Epson R-D1: Sensor cleaning

Dust is a fact of life, and gets everywhere – and it will get into your camera, however careful you are: sooner or later, your sensor will need cleaning. Sensor cleaning is not something I do regularly, only when I notice tell-tale blobs on my photographs. To check the cleanliness of your sensor, take a photograph at the smallest aperture (e.g. f/16) of a bright, featureless background (e.g. of the sky, whilst moving the camera) – any dust and dirt on the sensor will appear as dark spots.

The nature of dust

The size of a print, even a small one, is many times the size of a sensor, so even microscopic particles (0.1 mm) on the sensor, invisible to the naked eye, can cause spots on photographs.

Small particles such as dust adhere to surfaces in two main ways, depending on what they’re composed of: electrostatic attraction and surface adhesion. The first mechanism works by attraction of opposite electrostatic charges: positively charged dust particles gravitate to the negatively charged sensor. This is the same phenomenon that makes your TV or computer screen dusty. The second mechanism is chemical attraction, and is a much weaker force than the first: when dust particles encounter the sensor or each other, very weak chemical bonds are formed.

Both forms of adhesion are weak, and the particles are easily removed.

The majority of contaminants found on a sensor are of the above types, but occasionally more stubborn particles, or stains, are encountered, such as pollen, or spots of oil from the shutter mechanism.

Method 1: blower bulb

Blowing is the easiest and most convenient method, and should be used first (and as the first step in the other cleaning techniques). It is also the method suggested by Epson. I use this technique most of the time. Note: use a bulb blower – never canned air!

Requirements

• A fully charged battery.
• A locking cable release.
• A powerful rubber blower bulb (e.g. the largest Giottos Rocket).

Procedure

1. Screw the locking cable release into the shutter button.

2. Remove the memory card, detach the lens, and turn on the camera’s power switch. The memory card is removed to prevent the camera from powering up the sensor (a ‘live’ sensor creates an electric charge that attracts back the dust you’re attempting to remove).

3. Set the shutter speed to ‘B’, and lock the shutter open with the cable release. Then, hold the camera with the lens mount pointing downwards, and gently blow the dust off the sensor and surrounding areas with the blower bulb, making sure that you don’t let the tip of the bulb touch the sensor.

4. Unlock the cable release, switch off the camera, and replace the lens and the memory card.

Method 2: sensor brush

The second dry method is to use a brush to sweep up dust particles. This technique is less convenient than blowing but will remove all but the most tenacious dirt. Also like blowing, it is extremely unlikely to damage your camera.

Choice of brush

You could use the well-known VisibleDust sensor brush, but it’s extremely expensive. Also, as a chemist and science writer, I’ve long been annoyed by the pseudo-scientific spiel from some manufacturers of sensor brushes, designed solely to baffle people without a technical background and convince them to buy their brushes at hugely inflated prices: a sensor brush is nothing more exotic than a brush with fine plastic hairs. Sensor-cleaning companies also promulgate the myth that sensor cleaning is a delicate operation fraught with danger, and discourage you from using brushes other than theirs with dire warnings. This again is distortion: the sensor itself is delicate, but it’s protected by a thin layer of a very tough glasslike material (lithium niobate), although some sensors have an additional softer antistatic coating – in short, a sensor is no more susceptible to damage than a camera lens.

Copper Hill sells brushes that are just as good but far cheaper, and sensor brushes are also available from eBay. Alternatively, go to a local shop and buy a suitable synthetic artist’s water-colour brush for a couple of pounds. There’s nothing special about a sensor brush: it’s just a flat brush with fine plastic (e.g. nylon) fibres, which by their nature attract dust. What is important, though, is that you must clean the brush scrupulously after purchase – again, nothing special about this: just use dishwashing liquid.

If you want a do-it-yourself sensor brush, you should first read ‘The Pixel Sweeper’ by Petteri Sulonen, which explains which types of brush are best, how to check that your brush is clean enough, how to use the brush, etc.

Method 3: wet cleaning

Occasionally, a particle adheres to the sensor that can’t be removed by blowing or brushing (pollen grains are notoriously sticky), or it may be contaminated with, for example, oil from the shutter mechanism. Such dirt can be removed by wet cleaning: wiping the sensor with lint-free tissue moistened with a solvent, wrapped around a spatula. Several commercial products are available (e.g. Sensor Swabs), or you can use the original do-it-yourself technique (the ‘Copperhill method’). The solvent is purified, contaminant-free isopropyl alcohol (if you can’t swipe some analytical-grade solvent from a lab, it is available as Eclipse E2 sensor cleaner).

A common mistake when wet cleaning is to use too much liquid on the swab, which instead of cleaning the sensor, adds smears: the swab needs to be barely moist.

Personally, I use wet cleaning as a last resort: it’s time-consuming, and there’s a slight chance (albeit very unlikely) of scratching the sensor with a trapped particle if the sensor swab is used too vigorously. So far, blowing or brushing has removed all the dust from my sensor.