Friday, 19 November 2010

Unit 310 Photo Imaging Output Evaluation

In this Blog entry I will be providing a technical evaluation that demonstrates a high level of knowledge of digital imaging systems,and color management from the taken image through to the pc screen to the final output of the the printing device, be it local or remote such as an online printer. digital imaging systems,and color management is the controlled conversion between the color representations of various devices, such as image scanners, digital cameras, monitors, TV screens, film printers, computer printers, offset presses, and corresponding media.The primary goal of color management is to obtain a good match across color devices; for example, a video which should appear the same color on a computer LCD monitor, a plasma TV screen, and on a printed frame of video. Color management helps to achieve the same appearance on all of these devices, provided the devices are capable of delivering the needed color intensities.  In this case it will be from a digital camera through my iMac with the output being Bob Books and online printer.

Parts of this technology are implemented in the operating system (OS), helper libraries, the application, and devices. A cross-platform view of color management is the use of an ICC-compatible color management system. The International Color Consortium (ICC) is an industry consortium which has defined an open standard for a Color Matching Module (CMM) at the OS level, and color profiles for the devices and for working spaces (color spaces the user edits in) as also devicelink-profiles representing a complete color transformation from source to target.
There are other approaches to color management besides using ICC profiles. This is partly due to history and partly because of other needs than the ICC standard covers. The film and broadcasting industries make use of many of the same concepts, but they more frequently rely on boutique solutions. The film industry, for instance, often uses 3D LUTs (lookup table) to represent a complete color transformation. At the consumer level, color management currently applies more to still images than video, in which color management is still in its infancy.

I will start this journey through this process by first telling you what equipment I have, The capture equipment I have is two digital cameras, one a full frame 21 megapixel, the other a 1.6 cropped sensor with 12 megapixels, both of these cameras I use the RAW setting to the highest quality. The RAW format is very similar to the film negative before it is processed as it contains all the 'raw' information taken by the camera. to process this information I use Adobe Bridge and its RAW processing software for the basic batch adjustments such as white balance, for more detailed individual adjustment and amendment such as removal of blemishes of skin etc I continue through to the full Photoshop program. Alll of my images are veiwed on my 24" iMac desktop system  with OS Snow Leopard operating system which I calibrate using my  Pantone Huey Pro, this is one of a multitude for devices which provide you with an automation screen calibration. I have a Canon MP160 3 in one printer, and I use an online printer company called DS ColourLabs

Screen Calibration
I feel that accurate colour is essential for anyone involved with digital imaging, and monitor calibration should be as essential as remembering to put your memory card in the camera.. My package included an installation CD  (this is where these images are from), with drivers for both Windows XP and Mac OS so I use it on my Windows based laptop as wll, although the screen on the laptop is not as good a quality as the Mac, it also come with the huey unit itself, a desktop cradle and USB extension cable, some screen monitor cleaning wipes and a quick start guide. Following the quick start guide to the letter, first clean your screen with the wipes. Install the software and re-boot on completion. Once the computer has restarted you connect the huey to your computer via the USB cable extension cable. Place the Huey on your desk facing you and it reads the ambient room light, once completed you are prompted to attach the huey to your screen.

 The first thing that strikes me is its small size, its about the same size as a Wacom pen. The huey has eight tiny suckers which hold it in place on the screen and it can be used for both LCD and CRT screens (and laptops). I was reluctant to use this on the delicate surface of my LCD screen. The suckers need a slight amount of moistening, I resisted the temptation to lick the suckers and used a damp cloth. A small amount of pressure is required to make the huey stick to a LCD screen, but not enough to cause any damage. For CRT screens there isn’t a problem, just whack it on.

 Once fitted in place the screen rotates through a series of colours, this process takes about 1 minute. Your monitor's profile is saved and automatically applied as the new default setting. You are prompted to remove the huey and place it back in the cradle in front of your monitor.

 The huey will continue to read the ambient light and adjust the brightness of the monitor all the time your computer is switched on. - very clever stuff. There is an adjustable slider in the preferences that gives you the choice of how frequently you want huey to measure the ambient light.

You can also select the kind of work you do from; gaming, web browsing and photo editing, graphic design and video editing, to warm low - medium - high contrast and warm low - medium - high contrast. This changes the appearance of the image displayed on your screen, which in my opinion rather defeats the purpose of creating an accurate profile by does give the option to have your own settings to suit your own taste, I like mine reasonably warm. The huey measured the monitor as is, and at no stage was I prompted to alter my monitor's brightness and contrast settings. I adjusted the contrast at brightness when I received my first print back so that the original on screen image matches the printed version thus gaining consistency for future prints from this supplier.

