that its long U shaped bulb was in contact with the edge of the screen, and sloped back behind the SpyderPrint unit, thus producing ambient light at all reasonable angles, did not increase the Offset values.

So, of all these values, which ones have merit? Perhaps none, but the Unibody to Retina black measurements do reflect what the eye sees, in terms of a notably lower reflectance on the Retina display than the Unibody display.

Credits: C. David Tobie, Copyright 2012. Website: CDTobie.com Return to Blog’s Main Page

Color Gamut of Retina Display MacBook Pro

When Apple announced the Retina display MacBook Pro, they made a number of claims about its improvements. Beyond the obvious improvement in resolution, these were a bit vague. I will be publishing an article on the reduced reflectivity of the screen later today. But first, I wanted to show the color gamut of the new Retina display, and compare it to that of my earlier 15″ Unibody MacBook Pro.

Retina Display Gamut in Red, sRGB in Green.

Earlier Unibody MacBook Pro Gamut in Blue, sRGB in Green.

As you can see from the gamut graphs above, Apple has done much the same thing in moving to the Retina display on the MacBook Pro that they did when moving to the Retina display on the iPad. The gamut is no longer small and skewed; it is very close to sRGB. This means that non-color managed sRGB content, such as materials on the web, will be much more accurately displayed, and that the display will be more capable of displaying photos than earlier MacBooks, since even when earlier versions were calibrated, they could still only display about 70% of sRGB, rather than the whole sRGB gamut.

This gamut normalization and enlargement will do wonders for using MacBooks for photography work, and will even make advanced image editing possible. Other factors that are improved on the new Retina display will also be important, including its much improved viewing angle, and its reduced reflectivity. The Retina display is, simply put, the biggest advance ever, in laptop screens for photography and video work; and would be even without the resolution increase.

While the gamut of the Retina display is a good match to sRGB already, calibration made improvements to the white point and gamma which were crucial to getting good matching to a high end desktop display. Visual match to my calibrated desktop displays is excellent with the Retina display MacBook Pro.

Credits: C. David Tobie, Copyright 2012. Website: CDTobie.com Return to Blog’s Main Page

Photoshop CS6 on Retina Display MacBook Pro

When Apple announced the Retina display MacBook Pro, one of the applications which they demonstrated with it was Photoshop. But not a release version of Photoshop. The current release version of CS6 opens images at the same size, and the same resolution, as on a non-Retina display MBP. In comparison, Apple’s own Preview app opens images at half the width and height as 100% view, and displays all the pixels in the image at that size. For comparison here is an image at 100% view in Preview on the right, and viewed at the same size in Photoshop CS6 on the left. If you look at the narrow yellow leaf stems at the focal center of the image (left of center in the crops shown here), you can see the difference; be sure to click on the image to see at full size.

I expect that the Retina display update to Photoshop will be free… for CS6 owners. But it is unlikely that Adobe will update Photoshop 5 to Retina resolution, as one more reason for users to update to CS6.

Be sure to check out my articles on the Retina display MacBook Pro’s screen, reflectivity, and color gamut, as I publish them over the next day or two.

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Credits: C. David Tobie, Copyright 2012. Website: CDTobie.com Return to Blog’s Main Page