The Monochrome Issue – The Output Options

What’s Important?

It is worthwhile recapping on the parameters that are especially important to the monochrome specialist and describing how they are quantified and how they affect the look of an image.

This is the maximum black density achievable by the printer/paper combination. It has to be measured with either a densitometer or a spectrophotometer. It is a measure that is endlessly discussed on the specialist forums, often by people who have never even seen a spectro let alone used one. The pursuit of high Dmax is worthless if it is not accompanied by a clean transition from white down through the tone scale. The eye is very accommodating to a lack of a fully dense black as the mind shuffles the tones into what it perceives as being about right. So, although a matte art paper may only reach a Dmax of 1.5 it may not look markedly different to a gloss print with a Dmax of 2.2, especially behind glass. The Kodak Q13 Gray Scale, a well-known calibration device, runs down to a density of 1.9 in steps of 0.1. In other than good light, it is not possible to differentiate 1.8 and 1.9 densities. Differences between 2.3 and 2.4 are even more difficult. A traditional selenium toner will add about 0.1 to Dmax with an imersion of a couple of minutes – again quite a subtle change. A print having a larger Dmax is usually described by viewers as having “more depth”. Typical Dmax values obtained by us are as follows:

The Output Options

Tonal Linearity

A smooth transition between greys right down to the richest black without any irregularities or blocking is desirable. Whilst a straight line response may seem more correct, a gentle S-curve may produce a more pleasing result, by enhancing mid-tone contrast. A printer may prefer to roll off the top of a curve to retain highlight detail and so on. The business is made more complex by the eye perceiving tones in a non-linear fashion. To this end the Lab scale of progressive greys is mathematically distorted to more closely match human vision. If you create an RGB tone scale by dragging a gradient from full black to full white and then posterising it, the relationship between RGB value and Lab lightness value is not linear (see graph). In a profiled system you will find that RGB values below about 15 points will not be differentiated (ie 15 RGB points will appear the same black as 0 RGB points). This will depend upon the linearisation if the system is controlled by a RIP – linearisation is part of the process of profiling a RIPbased printing system. The bottom end of the tone curve (the shadows) is affected by the choice of media setting on an Epson printer and you should experiment if you are trying different paper types, starting with a guess at the closest match. As we reported in our review of the Epson 7800 some months ago, a choice of Textured Fine Art was poor in comparison to Smooth Fine Art when using Hahnemühle Bright White Photo Rag (see top graph).

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The Output Options

The graph, above left, shows the non-linear Lab response to RGB values. The pair below show the effect of changing the media setting while keeping everything else the same. The maximum black is reached with less ink for the Premium Glossy Photo Paper 250 than for say the Smooth Fine Art setting. The space between values is from 10% to 35%, quite a large difference. In practice this is to account for the art paper needing more ink before it becomes saturated. Correct profiling will account for these differences but it shows the importance of keeping to the same media setting between profile-making and usage. The graphs also show why you can make changes to your print density by deliberately using different media settings, something that you might try from a position of knowledge, rather than guessing!

One of the outcomes of this linearity (or lack of it) is that you may have to make additional corrections to your image after you have adjusted it to taste on your monitor. Experience teaches that the most unreliable aspect of monitor calibration is the mismatch between the grey levels shining out of the (transmissive) monitor and off the (reflective) print – they ain’t the same thing! The best tactic is to print out an RGB grey step scale, note the effect, in a print, using your preferred conditions and then develop a curve to true it up. This curve can then be applied before printing a monochrome. If you own profile editing software you could adjust your profile to take account of the effect.

As well as the media setting chosen for a print, the resolution also affects the density of the print. This rises progressively as the resolution is increased from, for example, 360dpi to 2880dpi. The graph (top) indicates about a 3% difference between 360dpi and 2880dpi when everything else is kept the same. The Dmax rises from 2.04 to 2.27 as shown in the table. These differences are smaller than the effect of the media setting.

Tonal Neutrality

The base tone of the print should be colour neutral or at least controllable for a warm or cool tone. The new Epson Advanced Black and White driver offers a superb way of controlling this effect. However you could use some of the techniques describe previously to either add a desired tone or even correct for an undesirable one. The Output Options

Tonal Cross-over

When all the colours of an ink-jet printer are used, the underlying base tone colour of the ‘neutral’ should not waver along the tone scale from black to white. This can occur because of a poor profile or a variation due to coloured inks being substituted, in varying proportions, with black and grey inks. Variations in the ¾ tones and above are particularly noticeable. In the example shown below, the lower quadrants of the Lab plot are shown. Pure neutral is marked with the white square. The print from an un-profiled ink-jet printer starts off slightly blue, the colour of the base of the paper. As the greys become darker, the tone bias moves ‘south’, ie more and more blue, until it peaks at the near-black, before returning towards more neutral for the true black. Plots such as these come in all shapes and sizes from unprofiled printers attempting to create monochrome, sometimes wandering back and forward across the neutral point, sometimes visiting every variation of tone bias. This example is quite strongly blue-biased – a good profile would keep the grey neutrality within a Lab point of the paper base – notionally shown by the red ellipse. Metamerism may also vary as different proportions of the coloured inks are mixed onto the print.

