Finding & Fixing Dust Spots a really neat way

Finding dust spot on the sensor has become a bit of an ongoing theme, having experiences some very dusty conditions recently I‘m very aware of the tiny pests and the havoc they can cause on a decent photo.. Because DSLR cameras have mirrors that flap up and down and you can change lenses, it is pretty inevitable that you will at some time experience dust on your sensor. The best way to deal with dust of course is to clean your sensor, and I’ve written about that a few times.

What is more interesting is finding ways to “detect” and “fix” images that do have dust spots. +Scott Davenport, a moderator with the Patch Community in google+ has a really nifty method of both finding and fixing dust spots, including a preset for perfect effects 8 to do this. The video below is from his blog post and explains the simple process better than I could.

Another Way to find Dust on your Sensor

Looking back over some google+ photo autoawesomes, of my autobacked up photos. Ok you got me, I do eventually look through them. I noticed that some dust particles I had missed in my sensor cleaning where really highlighted in any HDR images. I assume that this is because the detail of dust is strongest on the slightly over exposed image from the bracketed set, and the google+ hdr process is trying to preserve that detail. This is really an abstract and secondary way to check for dust I still recommend taking a direct image of the sky as a quicker and easier way to detect dust.

Dust, the natural enemy of DLSRs

Trying to photography in the Saudi Arabian Desert has highlighted the issues of dust and (mirrored) DSLR cameras. Basically each time the mirror folds up to take a picture and exposes the sensor. The desert wind pick up fine sand particles and dust and it penetrates everything from your ears, anything you touch and eat, even to filling your back pocket. When you change lens for example some dust can find its way inside your camera and onto the sensors. Leaving those annoying little spots on your image. The image above has the very clear black spot of a fine sand particle but also so many ghosted dots (also dust) that I gave up pointing to them all, in the photo above.

So what can you do about it?

The first thing to remember there are now good tools to recover any photos you have taken that have unfortunate spots. These are generally versions of cloning tools that allow you copy the texture/detail for a nearby area over the spot and thus erase it. In lighroom this is called the spot removal tools and cab be found in the development module. In Picasa it is called Retouched and found in the basic edit tools. In AfterShot Pro it is called heal (which just fixes circular blemishes like dust) and is found in their layer manager.
The better solution is to clean your sensor of dust as soon as you detect it. This is relatively easy for most camera but a few makers and models do recommend that you get the camera cleaned by the company or their designated agents (and that can be expensive!) For the rest of use check you camera manual and carefully follow the instructions. Some cameras like my Pentax K20D has a sensor shake mechanism to dislodge dusk particles, and often can do this at start-up. However bi also just find the setting to clean the sensor which lift the mirror and expose the lens. With the lens remove i them a conventional blower with the brush removes and with the camera upside down I give the sensor a good blast of air. Remember you must never touch the sensor with anything, hold the blower a couple centimetres away (approx. 1”) below the sensor and squeeze the bubble several times pointing at different parts of the sensor. I find this approach works well, if the dust is fresh. If the dust have been there a while it may take a couple of cleanings to get rid of all the spots. I have previously posted that a good way to find dust spots is to photograph a clear sky.

I have found giving my camera a strange turban-like bit of head gear, made from a face washer rather than the traditional tea towel patterned cloth in the saudi style, and a rubber band has helped a lot. Although it will never be white again. Those familiar with hitch hiker’s guide to the galaxy will know that a small towel is an essential travel necessity, (especially so for a photographers). And importantly I don’t change lenses out in the open.