In summary, the huey is very easy to set up and use on my Mac screen. The huey cost me £70 and I think represents good value for money, and it appeals to the keen hobbyist who doesn't want to splash £140+ out on a Spyder. Bearing in mind that is aimed at the hobbyist market I would have liked a few more options, such as being able to calibrate a TV screen as well as a monitor, basically it does what is says on the tin is calibrates your screen so that I can now set my onscreen images to what ever profile I require be it my local printer, or my online printer companies I use. Since using this device I have never had any colour problems on any of my returned prints. The important thing to do is to also adjust your brightness of your screen, Macs are notoriously bright at around 300 candelas, a candelas is a base unit of luminus intensity (power of light emited from a device). A common candle emits the same light power intensity of one candlelas. How I have set the brightness of my Mac was by getting a print of one of my images from my online printer and comparing the same image on screen then adjusting the brightness levels until I think the look the same, obviously you never get this excact as one is emmiting light whereas the other is reflecting light. I have set my mac to 3 bars on the scale and I ensure that I have it set at this level when I edit my images. When I use my local printer I use the same method as above and record the settings for later use.

Now that I have my on screen image is a bit more reliable, I find that those colour casts and defects on my prints are much improved. I find that if you I am using manufacturers inks and paper the printer profiles supplied by the printer and the paper manufacturer are often very good.
If printing from an application like Photoshop then I suggest the way is to use 'no colour adjustment' in the printer driver and use the appropriate printer profile in the Photoshop 'Print with Preview' window.

When I send my images to a third party or online printing for printing, it helps if you can send consistent data. Using standard colour spaces (such as Adobe98 or sRGB) you can be more sure of what you are sending, The company I use require me to send my images in the sRGB colours space. If your printer supplier is not able to answer basic questions about their colour management policy and preferred formats, then maybe consistent results are unlikely, and I would probably not use them.

Paper and inks
Manufacturers inks and papers may be more expensive, but until third party ink manufacturers offer printer profiles for various printer/paper/ink combinations you are just going to have to experiment. There is also the question of how long your choice of ink/paper is going to last, personally until the price of inks come down I will continue to use the online printers. none original replacement inks, I find never have the same consistency and is very difficult to achieve consistent results, so again I will keep using the online printers.

Of course you can produce your own printer/ink/paper profiles... This sounds expensive and it can be... The equipment to produce top quality profiles, and the expertise to do it does not come cheap. If you are just going to be using a few paper types then consider getting custom profiles made. You print a standard pattern, send it off, and a profile gets mailed back to you. The complexity and expense of this process varies, but it is pretty straightforward. You might wish to experiment with doing profiles yourself  but be prepared for plenty of experimenting. There are several reviews of colour management devices  which can help you with getting more accurate colour, most paper manufacturers supply profiles for their paper and some even offer their services to help set up your printer with a profile for their paper..If some of these solutions sound too expensive, then consider the real costs of getting it wrong. Factor in the time and resources lost in not getting things right first time.

Take time to learn the principles behind colour management because I think  it's well worth it . The better you understand what is going on, the easier it is to spot something that is not right, and fix it. Remember that the end result is what counts.

So now I have sorted out my screen calibration the next thing is to ensure that I have some method to ensure that the images I take can be calibrated through to the printing stage, there are two things we need to do one is to be able to achieve a true white balance, mos to the time this can be achieved when you are using RAW by using the eyedropper white balance tool/ selector to adjust the white balance by clicking on a suitable white area on your image in Adobe's RAW processing software, this is 99% of the time simple and easy some times when you have multiple light sources which are all different such as tungsten and fluorescent, so what can you do about this... well the answer is simple get a 18% grey card and have your subject hold this for the first image and use this to calibrate the white balance, you have to remember to use it every time the light changes.

I use Lastolite products and they also product some useful tutorials courtesy of Mark Cleghorn, as below

The second thing I need to do, especially if I do an advertising shot, is to ensure that my colours are true the the manufacturers specifications, fo excample the car I used for my calendar shoot was a ferrari and there colour red is there trade mark and had I been using this shoot to advertise their car the shoot would have been wasted if at the printing or projecting stage it wasn't the same red.

So you use a similar card to the 18% grey card, but this time a Macbeth colour chart, you put this card in the picture, just the same as the grey one. when your picture is one the screen, I make sure that I have set all my devices, Camera, Mac, printer and editing software to the same colour space, I use Adobe RGB 1998, then I turn off all the automatic settings.

 To enable me to ensure that the colours that the manufacture put on the car is the same that is reproduced on the printed output, I down loaded the colour reference, sometimes it is a pantone colour reference but in this case as it is a car they use a slightly different colour refernce scale this is a HEX colour chart.

Once I have the correct colour chart I sample the colour by using photoshopscolour sampling / colour balance pipett tool first on the manufacurers colour, noting what the colour reference is then sampling the out file colour and adjusting the colours to match. (by luck or experienced eye the colour on my prints and screen image/ car was a perfect match) The trick is to sample a section of colour with flat lighting on it an no reflections.

Luckily for me and the others, the college has conveniently calibrated a monitor and a local printer and to prove this here is the printer test sheets that is printed and compared against the monitor. 

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