Really wanna see if you have dust on your sensor?

480sparky

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Here's the method I use to clean my sensors:

I put on a lens, focus it at infinity, and turn off the AutoFocus. I use a plain white wall to shoot. I set my camera on Manual, aperture to f/8 or so, ISO to 100, and then find the shutter speed needed to create a 'correct' exposure. I then change the shutter speed to over-expose by 2 full stops. I actuate the shutter, and move the camera around while aimed at the wall. This will blur out any marks on the wall so they don't get confused as dust (plus, the camera is 6" from the wall but focused at infinity).

I check the image on the monitor to verify I have a nice, bright image, but use the 'blinkies' to make sure I haven't blown any parts of the shot out. I want to get it as bright as I can without blowing anything out.

I then load the image into GIMP (although most ANY software will work). To make the dust super-easy to spot, I crank the Sharpness slider all the way up. I know this will create a series of concentric rings, but that's not what I'm after... I can ignore the 'target' look.

If I have any dust spots, it/they will stand out like a sore thumb.

SensorClean1.jpg~original


Pretty obvious where the dust spots are, isn't it?

So, after a quick Mirror-Up-For-Cleaning and a couple dozen shots with a Rocket Blower, I repeat the steps to find I only got a third of 'em. So it's time to go 'hands-on' with a wet cleaning.

Results after the cleaning with a swab & fluid:

SensorClean2.jpg~original


I've found this method of over-exposing the test image, then cranking the sharpness all the way up, not only makes it super-easy to SPOT the dust, it also makes it bullet-proof to verify it's all clean!
 

Garbz

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If you have to go to those lengths to get the dust to appear, do you really actually need to worry about it?
 

Benco

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I do the white wall-infinity-small aperture test when I've found that there's a noticable spot on a photo (just to make sure that it's a bit of crap on the sensor), usually find that there's lots of dust but one or two big bits that are causing the problem, blow them off and then we're good again, even though there's still some dust it's not causing any noticable effect.

I suppose that one of these days I'll get a wet cleaning kit and have a go at getting the sensor really clean.
 

amolitor

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Dust that you can't "see" is still interfering with image sharpness in the general area. It depends on what kind of work you're doing, but it matters to some people.
 

SCraig

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I open a new window in my browser, maximize it, and use that for the background. Very high contrast and pretty much pure white. The first thing I do when I open the image is set a white point on the background.
 

Benco

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Dust that you can't "see" is still interfering with image sharpness in the general area. It depends on what kind of work you're doing, but it matters to some people.

Indeed, I'll get round to it I'm sure.
 

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