Yellow Moon

The full moon is not so much a harvest moon as just an indication of just how dusty it is out here

Dust removal & Advanced Brush Healing Tool in Lightroom5

Its been a long time since I first mentioned DSLR's dirty little secret, dust on the sensors. Back then (late 2006) I was also looking at the beta that was to become Lightroom and I was severely flamed in the user forum for asking about a brush adjustment. to fix dust spots among other things. The volume of negative comments didn't bother me because at the time I had already "discovered" how to fix the dust spots with a cloning tool. Well I lot has transpired since then and perhaps a little behind its counterparts Lightroom does now have good dust spot removal, shown here. Spot being the important word (it does circular clone or heal), so trying to fix a linear tear or hairline might involve a lot of fiddly cloning. In reality I still prefer to do any dust and other tidying up in Corel Photo Paint. Now I find myself trying out the Lightroom 5 beta and the first thing that grabbed my attention is its Advanced Brush Healing Tool, which could well be the very tool I asked about 8 years ago. The "hardedge" surreal visualize spots view is particularly useful, like my photograph the blue sky trick, at helping you find the dust spots. I think a fair bit of drudgery might have just disappeared. This time I dare not ask the obvious question about synchroninzing these fixes across a series of photos (because the dust spots will be in exactly the same place). Phew someone has already asked that, thanks Juergen. Providing you just use the auto selected “source” for the clone or blend (blend is better) you can go ahead and synch the dust spot removal, with other photos, its just that occasionally you will want to shift the auto selected source location in some, hopefully only a few, of the synched copies. By the way you can do this in Lghtroom version 4 as well.

Adobe’s video on YouTube does a nice job of explaining the advanced brush healing features, make sure to pay attention to short cuts and tricks towards the end.

Lightroom 5 Beta is available for download now. Remember, as advised in the video, it is a beta version, so don't work on your existing catalogue, and don't use your original photos!

Dust Devil in the Detail

I wrote long ago about DSLR’s “dirty little secret”, dust on the sensor. Back in the film days and dust on the film plane generally stuck on the film and “ruined” just a single image. However in a digital camera dust on the sensor just sits there and leads to blemishes on frame after frame. Dust tends not to be a problem in compact cameras and cameraphones because they are sealed, but an SLR that takes different lens has a mechanical mirror that simply sits in front of the sensor and when the the lens is being changed the internal parts of the camera including the sensor behind the mirror are effetely open to the environment. Dust or fine sand particles, even insects can easily find their way to the sensor and because the sensor is frequently charged up and discharges as it records images and small statically charged particles are frequently attracted and stick to the sensor. So first rule is obviously not change lenses in a sand storm, or even a breezy day, or at least be careful. I take my cameras into a lots of hostile environments and I’m convinced with care and cleanliness in handling you will be fine but dust can suddenly turn up at the least expected times. Sometimes it is very obvious, like the dark shadow on the image below, and sometimes it is more subtle, like the fainter shadow on the left.

Some Cameras, like my Pentax which took the above photo, have special mechanisms that shake the mirror and this can be set to be operated manually or automatically at start up. Others like my canon have a feature that lets you photograph a plain white, or near white background, then detects dust marks and gives you the opportunity to remove then from the image beginning captured. Nice enough features but  still think that being able to manually cleans the sensor is the best option. [I must add a disclaimer here that may just be an urban myth, or worse a ranson-ware style fear campaign. There are lots of posts on camera and photographic sites that warn that manual cleaning a sensor may void a camera’s warranty. So check you cameras manual before you fork out a lot on having your camera “cleaned”] The procedure is pretty safe but requires the camera having a set up feature that will lift the mirror (both the Pentax and the canon have this feature). It is important that this next step is performed carefully, you simply need to use a gentle air stream to blow over the face of the sensor and carefully blow off the small particles. The sooner you get the dust of the easier it will be shift. Never use a brush or cloth on the surface of the sensor, Just a few simple puffs that direct a gentle airflow over the sensor is generally all that is needed. I have an old style lens blower brush and I simply remove the brush and use the blower by itself. but you can buy special compressed gas sprayers specially designed to clean cameras and lens if you want to spend a little extra. If you camera can be cleaned in this way you should find sufficient detail of the best procedure to do it in your camera manual.

