ICC Profiles

 

After writing about colour management, printer (and monitor) calibration and printing the photographs, both theory and practice at Burton College and via D S Colour Labs, I thought I had better do a short blog on ICC Profiles.

The term ICC refers to the International Colour Consortium.

Understanding what a profile is will help you fully comprehend what happens in colour-managed transformations. An ICC profile is a standard way of numerically defining the way a particular device (a scanner, camera, printer or monitor) renders colour for a human observer under average daylight conditions. Colour management involves linking these various device profiles together in a way that allows us to control the appearance of colours from one device to another. In order for this to work, a profile must reference the observable colours from a device to a device-independent model, a sort of absolute definition of colour. Profiles are static definitions, and the dynamic calculations that move an image file through various profiles to arrive at the final output are handled by a colour management module (CMM) that’s the mathematical engine for all the transforms.

Therefore, a profile is a special number transformer, a kind of black box called a lookup table (LUT), or more often a colour lookup table (CLUT), which takes a set of numbers and returns another set of numbers. The first set of numbers can be from any kind of colour device (RGB, CMYK or grey scale); the second set of numbers is the LAB definition of the colour represented by the first set.

The above might look confusing, but it is important to remember that all computers work on binary, and that even that picture you took on location or in Burton College’s studio, is seen by the computer as simply a series of 1s and 0s.

A profile “looks up” the LAB value for a colour in a specific colour space.

You can think of LAB numbers as being independent of any particular device but representative of colours observable under D50 graphics industry-standard lighting. Therefore, a profile gives us a real colour definition of the numbers from a digital file—in D50 light.

Some profiles are relatively simple rules based on a matrix with a few points defining a larger set of colours. Other profiles are larger plots of all possible colours in a particular set. Matrix profiles are commonly used for Photoshop’s working spaces and monitor profiles. Printer profiles are most commonly larger CLUTs, sometimes referred to as table-based profiles. The math surrounding all this is staggering. For the artist, a profile is merely a definition of the colour rendered by a device translated into LAB. When photographers need to transform one set of device numbers into numbers for another device, they use profiles to “look up” the LAB colours and generate new numbers for the next device based on those colours.

LAB Colour is the link between the two device numbers.

When the profiles for the devices you’re using are installed, you simply have to select the appropriate profile at the right time to manage the necessary colour transforms.

Printer Calibration

The final element of the digital work flow, the printer, has to be calibrated to ensure that all you hard work, composition, capture, conversion / processing, etc, is not all in vain.

 

Photographs looking different when displayed as opposed when they are printed is not a new issue that has been created with the digital revolution.  Paul, my brother, used slide film for years because he liked how the colours were more vibrant and true to what he saw when he took the photograph, when they were shown on a slide projector,  in a similar way to how our images look on the screen, but when prints were taken off the slides the photographs lacked the vibrancy and punch that he saw when it was projected on to a screen, in the same way as our photographs lack these features when our photographs are printed out.

 

It is important to note thought that a calibration has to be carried out for each printer / ink / paper combination, so basically it is best to stick to one make of ink and one type (finish, weight and even manufacturer) of photographic quality paper.  Some papers are promoted as bright white in colour as opposed to just white.

 

Some photographic paper manufacturers, for example permajet, offer a service whereby the photographer buys a pack of their paper, they produce a print using their combination of printer / ink / with the manufacturer’s paper, and send this to the manufacturer who analyses the colours against the original image.  The manufacturer then sends a custom ICC profile for their paper when used with the photographer’s printer and ink.

 

The ICC profile for a printer is created by comparing a test print result using a photometer with the original reference file. The test chart contains known CMYK colours, whose offsets to their actual L*a*b colours scanned by the photometer are resulting in an ICC profile. Another possibility to ICC profile a printer is to use a calibrated scanner as the measuring device for the printed CMYK test chart instead of a photometer.

 

A number of manufacturers, like Huey, Eye-One, etc produce kits which can calibrate monitors and printers, using colour photometers, to maintain full colour management from the beginning of the workflow right through to the end print.

 

Some software, such as Adobe’s Photoshop has a soft proofing option that can be used to simulate on screen how the photograph will actually look on paper, colour and depth wise as opposed to a simple print preview, which just shows how the image would fit on the page.

 

Below is an example of how an image looked on the computer screen, and how it looked on the soft proofing simulation from Adobe Photoshop:

This example shows how prints can lack the punch that on screen images have.

 

The problem is that no matter how ‘bright white’ you paper might be, it would never look as bright as a monitor screen.

