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Better Digital Black and White printing on your Inkjet printer
Black and white printer profiling (of a sort)
Although ICC profiles and calibration may be the best way to go, is there an easier and cheaper way?
Note: Keith has written a new article about his approach to printing digital black and white that reflects newer (2007) developments in the field and how he makes his prints.
Simple B/W printer profiling with a scanner
Keith wrote this article some time ago (2004) based on some of his teaching experiences with 'less than optimal' set-ups of computers and printers.
Much of what is mentioned is still very relevant to a basic understanding of printing and what profiles do.
We've heard from people who've used this technique with laser printers and other printers that you would not normally think of profiling.
Elsewhere on the site we have quite a lot about colour management and printing covering many of the methods of getting really good prints. These techniques are not that complicated, but are beyond what many people wish to spend. If you have converted some of your color images to black and white, using the techniques on this site you might well want to print them...
As a result of some of my teaching experiences, I've been looking at ways of improving printing results with a more limited set-up. The software you use, needs to support adjustment curves – I was using Photoshop, but other packages would do. Many people are disappointed with monochrome printing on Inkjet printers, but there is generally no reason that the printer itself cannot reproduce a good grayscale image.
At Northlight we have (2004) a range of printing solutions:
I use a fully color managed workflow with appropriate profiles for the paper types I'm using.
What about if you don't have ICC profiles for your printer, or have no way of applying them in your printing set-up? I decided to look at creating a set of adjustments that you could apply to an image before printing, which would act in the opposite sense to faults in the printer / printer driver / ink / paper combination. If you read my SpyderPrint article on printer profiling you will see that the process I'm describing here is a similar process, only rather less precise.
I'll stick with my color managed workflow for my final prints, but what about quick proofs and other experiments where I don't want to use expensive paper and ink? I have an HP K80 all in one printer/fax sitting in my office – it's a PC only printer (according to HP) but I've got it running as a networked Color Postscript printer using hpijs on a Mac.[Update 2014 - there are still many old printers supported on Macs, but you'll have to do a bit of digging to find what settings work for them]
The example discussed here shows how I managed to get appreciably better black and white prints from it.
The steps involved in the process are:
Repeat as necessary until you are satisfied, or throw the printer out of the nearest window.
First of all, make sure that your monitor is reasonably well set up – there is some more info on this on the Viewing page.
You will need a flatbed scanner to check your test prints – this will have its own errors, but we are not going for precision here, just a noticeable improvement.
Remember that this is a report of some experiments. By all means follow the steps below, but be prepared to see what works best for your own set-up. I really would welcome comments/suggestions...
This has a known range of gray patches which you will compare to what is actually printed in subsequent steps.
A range of bars from black to white in 5% steps.
There is also a continuous ramp and some larger patches of solid gray.
The numbers below the patches represent the RGB values for that patch.
You can download a (zipped) TIFF version.
Oct 2005 - I have also produced a special B&W printer test image that I now use specifically for Black and White printer testing
Photoshop tip - Making a Step wedge.
First, make a selection the size you want. Use the gradient tool to select from one end to the other. This will give a smooth ramp.
The stepped wedge was made using the Posterize command to posterize the ramp to 21 levels - giving 5% steps.
We know what the test image should look like, but what does our printer make of it?
Print out the image with your normal print settings, on the paper you will be using for your prints (you will probably end up using 3-4 sheets). It might be worthwhile first trying out this technique on relatively cheap Inkjet paper, rather than your best (expensive) photo paper.
Now leave it to dry – overnight is best. It really does make a difference.
Look at the print under a variety of lighting conditions and viewing angles. There will probably be an overall color cast to the print, with variations over the range of the print. Notice how some of the variations in the smooth ramp may not show up in the step values. There is no point in having a perfect print at 45,50 and 55 percent if there is a noticeable darkening at say 47 percent.
You should also try printing with just black ink (usually a setting when printing). Most likely the images will be more even in tone, but much coarser, with noticeable dots visible. It gives a good contrast with the color ink print and makes it easier to spot color casts.
As you will quickly appreciate, it is very difficult to quantify small tinges of color by eye ... and don't forget to allow for your own color vision in this
We now have a test print, which probably looks a bit different to the version on your screen. We need to quantify the differences before we can correct them. This is where our flatbed scanner comes in.
Scan the print at a good resolution into your image editing application (all the screenshots are using Photoshop 7 on a Mac).
I used an Epson Perfection 1200U at 600dpi. Since we are doing the final adjustments by eye, errors in your scanner should not cause too much trouble. I tried a cheap USB scanner as well. The differences were negligible.
My first shock was the colour of the scan. The actual print really did not look this magenta color (more a steel gray).
A detail from how my scanner saw the 50 percent bar (middle).
Notice the colored ink dots - this was printed at 300dpi on an HP K80
The dither patterns produced by the printer driver software are very apparent if you scan and enlarge an inkjet print. This would not be visible to the eye at normal viewing distances.
The dots make it difficult to get an accurate reading of RGB values with the eyedropper tool (even at 5x5 samples) -- so the image was given an 8 pixel Gausian Blur. The step wedge was then copied to a new document and desaturated to see just the luminance values. A histogram view confirmed the unevenness -- as well as the need for setting white and black points.
The scan is converted to a grayscale stepped wedge.
You can clearly see the non linearity in the wedge, with the right (brighter) half scrunched up, and some unevenness in the 100-80 percent area.
Setting white/black points
Using a levels adjustment to set black to 0 and white (actually the white of the paper) to 255 we get a histogram with even more visible unevenness.
