Sensor marks and spot problems

[David W. Taylor]

Over the last couple of years I've had quite a few instances of my movies suffering from marks on the sensor of my 5D2. These are usually visible in even-toned areas, usually skies. This is a pretty big problem for me...I shoot mainly aviation and landscapes!

I use a 'Visible Dust-Artic Butterfly' device which works wonders in removing any sensor spots and I usually do a 'clean' with the Artic Butterfly before a shoot and then view a test video pointed at a blank wall to check for an OK image.
However the marks do creap in during shoots sometimes...most frustrating as I change lenses with the minimum of exposure to the 'open air' etc.

I'm also aware that small apertures can reveal lens marks so avoid anything beyond f11 if I can. Having Lee ND and Grad filters stuck on the front of a lens also adds something else to worry about.

Anybody else suffer from this? I don't get it on my AF100 by the way...that's got a screen over the sensor.

David Taylor

[Jon Fairhurst]

I just ordered an Arctic Butterfly, a lenspen, and swabs for both oil and water-based spots. My sensor is overdue! I shot a timelapse at f/16 or so, and the footage is beautiful - if you ignore the spots. It's only a problem on small aperture shots.

Before I clean the sensor, I will be snapping a gray photo with the same lens and aperture that I will use as a mask when cleaning up the timelapse. :)

[Bob Hart]

There are some zoom lenses which are not helpful. Some examples of the two-part body style which extends out of the front, can pump gusts of air in and out of the sensor chamber and through the rest of the camera body, agitating any particles which might be sitting around near the sensor.

[Nigel Barker]

We suffered a lot from sensor dust when we first started using the 5DII & have all the cleaning gear from Visible Dust & others but I honestly cannot remember when I last cleaned one of them. It's mostly down to more careful attention to lens hygiene & use of this when changing lenses

Giottos AA1900 Rocket Air Blaster Large

 

Giottos AA1900 Rocket Air Blaster Large

[Jeff Murray]

I agree with Nigel I use the Jessops Rocket similar to the Giotto for £10 for those in the UK.

(I did use a sensor cleaning kit until a photographer friend told me of his experience dragging a grain of sand across his sensor - even after he used an expensive loupe to check it (somthing I hadn't read or heard of). His repair bill was $700 to replace the sensor on a 40D I think he said.)

Other tips:

- Change the lens with the camera front down (lock it on the tripod is the best way) - prioritise the camera body over the lens, ie: if your taking the lens off - put the cap on the body first.
- Change lenses indoors before shooting outside if you can (or in the back of the car, somwhere with a roof or cover over your head etc).
- You're right try not to shoot with the aperture wider than F11 shooting at the sky - this will need an ND filter. The smaller the aperture the more the dust is visible. In fact since I got my ND I haven'st seen dust like the original poster is talking of.
- Use the rocket after each shoot - beware the Rocket can blow dust into the sensor if your in a dusty environment.

Overall the ND and shooting wider is the best way to get rid of dust in a sky shot. Besides you get better Depth of Field (and more saturated colour) this way - if that's the look your after.

[Peter Riding]

This has been the bain of the lives of stills photographers using dSLRs for the best part of 10 years, though the automatic dust removal routine that the 5DII defaults to on start up and shut down has made life much easier as its surprisingly effective.

I have a full range of cleaning devices but since using a couple of 5DII's for the past couple of years I have hardly had to touch the sensors at all. I do however shoot mainly in the f2.8 to f5.6 range and as others have said the dust really starts to become intrusive at f8 and beyond unless its really bad.

Marks are usually dust rather than sticky grime and this means that it is very easy to remove them at no cost with a very effective device you will already own, A vacuum cleaner! You really don't need to buy into all the hype and surgical proceedures surrounding sensor cleaning. Just use your vacuum with a narrow nozzle attachment on the hoze and go for it. Job done in seconds. Obviously the manufacturers will not endorse this as they'd be vunerable to claims from ham fisted amateurs, but it really is as easy as that.

If you do have sticky grime you'll need to use a fluid and pads such as those from Eclipse but this should not arise often if you're careful with lens changing and storage. Canon "L" lenses may also help as they are environmentally sealed.

To make viewing and working on the sensor quick and easy use one of these magnifying loupes:
GGS Adjustable Sensor Inspection Loupe () - Warehouse Express

You'll find it cheaper if you shop around.

To test the effectiveness of your cleaning you may find it easier to shoot stills rather than video. Focus on an evenly lit white target such as a big sheet of paper hanging on the back of a door several feet away. Allow 2 stops of exposure compensation because of the white target. Shoot large JPEG rather than RAW for speed. Shoot tethered to a laptop for quick results. Bring the images into Photoshop and optionally apply auto levels. This will hugely magnify the effect of any dust on the image. You can then see whats left and where it is on the sensor. Also vary the f-stop because if the dust is only intrusive at say f8 but you know you're going to be shooting at no more than f4 then you're wasting your time doing any more cleaning.

Pete

[Nigel Barker]

I now change lenses carefully holding the camera facing down & preferably outdoors away from pet hair giving a puff from the rocket to both sensor & lens on removal & on fitting. To check that spots have been removed I stop down to F16 or F22 & then take a photo of clear blue sky (when I am in the South of France) or uniform grey sky (when in the UK). I haven't had anything other than dust spots for a long time so a quick puff with the Rocket fixes those. If they don't move after a few puffs & checking with another photo then you need to use the cleaners. The gentlest cleaning is to use a brush from Visibile Dust but sticky crap needs to be removed with a swab & Eclipse solution. However if you are careful with changing lenses then you should never need to use these measures.

[David W. Taylor]

I must confess that I can't understand why the marks I get on my sensor become more noticeable when I am 'stopped down'. Surely marks on lenses and filters will show more when stopped down but marks actually on the sensor would be sharp at all times wouldn't they? They must 'block' the light from be registered correctly after all.
I know that I can clear marks on the sensor by cleaning them carefully with the Artic Butterfly device....but I once again have to drop me taking lenses aperture to beyond f8 to actually prove that they've gone.
I did once shoot with some fungus on an old 2x converter and that became really offensive when I was at f16 or 22....and I can certainly understand why a converter lens needs to be perfectly clean as it's presumably built to be inserted where the film or sensor normally is.
DT

[Jon Fairhurst]

The low pass filter and other coverings on the sensor mean that the dust isn't right on the pixels, but up above them. When you're wide open, the light for a given pixel comes in from all over the back of the lens glass at odd angles, so a lot of the light on any pixel comes in from around the side of the dust specs. When you're stopped down, the light beams are narrower, putting everything in focus both in front of and behind the lens.