Dust

dlplumer · December 6, 2008

I'm sure this has been discussed many times, but here goes. I have dust in my new 50D up in the prism. So when I look through the viewfinder, I can see these sharp particles against the sky. They do not affect the picture at all since they are not on the sensor. I took it to my local shop, and they took the viewfinder interchangeable filter out, but is up in the prism apparently. We have tried to blow it out, but to no avail. It is not a huge deal, just annoying. How many of you have the exact same problem????:scratch

Thanks,

Dan:D

ziggy53 · December 6, 2008

Dan,

If you see sharp specs it almost has to be on the viewfinder focus screen itself. I would take another look. If they were fuzzy or soft then they could be up in the penta-prism, but sharp focus only occurs at the screen in the viewfinder.

Take a look with the screen removed, to be absolutely sure.

Candid Arts · December 6, 2008

I have this same problem on my 50D. But the specs are not sharp, they are blurry.

So how do I clean the penta-prism?

dlplumer · December 6, 2008

ziggy53 wrote:

Dan,

If you see sharp specs it almost has to be on the viewfinder focus screen itself. I would take another look. If they were fuzzy or soft then they could be up in the penta-prism, but sharp focus only occurs at the screen in the viewfinder.

Take a look with the screen removed, to be absolutely sure.

Is it common and do I need to be anal about it?

Candid Arts · December 6, 2008

dlplumer wrote:

Is it common and do I need to be anal about it?

I don't know if you need to be, but I am.

dlplumer · December 6, 2008

Candid Arts wrote:

I don't know if you need to be, but I am.

John Mueller · December 6, 2008

On my 40D,50D and MK3 all I had to do is gently blow it out

Now if its stuck up top,that's horse of a different color.

PixNW · December 6, 2008

The focus screen is pretty easy to take out if you have the little tool from Canon designed for it.

Robinivich · December 6, 2008

It wouldn't be "in the prism", since that's a solid hunk of glass, and even if it had gotten in there in manufacturing, I think it'd be out of focus (not sure though). The focusing screen is a different matter. I have a bunch of gunk on my rebel's focusing screen, but besides sometimes being a little distracting, it's no problem, as the AF doesn't operate through the screen, and it's not in the path of light hitting the sensor, so it's not in your pictures. I suppose eventually it could affect metering, which does go through the matte, but you'd need a LOT of dust.

PixNW wrote:

The focus screen is pretty easy to take out if you have the little tool from Canon designed for it.

I bought the precision matte screen for my 40d (same as for 50d). It comes in a kit with a little grabber tool for removing and replacing the screens. Once you work out exactly what goes where, it's as simple as anything to remove the matte, once it's outside the camera, give it a good blow with a rocket blower or whatever, and stick it back in. Be careful about letting anything touch the screen though, as I doubt you'll have a satisfactory job cleaning it out.

You have two choices (IIRC) for another screen if it bothers you enough, the precision matte, for f2.8 and faster lenses to guide manual focus, and the gridlines, which is the same as the factory included one except it has a "rule of thirds" grid. Ordered in the States, these are cheap ($35), Canada costs a fair bit more these days ($70 :cry).

ziggy53 · December 6, 2008

dlplumer wrote:

Is it common and do I need to be anal about it?

It is pretty common to have dust on the focussing screen and I try not to let anything that doesn't affect the actual recorded image affect me.

dlplumer · December 6, 2008

Robinivich wrote:

It wouldn't be "in the prism", since that's a solid hunk of glass, and even if it had gotten in there in manufacturing, I think it'd be out of focus (not sure though). The focusing screen is a different matter. I have a bunch of gunk on my rebel's focusing screen, but besides sometimes being a little distracting, it's no problem, as the AF doesn't operate through the screen, and it's not in the path of light hitting the sensor, so it's not in your pictures. I suppose eventually it could affect metering, which does go through the matte, but you'd need a LOT of dust.

I bought the precision matte screen for my 40d (same as for 50d). It comes in a kit with a little grabber tool for removing and replacing the screens. Once you work out exactly what goes where, it's as simple as anything to remove the matte, once it's outside the camera, give it a good blow with a rocket blower or whatever, and stick it back in. Be careful about letting anything touch the screen though, as I doubt you'll have a satisfactory job cleaning it out.

You have two choices (IIRC) for another screen if it bothers you enough, the precision matte, for f2.8 and faster lenses to guide manual focus, and the gridlines, which is the same as the factory included one except it has a "rule of thirds" grid. Ordered in the States, these are cheap ($35), Canada costs a fair bit more these days ($70 :cry).

Thanks.

I just ordered the precision matte focus screen. I am sure as I was attempting to clean it (the wrong way) that I embedded some particles in it, although they are not visible to the naked eye.

Dan

dlplumer · December 6, 2008

ziggy53 wrote:

It is pretty common to have dust on the focussing screen and I try not to let anything that doesn't affect the actual recorded image affect me.

Thanks Ziggy. That's what I thought, but since it is so easy to change I just purchased the precision matte screen with the tool.

Robinivich · December 6, 2008

dlplumer wrote:

Thanks. I just ordered the precision matte focus screen. I am sure as I was attempting to clean it (the wrong way) that I embedded some particles in it, although they are not visible to the naked eye.

Dan

Glad I could help! Let us know how things go.

Tee Why · December 7, 2008

Soon as they are cleaned off, more dust gets in.
I do my best to just ignore them.

Maestro · December 7, 2008

dlplumer wrote:

Thanks Ziggy. That's what I thought, but since it is so easy to change I just purchased the precision matte screen with the tool.

This happens all the time Dan. I just ignore it since it doesn't affect the picture. Now dust on the sensor is a whole different story.

pathfinder · December 7, 2008

Dust on the focus screen, that you see when looking through the viewfinder, while annoying, has no effect on your images.

I have it in some of my cameras and just try to ignore it if at all possible. You can use a bulb blower to try to dislodge it but usually it is not worth the trouble. I suspect you could use a micro fiber cloth wrapped around a sensor swab and just touch the matte screen and get it off if it is on the lower surface.

dlplumer · December 7, 2008

pathfinder wrote:

Dust on the focus screen, that you see when looking through the viewfinder, while annoying, has no effect on your images.

I have it in some of my cameras and just try to ignore it if at all possible. You can use a bulb blower to try to dislodge it but usually it is not worth the trouble. I suspect you could use a micro fiber cloth wrapped around a sensor swab and just touch the matte screen and get it off if it is on the lower surface.

I believe I made it worse by rubbing it with lens tissue. Blowing does nothing. I'm replacing it, and will take better care next time.

thanks

Dust

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