Tag Archives: Sensor Dust

Spot Visualization

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You know those sensor dust spots?

Yeah, I hate them too. When you shoot a sky at a small aperture like f/11, you will see them, sensor cleaning notwithstanding. They’re always there, like little poltergeists that are there to upset you and destroy your images. Modern sensor-cleaning cameras are a little better, but nevertheless, even when 99% of the dust is removed, that leaves the other 1%.

And that is enough. If you look carefully at this, full-sized (keep clicking), you will see some, e.g. top right.

But Lightroom comes to the rescue. In the DEVELOP module, at the top, select the clone/healing tool, set it to healing, and now at the bottom, activate “Visualize Spots”.

You see no spots? Drag the slider at the bottom to the right so you see them all:

Ouch!

OK, now that you see them, zap them all:

Now go back to normal view, and your image is cleaner than clean. Here;’s my final version (again, for best effect, as with all pictures here, click through to see large):

No dust. Thank heavens.

 

I have seen the enemy, and he is…

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…dust! Dust is the enemy of photos. Sensor dust, to be precise. Tiny pieces of dust that stick on your sensor.

Look at this image of model Danielle on the beach yesterday:

Now look at a small section, with slightly enhanced contrast:

See all those blurry specks? View at full original size (click through twice to do that) and see how terrible that dust really is.

And you see it when you are both:

  1. Shooting at small aperture (like my f/14 all day yesterday), and
  2. Shooting against an even surface – like the sky.

In other words, you get this on sunny days outside!

Solutions? In order of dangerousness, with the safe options first:

  • First, use the built-in dust removal function in your camera repeatedly.
  • Or have Canon/Nikon/etc do it (but this will cost money and take time).
  • Then, with a full battery use the “manual cleaning” option – the shutter stays open while you blow with a rubber bulb blower. Blow with that blower  without touching anything, repeatedly, and try again.
  • As a very last option, use liquids and special pads, but use the right liquids and brushes specifically for your camera 9ask the manufacturer if in doubt), and be very, very careful – a destroyed sensor is not covered by warranty and can cost more than the camera.

Or.. live with them, and remove them in post-production.

TIP: if you do that, do it before you crop, so that you can copy/paste the adjustment to all images with sky.

___

I am teaching this weekend: tomorrow at Vistek in Toronto (“Macro”), and Sunday “The Art of Shooting Nudes” in Hamilton. Book now – there is space.

Keeping It Clean

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It is very important to keep your camera’s sensor clean.

Dust shows at small apertures, like f/16:

f/16, and that looks OK until you look at the small

See those dark dots? That is sensor dust.

You can try to get it off with the self cleaning mechanism, see the top picture. Or with a blower (be careful – use a full battery). Or with pads and liquid, but that is potentially dangerous – one mistake and your camera is toast.

So the best way is to keep the dust off in the first place, and to minimize the effects

  • Use the self cleaning mechanism.
  • Avoid lens changes unless necessary
  • Shoot at larger apertures if it’s all the same to you 🙂
  • When changing lenses, try to do it in a safe dust-free place
  • Hold the camera upside down (-ish) when doing it, so that large dust falls out of, rather than intio, the camera

I regularly clean my sensors -looks like my 1Ds is ready for another cleaning, from that photo.

Bonus question: how do you know I was shooting at a small aperture?

Answer: because of the starburst from the street light. The smaller the aperture, the more starburst effect.

 

Dust to dust

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So why do sensors collect dust, and how do you detect it, and what do you do about it?

A sensor is just an electronic negative. But it collects dust for two reasons: one, it never changes (unlike a real negative, which changes for ever shot); and two, it is electrical and can therefore get electrostatically charged, meaning it attracts fine dust particles.

This dust can show up in images where you use a small aperture (like f/16) and have an even surface (like the sky). It looks like this:

So how do you know if you have dust on your sensor?

You do. Everyone does. Do not worry about it unduly – unless it shows up in images! But if you really want to know, here’s how:

  1. Set your camera to aperture mode (A/Av).
  2. Select a low ISO.
  3. Select an aperture of f/16 or f/22 or even f/32.
  4. Set the lens to wide
  5. Focus manually to the closest distance
  6. Point at, and fill the entire frame with, a clear surface like a white wall
  7. Shoot – and move your camera about while shooting.

