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How to Remove Sensor Spots

How to avoid dust spots on your images, and how to remove them if it was too late

Wel­come to the won­der­ful world of dust and soft­ware. The epic bat­tle between the phys­i­cal and dig­i­tal world. Or how a sim­ple piece of dust can spark a shop­ping spree.

The above para­graph makes no sense to you? Fear not, it is easy to explain.

What are sensor spots?

Here is a test image. Can you spot the spot(s)? Looks clean to me.

Chalice in Christchurch
Chal­ice in Christchurch

Let us look clos­er. Zoom in to 100% mag­ni­fi­ca­tion, left upper part of the image:

Two spots are visible in that area
Two spots are vis­i­ble in that area

That is an old­er image, so I can’t check any­more if these spots are sen­sor spots, but they appear like them.

So what is a sensor spot?

A tiny piece of dust stuck to the fil­ter in front of the cam­era sen­sor caus­es a shad­ow on the sen­sor. The shad­ow is now vis­i­ble on the dig­i­tal images the sen­sor pro­duces, until you or the cam­era remove the dust. Depend­ing on the aper­ture of the lens, the shad­ow is more pro­nounced (small Aper­ture, e.g. f/16) or bare­ly vis­i­ble (large Aper­ture, e.g. f/1.8). For sim­plic­i­ty, I will con­tin­ue to call it “dust on the sensor”.

If you feel the urge to remove the lens and blow the dust away, please don’t do it just now. You will only end up hav­ing more of that stuff on your sen­sor. Let us explore what we need to fix the issue, with­out caus­ing mayhem.

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Remind me, why do we not want dust on the sensor?

Before we move on to the solu­tion part, we should stop for a sec­ond and think about why we want to get rid of the spots. They don’t harm you, right? Tiny insignif­i­cant pieces of dust don’t cause skin rash, do they? Well, they might, if you are a com­pe­ti­tion judge look­ing at sen­sor spots on com­pe­ti­tion images, but that is a top­ic for anoth­er day and has been cov­ered more than it should have.

Do not fix some­thing if it is not bro­ken. It is only bro­ken if the spots both­er you or the judge at your pho­to club com­pe­ti­tion night.

But think a lit­tle ahead if you want to print your images in a beau­ti­ful large for­mat. It will enlarge every micro­scop­ic thing. You see where I am going with this? A spot I can bare­ly see on a 10cm x 15cm print does not both­er me. But on a 1m x 1.5m print it will be high­ly vis­i­ble and incred­i­bly expen­sive if you need to re-print that monster.

Dust on the sen­sor does not come off on its own unless you remove it. It con­tin­ues to spoil each of your images until the death of your cam­era, or your own, what­ev­er comes first.

That was dark.

I assume your cam­era dies ear­li­er. Or more like­ly: you buy a new cam­era (voice from the off: “No! Only over my dead body!”). I’m dig­ging a hole here. I need some space to free my thoughts…

Where was I? Ah, sen­sor dust not com­ing off, that’s why we don’t want it. It stays there. Yes. Dif­fi­cult to remove.

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How to prevent dust from entering the inside of your camera

What can we do before it is too late?

How can you pre­vent the dust from enter­ing the holy halls of sen­sor enlight­en­ment? Don’t take the lens off. That’s easy. But what would you then do with all the oth­er 10 lens­es you bought when you were giv­ing in to your GAS (Gear Acqui­si­tion Syn­drome)? Sell them? (a voice from the off shouts “YES! Sell them and buy us a house instead!” That was the voice of your sig­nif­i­cant oth­er, if you have one). Where was I? Right, the lens attached to your cam­era. You will remove it even­tu­al­ly to make use of all the oth­er 10 lens­es you nego­ti­at­ed over decades with your sig­nif­i­cant oth­er (bet­ter?).

When you take the lens off, hold the cam­era fac­ing down­wards. Dust reacts to grav­i­ty and sinks down. Not always, e.g. when you blow into your cam­era. But most­ly. I think.

Where was I? Using my 10 lens­es, yes. Don’t expose your cam­era sen­sor for long, dust will find its way into the cam­era body. And make sure the part of the lens which faces the cam­era body is dust-free when you re-attach the lens.

Some cam­era man­u­fac­tur­er invent­ed ways to get rid of sen­sor dust by vibrat­ing the fil­ter in front of the sen­sor, shak­ing the dust off. I once had a Canon dig­i­tal cam­era, it boast­ed the “EOS Inte­grat­ed Clean­ing Sys­tem (ICS)”. It worked well, I had no issues with sen­sor dust. Look up your cam­era mod­el if it has some­thing like that, Canon is not the only man­u­fac­tur­er who does that.

