Članki


Photographers in fear of the dust
By Matjaž Intihar; Translated by: Gregor Boroša
Jul 10, 2005, 15:00

 

After countless debates about resolution and noise, there's a new writing on the wall of the digital photo technology! I believe that anyone who sees such dust spots on his photos is horrified and is ready to spread the word about "the serious dust problem in photography." But is this necessary, is this visible on our photos and how to remove dust, these are the topics of this article.

 

"If you are photographing a scene with lots of details, with no clear areas (sky, water) and at middle or dark tones, then you won't notice any dust. However, sky, skin and other clear and bright objects are very popular in photography and so there are chances your photos will show the dust on the sensor of your camera. Visible Dust is a tool with which you can remove the dust with a delicate touch."

 

In an article on the front page of e-Fotografija.com it was already published that special brushes for cleaning CCD/CMOS sensors are now available in Slovenia also. The dust can damage our photos and a number of photographers were complaining for it, so I have decided to review this product in detail.

 

Photographers in fear of the dust

There are more and more users of DSLR cameras. Some of them make various tests of their equipment even before they go out and shoot in real life. The internet is crowded with posts about »one of the biggest« problems in digital photography at the moment, dust on the sensor. Here's my experience. I have my EOS D60 for three years. Of course there is dust on the sensor, but I don't specifically search for it and I know how to remove it if need be, so I never worry about dust much!

 
Photojournalists were using digital single-lens reflex (DSLR) cameras back in 1996 at the Olympics in Atlanta. And until 2004 the dust was a marginal problem. Not that it didn't exist, but professional photographers focused on photographing, not on searching for troubles and only once in a while they took their cameras to experienced technicians or they even fixed problems themselves. Through the years of using their cameras, even film ones, they gathered enough experiences to do the job. If the dust was there, they could remove it in post-processing. Those users who were used to work in the dark room or in a photo lab, knew, that dust is a problem and in the past it was only worse. But it was a thing that average users didn't take part in, it was the job of photo labs.

Modern technology makes it possible to repair many problems, even dust spots, and print perfect photos by minilab machines and such. To summarize, the dust was a problem in the film era, too, but not so in the stage of capturing images, but in reproduction. Even on dia projections there was more dust visible than it is on our digital photos. And modern LCD projectors are dust-proof.

 

In 2002 only few of us switched to digital SLR cameras. The price of the equipment was still too high for hobby photographers. It was only a year later that I read about the dust on the sensors on internet forums. So I was staring in my photos on the screen at high magnifications, yet I didn't see why people are complaining. Then I was reminded to check photos made at lens stopped down, at f/32 if possible. And even then I didn't find anything disturbing. Then I received new instructions. »You are joking! Take a photo of uniform tonal values, then readjust the levels with some software.« That was the moment of my first contact with the word »technical photographer.« It marks people who are endlessly looking for technical errors, which are not even visible by normal use of the equipment. Of course by following all these instructions, it is easily to find the dust. However this has little to do with photography in most cases.

 

Two years ago I spotted some dust on the sensor for the first time. One year old (2003) EOS D60, EF 28-135mm, f/13.

 

On the areas with similar tonal values I've found two spots, but nothing to worry about. It takes two clicks with a mouse and problem is solved.

 

For this article I've searched for some old photos and adjusted the levels to easily find any dust spots. If dust is hardly visible on the original photo, it can be seen much better after some experimentation by any photo editing software, when you alter the image so hard, that it's not suitable for printing anymore.

 

To find as many dust spots as possible, I've done some hard corrections to the photos. The dust was, of course, there. However it has never bothered me on if I've done only ordinary image manipulation on the computer, even if I've enlarged them or printed them in my magazine. But it is true, that I've removed some spots manually on the computer.

 

With the arrival of the EOS 10D, 20D, Nikon D70, Pentax *ist Ds, Konica Minolta 7D and above all with cheaper cameras EOS 300D, EOS 350D and Nikons D70s and D50, digital cameras became more and more popular among hobby photographers. Even before the actual purchase, buyers were reading about the dust on the sensors. Many will make a thorough dust test as soon as they will get hold of their camera. As always, he who searches, finds. In this case, the dust can be found, but it is something that will rarely be visible on your photos, which is perhaps most important. Loads of posts about such problems on the internet make everybody start looking for problems on their equipment and of course the dust is everywhere.
How it impacts your photos, when it is visible and how to remove it?

 

Why I'm not concerned with the dust

In three years, my DSLR camera has undergone lots of situations. I've been changing lenses so many times, as most of hobby photographers will not in their entire life, more so because they are so afraid of the dust. I've lent my camera even to some professional photographers, who were still using film and didn't have their own digital cameras, but wanted them nonetheless. Many wanted to try it only to see how digital photography is developing. I am sure that most of them didn't handle my camera very gently and of course, when they first saw a digital camera, they removed the lens, set the camera on bulb and try to see how the sensor looked. Which means I knew that in three years I’ve gathered much dust in it? However it was only rarely visible on my photos and I wasn't concerned with it. As long as you don't see any dust, it's a waste of nerves to think about it. The only company which probably doesn't suffer from dust is Olympus.

