– Fine Tuning Your Monochrome Output Challenged at a recent Epson Print Academy session we set about adding some flesh to the bone on the problem of predicting the result of changing the custom tone settings in the Epson Advanced ABW Black & White Driver (the ABW). But we are getting ahead of ourselves – what are the ABW settings? What does the ABW Driver do? Cyan and magenta inks are termed strong colourants, that is they exert a greater influence on the ‘look’ of a print than other weaker colours. By the same token any deviation from the expected level of strong colourant inking will have a significant influence on any colour bias in a monochrome. The clever trick that ABW performs is to slice magenta and cyan out of the equation and use only the other inks to create the image. The light cyan, light magenta and yellow are also used to provide the bias or toning of the print when required, otherwise simply using Black, Light Black and Light Light Black inks would be on the cards. So far so good but now we have an additional optimisation to perform. The human eye is very sensitive to differences in greys (neutrals) and particularly good at spotting colour bias in the grey parts of the gamut. This immediately poses the question ‘what is neutral?’ In Photoshop terms neutrals are those ‘colours’ which have equal values for red, green and blue components. This translates to Lab values of a=0 and b=0. For the viewer ABOVE: The test image consisted of a though there are two additional complications, the colour of monochrome seascape with swatches the viewing light and the intrinsic properties of the underlying at 80%, 50% and 20% Lab Luminance print media. This opens up another can of worms! values Most papers are coated to be blue (cool) as this creates an impression of ‘brightness’ – indeed the ISO measure of paper brightness concentrates on the blue part of the spectrum only. LEFT: You could To match this base tone the inks from the printer must be be forgiven for arranged to deliver a similarly cool tone. In technical jargon this thinking that is called ‘mapping to the white point’. In other words the icc measuring how profile measures the base white during profile making and sets white a piece of out its stall to match this in the illuminant colour chosen (which paper is were a traditionally is D50 for profiles). If this match is not good, the trivial task. It is not! very light greys (which contain a substantial contribution Note that we wrote from the paper tone) will be a different colour to the deeper the measurement greys which are built up with lots of ink. The problem tends to technique up in go away as the shadows are reached because the eye is not the January 2012 as good at discerning colour in deep shadows. Overall, then, issue. this is the requirement – the ink laid down has to match the ABW Driver from Epson coolness or warmth of the paper and should ideally do so right This utility is proved on all the modern Epson printers and down the tone range from highlights to shadows. is available through the panel that appears when you click File>Print>Print Settings and change the drop-down in Toned or Biased? media Settings to ‘Advanced Black & White Photo. Now Photographers are a fickle bunch and whereas one portion of when you click Custom and then Advanced buttons under them are striving for perfectly neutral prints (whatever that Mode, the Color Controls panel appears from where you can is!), the others are looking to significantly bias the tone in one change the base tone colour of the monochrome print. direction or another – traditionally with a bunch of chemicals of rather dubious health benefits! Roughly gold toning cools So far, so good, but although this method is, bar none, the a print, thiocarbamide toning warms a print towards sepia, favoured route for monochrome printing, the Before-After selenium pushes towards purple/magenta (and don’t write preview box only gives a rough indication of how the print in – this is a generalisation of toning!). The one tone bias that will turn out. This is a forgivable sin because neither Epson is generally unfavoured is the olive green that can result from nor the print driver have any idea of how blue (or warm) certain development conditions with silver halide prints, an your paper is. The preview window is also very small which effect particularly disliked by Ansell Adams. makes judgement difficult; you need a larger area to look at and if it is of your own image things are even better. This 118 » is the basis of the following but it is a complex subject and requires careful reading and understanding! LEFT: The sequence for activating the ABW driver on an Epson printer. TOP: The matrix used for testing; each variation had to be individually printed. professional Imagemaker 116 62 117 62 ABW – Fine Tuning Your Monochrome Output » 117 LEFT: Testing The basis of the soft Choosing the paper proofing outlined. We cast around for a paper to act as a solid baseline. Previous 2 The Solid Color trials with brightened paper (Kirkland) were compromised Adjustment Layer is by the difficulty of measurement – the spectro is fooled made at ‘A’, double by the OBAs in Kirkland and the cool bias carries numbers Full Black clicking it reveals the that are larger than the ABW adjustments! Canson Baryta 1 panel shown at ‘B’ Photographique was the strongest contender. This is a where a setting of -7 is baryta paper with no OBAs and a near neutral coating. It Pure Neutral input at ‘C’. Note at ‘D’ had audited well back in 2010 using an Epson 3800 but that that the monochrome printer is no longer with us and so we had to start again 0 file now has a green with the Epson 4900 and its high gamut ink set. We were not -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 bias of a = -7 disappointed, the audit produced a set of statistics which equivalent to -70 as far as we can recall have never been bettered, so good points on the ABW indeed that we have given the media its own place in the sun -1 scale. after this feature! The struggle to keep the greys under control with a brightened paper and the improvement from using the -2 Canson paper is illustrated in the graph. Here the tone parameters (Lab a and b values) are plotted for greys right down the tone scale from white to black. The base tone of the brightened paper is moderately cool (-6 Lab b points) -3 compared with some papers we have tested (we have measured as cool as -11 points) but you can see the tones tracking towards more neutral from white towards back. By comparison the Canson results start near neutral and -4 stay there, any variations are more statistical noise than any definite bias. The graph also illustrates the dilemma we have for these tests, a -6 value can be the result of 60 points in the ABW scale but this is just for the paper on its own. -5 Printing the tests Having set the scene, we created real prints using matrix (ring around) of ABW settings. Previously we have done this test matrix on a single sheet of paper by passing it through -6 the printer 10 times at different settings and printing each Paper White variant. This is no longer possible with the 4900 as it looks at the paper after the first pass, decides it has an image on it and spits it out! Scoping trials had suggested that 10 ABW -7 points was a little indistinct and so we chose variants based on 20 units and 50 units in the ABW colour wheel. We also printed on the diagonal values of 50:50, 20:20 and all the Canson Photographique Brightened Paper negative values as well. It should be remembered that a LEFT: 50 point variation in a single direction is smaller than one Screen grabs with soft proofing using the which uses 50:50 which is 1.4x larger (by Pythagoras – it’s ‘Simulate Paper’ settings. The top grab x √2). This showed both on screen and in the prints, ie the 3. Set the adjustment layer mode to ‘color’ which should recover is imitating the paper colour for Epson discrimination was sufficient at this level. the image view to the original, neutral monochrome. Premium Luster Photo Paper, a slightly 4. Double click the adjustment layer to reveal the ‘Pick a Solid cool media. The first question we had to answer was how big is the size of Color’ panel. the shift in a print for a point shift in the ABW colour wheel. 5. Change the Lab values to 50% L and then an a or b setting to ABOVE: Mathematically this is quite tricky to compute because of the match one tenth of the proposed ABW settings. In this case the The media is selected in the ‘Device to negative numbers that are kicking around in both the Lab a value (plus or minus) is equivalent to the horizontal value in Simulate’ drop-down, the ‘Simulate plot and the ABW Color Wheel. A bit more squaring, square ABW, the b value is the equivalent 1/10 of the vertical value in Paper Color’ is the checkbox in the lower rooting and Pythagoras sorted that out and eventually we ABW.