 

 

Using ICC profiles

 

When you choose the print option from Adobe Photoshop, you will get this requester:

 

When the print dialog comes up, make sure you have Colour Management selected in the drop-down at the upper-right corner; most of the important printing options for our purposes are in this area (Figure 4). This is where you set up all the Profile options for your prints.

At the centre of the dialog, Position controls how the image lays out on the page. The Centre Image check box provides a quick way to place the image. Directly below that is the Scaled Print Size area; by default, this is set up for 100%. If the image is way too small or way too big on the page preview, click the Print Settings button and make sure you’re using the right-sized paper. Checking the Scale To Fit Media check box is a quick and dirty method of sizing the image to fit the paper; just beware that your quality will suffer if the reported Scale percentage is overly high. It’s far better to set the size properly in Photoshop before using the dialog. The Bounding Box check box is useful when you have an area of white canvas in your image—the bounding box shows the edges of the image against the white of the paper.

 

The important colour settings reside in the right third of the dialog box. The two radio buttons directly under the Colour Management drop-down identify whether you’re going to print the document directly or generate a simulation proof; if you’re making prints for your portfolio or to sell to a client, you’ll probably check Document because this generally will provide the highest-quality print for your image. This sets the profile to the document colour space and determines from where the colour starts in its journey to the print.

Next is the Colour Handling area. For RGB images, the Colour Handling drop-down shows Photoshop Manages Colours, Printer Manages Colours or Separations.

 

Photoshop Manages Colours. Selecting Photoshop Manages Colours allows you to select the Printer Profile in the drop-down menu just below this one. This is the most straightforward way to set up colour management for the print. If you select Photoshop Manages Colours, remember to turn off colour management in the printer dialog!

 

Printer Manages Colours. If you select Printer Manages Colours, the Print Profile option will be greyed out, and you’ll have to set the Colour Management options in the printer driver. The Printer Driver dialogs are usually a lot more confusing in this regard, so you would be wise to stick with Photoshop.

 

Separations. Separations will be available only if you’re printing from a CMYK document; otherwise, it will be greyed out. This is used only when printing separate cyan, magenta, yellow and black “plates” or simulations, and for the most part, you can ignore it.  This type of printing is only really for use with printing companies who use the traditional plates method of printing.  Below is a screen grab from PhotoPlus with the colour separations and Prepress options:

 

The last choice is Rendering Intent. Here you can choose: Perceptual, Saturation, Relative Colorimetric or Absolute Colorimetric. 90% of the time, Relative Colorimetric will give you the best result. Occasionally, certain very saturated colours will tend to posterize and lose detail in the print. If this is the case, you can try to solve the problem with Perceptual rendering.

 

Generally though, Perceptual rendering will give a less saturated colour in the print, and your skin tones could become dull. The other renderings are applicable for custom profiles and unusual circumstances; however, for the most part, you can ignore them with people images.

 

Beginning with Photoshop CS5, the large preview in the dialog is colour managed and has some check-box controls underneath the preview. Checking Match Print Colours, by default, checks the other two boxes you can uncheck them if you desire. Gamut Warning renders flat areas of grey over any colour that’s out of gamut for the selected printer profile. Show Paper White puts a tone into the white areas of the preview in an attempt to simulate the effect of the paper colour on the image (much as you can with the Custom Proof Setup under the View Menu). The preview also can be used to reposition the image directly. If you uncheck the Centre Image check box in the Position area, you can click the image preview and move it around on the page and/or rescale it by dragging on the corner handles in the bounding box (if you uncheck the Bounding Box, you won’t be able to do this).

 

Once all your options are set, you’re free to click Print. The only additional thing you need to remember is that if your colour management options are being set in Photoshop, you have to turn off any such options in the Printer Driver dialog. All of the colour transformations will have taken place already in Photoshop before the data hits the printer driver, so make sure you don’t “double colour manage” and introduce an additional transformation. Every printer driver is a little different, but yours will have some option to select no colour management in the printer driver.

Evaluation: Print Run 2 - College

Initially, there were problems producing the print, with printer errors.  After these few problems were taken care of the image was printed.

There were clear signs of banding on the image, mainly on areas where there was darker colours.  On green areas there was no sign of banding at all, which suggests it involved the magenta print head may have a blockage.

 

The finish on the paper was matt like, which I felt suited the image nicely, because sometimes using gloss finished papers the sheen can detract from the image, and even show up any problems at the mounting stage, in the form of lines across, or down, the print.

 

The colours that were printed were an accurate reproduction of what was on the computer screen, with the obvious exception of the banding.

Other than that I was happy with the print quality, and would like to thank all those concerned with their efforts in solving these issues enabling me to print this image.

