Sensor Dust

Looking at the images displayed during the opening evening, some of the images had sensor dust spots on them.

Now the authors may or not have noticed them, in the past I have found that some people do not notice these spots until they are pointed out to them. It was the same with slides, when at times I used to point out scratches.

I think it is a bit like lamp posts sticking out of peoples heads, etc. It takes a bit of practice.

I think everyone is aware of what sensor dust is, but are wary of cleaning their sensors, it can be expensive if you make a mistake. Having said that every photographer should be able to perform a basic clean.

Sensor Dust on Image

Sensor Dust on Image

I have marked some sensor dust spots on the image above, if there is a hair, or strand of fibre this will show as a strand. Dust will stand out against light and plain areas of the image.

The first step is to see how dirty your sensor really is. The best way I have found to do this is to select a low ISO, and an aperture of about f22 and a shutter speed slower than 1/2 sec (if possible, the important setting is the f stop). You will also need a light coloured plain background, a wall or a blue sky will do.

Check that the exposure is slightly over exposed. Point the camera at the wall and take a photograph. If you have a slow shutter speed, move the camera so that the background will be blurred. This makes it easier to see any marks from the sensor and not to confuse them with marks on the wall.

Now that you have found that your dust you need to deal with it.

1. The first thing could be not to use a small f stop, which you probably shouldn’t be doing if you want your image to be sharp.

2. Clean the sensor with the camera’s built in cleaning, some cameras allow you to turn this function on, so that each time the camera is turned on and off it will carry out a clean. All this does is vibrate the sensor, so that any dust will drop off the sensor. Therefore I would recommend either having the camera facing the ground, or as if you are  going to take a photograph. This will shorten the life of the battery.

3. Remove the lens, and use a blower (not a brush and NOT a spray can) to blow the dust out.

One of these is a Giottos GTAA1900 Rocket Air Blower – Black – I would paste a link, but just cut and paste this phrase into the Amazon box at the bottom of the page to assist the club.

None of the above require you to touch the sensor, if you are confident then you can do the following 2 which I am not going to go into detail here.

4. There are brushes that you can but (Artic Butterfly) which you charge with static before using in order that it picks up lose dust.

5. Wet cleaning – which requires you to wipe the sensor with a pad and liquid designed for cleaning sensors

6. The last option is to pay for the job to be done.

Your camera is your responsibilty and I would advise you not to carry out any of these options unless you are confident.

So you now take care of your sensor, but how do you check your image? This depends on your editing program. The one thing that is common, is that you should check it at 100%.

In Photoshop and Lightroom, zoom to 100%, you then need to scan the image, in Lightroom and Photoshop, press the ‘Home’ key and this will take you to the top left of your image.

Press the  ‘End’ key and it will take you to the bottom right. In both programs, if you use the ‘Page Down’ and ‘Page Up’ the area zoomed in will move up and down.

So press the ‘Home’ key and start at the top left, press the ‘Page Down’ key to move to the next portion of the image. Check for spots and deal with them (using the healing brush) before moving on to the next section.

When you reach the bottom of the image, Lightroom will take you to the top of the next column, so all you need to do is use the ‘Page Down’ until you get to the bottom right of your image.

With Photoshop, when you get to the bottom of the column you will need to use ‘Ctrl’ and ‘Home’ to move to the next column.

Here are some keyboard short cuts for Photoshop.

Home = move to top left corner
End = move to right bottom corner
PageUp = move up one page
PageDown = move down one page
Ctrl+PageUp = move left one page
Ctrl+PageDown = move right one page
Shift+PageUp = move up 10 pixel
Shift+PageDown = move down 10 pixel
Ctrl+Shift+PageUp = move left 10 pixel
Ctrl+Shift+PageDown = move right 10 pixel

There may be other spots that are not immediately obvious and there are techniques to make it easier to find those that are not visible straight away.

I will cover these some time later.

 

Ray

 


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