Total Cross

Metamerism

The colour appearance should be relatively stable in different types of illumination. Metamerism has been described before in Professional Imagemaker. Typically a print will appear neutral in tungsten light but turn an unpleasant green when viewed in daylight. The metameric index is a measure of the size of the colour shift. It varies according to the colour and so we standardise on a 50% neutral grey changing from D65 (daylight) illumination to Illuminant A (tungsten). The measure is expressed in Lab units as a delta E (ÄE). For more detailed studies we assess metamerism along the length of the tone scale from black to white to assess the effect of changes to the grey make-up.

OUTPUT OPTIONS

From the outset you have had two options – to make a colour to mono conversion and then print this uncoloured RGB file or to go straight from the coloured RGB file and print it either with black ink or a mix of nearblack inks. The latter, of course can give you a toned print on demand.

While many specialist monochrome workers will want to have the total command afforded by conversions at the Photoshop stage, there also exist a large group of social photographers who may wish only to get a commercial quality monochrome to their clients and move on to the next portrait commission.

We set out on the previous pages what to look for in a quality monochrome print, now we look at how to get there from an image. If you have to print mixed colour and monochrome images on the same page your choice is very easy – you go for the Epson UltraChrome K3 ink set, which is superb on both colour and mono. It is also true that this solution would be commercially just right for many professionals who were not specialising in fine art monochrome output.

If you are fanatical about your mono printing and are really trying to emulate exactly what you make in the darkroom then you have some important decisions to make – read on!

Staying in the Black

The Epson 2100, 2400, 7600, 7800, 4000 and 4800 printers all provide the option of printing using the “Black” radio button, as shown in the screen grab. The Advanced dialogue provides for variation in Contrast and Brightness as well as a gamma setting. The gamma setting also controls the overall lightness and darkness of the image; a setting of 1.8 creates a print that is about 5% lighter than one using a gamma of 2.2. The results using these methods are less smooth than when all inks are employed and are best described as slightly gritty. They are, by default, almost totally neutral as only black inks are used. In practice pure carbon black has a slight brown (warm) tone, which sometimes shows through in black-only printing. Some enthusiasts overcome the lack of ink coverage (the source of the grittiness) by passing the media through the printer twice – not really a professional solution but some like it.

The Smooth Option – all the inks

Firstly you have to decide if you want the life of pigment ink or can accept the lower expectations of dye ink sets. This mainly affects metamerism. Assuming that you go for pigment you have to decide on the level of metamerism that you are prepared to put up with. More than 3, you can go to UltraChrome ink and the Epson 4000, 7600 or 2100 – but be quick, they are now discontinued for all practical purposes. If you want a Metameric Index of less than 3, you have to look at UltraChrome K3 ink (Epson 2400, 4800, 7800, etc) or maybe a Colorbyte’s Imageprint RIP which can get UltraChrome below 1 with a bit of care.

Moving away from Epson (printer and ink) your options are many. If you wish to tone your prints at the printing stage (rather than in Photoshop) you have to move to Epson K3 UltraChrome, Permajet MonoChrome Pro, Lyson Quad Black, Lyson Small Gamut, or go abroad for the MIS UltraTone, Media Street Generations QuadBlack or Piezography Neutral K6 or K7 ink sets. All of these may be driven through the freeware, QuadToneRIP (www.quadtonerip.com). One of the interesting outcomes of our research at Focus was that all the suppliers were a little downbeat about multi-black – all felt that it would wither on the vine as the Espon K3 ink set was easily capable of doing the job. This is not a view shared by the specialist monochrome groups but they tend to focus on method and effect, rather than earning a crust – there is a huge difference! Options

Once you have moved to pigmented inks you are almost committed to the use of fine art and matte papers. In the main, gloss and lustre papers do not accommodate pigment black without some flouriness and delicacy of surface. If you are using K3 Ultrachrome ink you have to choose between the all-surfaces-compatible PhotoBlack ink and the matte/fine art-only MatteBlack ink. The penalty for using PhotoBlack K3 instead of MatteBlack is a small loss of Dmax. This is not a problem for commercial work but does bug the specialist monochrome printers. The inks may be switched in the Epson x800 series printers, but it wastes about £45 worth of ink. There is a solution called “Phatte Black”, which is based around the Colorbyte RIP and replaces the K3 Light Light Black with a full black so that the x800 Epson series printer can have both Matte- and PhotoBlack resident on the same machine. This strikes the writer as a bit of a dog’s dinner solution. The Colorbyte RIP costs almost as much as an Epson 4800 so why not buy two printers!

