Creating perfect photos from your slide and negative scans with ColorPerfect: Canon, ScanGear, CanoScan
Increase the quality of your slide and negative scans from Canon ScanGear with ColorPerfect! Find out more about how to scan with your CanoScan. ColorPerfect processes scans with color integrity and gives unprecedented flexibility in creative image editing. To harness the full potential of our Photoshop Plug-in it's important to obtain image data that has been subjected to as little processing as possible (RAW data). The following tutorial gives a step by step explanation on how to achieve this with Canon ScanGear.
Creating linear scans of slides and negatives with Canon ScanGear
To create suitable scans of slides and negatives with ScanGear first select the "Advanced Mode" tab. 
The following screenshots are from a German ScanGear interface. I determined what the required settings are called in English but do not have pictures at this time. If you could e-mail screenshots of the two tabs we are going to look at next to info(at)colorperfect.com I'd appreciate it.
After bringing up the Preferences window choose the "Scan" tab. On it make sure that the option "Enable 48/16 bit output" is checked. Next select the "Color Settings" tab and activate the radio button "None". This will make the Screen Gamma setting accessible which you need to set to 1.0 in order to create linear scans. After making sure that these parameters are set up correctly exit the window by clicking OK.
Now all required settings on the Advanced Mode tab are accessible. Regardless of wether you are scanning slides or negative film choose "Color Positive Film" in the Input Settings area and then select "Color (48 Bit)" as the Color Mode. Now set the Output Resolution which is in the Output Settings area to the maximum physical resolution your scanner is capable of. ScanGear is now configured to create linear scans and you can commence scanning using the Preview and Scan buttons. The Image Settings area in the screenshot has been shortened somewhat as all settings therein should remain disabled.