Month: November 2010

Sensor cleaning – Go ahead, do it yourself

First things first. If you choose to follow this advice, you do so at your own risk – if you damage your sensor or your camera, well, it’s your fault, not mine.

Having said that, be aware that you will not actually be cleaning the sensor – rather, you will be cleaning the glass in front of the sensor. In the trade, this is called a “hot mirror”. It is a rectangle of glass, coated with an infra-red cut filter layer (amongst other things). Having successfully converted a Canon 300D (Digital Rebel) into an IR-only camera last year through a sensor transplant that I undertook myself, I can speak with authority that the coated surface of the hot mirror that you will be cleaning  is extremely tough. I deliberately attempted to scratch the removed filter’s surface, and it took a lot of doing with a toughened steel screwdriver. I am not convinced that cleaning with a slightly damp piece of tissue represents a risk.

My Canon 5D seems to be a dust magnet – things get dirtier and dirtier until photos are ruined. It seems that Topaz Adjust makes the existence of dust even more visible, so this is important to me.

This is most important – fully charge your longest lasting camera battery, and put int in the camera for cleaning duty. Some cameras won’t even allow cleaning if the battery isn’t full, and the battery is providing the power to keep the mirror up and the shutter open, so don’t take a chance on it going flat.

On my 5D, the “sensor clean” menu setting is only revealed if you are not using the green rectangle idiot mode. As my camera is permanently set to aperture priority I didn’t know this until I cleaned a friend’s 5D and found this fact out.

Before you start, in order to successfully clean your sensor, you need to assemble a few bits and pieces.

  • A can of compressed air – I use canned air bought from Office Works, with a tube that fits into the can’s nozzle. A lot of people will tell you this should not be used. I agree with them – use this at your own risk, as if you tip the can over, you will get a messy deluge of frozen gas, that will dirty everything inside the camera, and might even kill it. I will say this – it has worked magnificently for me. Some people warn that canned air contains oil vapour, but I haven’t seen evidence of this. If you prefer not to risk things, then use a Giottos Rocket Pump instead.

Here is what does happen if you get a solid squirt of liquid gas – this will destroy life as you know it … so be careful and don’t tip up the spray can.

  • At least two wooden tongue depresser sticks . These are like oversized ice cream sticks, but are of high quality as they are destined for people’s mouths, and don’t have splinters or other bits of wood hanging off them. Perpendicularly cut off one of the curved tips of both sticks, as straight as you can with a Stanley knife (but I used scissors…)
  • A pack of the highest quality lens tissue you can source from your local camera shop. I have an old stack of Kodak tissue that is oversized that I use.
  • A few short (5 cm) bits of sticky tape.
  • A small spray bottle of high quality low (or better still zero) residue optical cleaner.

You need to wrap the cut end of the two sticks with at least two, possibly three layers of tissue. I wrap diagonally, then fold the surplus over and wrap again to get many layers of tissue over the end of the sticks – this is what carries the optical cleaner, and then removes it. Use the sticky tape to bind the tissue to the stick well above the end, so that the tape is at least 1 cm away from the end of the stick for safety’s sake.

Photo of this to come…

One stick is used to wet clean the sensor, the other stick is used to dry it off and polish. I only use two sticks, and re-wrap the sticks during the clean, as I occasionally need to do it a few times. You might choose to prepare six or eight sticks beforehand if you are feint-of-heart to provide sufficient stocks to clean and clean again.

Here is where the real work begins.  Get a clean sheet of white paper, illuminate it a bit, set your lens to f22, and make an out-of-focus image of the paper, filling the entire frame. This is your control image of your dirty sensor. Process it and adjust the brightness and contrast to best show the dirt specks. Keep this image open.

Remove the lens, and set your camera to its sensor clean function. On mine, this raises the mirror, opens the shutter and turns off the sensor.

Blow some air into the camera to blow out the big dust particles.

I then spray one small squirt of optical cleaner onto the end of only one wrapped stick so that is it is damp, not wet, and go to work on the sensor, noting where the dirt was heaviest from the dust picture you have just processed.Thanks to the magic of optics, remember the image you have taken of your dirt is upside down and back to front as regards its location on the sensor, so ft your crud was on the top right of the image, it is actually located at the bottom left of the sensor as you look into the camera. Hold the stick perpendicular to the sensor’s surface, and clean it in parallel strokes, covering the entire sensor.

Whilst the sensor is still wet, grab the dry stick, and again clean the face of the sensor until it is dry and sparkly clean. Blow some air into the cavity again to force out any tissue residue.

Switch off the camera, remount your lens, and again photograph the dust image, and look at it via Photoshop. If you are lucky you might have a clean sensor already. If there is still some dust, repeat the steps all over again until the dust’s’ shadow image is as clean as you want it to be for your circumstances. I even got rid of a persistent problem that I had even considered opening up the camera to address. This is obviously an iterative process until things are clean enough for your tastes.

You may well need to clean the viewfinder of the 5D after this process to stop seeing annoying dust in the finder, but that’s perhaps another subject for a blog entry for the future.

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Adventures at 3200 ASA

My astute readers will know that I have been looking for P&S nirvana in my journal over the past 6 months or so. Instead of dwelling on that issue in the blog, today I want to discuss my main tool, the mighty Canon 5D, but with a twist – what it can do at 3200 ASA, and what a spot of image tweaking can do. And not a camera picture in sight today either …

Here is a very dramatic image shot last night at twilight, immediately after a torrential rain storm:

I know I’m probably not objective, but I find this image breathtaking, because in my minds’ eye, this is how I remember the scene. Drama, color, light. It was shot at 3200 ASA, hand-held for 1/8 sec @ f4, and a tad underexposed. This is what 3200 ASA and a decent lens coupled with image stabilisation can do for you when you have forgotten your tripod. The insipid original, shown straight from the RAW file, looks pretty damn ordinary:

Just another dull, lifeless image. Well, that’s what I saw when I looked at the shots in Adobe Bridge. But how to bring it to life, to re-create the tension in nature that I had seen? Well, here’s what I did. Remove what noise I could fine to get a basis to start from – remember it was underexposed at 3200 ASA, and so had a few issues. Then, Topaz Adjust was run over it, to intensify colours and detail. Noise removal again, then a bit of adjustment to the curves, and voila. Oh, I also used the CS5 lens correction adjustment that is in ACR to fix the geometry and vignetting from the Canon 24-105 mm f4 L that occurs at full aperture use. And the picture jumps off the page…

Even as a mono it is strong:

In fact it was having processed it as a monochrome that inspired me to revisit it again as a hyper-real colour shot from a movie.

The moral – get out when the light is right. Look at your images, and think about how you can best represent what you saw. And revisit them a day later, to see if you can see something different. Oh, and clean your sensor. I did, using 2 tongue depressors, a few bits of lens tissue and some optical cleaner. Don’t pay $100+ for a shop to take 3 weeks to do it badly, do it yourself. Perhaps the next blog topic?

For the anoraks who may be wondering – the vertical white stick in the centre of the frame isn’t dirt, it’s the top of the 40 tonne stainless steel gargantuan flagpole at Parliament House a couple of kilometres away.