The X3F RAW data format for highest-quality images

Sigma believes that a digital SLR camera should empower the photographer in two distinct stages: during image creation and during image processing. Photographers should have all of the resources necessary to recreate the ideal image retained in the mind’s eye.

For this reason, the SD15 offers photographers the highest-quality data that is ready for professional finishing, broad in dynamic range and rich in harmony and color. For use in RAW mode in all of its cameras, Sigma has developed the .x3f format to capture the pure, rich data that a true full-color sensor has to offer.

Just as the best ingredients help create a gourmet dish, the finest data helps the photographer express individual skill and vision. RAW data in the .x3f format is what photographers require to do the very best work that only they can do.

Sigma’s proprietary X3F file format ensures outstanding texture and color

In fact, shooting in X3F format has other advantages too. In a digital camera, the image signal captured in RGB is recorded by being converted into what is known as YCbCr color space. The Y stands for brightness, and the CbCr stands for color difference. In an ordinary digital camera, a file format known as YCbCr 4:2:2 is used, where the color signal is set to half the brightness signal. This format was developed in order to send color information efficiently on the limited bandwidth available back when color television was first developed. Designed on the principle that the human eye is less sensitive to color data than to brightness data, this historical format has survived intact to this day, and is still used as the mainstream format in digital cameras.

However, now that digital camera performance has improved so dramatically, people are using their photos in different ways, displaying enlargements on their computer screens, and large photo prints are mainstream. Today’s output conditions are getting better and better. The old YCbCr 4:2:2 format was designed for efficient signal transmission, and not for high-quality output. To our way of thinking, this format is no longer adequate to meet the needs of all photographers.

X3F images preserve the balance of the natural data

The JPEG files from the sigma SD15 are output in YCbCr 4:2:2 in compliance with the Exchangeable image file format (Exif) specification, which is the standard specification for file formats. But in the direct image sensor, each pixel location captures the full complement of RGB color data, so in X3F files, which is the RAW data format, brightness data and color data can be kept in a 1:1 ratio without relying on interpolation. When this image is processed in SIGMA Photo Pro, even if it is saved as a JPEG, if the JPEG quality-setting selected is 7 to 12, it will be saved as YCbCr 4:4:4.

The SD15's image quality, with its amazing vividness and texture, is really due to the X3F image data, which preserves the balance of the natural data. For the best photos with the best image quality, we definitely recommend shooting in X3F mode.

The X3F format offers outstanding imaging potential, with a rich and well-preserved dynamic range. You really need to experience it for yourself.

Featuring JPEG and RAW image format modes

Using the JPEG setting allows the SD15 to finish captured images as JPEG files inside the camera according to a specially developed Sigma formula. When these JPEG images match the photographer’s vision, JPEG mode is an extremely powerful and convenient feature of the SD15.

JPEG images are ready to print when the SD15 is simply connected to the printer, and the image data files are ready to share with friends and family. For ease of connectivity and convenient sharing, JPEG mode is an excellent choice.

Creating JPEG files in this way, however, subjects data to irreversible compression, leaving little scope for image correction afterward. Using a camera that offers only in-camera JPEG processing can severely limit a photographer’s artistic expression.

In RAW mode, the Foveon X3® direct image sensor outputs to .x3f RAW image format files, preserving the high-presence, high-quality, accurate, and balanced data that makes for truly emotional images and opens up new creative channels. Sigma believes that RAW mode allows photographers the clearest path to creative expression while supporting the best image quality and fostering the finest photographs.

SIGMA SD15 Special Contents