Canoscan FS4000US ICC Profile

I decided to get serious about profiling my Canoscan FS4000US slider scanner, due to having several years of slides from the period before my switch to digital.

My Canoscan FS4000US scanner is a couple of years old now (costing around $1500AUD when new), but provides high resolution images from slides and negatives.

For years I have wondered about what profiles to apply to my scanned slides. I tried hunting around on the web to see if there was some kind of boxed ICC profile available, but could not find anything.

For a while now my standard procedure has been to import the images from the scanner into Photoshop, assign the sRGB profile, and then convert to my default workspace profile of AdobeRGB. I have tried assigning AdobeRGB profiles directly to the scanned images, but it resulted in over saturated images.

Noticing my images were slightly washed out after conversion, I began to question how much color information has been distorted in the workflow process.

Producing the scanner ICC profile

The first step was to purchase a couple of IT-8 slide targets from Wolf Faust (www.targets.coloraid.de). They were well priced, supplied very promptly, and good quality. Wolf has lots of interesting stuff on his main site www.coloraid.de about color management.

To produce the profile, I then downloaded and purchased the Profile Mechanic software from Digital Light and Color, which made the process of generating a profile very easy, and gave me the ICC profile required.

The generated profile is specific to the individual scanner, settings used, and the type of film the images are shot on. Most of my work was on Fujichrome Velvia100 and Provia slide film.

Using the ColorThink software from Chromix, and comparing the new profiles to  the AdobeRGB and sRGB profiles, the scanner profile was surprisingly large.

The profile comparison above is for a Provia transparency slide, scanned at a gamma of 2.2.

The real world result

Scanning a sunset image, I assigned the CanonscanFS4000US provia profile, converted it to AdodeRGB, and then used the curves option in Photoshop to bring up the highlights.

profiled12

The curves screen shows the pixel input is distributed from 0 to 207.

Assigning a sRGB profile to a copy of the original image, and converting to AdobeRGB, the curves screen shows a gap in the area of darks and highlights.

unprofiled12

Using the curves tool to bring up the darks and highlights, the input pixels were distributed between 10 and 222.

Therefore the dynamic range of pixels is about the same in both images.

A closer inspection of the curves graphs show more pixel information in the shadows region of the curve for the ICC profiled image. This produces a more natural and correct result compared to the original scanned image.

I am now in the lengthy process of going through my slides and reprocessing them using the correct scanner ICC profile.

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