VueScan Scanner Colour Calibration

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Introduction

As some of you might already be aware, I rate the VueScan scanner software very highly. Not only does it produce excellent quality scans, it will also work with old scanners where drivers for the latest operating systems might no longer available. Whilst this alone makes it good value for money, it also includes some very good colour management features.

In this tutorial I will explain how you can use the VueScan software to produce a bespoke film ICC profile and improve the accuracy with which you scan colour. This is something a specialist will charge a lot of money to do for you or you could spend several hundred pounds on specialist software.

Before we start, it’s helpful to understand a little bit about colour management and why it is necessary.

Colour Management

When a scanner captures colour information in an image it does so using three colour channels, red, green and blue. Each colour can be represented by a combination of these three channels, for example 255, 0, 0 is maximum red (255), no green (0) and no blue (0). This colour would appear as a bright pure red to the scanner and should appear on the screen and printer as the same colour.

Unfortunately theory and real life don’t quite work the same. Equipment can vary as can factors such as film and paper. In the end, there are so many variables that it’s a wonder your prints look anything like the film you scanned in; in fact, they might not and you might have been wondering how to fix the problem.

When we calibrate our equipment we ensure that green appears as green and red appears as red and that our final printed output should match what was on our screen and also what was recorded on the film we have scanned in. The result of the calibration process is an ICC file which tells your software the unique properties of your hardware and how it processes each colour.

Calibration Target

As every scanner (even the same make and model) will vary in how it reproduces colour from a scan, we need to start from a known set of colours. This is where the colour calibration target comes in.

There are different types of scanner target but all follow the same principles for use. Each target should also come with a data file containing information that describes each colour in the target. You can see an example in figure 1 below.

The process by which you would use the calibration target is a simple one:

• Scan the calibration target
• Load the data file describing it
• Process the scan with the data file in special software to produce an ICC profile
• Use the ICC profile within your scanner software for future scans

Figure 1 – Colour Calibration Tools

If you don’t currently have a calibration target and data file you will need to purchase one. These can be expensive however I have found www.coloraid.de to be an excellent source of cheap high quality targets that are a fraction of the price of the same Fuji or Kodak targets. I should also mention that each type of film also needs its own target and calibration data as all are slightly different. This means that if you intend to scan a Fuji Velvia slide you will need to scan it with an ICC profile created from a Velvia calibration target etc.

Steps to Calibrate your Scanner

OK, enough of the theory. Here are the steps necessary to create a film ICC profile using VueScan:

1. Turn on your scanner and start VueScan if you haven’t yet done so

2. Place your calibration target into the scanner as if you were going to scan it

3. In the Input tab in VueScan select the “Task” as “Profile film”, “Source” as your scanner and Mode and Media to match what you are scanning e.g. Slide Film if your calibration target is a slide. You can see how I have my software set up from Figure 2 below. I also tend to set the “Preview resolution” to 800 or 1600 pixels, which isn’t shown in this illustration. It makes working with the calibration overlay in step 8 much easier.

Figure 2 – VueScan input tab configured for calibration

4. On your “Color” tab set the “Color Balance” option to “None”. This prevents the software from making any adjustments prior to creating the ICC profile. This step probably isn’t necessary but I like to do it to be on the safe side.

5. When you purchased your calibration target you should have been provided with calibration data, probably in a text file on a CD or DVD. Copy this onto your hard drive and make a note of the location. I tend to copy mine to the VueScan folder.

6. In the VueScan “Color” tab set the “Film IT8 data” to be the file you copied in step 5.

7. Once you are ready, click the “Preview” button to start. A preview scan should now be created and VueScan will display a grid like overlay on top of the preview.

8. Resize your overlay to match the preview of your slide. This might also require you to rotate the image until you can get the two to match and line up. An example can be seen in Figure 3 below.

Figure 3 – Preview scan with calibration overlay lined up

9. Select “Profile | Profile Film” from the menu. VueScan should respond with a message telling you that it has created an ICC file.

10. Find this file on your hard drive (it will probably be in the c:\vuescan folder) and then move it into the folder where you will store your profiles. As VueScan creates the profiles with the name specified in “Film ICC profile” box (see step 11 below) you should rename the ICC file to the type of film that you have just profiled e.g. Velvia. Take care that when making new profiles you don’t overwrite existing ones.

11. In the “Color” tab select the “Film color space” drop down to be “ICC Profile” if it isn’t already. Next set the “Film ICC profile” to be the location of the file you created in step 10 above (just remember to clear this before you make your ext profile). Finally in the “Film ICC description” type a brief description of what this profile represents e.g. “Fuji Velvia ISO50”. This is just a description so that you realise how the scanner is calibrated.

12. You are now ready to start scanning your films with a calibrated scanner. Also remember that your equipment can vary over time so I would suggest repeating the above at least every 6 months to produce a new calibration.

Screen Calibration

Having followed the steps above you might still not be happy with the scans you produce when you view them in your image editing software. This could be because whilst your scans are calibrated your monitor isn’t. This could make colours like white appear to have a blue or red tint. If this is the case then you should also calibrate your monitor.

In truth I would recommend calibrating your monitor on a monthly basis. The best way is to use a dedicated tool such as X-rite i1 which is what I use. There are much simpler and cheaper alternatives such as EasyRGB which can be accessed on the Internet. Check out the link in the Resources section of the Lenscraft web site.

If you follow the steps in this tutorial you should be able to produce consistently web balanced images from your scanner.