HOW does dust get IN a non-extending prime lens?

I got a brand new 85 1.8 a few months ago, which I inspected carefully when buying. I have used it only 3-4 times, and only twice outside, in my backyard for brief periods of time (15-20 minutes each).

This morning I changed lenses and noticed 2 small dust specks INSIDE the lens (behind the front glass). They are more like 2 very tiny pieces of fiber. I am sure that they do not affect the image quality, but I wonder how they managed to get into the lens.

I used the lens on my new 50D, so I am sure the dust was not from the camera. I use a lens hood all the time but I admit I did not use a UV/clear filter on the 85. I inspected my other lenses (24-105L, 50 1.4, 18-55IS, 135L). All of them are clean and have been used much, much more than the 85, both inside and outside. I only use filters in parks, zoo, playgrounds, etc. where the air can be dusty.

How did dust get into the lens? Could it have been avoided if I use a UV/clear filter?

I know this topic has been discussed to death, but it bothers me that my other lenses are used much more but OK.

Gnomes.



Dust happens. I don't believe that lens is weather sealed, so there are plenty of ways for dust to find a way in.

Yes, Gnomes and Elves. On some lenses a UV filter will help slow it down. Some lenses are weather sealed but I'll bet given enough time and opportunity, dust will find a way in.

via the back door, is most likely.

The 85 1.8 is a dust vacuum.

You can send that into canon to get it cleaned out right? If so I'm...gonna send them my 17-55, **** got toreee up here in Iraq.

When I bought my 85 1.2 it had more dust in it then i have under my Bed! Well almost .

Anyway I just sent mine back and they told me that they could have it cleaned, I was not so interested having them opening up a brand new lens so I just demanded my money back hehe.

Lenses are not assembled in a "clean room." The assembly areas are no cleaner than a normal Japanese office environment.

RDKirk wrote in post #8246934
Lenses are not assembled in a "clean room." The assembly areas are no cleaner than a normal Japanese office environment.

Wow, I'm a bit surprised to read this.

If you send your lens to Canon just to be cleaned they will charge you. If it is there under warranty repair for some other problem and you mention the internal dust, they probably will clean it out no charge. That's my experience.

viet wrote in post #8246258
The 85 1.8 is a dust vacuum.

Really? I have had one for quite a while, and used it in some dusty conditions, and mine has exactly 2 specks of dust internally, and they were there when I got the lens new.

The 85 f/1.8 is not sealed - most lenses are not completely sealed (even weather sealed lenses allow some air to move in and out of the lens). The fact that it's a prime lens means that less air (and dust) will be introduced into the lens by the act of zooming, but the internal elements do move during the focusing process and air will be pulled into and blown out of the lens, even if it's only a slight amount.

People worry way too much about little specs of dust in their lenses. All lenses will get a little dust over time - it's not going to effect image quality in the slightest unless you get a massive amount of dust in there - and that's not very likely at all. I have lenses that are over 20 years old. Yes, they have a bit of dust, but the images are just as good as when they were new.

I wouldn't worry too much about dust. I used to but have learned to not worry about it because you'd have to have a very serious amount of dust in there before it would impact your images.

Dust will never show up in an image. It is impossible. Your lens is always focused many inches in front of dust on any piece of glass. It will never produce spots like dust on the sensor as they are many inches in front of the sensor. The only thing they will do is reduce the amount of light hitting the sensor a very, very, very, slight amount. So small that you would never notice.

I hate seeing dust in any lens I own (regardless of whether it affects IQ or not).... I always use a UV filter on day one.

zoom_zoom wrote in post #8249199
I hate seeing dust in any lens I own (regardless of whether it affects IQ or not).... I always use a UV filter on day one.

I'd rather see dust than flare and ghosting....