Understanding RAW Files

Understanding RAW Files

RAW image files (RAW file format) are sometimes referred to as "digital negatives" as they contain all the image data captured from the camera sensor and can be saved in uncompressed (or sometimes "lossless" compressed) form.   The primary benefit of saving images in RAW file format rather than TIFF or JPEG is that the images are unprocessed. This means that settings such as white balance, hue, tone, and sharpening are not applied in the actual image data; rather, those values are retained as an instruction set. This makes it possible to process the source image multiple times without ever destructing the original RAW image data. Also, depending on the camera, the RAW file format retains 12-bit or 14-bit data, resulting in an image with a far greater tonal range than an 8-bit JPEG or TIFF file.

The NEF (Nikon RAW file format)

Nikon refers to images saved in the RAW format as NEF (Nikon Electronic Format) files. RAW mode allows you to shoot an image as a raw image. A raw image is the pure data directly saved from the camera's image sensor onto the card. With other image formats, the camera processes the raw data and converts it to TIFF or JPEG, but with RAW mode, the pure data is saved and can be edited later. Since no corrections have been made, there is more opportunity to edit the file later. RAW images are larger than JPEG but not as large as TIFF.
Depending on the camera model, you can choose the most suitable NEF format that works best for the scenario within the shooting menu.

Type of NEF(RAW) available

Note that some options are only available for a specific camera model, please check the respective manual for details.

Lossless Compressed

This method uses a compression algorithm that is reversible.  This means that the images are compressed to save space on the card but the type of compression used can be reversed so that the image is restored to its full quality when opened. 
Lossless compression allows the best image quality to be recorded whilst saving space on the memory card. This method of saving RAW files is ideal for users of NX Studio.

Compressed

This method also compresses the data to reduce its size on the card but this method uses a non-reversible algorithm.  Therefore data that has been removed from the image cannot be restored later.
Compressed is most useful where available space is an issue on cards but the NEF format is still required.

Uncompressed

This file format does not apply any compression to the images when recorded on the card.  This means that files will be larger and take longer to write to the card than when using compression.
Uncompressed offers the best image quality without applying any compression to the file.  

HE/HE* (High Efficiency) compressed

This method uses the latest, high efficiency codec to compress the data to reduce its size on the card.  Although this method uses a non-reversible algorithm similar to compressed mode, the result is a smaller file size while maintaining the same quality, effectively making this more ideal solution.  
HE modes are most useful where a large numberof images are expected in a continuous burst sequence, allowing a high-mega-pixels camera such as the Nikon Z 9 to capture extensively and at a higher speed without overflowing the buffer.

The file size that is recorded in the camera is dependent on the type of RAW compression used.  The chart below shows the percentage of reduction in file size depending on which method of storing the file is used.

12-bit & 14-bit recording modes

• 14-bit RAW (NEF) file recording is available on certain Nikon cameras.

• The file size of images recorded at 14-bit is approximately 1.3 times larger than those recorded at 12-bit, however, the extra data provides more latitude for post-processing making a richer expression of tones possible and ultimately will provide superior quality output.  When evaluating the effect and comparing between 12-bit and 14-bit, the area that will show the most significant improvement between the two options is in the shadow detail.

• 14-bit will give you four times the information overall, but the shadow areas which receive much less exposure generally than mid-tones or highlights will have far greater detail. 

• A binary number with 12-bits of precision can record a number with 4096 different possible values (2 to the 12th power).

• 14-bit technology gives up to 16,384 possible values, four times as many compared to 12-bit.

• Increased bit rate does not result in more pixels or a wider range of colours, but rather more accurate precision on each pixel. 

• The frame rate at which images can be captured is slower with 14 bit as it takes the processor longer to write the increased volume of information to the memory card.  So when shooting with the 14-bit setting activated, you need to evaluate how important your speed of shooting is in relation to the quality of the final image, as one will be affected by the other.

Using the NEF file format

• Post-processing of NEF (RAW) files is possible in both the camera itself or Nikon software - NX Studio.

• RAW image files can be converted into other formats such as TIFF or JPEG for additional processing.

• Some 3rd-party applications such as Adobe Photoshop, Capture One and many more support the use of Nikon NEF file format, please refer to the respective product page for details.