Dust and the DSLR
The greatest weakness, up until recently, with all Digital Single Lens Reflex (DSLR) cameras is dust. Even if you never take the lens off as lenses cannot be air tight, as the focusing usually requires that they move in and out, dust can get in.
As the sensor has a static charge any dust that gets toward it is attracted and then tends to stay. The dust does not go onto the sensor as such but onto a filter that sits in front of it.
When we have dust on the sensor filter it shows up as a dark mark on the print, or screen, and is most noticeable when it appears in skies. If its lower down and in countryside or wildlife views you may not notice it at all. It also becomes more noticeable when you produce larger prints. It is more noticeable on a screen than in a print as light areas being back projected are brighter and the contrast is therefore greater.
It is not unique to detail, film also had a number of similar problems including dust, and drying marks on negatives. With film however dust tended to stick to the film and was therefore advanced and did not appear in the same place on each image, as it does with digital. As time has gone on we have become perhaps hyper critical and looking back at film prints we were delighted with just 10 years ago, we find they now fall so far short of our current expectations.
Could we just put up with them
Many people wonít spot dust marks, they tend to see a bird flying or something where a mark appears, but you having noticed it will become aware that this mark is occurring in the same place all the time.
It may be that if we are not blowing prints up to large sizes, or where we are using images on websites that we wonít need to do anything at all, as the dust will be insignificant to the image. You will see very many pictures used on this website, and on the training website, as they need to be able to both load quickly and show within at least most browsers, we cannot use large files producing high quality images, but have to settle for low resolution Jpg images, that have lost detail and other shortcomings. As everyone has the same problem they have become an acceptable quality at present for web images. We donít routinely take any action when editing these images to cover up dust and its not a problem in this case. You may if you go and look for it find that in occasional images you might just see some dust, but without looking specifically for it you won't spot it. The same applies to the Photochrome collection we have available from the location section showing re-photographed old prints from about 1990. The limited edition works we market are of course fully edited and dust free, but the version of the images you can see from this website were spun off and converted to small jpgs at a stage before the dust and some other more detailed editing was done.
Many of you will have had prints made, and not noticed small dust spots and if its not a problem for you then there is no need to seek a solution.
Even where you had your camera new, unless it was a Nikon D300 or D60, you probably had some dust on the sensor, and if you sent it away for cleaning, by the time it has been tumbled through the post or carrier, it usually has found some more. Over time it will have attracted more.
There are a few things you can do to minimise it:-
You can check the camera for dust quite easily without taking it apart or using any special equipment, and this is worth doing regularly, particularly if you are away or about to take some irreplaceable shots. If you donít know how to do this click here for a detailed description.
All the Nikon DSLR models except the D300 and D60, have no inbuilt means to get over dust, and you then have to either:-
The D300 and D60 have a built in means to deal with dust and we have a description of this in a separate article. Click here to read this.
The dust off option works well when its only small bits of dust, but does not work well when its hair, a piece of straw or other more major distraction that is presenting the problem. You can also only use this method when editing using Capture NX and using Raw files. If using any other editing tool you would first need to do this in Capture NX and then save a Tiff file for onward processing in another package. This is achieved in two stages, the first is to take a dust off reference photograph with the camera and the second stage is within Capture NX, this moves in pixels around dust to cover it. To see a fuller explanation on how to undertake all of this click here.
A clone tool is not provided in Capture NX, so you have to use another package like Photoshop Elements or CS3. Cloning involves copying a small part of the image over the affected area. You can clone out dust or larger items that are distracting in the photograph, but donít do this in images that are being used or offered for use as images for the media to use, as modifying images is something that can cause a lot of upset, even if the alteration in your opinion is not a major one. One photographer in the USA who had worked for many years for a major publication got sacked for cloning out legs of someone passing where just the legs showed under a bill board. Many photographers now choose to avoid the risk of it being suggested they manipulated images, by using the image authentication facility. So if using cloning, be careful when and how much you do.
Removing dust from the sensor filter is something that you can do yourself, and taking it elsewhere to be done is likely to involve you in travel and cost, and all the person cleaning the sensor can do is what you could do yourself. There are several ways to clean a sensor filter and this is the subject of another article, click here to read this.
Quick Links: See also other related DSLR and Dust articles by taking each of these links: