– 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. Thus if you wish to soft proof ABW values of 50v: -30h you left. arrived at a value of 10 as the multiplier – that is 10 units would set a to -3 and b to +5. on the ABW scale produces a 1 Lab unit change in the tone At this stage your screen view should show the bias you have values of the print. The reality is more complex because of chosen. The method can be further refined by clicking on View>Soft the offset produced by the paper white (even the Canson was proofing>Custom and selecting a profile for the media you intend to a little off white) and statistical noise within measurements. use (this lets Photoshop know the expected white point), now if you We noted that points on the green and yellow scales in ABW check the ‘Simulate Paper Color’ box the whites are mapped to the seemed to reproduce a larger effect than anticipated, those paper. Be aware that this is a subtle change and a subtle effect which in blue and orange lesser than anticipated (by this time we might not even show on an inferior or uncalibrated monitor (we had run out of paper!). However, as a first cut the concept can’t solve all of your problems in one sitting!) The change might or works moderately well and so we progressed towards solving might not show in the magazine but we have placed the file in hope. the soft-proofing issue. In practice the system worked reasonably well when we blind tested using a high-end, calibrated monitor and controlled viewing Soft proofing conditions. We were able to adjust accurately to within a few points To bias a monochrome view in Photoshop by a specific and although the size of the correction was sometimes a little off we amount we used the following method: always erred in the right direction, that is we always made a yellow 1. Open the target monochrome image in Photoshop, bias match a yellow bias even if we were out on the strength, we which should be flat for simplicity. never made it blue or neutral. The ability to use your own image and 2. Make a new Color Adjustment layer and choose a 50% at large sizes was an obvious and measurable boon and the method grey. is far superior to the preview window of the ABW dialogue box. 120 »
professional Imagemaker 118 62 119 62 » 118 PROPHOTOPRINTS Summer Promotion Maths for Colour Geeks Expected v Actual Print Values Based on an analysis of real prints we computed the PROFESSIONALS SERVING PROFESSIONALS FREE expected effect of changes to the ABW settings. In the 8 15 SHEETS PAPER graph the red squares are the expected values (based on Large Format Print & Canvas Wrap Specialists 30% EXTRA the regression analysis on the right). The blue diamonds are FREE the measured values off a Canson Baryta Photographique 6 EXTRA print. The best we can say is that the data points arrange themselves in the correct order and locations. There are, however, annoying variations, the greens for example are 4 FREE twice the expected value. when you buy The regression analysis of the ABW settings against measured 50 sheets of outcome is an attempt to find the scaling factor between 2 them. The slope of the line is almost exactly 0.1 (0.0996 to be selected A4 or A3 precise) which puts the scaling factor at 10x. The statistical Fotospeed paper fit is rather poor an R2 value of 0.74 is nothing to write home 0 about (it improves to 0.94 if you remove the outliers from -10 -8 -6 -4 -2 0 2 4 6 8 the analysis but that is cheating). Having run out of paper we were unable to refine the calculations. -2 GET MORE - PAY LESS! Michelle Heseltine imagineaworld.co.uk We use the very latest 12 ink large format printers with manufacturer’s original pigment Inks -4 and Fuji’s Premium Satin Paper and Artist Canvas to ensure the highest quality results. 10 POPULAR LARGE FORMAT CANVAS COLOUR MANAGED LARGE FORMAT SIZES PRINTS WRAPS * 9 PRINTING SERVICE FOR PROFESSIONAL PLUS WIN UP TO £50 OFF YOUR NEXT ORDER -6 18’’x 18’’ £6.75 £33.75 PHOTOGRAPHERS. 20’’x 16’’ £6.50 £37.50 8 PLEASE VISIT OUR WEBSITE FOR FULL Actual Lab Values Expected Lab Values 24’’ x 16’’ £7.25 £41.25 RANGE OF SIZES AND PRICES GOLD 7 30’’ x 20’’ £14.00 £52.50 SILVER BRONZE 36’’ x 24’’ £17.25 £63.75 ALONG WITH INSTRUCTIONS FOR 6 38’’ x 38’’ £28.00 £97.50 PREPARING AND UPLOADING YOUR FILES. £50 £25 £10 Grey Tone Reproduction 46’’ x 12’’ £17.50 £49.50 THE HIGHEST POSSIBLE QUALITY AT THE OFF OFF OFF 5 LOWEST POSSIBLE PRICES. 6 54’’ x 34’’ £41.25 £116.25 60’’ X 38’’ £45.25 £127.50 Prices inc. VAT but ex. P&P. 4 ABOVE: The plot from which the 4 Discover a medal in a Summer Promotion pack and redeem it data used to create the statistical 2 against your next paper order. Available whilst stocks last. 3 www.prophotoprints.co.uk 0
Lab Tone SHift Value (regression) analysis on the left was Near Neutrals Ref For more information or to fi nd your nearest stockist, please call us -10 -5 0 5 10 2 y = 0.0996x + 1.0905 made. -2 Near Neutrals Print ProPhotoPrints,1 Market Arcade, Halifax. HX1 1NX. on 01249 714 555 or email [email protected]
R² = 0.7435 Lab b SG Greys Ref -4 T: F: E:[email protected] * 1 01422 354008 01422 351531 Full T&C’s available online. www.fotospeed.com SG Greys Print RIGHT: The issue of brightened -6 Great Convention Feedback and Orders 0 papers in a nutshell. This very bright -8 0 10 20 30 40 50 60 70 80 paper has driven the grey’s matrix -10 ABW Setting (blue box) downwards by 10 Lab -12 points (pink box), a larger shift than the bias values we are trying to Lab a introduce – just on the paper!
CONCLUSIONS
This has been one of our more complicated escapades! The test series indicates that it is possible to achieve a very good representation of the expected result from a given ABW setting and to display this accurately on high-end monitors. The use of custom soft proofing and the simulation of the paper base tone is essential to this outcome.
Judgement of the shades of grey proved to be tricky even though the eye is most sensitive in this region. One piece of good news is that when we made test arrays onto brightened paper the eye accommodated so well that yellow biased attempts looked yellow even when the measurements of the grey suggested they were almost neutral. As expected the eye was perfectly adapting to the surrounding cool white borders and thus ‘seeing’ the neutrals as a little yellow.
In terms of settings we suggest that it is only worth dealing in increments of 10 units in the ABW Color Wheel, anything less will almost certainly be lost. So, if you make a print and decide you want it more toned, bang in at least 10 more points or more likely another 20 points. From a neutral starting point we would suggest that a 20 point change might be used to correct a subtle bias and that a 50 point change should be used to create a distinct (ie deliberate) tone effect.
professional Imagemaker Just how good is Canson In nity Baryta ?…reviewed in this issue…see overleaf 120 62