Photographers in fear of the dust / page no. 2
By Matjaž Intihar; Translated by: Gregor Borosa
Jul 10, 2000, 15:30
|For another test I had three completely new cameras, which I've checked if they have any dust in the first place. Well, yes they do. But only if you're looking for it. On normal pictures you will never see it. And even if you have one or two dusts, don't worry; soon you will have hundreds of them. Even changing the focal distance, focusing and zooming can cause some dust to get into the camera and lens. As you've seen on the first page of this article, I'm not concerned about the dust for more than three years. I have it plenty, though, so I used this testing of cleaning devices to finally get rid of it.|
The day has come
More and more hobby photographers are on the hunt for the dust, so I've decided to find out how big of a problem it really is. I've used an excellent tool for the job, the one that received many praises from its users, a tool from the company Visible Dust. My three year old DSLR camera has never been cleaned till now, so it was perfect for the job and we could really see if dust is a problem or perhaps not.
As a first thing, remember that dust is something you already have when you buy your new camera. Some people want to exchange the product they bought with another one. Making photos at aperture 22 or even 32 and some contrast shifting on tonally uniform areas, you will see some dust spots almost for sure.
Believe me, each new camera has some dust on its sensor. There's even more dust in the mirror compartment. Cameras are not assembled in sealed environment, nor are cameras sealed themselves. This raises the question of when we see dust spots and does this affect our photos normally enlarged (photos on page 1).
For the test I've got myself three new, originally sealed cameras EOS 350D. I've taken a couple of shots of the sky with each at different apertures and then applied some software manipulation. There was a proof that cameras have some dust inside even well before the first shot has been made. Now I understand that manufacturers had to protect themselves with standards about when customers are entitled to free cleaning of their sensors. However some dust will always stay inside the camera, it's a fact. Even if you've just cleaned your sensor, some dust might fall on it just at the next shot you made (when opening the shutter). I've seen it myself.
|Photo of the sky at aperture 16 with a brand new EOS 350D shows no dust spots.|
|At aperture 32, there are a few small spots. For those photographers, who often shoot at these conditions, will at tonally uniform pictures face some problems. However that should not be the case in most cases.|
|The same shot as above, just with shifted tonal values. We can see that the sky is not uniformly illuminated, light is coming from lower right side. The spots are visible and pretty much alike with all three cameras. The dust is inside new cameras, too and it's not just Canon. The dust is a common fact with cameras of all manufacturers.|
|First cleaning with a brush and shaked spray. If we look at the picture above, we see that CO2 under pressure only makes it worse and I was lucky. If I'd use a different spray, I might make the sensor so dirty, with garbage glued to it, that it would take a wet cleaning to remove all. So here's the first advice: before spraying inside the camera, for a second or two spray it away and never shake the spray while cleaning your brushes.|
|Second sweeping, this time with a brush and a small hand pump, aperture 16.|
|Second sweeping, this time with a brush and a small hand pump, aperture 22.|
|Second sweeping, this time with a brush and a small hand pump, aperture 32. The difference is clearly visible. There are some spots still there, but it's much better than when using a shaked spray.|
|Third cleaning, now again using CO2 spray. At aperture 16, there are still two spots visible, but only under heavy tonal adjustments.|
|At aperture 22 there's still one spot.|
|At aperture 32 and some tonal adjustments, three spots remained. In the fourth sweep I've managed to completely get rid of the dust. But! I've repeated the test after three days, took less than 100 shots and again I've got myself some new spots. This game is just not for me. The dust will bother me only then, when I'll see it on ordinary photos and when it will be too complicated to remove it in some software.|
The real test was the second one. It answered some of my most interesting questions, how much dust really is inside the camera, how it affect the picture, when we see it and how do we clean it.
Despite my D60 not being cleaned for three years, dust spots on my photos were very rarely disturbing. It happened mostly on the pictures of the sky at high apertures, which I've talked before. I've found that the biggest problem is at apertures 8 and 11, when dust spots were smudged across a larger area, making some kind of a soft circle. At these cases I've used some software for editing photos and removed the circles. I didn't make a fuss about it, just simply solved the problem. Taking my camera back to the store to fix the problem in this case wouldn't be worth it, as the dust might come any moment after the sensor has been just cleaned. The dust is not just on the sensor, it's everywhere inside the camera, so sooner or later it will fall on the sensor.
When testing cleaning brushes, I've photographed directly into the sky at all apertures of the lens EF 50mm f/2.5 macro, from 2.5 to 32.
At aperture 2.5 I couldn't see any dust spots even after heavy software manipulation. At aperture 8 there were some soft spots, which became more defined after tonal readjustments. At f/16 some spots were visible even without shifting the levels and at aperture 32, spots were of course there, easy to see.
