Grease And Grunge and Cotton Buds. A Morality Tale For Our Times


When I went over to Micro Four Thirds around 5 years ago, there was one unexpected bonus. Dust and dirt on the digital sensor ceased to be a problem. I was very happy about that.  It had always irked me a bit with my DSLR, that dark blobs would appear on my pix, particularly noticeable on large plain areas such as a clear blue sky. I had the sensor professionally cleaned now and again but it annoyed me forking out £40 or more each time.

With film, of course, every frame is a new sensor and freshly installed in position from the cassette, so dirt and dust isn’t a visual problem at all.

On a DSLR there’s a mirror and shutter between the sensor and the  world so I reckoned that muck would be a headache  with my new Micro Four Thirds bodies, given that the sensor faces the elements directly when the lens is changed. Plus, any particles on the rear of a lens when fitted on the body can just fall straight on to it .

I was pleased to find I was wrong and that a dirty sensor was, judging by my results,  a thing of the past.  I didn’t know why and put it down to the automatic sensor cleaning routine operating on start-up and the extra care I took when changing lenses. In particular air dusting the lenses frequently and holding the camera maw facing downwards during the un-bayonet/ bayonet routine.

But then I bought an Olympus macro lens, of necessity stopping it down to f/22 for depth of field sometimes –  and hang the diffraction. And suddenly there they were, the little bas****s, the devil’s blobs.  I was about as pleased to see them as I was a scratch on a  new Steely Dan album in the 70s.

I bought some very expensive swabs and paddle things but was loath to use them because of all the dire warnings of terrible damage to the sensor. Then I read that that the sensor itself was covered with glass for several reasons, among them presumably, protection

It all seemed a little less dangerous so I used a blower, swabs and paddle thingies now and again to budge the stuff the built in high frequency sensor cleaning routine didn’t shift. It never got rid of everything but it made a reasonable job of it. I’m not a fussy person and I rarely open up a lens beyond f/4 anyway. Nonetheless, it niggled me that I couldn’t clean it properly. Having seen cleaning being done in a camera shop, there’s nothing magic to it. They didn’t have any special equipment that I didn’t, apart from a loupe with LEDs built in.

Then, while fitting the 12-40mm Olympus Pro lens to my little GM1, I lost my grip on the camera and it slipped out of my hands – with no lens on it, of course. I caught the GM1 one handed as it dropped. Being one handed, I clawed at it to stop its fall. My thumb went to the back and one finger finished my pincer movement neatly and luckily gently. Excellent! I had caught it. Less excellent, I had caught it by the back and…..sensor.

I could see my paw mark with my naked eye. A beautiful clearly delineated 3rd finger print worthy of Scotland Yard itself.  Smack bang on the GM1’s delicate little sensor. Great! Now I would be shooting pictures with an £800 piece of state of the art optical design – but focused onto what looked like the greasy bottom of an unwashed frying pan.

I tried to clean it with those paddle things and a drop of cleaning fluid.  It worked ok but still didn’t look right, certainly not perfectly clean. And I’d run out of paddle swabs and cleaning fluid. So I put a cap on the camera body and sent for an LED equipped loupe like the big boys have. I was a bit shocked by what it revealed. There were a few little dots of dust or pollen or whatever, nothing to particularly worry about.  But there were also smears to be seen. The beauty of the loupe is that you can clearly see all the grease and grunge on the sensor. It’s not a pretty sight.

So , another professional clean then? After all, the swabs and paddles hadn’t done the job and I wanted the sensor spotless. Then, trawling around the net for ideas, I saw someone who swore by Q Tips,  generically, cotton tips or buds and isopropyl, which I use for cleaning lenses and electrical contacts. Since I was going to send the camera away anyway, if I didn’t use violence on the sensor, I wasn’t going to do anything that couldn’t be undone by the professionals. So I gave it a try.

