Not Your Everyday Banana

by Bart Arondson

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I need an advice

I have dust spots appearing systematically on pictures (with blue/white/grey skies & aperture > 9) I understand this can happen, I understand how and why it happens, especially with HDR... I also know I should pay attention not to change my lens in a dust environment; I know that compact camera should not have the problem when DLSR are more proned to it.

My question is : - should I consider it is normal to have dust spots (even after cleaning), and noone is really talking about it, but HDR requires to have a special post treatment to remove these spots - should I consider it is normal but there shouldn"t have dust after cleaning - should I consider it as abnormal and I should change my camera

What is your opinion ? Sincerely

Michael

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How new is your camera? How are you cleaning it? Are the dust spots there right after cleaning? –  mattdm Mar 20 '13 at 16:46
    
Dust spots appear often or all the time? Are they always in exactly the same spot? –  Itai Mar 20 '13 at 16:52
    
This might be informative to you: photo.stackexchange.com/questions/13809/… –  Regmi Mar 20 '13 at 17:45
    
What they all said - BUT - immediately after cleaning I would not expect any 'dust' spots to be ones which had been in the same locations previously. Sometimes cleaning can rearrange the dust spots as much as removing them and it can take several attempts to get the count down to zero or near zero BUT if a spot or spots remain resolutely in the same place and all your efforts do not move them then I'd consider using an experienced commercial cleaning service with the proviso that you are paying specifically to have the "fixed" spots removed. ... –  Russell McMahon Mar 21 '13 at 0:17
    
... I've had good results removing my own using solvent and wipe techniques. Sometimes it takes several passes to get a clean sensor but given enough work I can usually get it absolutely clean using eg a blue sky on long exposure at f/22 or smaller aperture as a background. –  Russell McMahon Mar 21 '13 at 0:19
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3 Answers 3

Is dust on the sensor normal? Unfortunately, yes. One of the few disadvantages of digital vs. film is that the recording medium isn't changed every time we swap out a roll of film. Over time dust will find its way onto your sensor. There are several precautions you can take to minimize the impact of dust on your sensor.

  1. Change lenses as rarely as possible, and in the cleanest environment that is feasible. If you must change lenses out in the field, place your back to the wind and hold your camera at an angle down and away from the wind. Blow out the back of the lens before placing it on your camera. Run the automatic sensor cleaning cycle each time you change lenses and before and after every shoot. De-energize the sensor by turning the camera off whenever the body is open.
  2. Keep your camera in as dry an environment as you can. When not in use, store it with a desiccant. Avoid rapid temperature changes, especially from cold to warm. Stow the camera in the bag in the cold outside and then leave the bag shut for an hour or two when you move indoors. In the summer take the camera outside in the bag and leave it for a while before removing it. Moisture can turn an easy to blow off speck of dust into an almost impossible to remove spot of dust.
  3. When you do have dust that the automatic sensor cleaning won't dislodge after a couple of cycles, clean in the following sequence until the dust no longer appears in a test photo. Blower -> Brush -> Liquid -> Tape (if you dare). Each method can remove progressively more difficult dust, but also carries progressively greater risk of damaging the IR filter that covers your sensor. Each method has a learning curve before you can maximize its effectiveness. For example, I still struggle with leaving dust in the extreme corners of the sensor when I use a swab with liquid.

Once you have taken images that have dust spots, you will need to edit them out in some way.

  1. Follow your camera's instructions to take a Dust Delete Data picture. For some cameras you need to do this before you take any pictures you want to apply the data to. Canon cameras, for example, append the current Dust Delete Data saved in the camera to the meta-data for each file as you shoot, then gives you the option to apply it using Digital Photo Professional in post processing.
  2. Depending on your workflow, you can do dust removal on each image before combining them for an HDR image. If you are manually using a clone/repair tool, temporarily turn the contrast and sharpening up and the exposure/brightness down while hunting for and repairing dust spots. This will help you see them better. Once you've cleaned the dust spots, adjust the other parameters to your liking and export the image as a TIFF file to use in your preferred HDR software. I've found this much more effective than trying to remove dust spots from a finished HDR image.
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You can use a dust delete image to help minimize the distortion caused by dust, but the best bet is typically to clean the dust out. Using a bulb duster can normally gently blow away dust. If this doesn't work, it may be worth sending in your camera for cleaning if it is a significant enough problem. It is also worth mentioning that sometimes DSLRs can develop dead pixels which cleaning will not help with.

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Your sensor requires cleaning. How often depends on a lot of factors, from the environment you're shooting in and how often you swap lenses to whether you hold your camera up or down when changing lenses (hint: hold it so the sensor well faces down, so any dust in the air won't settle on it).

If you have a new body, it may come with a sensor cleaning mode (using a rapid vibration of the sensor to knock the dust off). use it: I turn my camera body off and on prior to every shoot. If I'm in a dusty situation and changing lenses, I turn it on and off occasionally during shoots. I also turn my camera off before changing lenses. First, it forces a sensor cleaning before and after every lens change. Second, some people have claimed that a sensor that's powered up can carry a static charge, and that static charge will attract dust to the sensor, so you want your sensor powered off when the chamber is open. I don't know that this is true, but my old canon 30d sure acted that way. It was a true dust collector.

If you have an older body without sensor cleaning, do it yourself. Use an air blower on a regular basis to clean the sensor. I used to do it before every shoot, and I used to do it at the end of every shoot (now my bodies have the auto-cleaning. I don't use an air blower unless that doesn't solve the problem. Id' rather leave the chamber closed and not expose it to dust)

At some point the blower won't remove the dust. Moisture can "weld" a piece of dust to the sensor so the blower won't remove it. This is more common in humid locations, and it is more likely to happen if you don't get in the habit of regular cleanings of the sensor via the vibration or blower method.

At that time, you'll need to wash your sensor using brushes and solvent. This step scares more photographers the first time or two they do it; it's not THAT bad, but you need to be careful. There are various products for this; a good site to investigate options is http://www.cleaningdigitalcameras.com/

If your camera hasn't been cleaned in a good while, I recommend a professional cleaning. Find a local camera shop and have them do it, or sites like http://www.borrowlenses.com/ will let you ship the body to them and they'll do it. This can run $35US to $70US, from what I've seen. I also think it's a good idea to let the pro clean the sensor once in a while (like once a year under typical use) whether you think it needs a wet cleaning or not.

If you're seeing dust spots on your images, clean your sensor. If you haven't cleaned it for a while, let a pro clean it, then learn how to keep it clean on your own. Buy a good air blower, pick up a wet cleaning kit for your camera. Get in the habit of dusting off the sensor before you start to remove whatever settled in while it was idle, and at the end to remove anything that showed up while you were shooting. That'll limit the chance of a fleck of dust welding itself to the sensor requiring wet cleaning. Learn to wet clean and get comfortable doing it in your home BEFORE you need to do it in an emergency and in the field. Trust me on that.

This is all something that should be part of your regular camera maintenance, along with wiping clean bodies and lens bodies and removing fingerprints from lenses and filters. If you get in the habit, you'll have fewer problems to fix in post (I hate dust specks), you won't have a badly placed dust spec ruin an unfixable image, and your gear will typically last longer. And you won't end up in the field trying to find a moderately clean area out of the wind to do an emergency clean-ectomy on the sensor because a dust spot's welded right where you want your subject image to be...

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