Evaluation: Print Run 1 - D S Colour Labs

Collected the prints today from the Burton Sorting Office.  I was working outside in the garden for about half an hour, after waiting in for them to arrive, only to find that they had been and left a card for me to take to the sorting office to collect it.

In evaluating the the prints, I will also look at the condition of them from the point of packaging because this is important as it protects the prints from damage during transit from the printers to me.

Packaging

When D S Colour Labs send out prints they take great care in packing them between two plastic / cardboard sheets taped together to form an envelope, with the invoice attached, to keep them flat and protect them from creases and folds.  This is inside a strong corrugated cardboard box, clearly labelled with the addressee’s name and address with a return address in case it could not be delivered.

The box was in good condition when I collected it, with the prints safely inside, protected by the plastic / cardboard, with the tape in tacked.

Print Quality

The print quality is very good, with no signs of banding, or any other printer faults, and by selecting the auto corrected option, where the image is lightened slightly, (especially after finding some previous prints seemed to come out darker than what I expected), the prints matched the images on the computer screen.  So obviously D S Colour Labs have responded to peoples comments about the darkened prints, and provided an option where this is automatically corrected.

Finish

The finish was very good, with a matt like finish which seems to provide a more clear and defined edge to lines which gloss finishes can sometimes lose. 

Colour Management

The colours were faithfully reproduced, but without too much saturation, which I have heard some companies do to emphasise the images too much.  The whites were white without any colour cast and details remained sharp.

Crop

The images were as I uploaded them without any form of crop, with a narrow band along one edge.

Overall Evaluation

Another case of a fast turn around from uploading the images to receiving the finished prints, with a very high quality print quality, good finish and accurate colour management.  D S Colour Labs have obviously listened to peoples concerns over darker prints and provided an option on the print size and finish menu to correct any problems.

 

My only comment, which has nothing to do with D S Colour Labs, but an evaluation of one of the prints is that on 'Cooper's Square' the image is a little pixelated, but this is more due to the camera I used, on a mobile phone, which would never deliver the quality of a SLR.  But this shows what a mobile phone camera can deliver, and it's limits.

 

No prizes for guessing where my next set of A3 prints will be printed !

Macro Photography Techniques

Having covered product photography during the last course, I learnt a few valuable techniques for this assignment.  But this time, I wanted to photograph the subjects using the Pentax DSLR and not rely so much on the Fujifilm S7000.  This combined with the subjects being natural and situated outside in the garden.

The first consideration was the light, which was not as controlled as when I was taking the product shots, because now I was photographing the subject outside the house, where I wanted to use the natural light, only using a reflector when necessary to illuminate any dark areas that I wanted lighter to show the detail, as opposed to using the studio lights in the Burton College photographic studio.

The next consideration was focusing.  The S7000 has a macro mode and a super macro mode, the latter of which can focus down to 25mm.  Although I do not own a proper macro lens, some of my lenses can focus down to 450mm.

So this meant that that I could not get as close to the subject, as I could with the S7000.  This meant zooming in closer.  With the Tamron 18 - 200 mm lens this zoom range was the whole 18 - 200 mm, where as with the Sigma 75 - 300 mm lens only the focal range of 200 - 300 mm was available for macro use.

Next, I chose a large aperture to concentrate the viewer on the subject, rather than the background.  Working at larger apertures kept the depth of field shallow, blurring out the background.

 

Proper macro lenses have a reproduction factor of 1:1, life size, other lenses which can be used for macro work sometimes do not offer this.  But to me if the image is to be printed so people can see it clearly I will accept this and not buy proper macro lenses which cost more and, like the tilt and shift lenses used for architectural photography, have their own specific uses.

Preparation for Printing

I have decided to produce two A3 prints, one from each section, via the college printer, and the remaining eighteen prints via D S Colour Labs.

The paper used at the college is HP Satin Matt A3+ 250g/m2 (Q5462A):

Specifications shown below:

for which their HP Photosmart B9180 printer is calibrated for.

Above the printer is a set of calibration charts that have been used during the calibration process, just in case there is a problem later, where the original charts can be compared to newly printed charts.

Because the printer is calibrated to suit the paper that the college request the students to use on this printer, the images should come out to match the image perfectly.

This paper will give a fine finish to the printed images, without reflection or glare, which I found when I had some prints for last year's exhibition, twenty-ten at the college.  The reflections that resulted as a result of using pearl finish paper, which is glossy, showed up any marks that were the results of the photograph being mounted, which I felt let down the final work.

The printers use genuine HP ink cartridges and are checked on a regular basis to prevent any common printing problems such as banding (horizontal lines), ink run (vertical lines) and general poor printing quality.