I put a tiny amount of the isopropyl cleaning fluid on a cotton bud and went for it. Using the loupe, seeing what I was doing was easy and light rubbing removed the grease and the spots very effectively. I was very pleased to see the spots go, because I think they were probably sticky pollen and the camera’s sensor cleaning routine has no effect on that at all.

My cotton bud did, however, leave a few streaks. A light to and fro with a fresh dry cotton bud got rid of those without trouble leaving one tiny fibre which a quick blow from my Giottos Rocket Blower made short work of, leaving me with a sensor with two tiny spots visible only lightly at f22 on a white surface. I contemplated running the GM1 through the dishwasher to be certain of eradicating them but it seemed a bit extreme. Maybe the Karcher pressure washer? A new GM1? That’s a it like changing your car because the tyres need pumping up. Maybe just live with it?

I wonder if it is possible to get a completely and utterly clean sensor? Maybe there’s a point at which you have to say that good enough is good enough? Certainly, a sensor which looks pristine to the naked eye is less so when looked at through a loupe(UK)/(USA).

It’s like pixel peeping. You have a razor sharp lens, you’re delighted with it and then you look at 100%. Or even 200%. OMG!  If I make a print  6 feet across it won’t be razor sharp viewed from 6 inches! I’m reminded of an old Tommy Cooper joke where he goes to the doctor and tells the doctor “doc, it hurts when i do this”. And the doctor replies, “well, don’t do that!”.

If you stop a lens down to f/22 and then photograph a sheet of out of focus white paper and g and there are a few dust bunnies to be seen, maybe the answer is, as the doc says, “well, don’t do that”. Certainly, the spots I’m talking about aren’t visible in normal use. Do they matter? I suppose not. Trouble is, thanks to the loupe, I know they’re there.

The funny thing is that film negatives regularly got scratched in handling and filing. The answer to that was the pole opposite to cleaning a sensor. You’d rub your finger over the top of your nose and then rub it over the scratches. Hid them beautifully. Don’t try that on your E-M1, though.

Like all good stories (and this one), there is a moral point to it. As happens so often, Confucius put it well – “Wise photographer never look at sensor through loupe”.

And please, please note – I am not recommending my method. Using cotton buds and isopropanol comes in at about 1/1000th the cost of professional cleaning. It is only for cheapskates and chancers like me. 

18 thoughts on “Grease And Grunge and Cotton Buds. A Morality Tale For Our Times

  1. Olaf

    Hi david,
    Like this post and your blog a lot. A true inspiration. I own a pana fz300 and am looking forward to switching over to m43 land in 2018.

    Cheers Olaf

  2. Steve Mallett

    David, Found your blog via Youtube after first seeing your review of the Pen-F. Really enjoying it!

    The dirt on sensor is what, indirectly, drove me to the world of m43. I had a Nikon D600, after owning a D70 and a D90, both of which I loved. I was bedevilled with the lubricant spots that the shutter mechanism of the D600 sprayed all over the sensor. The camera went back to Nikon a number of times before they released the D610 to solve the problem. Whilst in my local retailer arguing about what I was going to have to pay to trade my 600 for a 610 I idly picked up an E-M1, looked through the EVF and saw – the future! It was love at first sight. Admittedly I had fallen deeply out of love with Nikon with their total lack of interest in my woes with their equipment. I went home did a bit more research, bought a used GM1 kit for £100 on e-bay, played with it for a week before selling all my full frame Nikon kit and buying and E-M1 with 12-40 lens. That was two and half years ago and I’ve not looked back and I enjoy photography more than ever. And I’ve not had to clean a sensor in all that time – and I won’t be buying a loupe any time soon!


    1. Post author

      Yes, wise no loupe. It’s your remark about enjoying photography more than ever that strikes me most. The Micro Four Thirds stuff gives so many choices. It’s the only true system out there apart from DSLRs and your experience, first a GM1 and the an E-M1, extremes of the spectrum of the system shows how versatile the format is. Glad you like the blog.

