Canon Lens Coating Issue

Fotoguy20d · Jul 9, 2009

I'm looking to buy a Canon 70-200 f4L from a co-worker but the lens has some weird spots on the front glass (the protective "filter"). I suppose I could get that glass replaced but anyone have any idea what's causing this?

THanks,
Dan

hoffy · Jul 9, 2009

I'm no expert, that looks nearly organic. I won't say fungus....yet, as the fungus I have seen looks a bit more spider webby

archphoto · Jul 10, 2009

Some kind of etching ?
Is it realy on the front surface of the frontlens ?
Having the frontlens replaced could be a tad expensive and I wonder if you would see any effect of it on your photo's.....

Put it onto your camera and see what kind of result you get and if it does not show up at high maginification get it for cheap.

Peter

Rol_Lei Nut · Jul 10, 2009

Hello fungus my old friend....

Try keeping the lens on a sunny window sill for as long as possible (weeks, months) to kill/stop the growth.
Try to determine if any inner elements are affected.
Get an estimate for a clean-up.

A good way to bargain the price down, though.

hoffy · Jul 10, 2009

As I thought. Fungus is treatable and if caught early enough will not damage the lens.

I have just had one cleaned from fungus. It was there and it was not overly big. It cost me $45Aust. I have to admit, I haven't seen a lens element as clean as the job that I had done!

Mind you, this was an enlarger lens. I could imagine a 70-200L might cost a tad more, especially if then need to get down to the nitty gritty

Rol_Lei Nut · Jul 10, 2009

I've had several lens with fungus like yours and most cleaned up nicely. Even the worst cases (within reason, when the fungus looked a bit like yours - I've seen lenses which looked like someone had stuffed a cotton ball inside) left tiny specks on the coating which are insignificant as far as the image is concerned.

In some cases, though, the fungus returned after a few years and those lenses are on my windowsill again...
:-(

Incidentally, they seem to be the lenses which have gotten the least use, so maybe regular use lets through enough UV rays to keep things under control.

clayne · Jul 11, 2009

Looks like some kind of fungus/etching which you can definitely use as a bargaining point.

It won't affect image quality with the way it is now. Atleast, not in any way you'll be able to spot with your own eyes.

Rol_Lei Nut · Jul 11, 2009

clayne said:
It won't affect image quality with the way it is now. Atleast, not in any way you'll be able to spot with your own eyes.

Here I have to disagree... Uncleaned, that kind of fungus will affect the lens' transparency and lower the contrast, especially in flare-type situations.

Cleaned, I agree that it will not affect quality.

Fotoguy20d · Jul 12, 2009

I was afraid it was fungus. I don't think the lens has been used much, if at all, for the past few years. I tried it out over the weekend and it yields nice images - whether there's degradation due to those spots, I couldn't say though. The reason I'm looking to buy the lens is to take on a trip to Rocky Mountain National Park in two weeks (instead of my 70-200 f2.8L IS, which I don't want to leave in the car while hiking, and which is too heavy to carry on some of the hikes we're planning). I'm thinking this lens is still better than Canon's 100-300 f4.5-5.6 (which I can pick up from KEH in EX+ for around $150). What do you think is a fair price for it in its current condition?

THanks,
Dan

djohnfot · Jul 13, 2009

You might try cleaning it off with some ROR (Residual Oil Remover) which should be available at a good camera store.

I cleaned fungus spots like those off the front element of a Minolta lens using plain white vinegar. It did a great job. I followed that cleaning with a more routine cleaning to get rid of any possible vinegar residue. I, however, cannot recommend you use this because the vinegar may, since it is acetic acid, be harmful to the lens coating. It didn't hurt that old Minolta lens but I would hesitate before I used it on one of my newer Canon or Nikon lenses.

Once you get it clean, make sure you store the lens properly. If you keep it in a case or bag, make sure you keep a bag or two of desiccant in with it.

Poisson Du Jour · Jul 13, 2009

A "Canon lens coating issue"!? Not on an L-series!
That is fungus and needs a professional service if inside (I have seen 2 incidences of fungal growth from optics used in far north Queensland here in Australia necessitating a complete disassembly of the lens, and that is costly). Fungus is common in tropical/moist conditions, moreso if the lens has been stored in a humid environment. If there is fungus up front, chances are, it could have penetrated deeper.

