Remove dust specs

That’s it, have you been wandering in wheat fields during harvest? Or was it hiking on windy cliffs? Or you just use your gear a lot, and it gets inevitably dirty? Anyway you got visible specs of dust on your photos, and here are a few steps to get rid of it.

Where is it?

The dust you see can be in different places in your camera. Where it actually is depends on a few observations:

– Is the dust spec visible from the viewfinder, but not on the photo? Then it must be either on the internal mirrors or directly on the viewfinder lens. Cleaning the viewfinder usually sorts it out.

– Is the dust grain visible on the photo? Are your front lens and filters clean? It is always useful to clean those once in a while with a microfiber cloth or a blower.

– Your gear was pretty much clean on the outside, but the dust is still visible? You sensor might be in cause.
Do a quick test to spot dust on your sensor: take a photo of a bright and clean zone (like the sky or a white wall) at the lowest aperture your lens provides (i.e. f/22). Low aperture is needed because of the lens optical properties, which will blur sensor dust specs to the point of hiding the smaller ones at high apertures. Carefully look at the resulting photo. Any dark dust specs should pop up pretty easily on the bright background.

How do I remove it from my photos?

You will need a tool that allows to cover the dark spot created by the dust blocking the light from being captured by the sensor. The most natural method to remove the spot is to blend it by covering it with the surrounding color and texture.

In Photoshop, tools capable of doing this are either the clone stamp or patch tools.

Patch tool retouches an image using sampled pixels or pattern.

First, select with the tool one or several zones you wish to retouch, then grab the selection to an area that matches the content you wish to overlay.

Once you release the selection, Photoshop runs the tool algorithm that will try to blend the selected areas as well as possible, using the matching area you provided as an input.

This tool can come in handy but it is not flowless.  For example, it generates artefacts near the selection border, especially on noisy pictures (see below). It also does not blend delimited high contrast zones when the contrasted area is near the selection edge.

That’s why I often prefer using the clone stamp tool for this task.

Clone stamp tool allows you to copy from one area of a photo to another using any type of brush.

Start by sampling the area you wish to copy by maintaining the Alt key pressed (a target cursor appears), then click.

Adapt the size and hardness of your brush to the size of the spec to cover. Edges may be too visible with a brush too hard. I usually use a brush somewhere between 0% and 50% hardness.

Photoshop shows you a preview from the previously sampled area inside the selected brush so you can appreciate whether the color and texture would fit.

The result is much more seamless in this case.

Some prevention

Keep in mind that a camera in use will anyhow naturally get dirty. However, a few things may prevent you from having to deal with unwanted dusty shots:

– Clean your gear !
Take the time to thoroughly clean your camera and your lenses before any travel. While on the road, check your gear every day, especially if you shoot in difficult conditions, and do some more cleaning if needed.

– Be careful of your gear in difficult conditions. Avoid changing lenses near places that produce dust (dirt paths, barns, you name it). Try to do so when the wind is low, or at least make the back of your camera face the wind so it won’t blow in the opening.

– For the most wealthy of you, invest in seal-weathered gear. Seal-weathered means hermetic. It is not only useful when it comes to wet weathers, it also works to prevent dust from entering your camera, though it will not prevent it from getting covered.