  3. Timothy Bates

    Just tuned into your Blog. My brother put me onto you after explaining to me that it wasn’t just my very convincing lectures on the benefits of m4/3 that caused him to by a GH4 and a swag of lenses but some guy called David Thorpe.
    Had to smile about the devil’s blobs. Had my 5Dmk2 cleaned once by a very dry humoured soul. After picking up the newly cleaned camera I was very keen to check his handy work. I sat in my car across the road and squirted off few quick shots. After a little scrutiny, I found there appeared to be more of the devil’s blobs than ever before. Perplexed and a little annoyed I returned to the camera shop and gently asked the obvious. He had a look at my not so very scientific test shots and said, “did you shoot these through the windscreen of your car or something?”
    By the way, haven’t seen any devil’s blobs with my m4/3 gear either and now I’m definitely not getting a loupe.

    1. Post author

      Sorry to be so slow answering these comments. For some reason that I’m about to put right, I’m not getting notifications on comments. I just thought nobody had read this!

      I’m always a bit concerned when I have influenced anyone about their buying choices. It’s not my intention to do that, just to give my thoughts from my own experiences, for what they are worth. I do have a lot of enthusiasm for the Micro Four Thirds system though and I suppose that is what has the influence. Happily, I’ve yet to hear from anyone who has bought into Micro Four Thirds and hated it!

      The loupe, yes, don’t buy one. I’ve put mine in its box and it will only come out under extreme circumstances in future.

  4. Archer

    A professional builder of astronomical instruments once told me that only amateurs have clean optics, or mirrors that are figured correctly out to the edge. The same seems to apply to sensors.

    1. Post author

      Haha! Yes, there’s a level of imperfection that is acceptable professionally because perfection is unnecessary and could take up all your time. I’m blithely unworried about extreme lens sharpness, simply because after a lifetime of using lenses of all types, I know that ultimate sharpness is not not necessary for a successful picture. In my days as a news photographer, the feat was getting an image at all very often. Niceties like sharpness didn’t earn you any extra money so if it was sharp, nice but if not, well there you go. You always tried for a sharp pic of course but when some rioter is going for you, it’s the image that counts!

  5. Tyrone White

    Wonderful article, David. I haven’t had an issue with my m43 cameras yet as, like you, I hardly find any need to stop the lens down past f4 except for macro. I actually winced when I read that you caught your camera by the sensor. I am glad you managed to clean it but I hope that never happens to me. Hopefully time will make you forget about the specks still left on it, much like the scratch on my car I received a few years ago.

    1. Post author

      Glad you enjoyed it, Tyrone. Good point about the car and it relates well to the specks because if we can accept scratches we can see, we can accept specks we can’t unless we go looking for them.

  6. Brandon Scott

    As always your posts and videos are most informative. Can you tell us what brand of loupe you used? That would be helpful. Also a video some day on “what’s in my bag” would be very interesting. Thanks and keep up the great work. PS–love the pics at the top of the post. Brandon Scott

    1. Post author

      Thanks for the kind words, Brandon. The loupe I used is a reasonably priced one from Amazon – I’ve put a link to it in the blog if you take another look. I’ll remember a what’s in my bag video, thanks.

  7. Guilhem

    Hi David, I can relate to this very morality as well 🙂 But in fact, after reading it, had to check my sensor out too, noticed spots and you know the rest… Thank God i don’t have a loupe 🙂
    Have you tried cleaning the sensor with a lenspen? I had good success for my greasy fingerprint, however it may leave dark coal dust behind, it is usually easier to blow off than sticky pollen…

    1. Post author

      Hi Guilhem – lucky you, no loupe! I haven’t tried a lenspen but it seems the more cleaning stuff you have in your armoury the better. Something should work.

    1. Post author

      It’s a fancy name for a magnifier really. It is specialized, in that it has frame which acts like stilts, it so that it sits above what it is magnifying. They were used a lot in film days for taking a close look at negatives to check for sharpness. The one I used is meant for DSLRs so you need to hold it a little above the camera body. It has LEDs built in to light the sensor. Unless you are seeing blobs on the GH4’s sensor, I’d leave it alone!


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