How does 'Image Dust Off' work?
Nikon digital SLR cameras are designed to be used with interchangeable lenses; some foreign matter may enter the camera over a period of time when lenses are removed or exchanged. Once inside the camera, this foreign matter may adhere to the low-pass filter and may appear in photographs taken under certain conditions.
Nikon asks photographers to take normal precautions such as not changing lenses in dusty environments, to keep the lens mount pointing down when replacing lenses and using the body cap when lenses are left off for some time. Also, try to occasionally remove loose dust in the camera lens mount with a blower and to return cameras to Nikon Service for regular cleaning and checking. However it is inevitable that sometimes images will be taken with dust visible on the image, with this in mind Nikon developed a new technology called 'Image Dust Off' in Capture NX, NX2 and Nikon Capture 4 which provides an immediate solution to this issue.
How it works:
'Image Dust Off' is a software tool which, when activated, can remove dust from RAW (NEF) digital images. All Nikon D-SLR cameras (except the D100 and D1 series) have a 'Dust Off ref photo' setting in the Setup menu. When this is selected, camera settings will be automatically adjusted and 'rEF' will be displayed in the viewfinder and control panels. It is advised that if the camera has a sensor cleaning option this should be actiavted first before a dust off reference image is taken. The camera will record a reference photo, which must be of a blank white object, the file produced has an .NDF extension which is recognised as a reference photo by Capture NX, NX 2 or Nikon Capture 4 as shown below.
The dust off ref photo display on a D700
If the image data captured is not correct this message appears on the camera display. If the amount of dust is so great it can not be compensated for then a 'Return for Service' message appears.
The image can then be transferred to a computer and opened in Capture NX, NX 2 or Nikon Capture Editor software. The reference image data itself cannot be viewed using computer imaging software but will appear as shown above.
Selecting a 'Dust Off ref photo' image:
First the image effected by dust should be opened in Capture NX /NX2 or Capture Editor software, then a Dust Off ref photo taken recently can be applied to the image using the Dust Off tool shown below. Reference photo's should be recorded regularly so that the dust data contained within the image reflects the dust present in the camera. The frequency at which reference images are recorded depends on the amount of use the camera gets, the number of times lenses are changed and local conditions when lenses are changed. For a professional once a week should be adequate.
Image before 'Image Dust off'
Image after 'Image Dust off' applied
The 'Image Dust Off' tool "knows" where the dust is located on the image from the reference photo, it then uses replacement pixel data technology from adjacent pixels to replace data where the dust is located
- Capture NX 2 / NX 'Image Dust Off' tool is compatible with all .NDF files or D100/ D1X/ D1H NEF file (D1X/H must be firmware v1.10 or later). Compatibility of NDF files with versions of Capture 4.x, depends on the cameras compatibility with Nikon Capture 4. Previous versions of Nikon Capture do not support this tool.
- Dust Off ref photo is only available when a CPU lens is mounted on the camera. We recommend using a lens with a focal length of at least 50 mm. Reference photo acquisition with a non-CPU lens mounted on a camera which supports non CPU lenses, is not possible even when lens information is manually entered for the lens.
Camera setting requirements:
A featureless white object about 10cm from the lens should be captured for the reference image (the closer the subject is, the better), the reference image is not affected by camera shake.
D100/D1X/D1H Camera and lens settings should be adjusted as follows:
- Image quality: NEF (RAW)
- Sensitivity: minimum setting
- Exposure mode: aperture-priority auto (A)
- Aperture: minimum aperture (largest f-number)
- Focus mode: manual focus (M) set to infinity
- When a zoom lens is used: set to Tele
All other Nikon D-SLR cameras Settings are automatically applied by the camera.