Dust Off and Nikon Capture NX
We are able, when taking raw images and editing with Capture NX, to use the Nikon Dust Off option to eliminate most smaller dust problems, lets look at how this is done.
The Nikon DSLR cameras are able to take a Dust Off reference shot. This is done by taking the selection off the setup menu labelled ‘dust off ref photo’ or similar, this instructs you to point the camera at a white item near the lens and press the shutter. It only works if there is quite a lot of light, at other times it just gives a message saying the exposure conditions are not satisfactory. This is the weakness of this approach in that in many cases when you would like to take a reference dust off shot at the end of the day to add to your card before uploading it can't be taken, you therefore have to remember to catch one another day when there is enough light.
Having taken the dust off reference shot, you are unable to view it, it shows up on your camera rear panel as an image with a pattern on, labelled as a dust off reference image. It may be an ideal opportunity to also take a reference photo of the dust that you can see, click here for instructions on how to do this. These instructions cover how to use it using the rear panel to check for dust, but you can also keep this and upload it for later inspection with your editing program.
When we look at an image with Capture NX, we can use the Dust Off reference files we have created above. The image has to be a Raw, rather than a Jpg or Tiff image.
Once we have the image loaded in Capture NX, we are able to link up the dust off reference file, to do this;-
You will find that keeping them with the images, is probably the easiest course if you are in the habit of regularly taking dust off reference images. If you take them infrequently then you may find it easier to have them on a separate directory and change their file names to the dates taken.
Capture NX uses the information within the dust off reference file to know where dust is located within the image and then moves in pixels from each side to cover it up. This works well where the dust particles are small, but often with larger bits of dust where they are not long, for example an hair or straw piece, it does not do anything like as good a job with these, and although covering it, you can see where it is.
If you have a load of pictures that you want to do the same with, you can use the batch operation either by adjusting one picture and then saving this setting as a setting file (cogs under edit list) and then using the batch commands apply it to a load of images or by just copying the setting and pasting it to individual other pictures. You have access to the batch commands wherever you can see the cogs, and also from the top menu bar under batch. You will find that operating on a load of pictures in batch mode is not fast, and you may want to set it going and then go and do something else while it slowly works through them, it has to load each image, make the change and save them away, before moving on to the next. Of course you may be able to let it also do several other things for you at the same time.
When we first used the Nikon DSLR’s we did not have the ability to identify and remove dust as easily, so at that time at the end of each day we took a dust off reference shot on any camera that had been used. This was before the dust off was on the menu, and we did it using the same method as we now use to produce visible images, and if you are using a D100 you would still need to produce the dust image this way. After the dust off facility was introduced to the menu on later cameras, and we needed to take it this way we had difficulty at the end of many days producing it as we did not then have enough available light, also when away it was often a problem. The solution was therefore to take a dust off reference at the beginning of each day, and this worked we just had a little more problem in finding the matching images on occasions. By moving the images to another directory (one per camera) and labelling them by date resolved this. However then just over a year ago we were able to check the sensors and clean them easily when we wanted, so there were fewer occasions when dust was going to be present, and we dropped the habit of taking the dust off images. As we have a load of cameras, it was difficult to remember when we needed to make these later images, and often when getting ready etc it was overlooked.
I think it would be worth doing routinely, even if we did not use them, and perhaps I should make a more determined effort to capture them. The weakness is that you cannot take them when it would often be the best time, but perhaps I need to experiment with using brighter spot lights to set up a way to allow this to work or perhaps playing with a light box. As dust is not a problem with the D300, its fairly low on my list of things to do.
See also other related DSLR and Dust articles by taking each of these links: