Exercise: Correction

For this exercise, look through your image collection. Try to find one photograph that contains dust shadows. Find a second which contains a polygon flare.

If you can’t find any in your own photographs, used the images provided in the key resources section of the student website.

Before I began this exercise, I decided to research dust shadows and polygon flares.

Dust Shadows/Dust Spots:

When you look back at the images you have taken, on the computer, you will sometimes encounter small dark spots in some areas of your image. Sizes and darkness can vary depending on the aperture of your camera at the time of shooting. These dark spots are small dust particles on your camera lens or camera’s sensor.

The key to dust reduction is to try to avoid it altogether. This is one of the big advantages of using cameras with fixed lenses. If you use a Dslr camera, dust is part of life, even with cameras incorporating sensor cleaning systems. Dust does not lie directly on the sensor, but on the protective plate, so specks are not sharp edged, but usually appear as blurred dots. As a result, they may not be immediately visible when you open an image. The best strategy is always to assume that there is more dust on the image than you are able to see. The smallest specks remain invisible until you apply sharpening or increase image contrast. You can pre-empt the problem by increasing image contrast using an adjustment layer in your processing software, to reveal the dust specks as dark spots.

Dust particles on your camera’s lens show differently to dust particles on your camera’s sensor.

Below is an example I have found online, showing the differences between both.

Dust or dirt particles on the front of your lens, will not make much of a difference to your image. They are hardly visible, and sometimes only cause a slight haze or blur to an image.

Dust particles on the camera’s sensor will however, cause prominent dark spots. There are several ways in which you can tell whether or not you have dust on your camera’s sensor.

  1. The first being that dust particles on your sensor will always stay in the same place within an image.
  2. They will never show up through the viewfinder. You can only see them on your image. Depending on how large the particles are, you may see them straight away on an image, or in some cases, you may have to zoom in 100%.
  3. Depending on what aperture you use, you may not be able to see them. If you use a maximum aperture eg. F/1.4, you may not notice anything, but that does not mean that dust particles are not there. If you use a small aperture eg. F/4.0 and higher, the dust particles may appear darker and the size of them will become smaller, but more pronounced.

Below is an example of sensor dust.

 There are ways of cleaning dust particles from your camera’s sensor, I have provided a link below to a website that has a step by step guide. However, dust particles inside your camera’s lens, are slightly more difficult to clean, and it is suggested to either pay professionals to clean the insides or, to not worry about it.

Sensor dust particles:


Inside lens dust particles:


Polygon Flare/Camera Lens Flare:

“Lens flare is created when non-image forming light enters the lens and subsequently hits the camera’s film or digital sensor. This often appears as a characteristic polygonal shape, with sides which depend on the shape of the lens diaphragm. It can lower the overall contrast of a photograph significantly and is often an undesired artefact, however some types of flare may actually enhance the artistic meaning of a photo”  CambridgeInColour Article

Lens flare can take many forms within a photograph. The most common being the polygonal shape, it can be seen as large streaks from the light source in your image and rainbow circles or arcs. Lens flare may also cause bright spots within the image which can appear to be ‘Ghostly’.

Below is an example of a polygon lens flare.


Rays in Sunlight, By Bernd

There are things you can use or do, in order to stop or limit the amount of lens flare your image receives. Lens hoods are advised to be used when wanting to stop or limit lens flare. A good lens hood should stop the majority of stray light from outside the angle of view, which then causes lens flare. If you are planning on using a lens hood, it is advised that you choose a lens hood that does not contain a reflective inner surface. A lens hood which contains felt on the inner surface is a good idea, just make sure that there are no bald patches, which may have been rubbed off.

There are different types of lens hoods. Some may already come with your lens when purchased, or you can purchase them separately. The two most common lens hoods are the Petal Lens Hood, and the Round Lens Hood. Many argue that the Petal lens hood protects your image from lens flare better, as they are shaped to match the aspect ratio of a sensor, and the field of view of a lens. Below are the examples of a Petal lens hood and a Round lens hood.

Lens Hoods

Lens hoods can be made from tough plastic, metal or flexible rubber. I have a selection of the plastic and flexible rubber. Lens hoods are not used by every photographer. Some reasons may be because they are too bulky to pack into your camera bag ( Even though the flexible rubber hoods can now fold away), or simply because with lenses now, they are protected in order to stop lens flare and glare, in which case, people don’t worry about having a lens hood. Depending on the photographer, and what type of image you are trying to create, using a lens hood is a personal choice.

Dust Particle Correction:

Beginning with the dust correction, there are now specific tools in all processing software, be it in Photoshop, Lightroom, Aperture or any other. The standard tool for removing dust particles from an image is the Clone Stamp Tool. However, copying an adjacent part of the image onto the dot easily produces artefacts. Tools have been developed in modern software which sample the contiguous area, immediately around the dot, and fill it with the contiguous pixels. This produces invisible mends but it creates artefacts if the speck lies on a patter such as netting or near a hard edge. For these type of dust specks, the Clone Stamp Tool is best as you can set its blend mode to lighten, instead of the usual Normal blend, when removing dots lying on light areas.

Scroll through the image at 100% magnification, identifying any dust specks and removing them. All of these tools, whatever the software, work by attempting to replace the area of the dust speck with the texture, tone and colour of its immediate surroundings. This is, therefore, actually altering the content of the image, although on such as small and trivial scale that few people would argue against it.

For this part of the exercise, I was unable to find a photograph of mine which contained any dust particle spots, as I take special care when cleaning my cameras on a regular basis. I usually try to clean them after every use, in order to keep them clean, tidy and protected. Therefore I was unable to find a suitable image, however, when looking through photographs I had taken last year of the snowfall that we received, I found an image which contained snow particles which were landing on the lens and falling snow. The final image contained specks which would need removing, similar to dust particles, only in my case, it was snow particles.

Original Image:

IMG_1132 - Copy

I opened this image with Photoshop Element 9. I zoomed in 100% on this image and focused on the top left hand corner. When I zoomed in, I could see a lot more white snow specks which were obviously falling snow. The larger circles in the image were caused by snow droplets which had landed on my camera lens, whilst I was photographing the tree.

Where the dust speck is in an area without nearby sharp detail, the tool works well. But if the dust speck is only a few pixels away from detail, or even sits on top of detail, you may find the result less satisfactory.

More effective in this situation, is the clone stamp tool, but you will now find that you have to make more of a conscious decision to replace the small area with something specific. Is this as ‘Innocent’ a correction as using the dust removal tool?

Also, if you work over an area of the image that includes random specks of similar size to dust, as in the example, you will have difficulty deciding whether a mark is dust or content. This raises another valuable consideration – is this particular speck real from the scene, or an artefact caused by dust on the sensor? Should you remove it? Does this bother you?

100% Zoom (Top Left hand Corner):

zoom 100

For this image, I decided to use the Clone Stamp Tool.

clone stamp tool

With the clone stamp, I went through the image section at a time, removing any specks. Below is the same left hand corner, with the specks removed.

zoom 100 after processing

Final Image, Specks Removed:


I agree with using the clone stamp tool for removing any dust specks within an image. I believe that it is entirely a personal choice whether or not you use it. With my image, some may disagree, and say that I should keep the snow particles in the image, as it shows that it is snowing and shows movement, however, with this image, I personally think that it has benefited with me removing the specks, as now, the viewers eyes aren’t focused on the specks, but are now focused on the tree. Perhaps if there was more snow falling, rather than small blobs, it may have looked better.

‘But if the dust speck is only a few pixels away from detail, or even sits on top of detail, you may find the result less satisfactory’. I completely agree with this. In the centre of my image, I had a large circular shape which was caused by a snow droplet on my lens. I used the clone stamp throughout this image, and zoomed in to 200% at this middle section, in order to try and remove this circular area. I was happy that I managed to remove most of it, however, when zoomed out, I can still notice some of the circular shape, which means that I was less pleased with removing this speck as it was sat on top of several detailed areas.

sat ontop of detail

Overall, I do agree with the use of tools in order to remove dust specks, as it really is down to personal choice. If by removing this dust speck, you have a better looking image, then why not remove the speck. I believe it is innocent, as you are not altering the entire image, you are only assisting the image, in order to make a better final image. It is similar to doge and burn with film images.

Lens Flare Correction:

Lens flare correction takes more skill and more intervention, as there are no tools specifically for the job. There are various possibilities, including attempting to make a precise selection of the flare polygons before applying, say, a curve adjustment. This is very difficult to achieve naturally, and I recommend a different, less invasive approach, as follows.

  • Use a clone tool, set to Colour to integrate the flare polygons to their immediate surroundings.
  • Use a clone tools set to darken, also set with a close neighbourhood source.

These two actions, performed carefully, should remove most of the apparent blemish, and possibly sufficient for the image.

For this part of the exercise, I decided to process two of my images. I unfortunately couldn’t find any images that contained the polygonal shape. However, I did have an image that contained a large circular shape, which was caused by shooting directly into the light when photographing a sunset. It caused a double effect of the sun as it was setting. This circular shape is directly in the view line and the final image would be better if the shape was removed.

Original Image:

2011_0424barbra0135 - Copy

For this image, I used the clone stamp tool. I set the tool to ‘colour’ and proceeded to clone the area. Unfortunately, it wasn’t having the desired effect for me, as it looked almost black and grey, rather than red. I altered the tool to ‘darken’ and that too didn’t work how I wanted it to. Therefore, I set the tool to ‘normal’ and proceeded to clone the area. This worked better, and it began to cover the area.

Circular Shape Removed:

spot removed

Final Processed Image:


I am pleased with the results for this image. I believe that removing the circular spot was justifiable, as this spot was a mistake, which unfortunately happened whilst shooting the sunset. I do however, think that the image is interesting with the circular spot left in, however, if you are looking for a more conventional sunset image, then removing something like this would probably be the best option. I prefer both images.

I have a second image which contains a rainbow circle and some streaks.

Original Image:


When I zoomed into this image, it was clear that there was a rainbow streak in the top right hand sky area, and a streak through the bottom of the image, on the sand.

top spot beach before

before bottom spot removed

I decided to use the clone stamp tool for this. I began with the rainbow streak in the top right hand corner of the image. I decided to use the ‘Normal’ Mode for this as it worked well on the previous image. Once the rainbow streak was cloned and removed, I then moved onto the sand area, where there was a visible circular shape and a streak. I used the same cloning methods.

sky spot removed

after bottom spot removed

middle spot removed

Final Image:


How justifiable do you think this exercise was? If the flare is considered a mistake (This is not always the case, flare can be used creatively in composition), is there an argument that it should be left as it is?

I am pleased with the final result of this image. The clone stamp tool worked well on this image, and removed all of the rainbow streak and circular spots. Yes, the flares were mistakes, as I didn’t realised I had any until I viewed the image on the computer. I believe that it is entirely up to the photographer, whether or not they remove the streaks or flares, as in some cases, they may help enhance an image, or in some, they may hinder it. In this image, I think it hindered the image, perhaps if the rainbow streak was closer to the sun, and fell more towards the sand, it may have created an interesting image. However, because it was in the far corner, it had no point or need to be in the image. Therefore removing it, and the streaks on the sand, have helped the final image overall.

Overall Opinion:

I have enjoyed this exercise. I haven’t used the clone stamp tool on my photographs before, so for me it was a interesting tool to use. Now that I know how it works and the different uses it can do, I will most probably be using it in the future.

I do agree with the use of tools like this on image processing software. As mentioned before, I think it is personal choice whether or not you use them. I don’t agree with complete alteration of an image to where it looks nothing like the starting image. I don’t see how altering and removing dust spots or flares, can be classed as completely altering an image so that it is classed as a fake image. I believe that using these tools helps images to achieve a better final image, and is innocent.

Now move up a level of intervention to perform actions designed to make the image look better in your eyes, in effect , interpretation. The next exercise concentrates particularly on local adjustment and the techniques of making a selection in order to alter a specific area of the image.

The idea of making local adjustments to an image is straightforward and widely used, most common for shadows and highlights. If you are familiar with the techniques of darkroom printing of film negatives, dodging and burning are classic local adjustments. We made use of the digital equivalents and in digital processing it is normal to distinguish between global and local adjustments.

There are many ways of making automatic selections, differing according to the software, some of them so automated that you are not made aware of the area selected. One such is the shadow/highlights tool, in Photoshop, and there are equivalents in other programs. This selects areas based on brightness, and also based on their position in the image, and then allows them to be lightened or darkened according to taste. A more obvious way of making a selection in Photoshop is to use the quick selection tool or the magic wand too, which chooses values similar to whatever point you click on.

But there is another selection method that relies, not on the tone or colour of the area, but on your perception. Imagine a scene containing a person who is wearing clothes that include both bright and dark areas. It would be obvious to our eyes that it was a person, and we would be able to draw an outline around it. But this would be impossible for an automated process, which has only the values of brightness and colour to go on.


Digital Photography Masterclass, Dorling Kindersley Limited, London, 2008. Pages 167-168.

ISBN: 9781856131315

Dust Particles Article, July 27, 2010 By Nasim Mansurov


(Dust Specks Image) By Vit Kovalcik, 26 November, 2014


Polygon Flares:

  • Understanding Lens Flare & Ghosting Article. By Todd Owyoung, 13 July 2011http://www.ishootshows.com/2011/07/13/understanding-lens-flare-ghosting/
  • 25 Artistic Lens Flare Effects in Digital Photography Article, By Alex 5 March 2011. Image Rays in Sunlight, By Bernd



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