Where can I find more information on Photo CD?
There are still some documents on the Kodak site, but the most comprehensive site that I know of is Ted Felix’s site
. Ted’s site also has links to a lot of other useful sites.
Is there a completely free way to convert PCD images?
Yes, there is pcdtojpeg
. pcdtojpeg runs on Windows, OS X and Linux, and uses the same decoder library as pcdMagic, and is open source GPL software. However, it's a command line program, and lacks several of the more advanced features of pcdMagic. There's a comparison of features here
Does the trail version of pcdMagic expire or have any adware in it?
No, the trial version never expires, and has no adware, doesn't install any other software on your system, doesn't ever "phone home", doesn't collect any information from your system, etc, etc. It is identical to the full version other than being restricted to only exporting up to Base resolution images, and not providing advanced interpolation.
How does pcdMagic work with OS X 10.8's "Gatekeeper" security?
As of version 1.1.1, pcdMagic is a code signed application that conforms to Apple's highest "Gatekeeper" security protocols as implemented in Mountain Lion.
Gatekeeper's default setting will allow you to run pcdMagic without any change. However, if you have difficulty, go the Gatekeeper settings in System Preferences > Security & Privacy > General, and select "Mac App store and identified developers" (pcdMagic comes from an "identified developer").
Is there a Windows version of pcdMagic?
Yes. You can find it here
Is pcdMagic color managed?
Yes, pcdMagic is fully color managed:
- Exported JPEG images are in the sRGB space, and are correctly tagged with the sRBG profile. So any color managed application will display colors correctly;
- Exported TIFF images are in the ProPhoto color space and tagged as such;
- Exported DNG images have no embedded color profile, but are encoded in such a way as to offer the equivalent of the ProPhoto space.
Why are exported JPEG images in the sRGB color space rather than something wider like Abobe RGB?
sRGB covers the entire normal PCD gamut, so if you have not extensively post processed the image (e.g., increased color saturation) there’s no loss of color information, and sRGB images have the best chance of displaying correctly on non-color managed systems. If you have extensively post-processed the image in pcdMagic, you should select the TIFF export option rather than JPEG. The TIFF option uses the ProPhoto color space.
Why are the color profiles required - I thought that the PCD scanning process automatically adjusted color?
As originally envisaged by Kodak, the PCD scanning process (and specifically the SBA or Scene Balance Algorithm) adjusted the scan parameters to get an optimal image, color rendering to a single standard, and adjusting exposure, contrast, etc. In practice, there are a number of problems. Firstly, the SBA required that film type be correctly identified. However, even if the film type was correctly identified, SBA's white balance algorithm was relatively easily fooled, and was often disabled. In addition, over the life of the Photo CD format, at least two different generations of scanners were used, and several versions of SBA were used, with different results. You can check the SBA status for each individual image in the metadata information that pcdMagic prints out. As a result, in order to get optimum color rendering, film and scanner specific profiles are required. Kodak eventually release six profiles (Kodachrome, other reversal and negative film stock for each of 4000-series and 2000-series scanners)
Why do I sometimes get better color by manually selecting a color profile?
Color profiles are normally automatically selected by pcdMagic, based on the film and scanner information as recorded in the image metadata. However, the Kodak scanners required careful setting up to give optimal performance, and to detect film type correctly. Unfortunately, in many labs this didn’t happen. As a result, pcdMagic also allows for color profiles to be set manually.
Can I use Kodak Color profiles - I've never been able to use them with any other software?
Yes, pcd Magic can use the original Kodak color profiles, if you have them available. The original profiles are YCC, not RGB profiles, which is why most other software packages can't use them. However, pcdMagic makes special provision to them. To use them, you need to do two things:
- Enable external profiles in pcdMagic's Preferences.
- Install the Kodak profiles as ColorSync profiles, as described in the Apple ColorSync Utility manual.
Is there a difference between the Kodak color profiles and pcdMagic's internal profiles?
Yes, there is a difference - pcdMagic's internal profiles are RGB profiles, designed to emulate the original Kodak YCC profiles. This both for reasons of copyright, and because RGB profiles give slightly faster image load times. However, in our tests there is no visible difference between the internal and Kodak profiles.
Other image conversion solutions, including most commercial software, blow highlights, get the colors wrong, or only convert at low resolution. What’s so difficult about PCD files?
The PCD format was developed in the early 1990’s, when many of the color standards that we take for granted today didn’t exist. In addition, the format was designed in such a way that it could display on the TV’s of the day with very cheap and simple hardware. The most notable “gotcha’s” are:
- Kodak has publicly released only small parts of the the PCD specification. Understanding it at all is a challenge - Hadmut Danisch reverse engineered the format in the early 1990’s and wrote hpcdtoppm based on his work. Subsequent to that, various additional pieces of information have leaked into the public domain, but despite Kodak abandoning the format, Kodak have declined to make the detail of the format public.
- The PCD color space is a TV color space (SMTPE), but Kodak allowed for levels of well over 100% of nominal. This is ok for driving an analog TV, but a problem when converting to modern digital systems. Virtually all color management systems on PCs today (be they Apple, Windows or Linux) are based on the ICC model, which simply has no concept of greater than 100% levels. As a result, a simple conversion into a modern color space will either result in incorrect colors, or blown highlights. Often both.
- The PCD format uses a form of gamma encoding that at first sight, looks very much like sRGB. However, it’s actually subtly different. Many converters assume that they can apply a pre-packaged sRGB gamma curve. Unfortunately, this results in an image with the mid-tones displaced.
- The PCD file format, because it was designed to allow display of base images by very simple, low-cost hardware, encodes images as a low resolution base image, together with a series of incremental resolution enhancement images, and then uses Huffman compression on the incremental images. In addition, the chroma is subsampled. These types of encoding algorithms were abandoned in the 1990’s as inefficient compared to e.g., JPEG encoding which compresses two-dimensional blocks of pixels. As a result, decoding images at full resolution is much more complex than is the case for most modern image formats which use a relatively small number of encoding techniques for which well established bodies of source code exist. For example, almost all modern raw image formats are simple variations of the EXIF format.