I also posted earlier that the best way to check for dust on the sensor is just to take a few pictures of a clear blue sky, I still think this is a superior method than taking a picture of an evenly illuminated light surface, as recommended in many photographic websites and books, because the subtle small dust shadows are much harder to see. Sometimes the dust can be on the lens (or within the lens elements) but this produces a much more defuse shadow and frequently has give away lens flares associated with them. External dust on lens can be removed with the same gently blower methods but internal dust and dirt within the lens does require skilled specialist cleaning

Even when there is a horrible big shadow on you best ever digital photo, all is not lost. There are lots of tools around to “retouch” blotches and spot that are perfect to remove these blemishes. If you software doesn’t specifically mention dust look for a clone tool. These usually have two small circular zones, the first read whatever is with the circle and the pastes it over in the second circle So all you need to do is locate the first circle over and un-blemished bit of photo close to the dust particle that has the same colour, tone & texture and then position the second circle over the dust spot, click the mouse and the blemish is gone The catch is they are usually often very manual tasks and take some time to do well. So its much better to keep your sensor clean.

Spring Cleaning

Its the first day with a really clear sky I seen in a while and a perfect time to check on the cleanliness of the sensor on my sensor. I wrote some time ago about DSLR’s dirty little secret and how to use a photo of the clear sky to detect the presence od dust on the sensor. My current Pentax D20 is a well engineered unit and includes a dust reduction, a dust detection and a dust cleaning system (it shakes the sensor, with the mirror lifted). However small dust particles always seem to be get into most cameras. So I regularly check using my blue method. Now I additionally slide the highlight and shadow bars across while zoomed in to help detect dust. Ok often its barely visible (And not seen by the Built-in dust check) but I now know it there. Generally just one or two runs of the dust removal procedure followed by another blue sky photo is enough to convince me my camera is clean.
On my Pentax dust removal involves taking the lens off holding the camera facing down and selecting the dust removal from the setup menu, the whole camera appears to shake for a couple of seconds, that's all it takes. Older SLRs, which don’t shake themselves, can be cleaned by selecting the mirror up and using clean air blasts (you can buy specialty air-pressure pack from a camera store or use an old fashion bulb blaster, just take off the brush) across the sensor area. It is important not to touch the sensor or mirror directly with anything.
WARNING some camera manufacturer/models, notably many Nikons, claim such air blast cleaning voids the warranty and you need to get a certified dealer to clean the sensor (check your camera manual)

Badge of Honour

There were big queues at the car washes, so my car wore the dust as a badge of honour

A dirty little secret

My new Pentax K100D isn’t even a week old, and horror, there is a black dot in the middle of the picture, there it is again in exactly the same place on the next frame, there again, and again…. My first thought was a dead pixel, nothing in the troubleshooting about that, in fact dots on pictures aren’t mentioned anywhere in the troubleshooting section or the index…. What it did find, after a lot of looking, was instructions to clean the CCD, and yes that was the problem. Something like dust on my CCD, that goes all the way back to my first photos I just didn’t notice them at the time. Yes tem, there were at least three. So the dust was in the camera when I purchased it (or as I screwed on the first lens)

Cleaning the Pentax wasn’t hard but it must be done with care, follow the instruction in the manual exactly. There is a menu item to lift the mirror and you can use a blower (not a brush blower) to gently blast air over the CCD. There are numerous warnings, to many to cover here. SO READ THE MANUAL! However I had to do it four times, which brings me to the real purpose of this blog post.

How do you know that your CCD requires cleaning?

It is easy to test for a dirty CCD. Aim you camera at the sky on a nice clear day, away from the sun, so the sky is evenly exposed. Take a few exposures moving the cameras around. A few clouds, a bit of a tree or horizon can help you make sure you do this. Then upload the photo to your computer and have a look at a large magnification, in software that lets to scroll from one image to the next. If to see a shadowy spot and it is the same position within the photo frame its very likely to be dust on the CCD


WARNING: looking around on the net with the key words like digital, slr, cleaning, ccd, cmos it would appear that the web is awash with complaints and horror stories. Also some of the articles may not be all that well informed. If you can not find instructions in your camera manual be careful about trying to clean its CCD. In fact don’t, take it back to the dealer, or a reputable camera shop. Nikon digital SLR owners must pay particular attention to Nikon’s disclaimers about this. If you own a Nikon I suggest you read the article by thom about cleaning your camera.