The multi-black ink systems comprise sets of up to seven black and near-black inks – ‘near’ being lighter or coloured, usually both. They are typified by the MIS UltraTone which contains

Eboni – Full Black
75% Black
50% Black
25% Black
Light Black
Cool Toner
Light Cool Toner

These are mixed by use of curves or the QuadTone Rip to create neutral or deliberately toned prints. By itself, pure carbon black is slightly warm (brown) and this is offset by the use of inks cooled with an inclusion of cyan.

The Permajet Monochrome Pro ink set adopts a slightly different approach in that the RGB image is manipulated in the Curves Dialogue, which then controls the mix of toned inks. You have to rely on experience to deliver the tone you are seeking with this system as the curves distort the onscreen appearance very significantly. Monochrome Pro is, by now, reasonably mature technology, it seems amazing that it was October 2004 when we reviewed it first in Professional Imagemaker.

Total ink LEFT: Metamerism is influenced by a number of factors including ink, paper and the actual ink mix density. In the graph, the data are actually quite good, but both the K3 Ink (4800) and Permajet Monochrome Pro are ahead of UltraChrome (7600) on Premium SemiGloss. The effect of paper in discussed later in this feature.

Grayscale

grayscale

QuadToneRIP

Not being willing to sacrifice one of the office printers on the altar of monochrome, we pulled in expertise from SWPP/BPPA member, Jamie Creed. By his own admission, Jamie has devoted considerable time to QuadToneRIP (QTR) with a view to achieving excellence in his monochrome output. He now feels that he has it under control, certainly enough to be mixing his own ink sets and developing user-curves to control it. QTR is a free down load RIP, specifically designed for mono output. It works with multiblack ink sets or full-colour ink sets such as K3, that have a number of monotones to play with. The pdf manual consis option ts of 26 pages and covers set-up, operation and tuning your output. The RIP will handle TIFF files in RGB or grayscale mode at either 16 bit or 8 bit.

The key feature of QTR is its ability to create, install and use curves, which govern the relative proportions of each “black” ink in the system. It is not worth typing out the entire method as it is freely available and comes with the software down load. Suffice to say that you print out a tone scale (see image) measure it and feed back the information to the

Below: The basis of the QTR is to mix together two different tone inks to control the final output colour. The interface is both clever and sophisticated – all for free! software/driver. In use, you blend a mix of warm and cool tone variants to create the “neutral” of your choosing. The control that you can achieve is impressive.

option

Dodging & Burning – Bit Depth

It is one of the ironies of digital imaging that those of us who specialise in quality issues (colour and image) spend our time imploring people to shoot RAW, stay within a single colour space at all times and avoid jpegs, etc – all on the grounds of avoiding pixel decimation. In the next breath the demands of composition call for the image to be darkened around the edges, blurred, glowed, burned in there, held back here, all of which produce untold amounts of pixel damage. The whole business is thus a matter of compromise. In a wet monochrome darkroom dodging and burning is absolutely routine, almost universal. If that fails to get the job done, out comes the ferri! The whole business was best summed up by a deceased friend of mine (who I think got the quote from a guy called Bill Hurst) namely, “print it how you wished it had looked not how it did look”. Paul Gallagher discusses the dodge and burn topic later, but the main difference between wet chemistry dodge and burn and Photoshop is the undo button, or, even better, the use of Adjustment Layers. A general rule though is that going back and forth should be via the History Palette, multiple undo or Adjustment Layers – plain dodging following by burning is a complete no-no; indeed you are best to avoid the Dodge and Burn tools altogether!

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This leads naturally to that old chestnut, 16-bit or 8-bit as your starting image mode? The pro 8-bit camp says that you cannot see the difference in the printed image. However there is an argument that if you are going to beat the heck out of the pixels you are best to start with more bit depth so that you have more editing leeway for pixel degradation. The combined screen grab shows histograms of masking channels from an image, manipulated in 8-bit and 16-bit. The missing data in the 8-bit histogram of the alpha channel is revealed by the “gappy” histogram in just the same way that you see gaps in the histogram of the image pixel data. Such deficiencies ring alarm bells and things are likely to worsen if you start to adjust the alpha channel by greyscale clamping and choking.

One outflow from this discussion is that you are no worse, but likely to be better, from deriving your mono image from a RAW file, desaturated and opened in 16-bit. To keep some perspective on this issue, if your images do not show any problem at the size you print them then stay with 8-bit. Reprocess any difficult images as 16-bit on an as-needed basis.

Eliminating Posterisation

This bit is robbed more or less directly from Ben Wilmore’s book, Photoshop CS Studio Techniques (Adobe Press). Given that you have ended up with posterisation, in spite of the precautions you have taken, here is how to get rid of it. Bear in mind it is quite a slow process. Set your Magic Wand to a tolerance of zero and click on a posterised area. The low tolerance is just the ticket for posterisation, which, by definition, is a reduced number of tones. Then click Select>Modify>Border and use a setting of 2 for slight posterisation, 4 if it is heavier. The apply Gaussian Blur to smooth out the area. You have to go all over the image doing this, which is why it is painstaking (and only feasible for really important shots!).

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