You will now, when you zoom right in, see the dust.

If is it annoying, then go about removing it in the following ways:

  1. Use the camera’s anti-dust feature repeatedly.
  2. If that does not work, ensure you have a 100% full battery and use a blower (set the camera to manual cleaning, or bulb mode, open up, and carefully use a rubber bulb blower.
  3. If that fails, the safest way is to have it done by your camera maker.
  4. Alternately, use the Visible Dust rotating brush first.
  5. And finally, when even that fails, use wet pads.

The wet pad process is annoying and scary. You will clean some dust but deposit new dust. (Test after each attempt). You will see smears. You have to carefully repeat this process a number of times until you are finally dust free.

Finally: prevention etc: always minimise lens changes and when you do change lenses, carry the changes out with the camera pointed down. Store your camera with a lens attached, always.

Sensorama

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I cleaned my sensors today. On the 1Ds Mark III and the 1D Mark IV. This took more than an hour.

So I thought this might be a good opportunity to talk about sensor dust.

Unlike a negative, which gets “replaced” for every shot, the sensor on your camera can gather dust over time. This then shows up under certain circumstances on your images.

When? When do you notice it?

To understand this, image a small piece of dust just above the sensor. If the lens has a wide open aperture, this piece of dust will not cast much of a shadow, because light from the left might cast a shadow on the right, but light from the right lightens that shadow. The wider the lens aperture, the less defined the shadow cast by the dust.

Now imagine a narrow aperture, a pinhole. Each piece if dust casts a nasty shadow. I.e. it is visible. That’s what dust spots are: shadows from dust specks.

Now think along with me. Say I want to shoot this, as I did during the Henry’s Creative Urban Photography session I taught in Oakville on Sunday.

Lion and Water

Lion and Water

Evidently I need a long shutter speed to blur that water: in this case I selected a quarter of a second.

For which I need a small aperture. f/22 or f/32. A tiny opening in the lens.

So then, when you shoot at small apertures (large “F”-numbers), and especially in plain areas like the sky, dust shows up. Which got me here.

To clean dust, you need:

  1. A freshly charged battery.
  2. A spare camera in case you break the sensor (which I have never heard of, but I am sure it happens).
  3. A rubber air blower, your first port of call.
  4. A rotating brush from Visible Dust.
  5. Also from Visible Dust, pads in the size of your sensor (1.0, 1.3 or 1.6), and the appropriate liquid.
  6. A healthy dose of patience, and a calm demeanor.

First, measure. Switch the lens to a wide angle, and switch to manual focus. Focus close, then while gently moving the camera, shoot a distant white wall, using an 8 second exposure at f/32 at 100 ISO. Adjust as needed to get white, but not blown out. Now check by zooming in and you see dust and smears.

Now clean. Make sure you have a full battery. Now use the manual sensor cleaning function on your camera to open the shutter. Then remove the lens. Carefully blow first, using the bulb blower. Now close the camera, turn it off and on, and repeat the test.

Then if it’s not yet fixed, repeat using the brush, which you first rotate for a few seconds first. You may have better results. But you will equally probably make it worse instead of better.

In that case, repeat again using a pad, after you drop 3-4 drops of liquid onto it. Again, you will make things worse before you make them better.

This is where the patience comes in: after using up three or four pads you will despair. Smears, dust: it gets worse and worse. Every time you remove one dust speck, you add two. Will you ever get it done? Is your camera toast?

And yet… after an hour you get to a point when suddenly, there’s no significant dust. That is when you stop.

So after more than an hour, I now have two as-new cameras.

Two more things:

My camera does this by itself! Yes, but it does not clean off all the dust with its ultrasonic shaker.

Is this not risky? Yes it is. Do this at your own risk. (That said, I have been cleaning sensors for a decade without any mishaps.) My advice: do this when needed, but do not obsess. If you never shoot at f/16 or beyond, don’t worry. If you do not see the dust, do not worry. But if you do – get it done.