So that's the dust I carried in my camera for three years. Most time I didn't even notice it, because I seldom use aperture 22 or 32. On usual shots you see it only after shifting the levels in software, but doing that makes the photo useless. On the other hand, photographing uniform areas with few or no detail, dust spots can be visible and can cause problems. To find out for how long I've carried the dust in my camera, I've searched for old photos, where the dust could be seen.
Occasionally, I've faced dust spots on my photos even before, but now that I was systematically looking for them, it was much easier to find them. To find the dust, you just have to follow some simple steps (shift levels of tonally uniform areas of the photo), but usually the dust will never be seen.
Still, why would I want any spots on my photos, if I could remove them easily enough with special brushes like Sensor Brush is. Many users like them for making the job well done.
When testing cameras I rarely read the manuals, but when I tested sensors brushes and CO2 spray, I read them all. They are short, but essential for successful cleaning. The most important thing is to have full battery. Otherwise we could damage the shutter and the mirror, as the shutter closes when the battery is empty and can catch our brush while we're sweeping the sensor. New cameras have a function called »Sensor Cleaning«, which opens the shutter and releases it only when we turn off the camera or the batteries are drained. So be sure you have inserted full batteries in your camera. Older cameras like my EOS D60 do not have this function, so you have to use the Bulb setting and manually hold the shutter release button until the cleaning is completed. This makes the job a bit more difficult.
For the cleaning of all of my test cameras EOS 350D and my D60, I've chosen the brush SB-16, which is suitable for APS-C sized sensors (crop factor 1.5x, 1.6x). Sensor Brush tools were at first used in laboratories for removing dust from the glass of microscopes. The dust is much bigger problem there, as it is magnified. This means that these brushes were already proved to be efficient, without leaving any marks or smudges on the cleaning surface. Brush hairs are positively electrified, while the dust is negatively electrified. This makes sweeping even more efficient.
After my experiences with 350D cameras, I've finally cleaned my D60, where I had to use the bulb function, as D60 doesn't have a »sensor cleaning« function. Since each cleaning takes only a couple of seconds, it can be repeated a number of times and with an extra care, with only a half full battery.
|After some practice with the sweeping, I've cleaned my three year old EOS D60. Here's the result at aperture 16. For what's left, I don't even need to clean it I think. You would?|
|At aperture 32, there were a number of very small spots. Since I never use this setting, it never bothered me. However this dirty old sensor makes an excellent opportunity for testing these Sensor Brushes.|
|Image taken with dirty sensor at aperture 2.5 and heavy tonal corrections. The dust is not visible. This is also the reason why so few photojournalists actually see the dust as a problem. They usually use apertures only to about f/8.|
|At aperture 8 there some are visible, but only after extreme tonal readjustments, which you would never use otherwise. We see larger blotches, which would be smaller and sharper if we would stop the lens down even more.|
|At f/16 spots are visible even without any software corrections. And after shifting the levels, everyone buying a DSLR camera would be horrified to see such a mess. If a salesman wants to sell you a compact camera instead of a DSLR camera, he might even show you a test like this to persuade you. However from the photos on the first page of this article, we've seen that we seldom use so high apertures and even then the dust is usually just not visible.|
|At aperture 32, all spots are sharp and I too am convinced that cleaning needs to be done.|
|This is how the sensor looks after two sweeps with a clean Sensor Brush. After cleaning, I've made some test shots at various apertures. This image was made at aperture 32. I've seen an interesting thing here. While photographing, I've seen a big dust spot at the top of the sensor only on this photo. It wasn't there before or after. This was in a time interval of two seconds and proves that the dust can move freely inside the camera. The mirror itself makes a nice draught while moving and helping the dust floating around.|
|A shot of the next cleaning at aperture 32.|
|After the third sweeping, what's left from the dirty sensor is only one small spot, visible at aperture 32. Now I have to seal my camera, put it in a treasury and never use it again. Not. Currently, I'm waiting to get hold of new cleaning tools and swabs for wet cleaning of the whole interior of the camera with the mirror and prism, too. Such cleaning would otherwise cost you around €40. Myself, I need it, as the sensor is also covered by a thin layer of all kinds of garbage, which already affect the contrast and can only be cleaned with special non-alcoholic fluids. There's also a lot of dust which remained in the inside of the camera, which can fall on the sensor any time. Personally, I'm not bothered much, but for some people, it will cost them a lot of time and nerves before they will finally realized it's not worth it and give up. However, cleaning brushes Sensor Brush have proved to work. If they've cleaned a three year old sensor, then they could clean newer sensors just as easily. How to clean and what do brushes look like, on the next page.|
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