Canon lens help

**Conundrum** · 01-07-2007, 10:41 PM

I'm a jong here. There are some specs of something on the inner part of the lens where there are three tiny screws to take off to get to it. Can I just buy a little phillips screwdriver, open it up and shoot some air in or is this a job for a professional?

It's a lower end Canon 100-300 USM. Also, would it be worth it to try to sell ? I just bought a new lens from Viva.

**mtbakerskier** · 01-07-2007, 10:48 PM

Originally Posted by Conundrum

I'm a jong here. There are some specs of something on the inner part of the lens where there are three tiny screws to take off to get to it. Can I just buy a little phillips screwdriver, open it up and shoot some air in or is this a job for a professional?

It's a lower end Canon 100-300 USM. Also, would it be worth it to try to sell ? I just bought a new lens from Viva.

In short, if you have to ask, you probally are not qualified to work on it. Secondly if its just a few specs of dust, don't worry about it, they will never show up. However if they are realtively large, post a pic of them, and the back / of the lense, and I'll tell you how to do it at your own risk.

BTW where are they in the lense, towards the back, towards the front, dead middle of the optics etc?

**summit** · 01-07-2007, 11:07 PM

I agree with MBS re lens dust probably being a non issue and probably being more dangerous to fix than the benefit.

The 100-300 USM is one of the best image quality budget telezooms that Canon ever made. IIRC it is 4.5-5.6 and a push pull with ring USM. It offers better IQ than any off the 75-300 type lenses. That doesn't mean it is worth a lot of money... but it offers good performance for it being a lower end variable aperture telezoom.

**Conundrum** · 01-07-2007, 11:32 PM

Cool that it's a non issue. If it were anything but a lens I got on the cheap that I'm replacing, I wouldn't have considered messing with it. I'll probably stick it on the shelf and keep it as a backup.

The noticeable specs are on the glass that is the first smaller diameter lens looking from the front of the lens. Here are the pics. The duse doesn't show and I checked some pics and doesn't seem to show up.

**mtbakerskier** · 01-07-2007, 11:51 PM

Those specs WILL NEVER show up.

Don't wory about them. Plus that element is a pain in the ass to get to in that lense. Bascially you dissasemble starting from the rear lesne mount, and contacs, than dissable the zoom couple before you can get to it.

In otherwords don't screw with it.

**pechelman** · 01-07-2007, 11:57 PM

zoom lenses are a big huge pain in the ass to take apart and put back together. If it was an older non autofocus prime, Id still say probably not to do it, but at least it would be easy to reassemble and take apart.

one of the reasons I love buying older cameras and fixing them up, cause theyre so darned easy to work on....I also love seeing how they timed shutter releases with different gear ratios. Freaking cool as hell.