HCT overview

Updated February 2012

Overview

The HutchColor HCT is a high-precision, individually-measured ICC profiling target for demanding scanner and camera users. With about twice as many patches, a better sampling of dark colors and three times as many gray scale steps as standard IT8.7/1 and IT8.7/2 targets, the HCT can characterize cameras and scanners more accurately, especially in rich colors and dark shadows.

Benefits

For scanner operators the HCT yields more precise color and tonal accuracy, especially in richly-saturated colors and very dark shadows. This translates into more precise scans and better correction of underexposed originals. To compare results from the HCT and IT8 target, click here.

For Photographers the HCT provides a much higher dynamic range and wider color gamut than typical camera targets, allowing a greater portion of the camera's color space to be characterized.

Limitations

The amount of improvement can be influenced by scanner setup, viewing conditions, subject matter and user-expectations.

As with all camera targets, HCT profiles are optimized for the dyes or colorants in the target itself. If the subject matter's colorants have different spectral curves, accuracy may be limited by "metamerism failure", for which there is no simple solution except manual editing in Photoshop.

Flatbed (CCD) scanners with serious optical flare or uneven illumination may show less improvement than drum scanners, however high-end flat-bed scanner users report significantly improved results compared to profiling with an IT8 target.

Media and format

The HCT is currently available in the following formats.

Reflection:

5x7 inch Fuji Crystal Archive paper.

Kodak Ultra Endura. (Out of stock till further notice)

Transmission:

4x5 inch Ektachrome™ and Fujichrome™.

6x7cm (2 1/4 x 2 3/4 inch) Ektachrome and Fujichrome.

35mm Fujichrome (35mm Ektachrome discontinued until further notice).
Note: 35mm and 6x7 cm targets are cut to size from 8x10 inch sheet film and are not created on actual 35mm or 120 film, however because similar dyes are used in all product sizes, they produce equivalent results.

Choosing an emulsion:

Either Fujichrome or Ektachrome HCT targets reproduce Agfachrome™, Ektachrome and Kodachrome originals quite accurately on Heidelberg (Hell) 3000-series and Fuji (Crosfield) Drum scanners, but other scanners like the ICG drum scanner and most CCD desktop scanners require custom Ektachrome or Fujichrome profiles for precise color matching. If only one emulsion is chosen for general use, pick the one on the film type you scan most often.

Differences from the IT8.7/1 /2 scanner target

The IT8 was designed in the 1980s as a visual scanning guide. It was adopted later for scanner profiling with virtually no redesign. By contrast, the HCT was designed specifically for scanner profiling.

With over 500 discrete patches the HCT contains around twice as many samples as the IT8’s 252 (Kodak) or 288 (Fuji & Agfa) patches.

The HCT specification does not define colorimetric values for any patch, but seeks the widest dynamic range and color gamut possible with the base material.

HCT colorimetric values are approximately proportional to, and distributed more evenly throughout, the media’s available color space.

Special emphasis is given to very dark patches, both colored and neutral, so the HCT can better characterize a scanner’s performance in deep shadows, which are virtually untested by the IT8.

Special manufacturing techniques give the HCT a wide density range that better represents the dynamic range of live originals, from base-density catch-lights to unexposed film border. This means there is less chance that an HCT profile will ‘clip’ or ‘plug’ important detail in over-or underexposed areas.

A 63-step gray scale improves the analysis of non-linear scanner performance, especially in very light and dark tone - especially important with older or imperfectly-calibrated scanners.

The gray scale contains 21 “nominally neutral” patches plus 42 “off-gray” patches (absent from the IT8) with subtle red, green, blue, cyan, magenta and yellow color biases, to more accurately define a scanner’s near-neutral performance.

Twelve scales of fully-saturated color extending from white through maximum saturation to black, replace the six scales in the IT8 which extend only from white to maximum saturation.

Requirements

To achieve the full benefit of using the HCT it must be in good condition, without fading, staining or other damage.

Each HCT is individually-measured and supplied with it’s own unique numbered reference file, which must match the serial number of the target.

Benefits will be most obvious in an ‘absolute’ reproduction workflow where scans or captures are made without any custom scanner or camera adjustments and all image optimization is done afterwards on the raw RGB image (see ‘Recommended Workflow’.)

As with any other camera target, extreme care must be taken to avoid surface reflections or uneven lighting when capturing the target.