Canon 17-40 weird white dots inside front element

I certainly would not describe a lens with these defects as being in "perfect condition." You need to make sure that these dots are not fungus which can spread to the lens elements and start to deteriorate image quality. And when you consider that you can get a good used lens from a reputable supplier such as KEH for $499 or from Canon as a refurb for $540, I would think about returning the lens.

p.s. I presume you read far enough in the disassembly guide to find that the author was not able to remove the spots once he had made all that effort.

Andy01 wrote:

Weird - never seen anything like it. Can you return it ?

As a side note, When I was looking for a wider angle lens a few years ago, and tested several in a large shop with my own camera and card and compared images, the 17-40L was without a doubt the worse of the bunch - probably on a par with the 17-85mm I had at the time. The Canon EF-S 17-55, 16-35L f4 and even Sigma 17-50 f2.8 & Tamron were all better / sharper. I was very disappointed given that it was a L lens - noticeably worse than my 24-105L at similar focal lengths.

Colin

that certainly hasn't been my experience with my 17-40 f4.0! i have taken some of my most memorable shots overseas with this lens. i tried it for a few months in the beginning and i hated it but then all of sudden it clicked with me and had nothing but fun, afterwards i haven't used my 1740 in a few years since i purchased my canon 24-70 f2.8 II. here is a gallery i have mad exclusively with my 1740 a few years back:

http://azbaha.zenfolio.com/p572883877

It takes 5 minutes to remove the front element. Remove the black plastic around the front element and unscrew the three screws that hold the front element.

https://youtu.be/ZCxeG3IQFTU

Kameratrollet wrote:

https://youtu.be/ZCxeG3IQFTU

If you try this, be sure to get JIS screwdrivers so you don't strip the screw heads.  Standard jewelers screwdrivers don't work as well.

looks like your illustrations of dismantling 1740 shows a different issue rather cleaning the front element, which goes quite deep into different elements and stages. but getting to the front element seems quite easy and effortless!

Abu Mahendra wrote:

Looks like classic case of Schneideritis. Google it.

I also seem to have a 17-40mm which 'caught this disease'!!!

Didn't use my lens for a few months, and moved over very long distances twice in less than two years and last week wanted to use my lens again and was greeted by a bunch of weird white spots in between the front lens group!!! Yikes, didn't look like anything I ever saw before (dust, mould, you name it!).

Posted a question about it here on the forum before I found this one but nobody really knew what the problem could be either...

Any who, what you came up with really seems to nail it!

Thanks!

Hi,

Did you ever find out what the problem was, or even better got it fixed?

My 17-40 got 'infected' too!!!

Anyways, if I ever find out from my side, I'll update on here...

Fotookes wrote:

Hi,

Did you ever find out what the problem was, or even better got it fixed?

My 17-40 got 'infected' too!!!

Anyways, if I ever find out from my side, I'll update on here...

hmm...i haven't checked my 17-40 in a while, i better check it soon

regladetercios wrote:

Hello!

I recently bought a used Canon 17-40L lens and noticed it has some white spots in the front element.

The spots seem to be in the plastic but don't affect the image.

I found this disassembly guide with someone with similar spots on the lens.

Any information would be appreciated.

The lens was $340 so it seemed to be a good deal, the lens is in perfect condition and has a UB date code.

Thanks,

Daniel

White dots with macro lens

that looks like water droplets that got molded and dried up! amazing how those droplets are in a row with almost equal space between them!

The weird thing is that, apart from the fact these spots managed to get in between two lens elements that are supposed to be stuck together, they also are more silvery than white...

Kind of reflective and perfectly round!

Now I did live in Sendai when the Fukushima reactors blew up, but I cannot imagine my lens became radioactive... No?

Anyway, mystery stays unsolved!

Indeed he does!