Out, damned spot! - sensor dust (part 3) - a post script

Well, not long after posting the second part of my piece on removing dust from DSLR sensors and a copy of "The Photographer" (the British Institute of Professional Photography magazine) lands on my doormat, proclaiming on it's front cover "On test: Dust-Aid sensor cleaner". This is a product with which I was unfamiliar, and I read the review by Steve Hynes with great interest. To describe the product briefly you get a plastic applicator which has stuck to it a foam pad. The foam pad has high strength adhesive on one side ( to stick to the applicator) and low strength adhesive on the other. You push the low-tack side of the pad on to the sensor (as we know, this is actually not the sensor but a sheet of glass in front of the sensor) and you hope that any dust sticks to the pad. The pads are removable and you get 12 pads with the applicator (for about £37).

A couple of points about the review. I have a high regard for Steve Hynes' reviews. Before becoming the editor of "The Photographer" he had two spells as editor of "Professional Photography" magazine, and on both occasions I think that magazine was better for his influence. He has also written many articles that I have found very informative.

You sense a "but" coming, don't you. Well, two actually. The first is that he states that "There are no signs of residual adhesive being left on the sensor", but from the review it seems that he only had one session of cleaning. I would be more impressed if he said that he had been using it every couple of weeks for six months and no residue was present - and detailing how this was verified.

The second reservation regards a bit of advice that he gives about sensor cleaning in general. He states quite rightly that several cameras can only be set to "sensor cleaning mode" if connected to a mains adaptor, and that mains adaptors cost "a stupid amount of money" (also true up to a point). His solution is to set the camera to the B (bulb) setting and lock the shutter open. My understanding was that cleaning the camera with the sensor powered up would be unwise as there would be a static charge present in the sensor and this would attract dust (generally unhelpful when trying to remove it). Prior to posting this piece I contacted Steve, and he said that he had used the bulb setting many times without problem and that there was not a significant static charge present. His point being that there is not a high enough voltage used to cause significant static. If he is right (well I'm not arguing with him) it means that the advice about always turning the camera off when changing lenses may also be unnecessary. All I can say at this stage is that I will still change lenses and clean the sensor with the power off, but I will try to find out more information and post it as soon as possible. As they say "you live and learn".

Image: Man o'War Beach, Dorset. April 2007

Out, damned spot! - sensor dust (part 2)

You can spend quite a bit of money on products to clean your sensor. But when considering a large purchase bear in mind that in a very few years sensor dust may no longer be an issue on new cameras. Several current cameras have anti-dust measures built in, but a recent test on "PixInfo.com" suggested that most of them aren't terribly effective, although anecdotal evidence indicates that they may do better in "real world" conditions. It seems that this is an area where further development is needed. However, the manufacturers do seem to have dust removal in their sights and I would think the problem to be largely dealt with in the next few model updates. My point is just that dust removal equipment should not be viewed as a long term investment (but then by that logic digital cameras can't either).

As I mentioned in my last piece, the dust is not on the sensor, but a glass filter a little distance in front of the sensor, so when I talk about cleaning the sensor you understand that it is really this piece of glass that is being cleaned. OK. To the job at hand. First, some things not to use - under no circumstances use canned air directly on the sensor glass. I heard of someone who used such a can, and the nozzle came off and projected itself towards the sensor with expensive consequences (this will not be covered under your warranty, mainly because all the camera manufacturers tell you not to do it). Nor should you use CO2 blowers. Both of these may contain contaminants which will likely stick to your sensor. Lastly, don't use anything that will come into contact with the sensor that you use on anything else - just common sense really.

How do you test weather the sensor needs to be cleaned. A shot of a white evenly lit surface will tell you (I use a light box, but a plain sky or wall will do). Remember that the shot is of the sensor dust, so you don't have to hold the camera particularly still even at long exposures. Use a long lens stopped down to it's smallest aperture, and focus manually to throw your white surface out of focus so that you don't see any texture. Overexpose by a stop and a half and you should be able to see the dust clearly on the computer monitor, particularly if you increase contrast. Don't panic if it looks bad. You never shoot like that do you (You do? OK. Panic then). You are unlikely to get it looking perfect, but if you have the sort of spots that you can see in normal photographs then you are clearly looking for a marked improvement.

Quite recently Delkin announced a sensor viewer to give you an enlarged and illuminated view of the sensor and it's dust, and reports (one such here) suggest that it works quite well.

The first tool that everyone should have is a bulb blower. There is plenty of choice, but the one I use it the Giottos Rocket (large size), and it seems to be generally well regarded. I have no reason to disagree. This is the only method of DIY cleaning that Canon recommends.

If that doesn't work I use a "Visible Dust" brush. The brush has nylon bristles and is statically charged with compressed air. The static charge lifts dust from the sensor surface. This will work most of the time if the blower doesn't, but there are times when the particles are stuck or contaminated with something like grease (most likely on new cameras). An alternative to the brush method is the vacuum system used in the "Green Clean" produce. I haven't tried this, as it wasn't available when I bought my sensor brushes.

Where the brush doesn't work, wet and/or dry swabs are needed. There are many on the market but I have been using the ones produced in the UK by "Intemos". The same swab can be used either wet or dry, and I have found them to work well. Swabs are really the only method to use if there are greasy smears on the glass, because the cleaning fluid is a de-greaser. Do not over-wet the swabs otherwise you will be left with smears that then need to be removed.

