How to check if your DSLR Sensor is Dusty

Dust is the photographers enemy !!  It can be very frustrating to spend a day taking photos, agonising over aperture, ISO, shutter speed, framing and focus, only to discover that your “Perfect’ shots have been ruined by dust.

Most photographers soon learn to become vigilant about cleaning their lenses before an important shoot, but a dirty sensor is harder to deal with.

DSLR’s use a digital sensor to convert light (from the scene you are viewing thro0ugh the lens) to a digital image.  The sensor is electronically charged and actually attracts dust.  It is not normally exposed to the environment, but is at risk every time you change a lens.

The chance of dust getting into your sensor increases dramatically if you change lenses regularly, or do so in a windy or dusty environment.  The best way to minimise the risk of dust getting onto your sensor is to be as quick and efficient as possible when you change lenses.

No matter how careful you are though, dust WILL get in, so over a period, you may start to notice dark spots on your photos (see images to the right), that show up in the same spot for different photos.

If you’ve encounter blemishes like this on your photos, it is probably because you have dust on your Sensor.

Dust spots on your DSLR’s sensor appear as tiny black specks on the image. You may not have even noticed the specks—they usually only show when you’re shooting a bright subject (such as the sky) at a small aperture. But if those specks have annoyed you, you can remove them from your image using image-editing software like Photoshop, or you might eliminate them from future shots by cleaning your D-SLR’s sensor.

DIY Sensor Cleaning ??

Although none of the major camera manufacturers recommend cleaning the sensor yourself and suggest that you have it professionally done, there seem to be plenty of stories about cameras coming back from the “professionals” with sensors dirtier than when they started.  There are also plenty of resources available online about DIY Sensor Cleaning. These invariably  come with warnings and disclaimers so if you do choose to have a go yourself – Be Careful !!

Some manufacturers (e.g. Canon) do include some basic instructions about cleaning sensors with a blower (NOT a blower brush) and as this is a non-contact cleaning method – is considered fairly safe.  This is a good way to get rid of loose dust articles, however, this will not remove more stubborn dust which is stuck to the sensor.

Does your DSLR Sensor need Cleaning ?

Before you rush into cleaning your sensor however- How do you know if your sensor actually needs cleaning in the first place ??

You may start to notice spots appearing in your photos (as in the sample images above)m, but the process outlined below provides a quick and easy way for you to confirm if your sensor is dirty.

How to Take a test Photo

To take a test photo, you can use about any lens you want but a prime or zoom lens works better then a wide angle. You want as much of an even exposure as possible from corner to center as you can get. You should also use the highest aperture setting possible; we suggest a lens that will stop down to f/22 or greater.

You should shoot something  plain such as the sky or – as we have outlined below – your PC screen :

• Create a new image in Photoshop or any other application (a blank Word document viewed in full screen mode is fine)
• Fill it with white (most any solid color will do, but we prefer a lighter one) and view it full screen
• Set the camera to the following:
  • Mode – Aperture Priority
  • Setting – Aperture to minimum f/22-f/45
  • Lens – Manual Focus set to closest focus setting (if shooting the blue sky, then infinity)
  • Features – Turn “OFF” all special function like “sharpening”
• Zoom in until it fills your screen
• Take a Picture – shoot camera facing your monitor. Depending how bright your monitor is, your exposure may be a couple seconds. During this exposure, move your camera back and fourth being careful to not to point the lens outside of your white box. Moving the camera during the exposure insures that you are not taking a picture of dirt on your monitor. This should be done within a matter of an inch or two from your monitor.
• Take the image into Photoshop (or any other image editing application) and do an “auto level” (this is “<CTRL><SHIFT>L”  in Photoshop).
• Inspect the Image – You should now be able to see where you do or do not have dust.
  What you are looking at is an image that is flipped 180° vertically (top to bottom) from when you’re looking straight in on your sensor. What shows on the bottom of the image will be towards the top of the camera and visa versa…

At first glance the original test photo looks pretty good.  It is possible (in the full size image) to see a few specks here and there but weothouit further processing you would probably assume it is OK.

 

 

 

After applying auto levels (in Photoshop) the dust particles become much more apparent.  Again, this sensor is actually not too bad – but worth trying a blower to remove any loose particles.

 

 

After the blower was used, another test photo was taken, auto leveled and this is the result.  There are still a couple of specks showing but it is a LOT better and not worth trying any more 9intrusive (and potentially harmful) cleaning processes.