The raw-3f file format, "Flexible-File-Format", is an extension of the TIFF standard specific to Hasselblad.
This format encodes and encapsulates:
- the raw-scan image (16-bit per colour channel)
- the complete history of image processings performed under FlexColor
- a thumbnail for quick preview under FlexColor
- IPTC metadata, including keywords to allow indexing of the image into a database
This is the encoding format of the output images of the scanner. Encoded images can be post-processed directly in this format using Hasselblad's FlexColor software or imported for Adobe Photoshop editing using a specific plugin. The manual settings made in FlexColor can compensate for the color profile of the film scanned as Photoshop allows you to go beyond, especially to mask the residual artifacts from scratches and dust. The interesting feature of post-processing work done under FlexColor is that they do not affect the raw scan image embedded in the Hasselblad raw 3f file. The parameters set during a work session are organized to form a recording block in a "history of settings." This history is updated whenever the FlexColor user triggers a backup or export to TIFF. The current FlexColor settings can be reset based on any record in the raw-3f file settings history. It is only when the user proceeds with an export that FlexColor applies the current settings to the produced image alone. The export is always done in a TIFF format. It is therefore possible to generate as many different renderings in TIFF as you want from the same raw-3f file. It is obviously possible to record a neutral set of adjustments, all linear curves, in order to produce an exact digital version of the raw image lying on the photographic film.
In conclusion, the raw-3f is the only format that embeds both the true "raw scan" image, in all its precision, while encapsulating at least one set of tone and colorimetric adjustment. This is the ideal format for any user who wants to maintain a custom 3f workflow under FlexColor to export as many TIFF files as desired renditions, with the understanding that localized post-processing should be done using other image editors, like Photoshop.
FlexColor software is freely downloadable from the Hasselblad technical support.
The plugin for Photoshop that allows you to import files in Hasselblad 3f format (suffix in "fff") is also available for free download from this same URL.
The TIFF-6.0 format was designed to carry a raw, pre-processed image, as generated by an image capture device. It is structured so as to adapt ideally to the encapsulation of this main image and all of its descriptive meta-data. It also has the ability to encapsulate one or more thumbnails for quick preview.
This format can also be considered the high standard to carry a full quality image in a post-processing chain. The basic version of this standard (baseline TIFF) can be enriched by many standard extensions that add specific features. This is for example the case of the Adobe-DNG format. It should be noted that, unlike the "baseline TIFF" version, not all extensions are supported by all image editing softwares. Furthermore, metadata included in the baseline TIFF version are already very complete.
DNG (Digital NeGative) is an extension of the TIFF standard defined by Adobe. This format was designed to solve the compatibility problems related to the diversity of proprietary raw formats that are produced at the output of various equipments (DSC, scanners, etc.). It is therefore supposed to become a generic raw format, in which Adobe has included a number of missing features in most proprietary raw files. The main purpose of the DNG format was to establish itself as the standard for encoding a digital equivalent of the film, commonly called "Negative".
Despite the fact that Adobe continues to evolve this format, few hardware vendors have adopted it, preferring to promote their own raw files. It should also be noted that DNG is still only partially supported by Adobe's image editing software.
The raw-3f format, the original raw-scan image format output from Hasselblad scanners, can not be converted directly to DNG format. The only way to do this is to go through a preliminary step of exporting the raw-3f file to a TIFF format from FlexColor and then convert that resulting TIFF to DNG.
JPEG-2000 (ISO/IEC 15444-1) relies on an image encoding system using wavelet-based binary compression techniques. The quality of the encoded main image is parameterizable, according to the requirement specification on the bit weight of the resulting file and the tolerance to possible loss of information.
This standard makes it possible to compress the data of the main image without loss of information while retaining the original colour depth of the "raw scan" (16-quantization bits for each primary R, G, B). In this configuration, the compression ratio is relatively low, but the full quality of the scanned image is retained.
The conversion to JPEG-2000 also involves a preliminary TIFF export of the Hasselblad raw-3f file, which can be done with FlexColor, then conversion of the resulting TIFF file to a final JPEG-2000 file.
JPEG vs JPEG-2000 comparison
While the JPEG standard (1992) has become the default interchange format for compressed images in binary weight, it should be remembered that this standard does not allow the coding of the full quality of the digital images produced. Its main shortcoming comes from the low colour depth that it allows to encode (8-bits per R,G,B primary). Even if the non linearity introduced by the gamma expansion (1/2.4) makes it possible to adapt this low quantization precision to the sensory characteristics of the human eye, that is to say increase the quantization precision for dark tones, this is done at the expense of midtones and even more of the hihglight regions. The drastic 8-bit quantization reduction per channel imposed by conventional JPEG is obviously not suitable for a use where the preservation of original quality becomes a critical requirement. A first consequence of this limitation is the maladjustment of conventional JPEG to image editing. More generally, this lack of precision in the encoding of hues and luminance reduces the dynamic range, or discernable colour range, to an unacceptable level with regard to the quality of the image signals generated by the high-end photographic equipments.
The dynamic range of the Hasselblad Flextight-X5 scanner reaches almost 16 stops (Dmax 4.9) at the imager output, which makes it possible to cover the densitometric range of the best silver emulsions. To preserve this richness in colour depth while proposing a compression of the binary weight of the digitized image, it was necessary to consider another encoding principle than the conventional JPEG.
This is precisely the raison d'être of JPEG-2000.