 

Photo of Helsinki, same timing, same camera, f/11. I had two large dust spots on all photos made in those days.

 

With some software image manipulation dust spots are clearly visible. This is only to show that dust can be found, it is not normal image processing method.

 

I am aware of the dust

On our forum at www.e-fotografija.com/forum/ I've regularly replied on questions about dust on the sensor. I've written many times that I know that I have some dust on my sensor, but I don't find it being a problem. Many didn't believe me I've never cleaned my sensor until now. Why?
I seldom use f/16 or higher, where dust is easier to see and if I do find any spots, it took me only seconds to remove them in some image editing tool. In most cases, people who frantically look for dust and make panic returning cameras to the stores, take photos of a wall or sky and then use some software to manipulate images beyond recognition only to see some dust. Let me tell you that Nikon's technicians have strict rules to only check for dust at f/16 and not higher. I've not yet received an answer about changing tonal values, meaning at what conditions they will admit dust.

I also know that I would clean my sensor earlier if there was an easy and safe method to do it. Dust is something you really don't miss when you don't have it. There were two articles about the dust already published in our magazine and on the website. One is even describing a technique of how to clean your sensor with a cotton swab. Only it needs multiple sweeps to do the job unless you want to leave some dust or cotton hairs there. It takes time, especially if you're doing it outside, because there's much dust in the air already and you don't want to have your camera body opened for more than is absolutely necessary.

I've been seeing the same dust spot even days later, when I was in Stockholm. It must've been really glued to the sensor to be staying there for so long and it was huge as it was visible even at f/8 on my EOS D60.

When preparing my photos for printing, sometimes with strong levels adjustments, I never noticed more than those two spots and even they didn't bother me, because I seldom use f/8 or faster..

Before I published the article, I looked at this photo again and readjusted the levels and with some experiments I've managed to find one more dust spot. But only at heavy software manipulation, when the photo was practically ruined.

Six months later I was in London. I see no dust at f/11 despite the fact that I intentionally readjusted the levels.

For this article I had to systematically look for dust spots on my photos. I've selected the sky and made heavy tonal adjustments – and then I saw the same spot I had six months before. So it was on all photos I made since visiting Helsinki (if not even from earlier time). The camera was also used by Veljko Jukic, photographing Formula 1, and nobody complained.

Here's a photo from London I made last year, which is six months after the previous photo. It was taken at f/16 with readjusted levels so as to see the small dust spot.

After some radical tonal readjustments there's plenty of dust to see. Notice, that with time, those two large pieces of garbage have fallen off by themselves, I didn't even notice when. When looking at old photos, I can say that with time there is more and more dust on the sensor. However at shooting ordinary images and using some basic software functions, there is nothing to be worried about. Once again it proved to me that you have to pedantically search for dust and only then you will find it to be your »enemy«.

Panoramas from lake Blatno jezero are tonally uniform. Perfect for the search of the dust. Looking at the original photo, made at f/8, there is no dust to be seen.

Tonal values readjusted and there's still no dust.

However when I've selected and readjusted only clear areas, some spots became visible. More so at aperture 16 or more. In any case, we only get small, sharp, dark spots, which are easily removable in some software, if their number is not really high. At apertures lower than 16, there's a bigger problem, as spots are smudged and are a bit more difficult to remove.

A shot of king Matjaz in Budapest at perfect conditions for seeing any dust: gray, cloudy weather. Aperture 10 and large uniform areas, yet I see no dust spots.

After some levels adjustment, some spots are revealed. Note that you would normally never shift levels as much as I did here. All spots can be easily removed.

Another shot of the sky at aperture 13.

The image has many details and dust is hard to find even after shifting the levels.

Aperture 19 and 800ISO. There's one noticeable dust spot.

Even though this image was taken when there was a lot of dust on the sensor, you won't find it. You will have to limit the search for the dust only to tonally uniform areas.

This group of photo salesmen didn't bother about dust on photos from travels. On photos like these, no one would see any dust. So what is the case with this dust anyway? On my EOS D60 I've gathered it a lot in these three years of use. On most pictures, those few spots can be very easily removed, but either case, it is obviously better to have as little dust as possible. More about how I've cleaned my sensor and how successful I was, on the next page.

Page 2


© Copyright 2003 by e-Fotografija in DigiFot.com

Na vrh

 
Vpiši novico | e-Fotografija |  

Obnovljeno: Mar 9th, 2007 - 10:08:49