Orquid "Phoenix"

Orquid "Phoenix"

by ceinmart

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My cheap point-and-shoot digital camera (BenQ DC C1035) has served me well for a year and a half but recently seems to have let some dust inside which results in smudges or blobs on every shot.

Since I'm hitchhiking around the world on a very low budget I don't have the means to replace the camera or have it cleaned professionally, and I don't trust myself to attempt to dismantle it to clean its insides.

So I'm wondering if there is some free image processing or photographic software which can attempt to correct such a condition - it must be a fairly common problem. I'm not expecting miracles, the photos are only snapshots, but anything that mostly improves the look of the photos without me having to be a good Photoshop/Gimp artist.

I imagine such a tool might take as input some photos of a blank background to learn where the smudges are then apply this to real photos to attempt to correct them. But maybe fully automatic tools also exist. One thing that makes it harder is the smudges very a lot depending on the zoom and/or focus of each photo, though they don't seem to move around over time.

Here's some photos I took against a white wall, converted to black and white, and did a white balance on to maximize the visibility of the blobs:
Blobs in my camera

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Just after posting this question a fellow traveller gifted me a much better camera which suffers from the same problem: A Panasonic Lumix DMC-FX35. This makes me less afraid to try to clean my old Benq but more afraid to try to clean the Lumix. –  hippietrail Jun 4 '12 at 15:25
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3 Answers

Depending on the camera model, some have a "Dust Delete Data" function, whereby you take a photo of a blank white wall, and the software (I can't remember if its in the camera, or if you have to use external software like DPP) basically maps the 'blobs' as seen on the photo of the white wall over the top of your picture and makes the adjustments in those areas.

I've never had need to use it myself, but is very clever in theory....

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That can sort of work with a JPEG or TIFF, but it's only really effective with raw sensor data. The big, ugly, fuzzy blobs in a "developed" image are the result of sharing the data recorded by the occluded pixels with the pixels around them as part of the demosaicing process. With a raw dustmap (which is generally pretty sharp), you can basically say "ignore these pixels in processing and fill in the blanks". Ignoring the occluded (and "hot") pixels keeps the shadow from cascading outwards into the rest of the image. Working with JPEGs and subtracting images won't give the same results. –  user2719 Jun 5 '12 at 21:20
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That's a lot of dust.
The blobs are so extensive and ugly that any software is going to have a very hard time making a good image from these.
Thje old saying is that "You can't make a silk purse from a sow's ear"and, unless these are vastly worse than actual, this seems to have got to sows-ear stage. A serious attempt at finding a low cost solution seems in order.

So - the following is about reducing the effect - not on post processing:

You will get more spot visibility on higher apertures.
Anything you can do that will keep aperture large (= small f numbers) will improve the result.
This is because, if the dust is close to the sensor it will be actively de-focused and large apertures increase this effect.

The C1035 has variable ISO over a wide range.
Try taking photos at the lowest acceptable ISO and see if it makes a visible difference.
Low ISO means the camera needs more light and will a lower aperture and shutter speed.

Downside: In lower light conditions this will lead to low shutter speeds and you may get blur you otherwise would not have. Large apertures give reduced depth of field so focusing is more critical, but in many cases with a small sensor that will not be too much of a problem. Try it and see.


You will pass this way but once, or maybe a few times in your case, you being more traveled than most. Years from now your photos may provide the major link to memories of your past. Spending the minimum necessary that is required to allow the photos to be a bearable record of events is an investment in your future. What country are you in at present? Depending on where you are, you may be able to get a good used camera that does a better job overall than the dusty Benq for perhaps $50. The Benq is 10 mp. A good 4 mp camera will provide a very adequate record in most cases. Investing in another camera may be a good idea.

You MAY be surprised how little a sympathetic repairer would charge to clean your sensor. If you can access the surface then a blower may help. Gentle brushing with clean lens tissue may also help. I would be personally prepared to attempt using eg soft toilet tissue a few turns inside the roll to ensure it is dust free. This is far far from lint free but stil usable en extremis. People sell replacement LCDs for the C1035 on the internet. They may be prepared to provide dismantling instructions for free that a competent person can follow. An evenings careful playing in a hostel dining room may be all that is required.

All care & no responsibility suggestion: I personally would attempt using a vacuum cleaner and great care to suck air through the camera - with due care to prevent full suction being exerted. With proper care this carries minimal risk of damage and a moderate chance of success. I'd open the lens fully out, remove the battery and apply careful sucction around lens tip and battery box. Fingers over hose end to stop it latching on and care so the camera never gets pulled hard against hose.

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The DustCleaner GIMP plugin may do what you want. I've never tried it.

There is also a much older dust removal plugin, but it looks like it's more intended for scanned photos than digital photography. Again, I've never used it.

And as @Mike mentioned in his answer, many cameras have Dust Delete Data capabilities, but as far as I know (at least with Canon) they require support on the camera and use of proprietary software from the camera vendor.

It would be wonderful (and I suspect not terribly hard, but I'm not sure) if someone could create a similar tool for GIMP or another 3rd party program, that would allow using a frame of a plain white/black wall as a filter to remove dust data from a normal frame.

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Sadly it doesn't seem to be ported to Windows but I'll see if I can get it running in a Linux virtual machine on my netbook ... –  hippietrail Jun 2 '12 at 0:05
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