Many digital cameras allow storing unprocessed photographs in a raw format. Those are frequently pixel by pixel copies of image sensor cells compressed for saving space. Apart from those raw pixels cameras may embed other information, like camera settings, photo parameters, and JPEG preview image. It is this preview image that is of great interest to ExifPro. Decoding real raw image is an arcane task that is camera specific, while relying on provided JPEG is safe for preview purposes.
Note: While using ExifPro's tools be aware of the fact that ExifPro is frequently showing just a camera provided preview image rather than decoding raw photo.
CRW is the original raw format used by Canon in cameras like EOS D30. This format has embedded JPEG image. EXIF block is only provided in a separate THM file. As long as THM images are present ExifPro will read them, so it may be a good idea to preserve them.
CR2 is a newer raw format storing preview image as well as an EXIF block. ExifPro can extract both. Please note that in no case is ExifPro decoding raw images. It is always using camera provided JPEG instead.
Note: CR2 support is experimental and was tested with EOS 20D samples only.
Nikon cameras have been using same NEF format for raw photos, although it has been changing internally to accommodate different needs. Some of the Nikon models, like D70 and D2X are capable of storing compressed raw data, big preview image (JPEG Basic essentially), and EXIF block. Earlier models, like D1, do not store preview image.
ExifPro reads NEF files created by Nikon D70/D2X extracting embedded JPEG image. This is very fast and accurate method of presenting preview of photographs. In this case decoding of actual raw image is not performed.
While ExifPro strives to extract preview JPEG it has to fall back on raw decoding in the absence of embedded JPEG. This decoding is experimental and may occassionally produce incorrect images (in respect to colors). So far it has only been tested with Nikon D1 NEF files.
Many digital cameras offer the ability to store both raw and JPEG versions of taken photographs. While this
is convenient due to the widespread support for JPEG images, it stresses even further storage requirements.
When shooting in raw mode it may be worth giving up storing JPEG alongside raw photos, knowing that preview
image is still being recorded.
ExifPro allows quick access to raw photos with embedded JPEG images making such approach viable.