If you are keen to read what the man­u­fac­tures do to pre­vent the dust from stick­ing on the fil­ter, read the tech­ni­cal arti­cle on Canon’s web­site: EOS Inte­grat­ed Clean­ing Sys­tem (ICS) (Note: The arti­cle is no longer on their cur­rent web­site, but you can access it through the bril­liant inter­net archive, the ‘way­back­ma­chine’) . It is worth read­ing, but brace your­self to read about “flu­o­rine coat­ing”, and “sta­t­ic charge” and “lens cap mate­r­i­al” and “piezo-elec­tric” and “ultra­son­ic vibra­tions”. Fascinating!

But what­ev­er you do, dust will find its way on to the sen­sor. How do you remove it? That’s where the shop­ping spree comes in.

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How to remove dust from inside your camera

Buy a sen­sor clean­ing kit. And mag­ni­fy­ing glass­es with light, if your eyes need help to look at tiny things at a close dis­tance. My set looks like that:

My unused cleaning kit
My unused clean­ing kit
my occasionally used magnifying glasses
My occa­sion­al­ly used mag­ni­fy­ing glasses
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I bought it because I thought I had a sen­sor spot, but it some­how removed itself before I had the chance to use the kit. I used the mag­ni­fy­ing glass­es for oth­er things, like remov­ing splin­ters from my fin­ger, but that is anoth­er sto­ry which has noth­ing to do with photography.

At the time I want­ed to remove my sen­sor spot, it was not there any­more. I researched how to do a test (see below), and end­ed up not clean­ing the sen­sor with the kit. Because of that, I can­not tell you if it works. Or how it works. I can still point out sev­er­al things you want to think about before you buy a kit.

  • What sen­sor size does your cam­era have? The kit swab needs to fit the sensor.
  • Be rea­son­ably sure that you have a sen­sor spot.

How to test for dust on the sensor

You can test for dust on your sen­sor with a sim­ple pro­ce­dure, cre­ate an ide­al envi­ron­ment for the dust to thrive, and then take an image:

  • Use a uni­form light back­ground for the sub­ject — a piece of white paper is sufficient.
  • Select a small aper­ture (high f/ num­ber, e.g. f/22) — put your cam­era in aper­ture pri­or­i­ty mode to select the aperture.
  • Turn on man­u­al focus and focus into the distance.
  • Take an image of the white paper, let it fill the frame, you want a white image.
  • Inspect the image at 100% mag­ni­fi­ca­tion to see if you can find spots, Adobe Light­room has the visu­al­ize spots func­tion, that is help­ful (see instruc­tions fur­ther below).

If you are lucky, or maybe you are just start­ing out and you have only one lens and you nev­er take it off, then you have no spots at all. Or your cam­era was able to fend off any dust. But if you have spots, then your soft­ware comes to the rescue.

We are now at the point where every­thing is too late. The sen­sor spot found its way on to the images you have tak­en already. Could be one image. Could be sev­er­al thou­sand. Let us hope that it is a small num­ber, and you already removed the dust from the sen­sor so it will not con­tin­ue to be an issue.

How to remove sensor spots from your images with Adobe Lightroom

If we con­tin­ue the exam­ple from above, we can quick­ly fix the issue by using Light­room. Switch to the “Devel­op” mod­ule, it should look like this:

Screenshot: Author — Adobe Lightroom visualize spots interface
Adobe Light­room visu­al­ize spots interface
  1. “Devel­op” Module
  2. Select the “Spot Removal Tool”
  3. The “Visu­al­ize Spots” tick box is here
  4. Slid­er for sen­si­tiv­i­ty of (3)

Tick the “Visu­al­ize Spots” box and watch what hap­pens. The image turns into a Black & White image with very exag­ger­at­ed con­trast. Use the slid­er to change the effect until you get rid of the noise and only see the spots.

Two spots

Can you see the spots now? You see many spots now, not only sen­sor spots. It is very easy to remove the spots, just tweak the size of your (now cir­cu­lar) cur­sor. The inner ring should just cov­er the spot. Click to remove the spot.

The pro­gram now search­es for an image area it can paste over the spot. Watch the ani­mat­ed GIF (it runs in a loop) to see how it works:

Spots anim

Summary:

Now you know

  • what sen­sor spots are and what caus­es them
  • why you do not want dust spots
  • how to avoid get­ting the spots
  • how to detect if you have dust on your sen­sor filter
  • how to remove dust from the filter
  • how to remove dust spots from your images with Adobe Lightroom

Have fun tak­ing pic­tures… spotless!

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Frithjof Moritzen

Photography Club Enthusiast

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