Dust in lens......question

GraphyFotoz

I noticed that my Canon 75-300mm USM has dust between the 1st and 2nd elements.
Yes it does affect my pics esp shooting bird twards the sky.
I see there are 3-4 phillips screws on the 1st element.....is it safe to take apart and clean?:scratch

Looks simple but I thought I'd ask before doing!:dunno

cmason

GraphyFotoz wrote:

I noticed that my Canon 75-300mm USM has dust between the 1st and 2nd elements.
Yes it does affect my pics esp shooting bird twards the sky.
I see there are 3-4 phillips screws on the 1st element.....is it safe to take apart and clean?

Looks simple but I thought I'd ask before doing!

I have no experience at all in what it takes to service a lens, so this is my personal opinion only: I would never, ever consider doing this myself. Maybe if I had $$ to toss out the window, and didnt care if I completely hosed my lens, I might consider it, just for fun.

A Lens is a precision instrument, and I have to imagine that a USM one is even more complex. Send it in to Canon.

Bob Bell

GraphyFotoz wrote:

I noticed that my Canon 75-300mm USM has dust between the 1st and 2nd elements.
Yes it does affect my pics esp shooting bird twards the sky.
I see there are 3-4 phillips screws on the 1st element.....is it safe to take apart and clean?

Looks simple but I thought I'd ask before doing!

Graphy, there is 0-1% change that you can even see an outline of the dust where it is in a picture. If you stacked up 50mm worth of Extension Tubes you might get close to seeing it.

In reality, dust in a lens has no impact. The 85mm/1.8 I sold had 20+ pieces of dust and you could never see them in a picture.

99% of the time when you see dust in an image its because of dust on the glass plate in front of the sensor.

GraphyFotoz

Bob Bell wrote:

Graphy, there is 0-1% change that you can even see an outline of the dust where it is in a picture. If you stacked up 50mm worth of Extension Tubes you might get close to seeing it.

In reality, dust in a lens has no impact. The 85mm/1.8 I sold had 20+ pieces of dust and you could never see them in a picture.

99% of the time when you see dust in an image its because of dust on the glass plate in front of the sensor.

Checked my sensor and there is only 4-5 specks on it right now.
I took this pic of this Northern Mocking Bird twards the sky.....there was a load of specks in the shot.
Looked at the lens and there is a lotta dust on the inside of the front elements. Only place I can see where all the specks came from.

Here is the shot in question...you see?

pathfinder

Listen to Bob Bell, he is right.:):

Dust between elements will not produce sharp, detailed spots in the image as you posted. That is debris on your sensor. Time to clean your sensor, Graphy.

Go out and shoot two frames of the evenly lit sky ISO 100 or ISO 200. One, at a very small aperture - like f16. Then another at f4. Adjust the shutter speed so the exposure is the same and focus at infinity by focusing on a cloud.

Take both images into photoshop, and hit Image > Adjustments >Auto Contrast.

I think you will find that the image shot at f16 will demonstrate lots of grunge on your sensor, and the image at f4 will look fine. That is the expected scenario with sensor dust.

Dust between the elements of a lens is rarely, if ever, significant!!

IF IT IS SIGNIFICANT, it only causes a loss of contrast or resolution, NOT distinct spots in the image. Like I said above, time to clean your sensor.

Start with a Rocket Blower, but you may need to use a Sensor Brush or an Artic Butterfly. Probably you need to use Eclipse and Sensor swabs. Welcome to the club. BT,DT!!

If you are convinced the lens is dirty in its interior, send it to Canon. This is not something I owuld want to try myself anyway. If you do decide to diassemble this lens, please post some shots of it after re-assembly and let us all see how it went. Might be interesting or at least, entertainling.....

GraphyFotoz

pathfinder wrote:

Listen to Bob Bell, he is right.:):

Dust between elements will not produce sharp, detailed spots in the image as you posted. That is debris on your sensor. Time to clean your sensor, Graphy.

Go out and shoot two frames of the evenly lit sky ISO 100 or ISO 200. One, at a very small aperture - like f16. Then another at f4. Adjust the shutter speed so the exposure is the same and focus at infinity by focusing on a cloud.

Take both images into photoshop, and hit Image > Adjustments >Auto Contrast.

I think you will find that the image shot at f16 will demonstrate lots of grunge on your sensor, and the image at f4 will look fine. That is the expected scenario with sensor dust.

Dust between the elements of a lens is rarely, if ever, significant!!

IF IT IS SIGNIFICANT, it only causes a loss of contrast or resolution, NOT distinct spots in the image. Like I said above, time to clean your sensor.

Start with a Rocket Blower, but you may need to use a Sensor Brush or an Artic Butterfly. Probably you need to use Eclipse and Sensor swabs. Welcome to the club. BT,DT!!

If you are convinced the lens is dirty in its interior, send it to Canon. This is not something I owuld want to try myself anyway. If you do decide to diassemble this lens, please post some shots of it after re-assembly and let us all see how it went. Might be interesting or at least, entertainling.....

Awwwww man I just cleaned the sensor a week or so ago! :splat
Just did a white screen test and I only see 4-5 specs.
I use the Copperhill method and it worked great.
But man sweated threw the whole process!!! :twitch

wxwax

pathfinder wrote:

Artic Butterfly.

Have you tried this yet, PF? Sounds great, those cans of compressed air are a nuisance.

pathfinder

wxwax wrote:

Have you tried this yet, PF? Sounds great, those cans of compressed air are a nuisance.

Yes, I bought one too.

M Reichman is a better saleman than a carny barker.:D

I really haven't used it that much. I don't care to fly that much, and the Butterfly's main raisone de etre' was for travellers on airplanes who cannot pack canned air, wasn't it??

I have Visible Dust Sensor brushes too - but I tend to find that either my sensor isn't that dirty and doesn't need any work, OR brushes just waste my time until I finally get down too it and swab away with Eclipse. I am not sayinmg that brushes are no good, just that they are not a true replacement for swabs as I had hoped they would be.

Usually, I prefer to ignore dust motes on my sensor until they are just horrid. I rarely shoot at small apertures, so I can frequently get away with this.

I DO plan on housecleaning before leaving for Bryce, as landscapes tend to call for smaller apertures sometimes.

I just use a Rocket Blower on my Sensor Brushes, rather than canned air. Or if canned air is handy, I might use that - I am not always consistent, but I sometimes am lazy.......:D

And that is why I almost negligent when it comes to cleaning lenses

I prefer to only clean lenses if things do not blow off easliy with a Rocket Blower. I prefer to do as little lens grinding as possible:D Sometimes a drop of Eclipse can be very helpful getting an oily spot of a lens element.

pathfinder

Graphy - did you recheck your sensor like I rec'd - shooting the sky at f16 and the examing the image on your computer after Image>Adjust>Auto Contrast??

Disheartening, isn't it?