Optimising Mono Print Settings

You might be forgiven for thinking that making a bespoke profile using thousands of pounds worth of equipment, auditing the profile to demonstrate it was really top-notch and then using it to make a print, would result in a near perfect black and white print onto matt paper. How wrong you would be!

This exercise began when we were proofing the pages for Trevor and Faye Yerbury's feature on the mono nude, and trying, at the same time, to link it to the Paper Chase feature on matt, Sugar Cane paper. The image in question relies heavily on the dark background surroundings to create the mood. However, the detail in the shadows is vital and if it were to disappear altogether the message of the image would be lost. We tried to make a print onto Hahnemühle PhotoRag UltraSmooth paper using matt black ink. The profile had audited particularly well with an average error of just 2.19ΔE 2000, compared with an overall average, across all tests, of around 3.3ΔE 2000 (smaller is better). The audit data include spectacular skin tone error values of just 1.2ΔE 2000 average. So where did it all go wrong and why was our printed image using the colour profile so lacking?

The plot of residual lightness error for the entire tone range of the test target reveals the problem. As will all statistics the devil is in the detail. Although the bulk of the data are very accurate, the high-error outliers are all the deep tones. In trying to get the best average error across the gamut, the profile-building mathematics has sacrificed the deep tones, the ones it cannot achieve because of the restricted Dmax of the matt paper. This shows as the bulk of the data points lying on or close to the red line (zero error) but the deep blacks, rich browns and the deep blue rendered much too light, ie below the line. What is showing here is the inability of the paper/ink combination to achieve the correct density. What actually happens then is the shadows are all massively compressed and what you see with a 'print in-hand' is a swath of blocked shadow information, ie large areas of solid black.

As our next move we tried printing a test target specifically designed to isolate the point at which the shadows blocked up. We used the fullcolour profile (printing in full colour) at both 'Relative Colorimetric' and 'Perceptual' rendering intents and three tone setting using the Advanced Black and White driver (Light, Dark and Darkest). We then examined the test prints and assessed where the shadow blocking occurred in both Northern Daylight (ie the office with the blinds open!) and a viewing booth set for the ISO standard of 2,000 lux and D50.

The image we used to test our print optimisation was Trevor Yerbury's image of the lovely Lozie. It is quite challenging in both content and tone range, but the detail in the shadow areas are vital to both mood and message of the image.

The source of the problems with the colour profile are illustrated by this graph, see the text for the details.

ABOVE: Our shadow and highlight detector image used for visual assesment of the printing drivers.

Having established the superior performance of the ABW/Light (our favoured setting anyway) we made a print and the shadow detail all came back!

Given that we established just where clipping of shadows was going to occur we could predict the effect on the file in Photoshop using either a 'Threshold' adjustment layer or by opening the file from Bridge in Adobe Camera RAW. Screen grabs from both are shown. The Threshold set to 6 RGB points shows much of the shadow area down at that value and so we now know from our test they will not print using the colour profile, but will print using ABW/Light. The tale is similar in ACR, with the shadow set at +3 units, the blue areas are those that will be clipped. A tactic that would be unlikely to work would be to adjust Trevor's shot, from the supplied JPEG. The bit-depth available at these low values is very restricted and was already starting to 'block up' with the JPEG compression. Changing the levels slider might have been disastrous! The trick is to guard your precious shadows at the image manipulation stage and have due regard to the possibility of eventually reprinting to a matt, restricted Dmax paper. Trevor and Faye are fans of Kevin Kubota's actions which certainly produce some of their most striking images, the downside is that they must be used with care or problems can crop up of either banding, pixel blocking or both.

 The Camera RAW dialogue allows you to review the shadow clipping. The areas marked blue are clipped below three units.

 The Threshold adjustment layer is set to a value of 6 RGB points and shows (as black) all values at that value or less.

When all the testing is done you have to examine real prints. The difference should remain detectable after the page has come out of the printing press as printing RIPs are usually more forgiving than inkjet prints in shadow detail. If all goes to plan you should see more detail in the left-side print which was made using ABW on Light.

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