The 'nicks' in the display are from the resampling that happened when changing the levels. A 0.5 pixel Gausian blur will smooth the graph.
I've overlaid some figures to show the uneven steps.
To the right, a 'perfect' histogram.
The aim of this technique is to produce an adjustment curve that you can temporarily apply to an image for printing.
It will introduce changes that correct those in the printing process.
If a tone is printed too light then you make it darker by the adjustment, so as to get the 'correct' tone in the print.
Crate an adjustment curve layer, and using the sample tool (eyedropper) look at the value for the 50% bar (even after the blur you should try several points and get an average - this is not high precision stuff).
Right: A first curve
The 50% point is too light on the print so we make it darker. This is the middle point on the line.
Several other points have been added, with the numbers (35,38) referring to the third point. Here we are making the image slightly brighter
It really is a matter of trial and error, but when you are happy with the curve, save it (with a helpful name). You will have a small .ACV file which you can load as an adjustment curve for other images. This is your 'printer profile'...
Now we have a curve, it is time to see if it actually works when applied to the printing of our test image.
Open your test image, add a curves adjustment layer and load your curve. The nice grayscale of the test image should now look somewhat less even.
Print the image with the same print settings as before — and remember to leave the print to dry. As I said earlier, overnight is best. If you are not quite convinced, do a scan as soon as the print is dry to the touch, and one the next day. The differences will not be huge, but we are looking to compensate for minor changes in this process.
Compare the two prints, the second one should look somewhat different — hopefully much more like the test image.
You have carried out much the same process as creating a custom ICC printer profile. Obviously much less accurately, but the principles are similar. If you have read my article on DIY printer profiling with the PrintFIX you should see the similarities.
Did it work well enough? This is where your judgment really comes in. For myself there is a point, much like working on a photograph, where I decide that it is 'good enough' and let it go. If you are a real perfectionist, this technique will use a lot of paper and ink. Then again, if you are that bothered, you ought perhaps be looking at special inks and 'proper' color management? I did say that this was an experimental technique...
There are several ways of proceeding now. You could go back to your first scan and alter the curve, or you can repeat the scanning process with the new print and make a second curve. The choice really depends on how good the first curve is. If it is fairly good, then it will be difficult to make the minor adjustments needed without upsetting other parts of the curve. If it's not very good, then have another go (now you can see why I suggested starting with cheaper paper)
This is the histogram of the second print, after blurring, desaturating and setting white/black points, as before. It was printed with the curve above.
A much better histogram in the top half, but a bit more work needs doing in the dark areas
I made a second curve with very minor adjustments
A second curve with small adjustments
Both curves are saved and applied to an image just for printing...
Right: Curves layers
That was about as far as I wanted to go, given that I'm using a completely uncalibrated scanner, and the test print now looks fine to me!
The problem of color casts in black and white Inkjet printing is a difficult (i.e. not cheap) one to solve. The manufacturers of the PrintFIX specifically point out that the solution is intended for color prints. If you want top quality black and white, then you are either going to need different inks, or a good professionally made profile.
That said, what can we do using the techniques outlined above?
Using the black ink only print of the test picture, we can get a feeling for how much of the color we are seeing in the scan is being contributed by the scanner and paper.
Right: Two 'Black and White' prints.
A much reduced scan (after Gausian blur) of two prints of the test wedge. The top one is with all 4 printer inks and the bottom is with black only.This really shows the color cast that the scanner picked up from the print. In normal viewing conditions the top print looked more of a steel gray color to my eyes.
As I said before, the colour cast in the top print really was not that bad! Assuming that any color in the bottom wedge is from scanning errors we can create a levels adjustment layer to bring it back to a grayscale. The black ink does actually have a slightly 'warm' tone, but for the purposes of this adjustment we will assume it is neutral.
Use the white balance eyedropper in the levels dialogue to make the 50% Black Only (BO) bar gray (r=g=b). You will have to experiment a bit to find the best part of the BO wedge to get a good Grayscale.
At this point the colours of the top wedge looked a bit more like the faint color I could see on the actual print - but too intense.
A Hue/Saturation layer was used to desaturate the image until the colors looked similar to the print (fortunately my monitor is calibrated, so that source of error is minimised).
We now have an image that looks pretty much like the print. With yet another (new) curves layer, we use the middle eyedropper to try and make the top wedge neutral gray. This really shows up the variations in color cast. It is perhaps best to take the sample from the continuous tone wedge for this.
Save this latest curve as your color adjustment layer. Use it and your levels adjustment layer(s) to do a test print. With any luck you will have a reasonable black and white print ...
... well at least better than you started with.
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Having done this manual profiling, perhaps you will have a better appreciation of the skills, hardware and software required to do the job well :-))
I've used my unprofiled K80 printer with two curves for doing quick drafts of black and white images I'm working on - it gives a good approximation of the tonal range I'll get with my 1160, without using up special paper and inks.
If you find this article useful or have any suggestions relating to the techniques outlined - please do let me know.
I've written a review of the Eye One Design from GretagMacbeth where I use the same K80 to check out the 'Easy RGB' profiling function. There is also a review of Scanner profiling which would make the process desribed in this article much more accurate.
There is also a review of the MonoChromePro ink set from PermaJet where I discuss setting up the shareware QuadToneRIP to get the best out of specialist pigment inks installed on an Epson 1290.
Using QTR and PrintFIX PRO for better black and white prints
Digital black and white printing
Unwanted monochrome tints
The views in this article represent those of Keith Cooper.
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