40D dust magnet?

edit:

so apparently it wasn't as much as my lens hygeine (since this has NEVER happened with my other two DSLR's) but rather a liberal treatment of lubrication on behalf of the nice folks who remanufactured my 40D, which was spewing blobs of lubricant onto my photosensor.

...

is there anything i can do to avoid shutter lube spray, aside from wet cleaning?

Keep the camera body facing downwards.

Common sense things:

• Turn off the camera
  
• Keep the camera facing down when swapping the lens
  
• Do it where the wind ain't blowing.
  
• If you can't do the above, changing the lens inside a clean plastic bag may help.
  

Scott_Quier wrote in post #10075018
Common sense things:

• Turn off the camera
  
• Keep the camera facing down when swapping the lens
  
• Do it where the wind ain't blowing.
  
• If you can't do the above, changing the lens inside a clean plastic bag may help.

But, that having been said ... I following the first rule and seldom do I have an issue.

Er, what's the point of the first rule?

The sensor isn't charged when you're not taking a pic.
The mirror and shutter are blocking direct access to the sensor.

Turning off the camera gives a better chance for any charge in the sensor to dissipate, or so is my understanding.

In any case, best to play it safe, yes?

Although, that said, i don't usually turn my camera off to change lenses.

What are you doing wrong?

dontcallmeash wrote in post #10074837
every lens change i do on the 40D, i have one or two big blobs of dust on the photosensor

If this is really true, and you really have to clean the sensor after every lens-change, I would hazard a guess that the problem lies in the way you change lenses as opposed to the camera / lens itself - or we'd ALL have this problem. What are you doing that causes so much dust to enter your camera when changing lenses?

I suggest that if you change your methods, the problem will probably go away by itself. After all, while every camera will attract dust over time, I don't see very many other complaints similar to yours.

Tiberius47 wrote in post #10080946
Turning off the camera gives a better chance for any charge in the sensor to dissipate, or so is my understanding.

In any case, best to play it safe, yes?

Although, that said, i don't usually turn my camera off to change lenses.

No, and it wouldn't be anything that couldn't just be blown off with a couple bursts from the blower either. The order of cleaning intensity for any stubborn spots would be:

1) automatic in-camera mode
2) blower
3) physical contact cleaning

More likely is that as you zoom in and out, the air does exit the back of many lenses, and any dust in the environment can be sucked into the lens and deposited out the back into the sensor box.

Optics and static electricity are a bad mixture but even so I only (dry) clean my 30D about twice a year and it does not have the 40D self-cleaning "shake and vac".

In normal shots I don't see the dust in prints, even if one or two do show up its easy to clone stamp or repair them. Theres no point in fretting about it too much.

Tiberius47 wrote in post #10080946
Turning off the camera gives a better chance for any charge in the sensor to dissipate, or so is my understanding.

The sensor is charged only while capturing an image and that charge has to be removed before the next image is taken (i.e. in less than 1/8 of a second) - so I doubt that the amount of charge remaining will be any different no matter what the state of the on/off switch.

Besides, like I said - it's hidden behind the shutter. Dust can't get onto the sensor while lens changing. Dust can get into the mirror box and later settle on the sensor, which is why keeping it facing down is a good idea.

When we say the sensor is 'charged', what is actually charged are the individual sensor sites (aka pixels) within the sensor. Each site is covered with a micro lens and the whole sensor is mounted behind several filters (IR, & Low pass etc) See -> http://www.sensorclean​ing.com/lowpassfilter.​php

CMOS runs at low voltage and power levels.. (Typically 3 to 5 volts). There isn't much of a 'charge there.. (It's not like the charge you would see on old CRT monitors or TV sets where you could hear a crackle when you put your fingers near the surface.. (They use thousands of volts) I can't see a tiny CMOS sensor site charge being passed from the sensor site, through the microlenses and then through the layers of filters placed in front of the sensor.

Even if somehow this tiny charge was present on the filter that is mounted front of the actual sensor, there is still a mirror and shutter for the dust to 'get around'. The shutters completely cover the sensor assembly. There's no way dust can get on it.

I think many who have done a sensor clean have seen the mirror flip up exposing the sensor.. They assume sensor is always exposed and liable to attract dust. But it's not. The mirror cleaning function lifts the mirror [I]and[/] opens the shutters. The sensor is always completely covered until it is actually activated. That's when it picks up dust.

I've never turned off a camera to change a lens and have had no ill effects as a result.
I don't know any other fellow photographer who does either.

hollis_f wrote in post #10080864
Er, what's the point of the first rule?

The sensor isn't charged when you're not taking a pic.
The mirror and shutter are blocking direct access to the sensor.

Maybe, but it doesn't hurt either. I've yet to have any issue with wearing out the camera power switch or to read of others having worn out the power switch on their camera. And, right, wrong, or indifferent - I've read the bit about giving the sensor time to dissapaite charge.

Another reason is the communication between the camera and the lens. I don't know if there is anything there when the shutter button is not depressed but ...

Scott_Quier wrote in post #10081830
Maybe, but it doesn't hurt either.

It doesn't hurt if you insist on wearing a purple tutu either, but it's just as pointless.

The 40D is NOT a dust magnet - the 5D IS!

Beasides the ones already sugested, try to Keep the lenses clean with the rocket blower.