As I have said, there are several methods, and you make your choice. However, most of these methods are not all things to all sensors. For instance if you start with a blower you may find that you can't get everything off. You might try a brush and find that some of the dust had grease on it so you now have to remove the smear (and clean the grease off the brush). What I am saying it that you will probably need several tools for different severity of dust, trying the simplest first (blower) and working towards the most severe (probably swabs) as the need arises - or as the severity of the problem rises.

Lastly, and as something of an afterthought, there is one other method of cleaning the sensor. You could send/take it to someone else to do. Some shops will do this (I heard of one charging about £200 - someone has a sense of humour) and of course the manufacturer of your camera. Either way this is not cheap, you will probably be without your camera for a number of days (Canon have just quoted me £30 inc. VAT to clean a 20D and £50 for a 5D and say it takes about a week) and there is no guarantee that the sensor will be spotless when it returns - in fact it's quite likely that it won't be. Let's hope that the camera makers get in-camera dust removal sorted sooner rather than later.

Some extra reading - www.cleaningdigitalcameras.com/ - Several links at top right - don't miss, also on Rob Galbraith's site and something from Bob Atkins.

Image: Isle of Wight, December 2006

Lens reviews on the internet

Some time ago I was asked if I knew of any web sites that had reviews of lenses. The only site that came to mind at the time was "The-Digital-Picture.com", which deals with Canon and Canon-fit lenses - as well as bodies and accessories. Since the person who was asking was interested in Nikon lenses that wasn't much help. I had forgotten about "SLRgear.com", which has reviews of many brands of lenses both by their own team and by users of those lenses (including a few added by me a little while ago). Some others that have quite a good selection of lenses covered and are worth a look are "PhotoZone", "Bob Atkins Photography" and "Photodo".

Of course many of the digital camera review sites have some lens reviews, but they tend not to have a good range of lenses covered. If you have any other suggestions for additions to the list feel free to contact me and I will put up a link.

Just one word of caution. Reviews are just that. Your experience with a particular lens may well be different from the reviewers, either because the lens you have is different (either worse or better due to production variations), or because you are using the lens in different circumstances or because your expectations from the lens are different. Camera manufacturers tend to have quite tight production tolerances, but even so there will be differences. Some of the third party lens makers seem to be a little more casual about tolerances. I have seen quite marked differences in Sigma lenses, but I am not suggesting that they are the only ones. My preference when buying (particularly non-Canon lenses) is to go somewhere where I can test the lens and see the results in the shop and leave with the lens that I tested. It is worth searching out retailers that allow you to do this.

Talking of lenses, the image above (Denham Village, April 2007) was taken with a lens that I will be discussing in a few weeks (it is still undergoing modifications/adjustments at the moment). It has up to 8˚of tilt in any direction and a total of 23mm of shift (also in any direction). The blur to the left and right of the image was not done in Photoshop (although the colour saturation was toned down), but in camera by setting the tilt on the lens to it's maximum (tilted to the left). More on this lens when the modifications are finished.

A day at Adobe's UK headquarters & the launch of Creative Suite 3

I was fortunate enough to be amongst about 15 people invited by Ian Burley of DPNow.com to attend a training day to mark the launch of "Adobe Creative Suite 3" at Adobe's UK head office in Stockley Park. In fact it should be "suits", as there are now seven versions of the Creative Suite, each designed to appeal to a different market. The day was an opportunity to find out more about the programs that make up this collection, in particular Photoshop and Lightroom. I went along feeling quite comfortable with Photoshop, but still unconvinced by Lightroom, and very curious to find out if this experience could spark my interest.

The training comprised an overview of the whole suite, followed by more detailed hands-on sessions (each person had the use of a workstation) with Photoshop and then Lightroom. Also provided, although not exactly part of the training was a very nice lunch.

As expected our voyage through Photoshop showed many of the new but well publicised features, and an opportunity to try out some new tools. As I said before, for me Photoshop simply doesn't need to be sold. It's worth is beyond doubt. I shall not go into the changes from the last version as there are already so many details on the internet.

Lightroom is another matter. It seems to be marketed primarily as a workflow tool. A piece of software designed to help you to be more efficient at dealing with large numbers of files. For photographers working with very large numbers of similar images that all need the same basic correction Lightroom is ideal. There were several people at this meeting who obviously felt that it was a major benefit to them. It fell down for me for a number of reasons. To start with I don't do my RAW conversions using an Adobe RAW converter. I use DXO Optics Pro, and having made a comparison recently I will keep using it. This breaks the workflow chain at the first link. This is not my only hesitation. I don't typically work with large numbers of similar images. I more often work with smaller numbers of images that need individual treatment. Once I have finished with an image in DXO, if I need to do extra work on it I need the tools that are in Photoshop, but are not present in Lightroom.

It was admitted that Lightroom is not yet a full asset management program (although the implication seemed to be that it might well become that). It can't merge libraries created on different drives (such as those on two different computers) and also can not keep track of images that are on drives that are not always accessible, such as CD/DVD's.

Life is full of ironies however. At the end of the session there was a draw, and my name was chosen and I won a copy of - you guessed it - Lightroom. So it seems that I will be using it after all. Time will tell if I become a convert.

My thanks to Adobe for their fantastic generosity and hospitality (including the delicious and plentiful food), to Steve Newberry who provided the training and to Ian Burley of DPNow.com for the invitation to attend.

Photo: Granada 2006