This optic is a much valued staple to my walking kit (and as you point out an equal performer to the heavier 2.8L version). The 70-200 f4L can fetch for up to 2/3 original value for a mint specimen — mint meaning no scratches, dents, scuffs or fungus. The ULD CaF2 inner element is chief among its costly features. I would be looking at a bit of heavy bargaining if the fungus is a concern, even though a mid-range Av will yield a most likely 'no show' in images. In common with the standard Canon optics vs the L-series, it is by far a much better performer than the 100-300mm 'pedestrian' Canon.

hoffy · Jul 13, 2009

Do I spot a hint of sarcasm in that last comment....

firecracker · Jul 13, 2009

Yes, that's fungus.

Fotoguy20d · Jul 15, 2009

A follow-up for anyone who's interested.

I tested the lens extensively with and without my 1.4X TC and shooting all sorts of conditions - low light, into the sun, angle to the sun without hood, close focus, infinity focus, etc. I have no source for comparison but the images struck me as being very good in terms of contrast, sharpness, flare, and quite acceptable. So, I don't intend to deal with the fungus before my Colorado trip but will see what's involved in cleaning it up afterwards. I had sent my co-worker the link to this thread and I guess he read this and did some on-line research. In any event, we came up with a fair price so I have a lens to take with me on my trip.

Thanks,
Dan

Rol_Lei Nut · Jul 16, 2009

Fotoguy20d said:
I don't intend to deal with the fungus before my Colorado trip but will see what's involved in cleaning it up afterwards.

Do take care of it before too long, though.

The fungus itself could continue growing and, worse, the damage done by the fungus to the glass (etching) will probably increase with time.

bob100684 · Jul 21, 2009

Having had a 100-300 f4.5-5.6, I can highly NOT recommend it. Autofocus is fast, but inaccurate, image quality is marginal until stopped down to f 11.

clayne · Jul 21, 2009

bob100684 said:
Having had a 100-300 f4.5-5.6, I can highly NOT recommend it. Autofocus is fast, but inaccurate, image quality is marginal until stopped down to f 11.

How is a 100-300 f/4.5-5.6 even close or equivalent to a 70-200 f/4.0L ? They're not even the same lens whatsoever. I don't even majority use Canon but I know a stupid comparison when I see one.

andrewkirkby · Jul 26, 2009

Hi there,

That does indeed look like fungus. This could be caused by water splashing onto the coating (and subsequently not dried) which creates an ideal place for the fungus to grow. Lenses also do not like humid environments and fungus often goes hand in hand with high humidity. Other problems like internal corrosion can also happen in these environments but this is greatly reduced by the weather sealing present on the "L" lenses.

I would test the lens to see how it performs. Shoot it on a full frame camera and see if there are any noticeable faults in the image - something that you will be unhappy with. (please do this with a freshly cleaned sensor to avoid headaches!). Sometimes these marks can be polished out but it will never be the same as you are taking some of the coating off the glass with even the finest of polishing compounds. Lens elements are expensive not only for the part but the amount of labour time required to install and calibrate to factory specifications.

Prevention: Store lens in case with dehumidifying material - silica gel. You can get it online in big packs for very little money. Also, stick a high quality Sky or UV filter on the front of the lens. You can get a 67mm B+W/Schenider filter for a reasonable price and it will protect against front element fungus, scratches and even some potential breakages!

if you have any questions, please send them along to me:

kirkby_andrew@canon.com.au

Andrew Kirkby
Canon Australia

Pumal · Jul 27, 2009

That is fungus, but that lens; in that condition will probably take great pictures anyway. Use it and when not in use; put it on a windowsill under the sun. After a couple of weeks you will have a care free lens.

domaz · Jul 27, 2009

If the fungus has eaten away the coating then your pictures will probably be useless. Your pictures will be sharp but the colors will look off and wrong where the coating is gone. Tread carefully.

clayne · Jul 27, 2009

domaz said:
If the fungus has eaten away the coating then your pictures will probably be useless. Your pictures will be sharp but the colors will look off and wrong where the coating is gone. Tread carefully.

Bogus.

Pumal · Jul 27, 2009

andrewkirkby · Jul 28, 2009

domaz said:
If the fungus has eaten away the coating then your pictures will probably be useless. Your pictures will be sharp but the colors will look off and wrong where the coating is gone. Tread carefully.

Incorrect.

If there was severe damage to the elements inside then maybe this is possible. It looks like there is very minimal damage to the front lens coating and this will probably not affect the final image quality to a great degree.

I have seen lenses a lot worse that perform quite well. Certainly not useless!

As i have recommended to the OP: Test before you buy!

Andrew Kirkby
Canon Australia

Fotoguy20d · Jul 31, 2009

clayne said:
How is a 100-300 f/4.5-5.6 even close or equivalent to a 70-200 f/4.0L ? They're not even the same lens whatsoever. I don't even majority use Canon but I know a stupid comparison when I see one.

Not a stupid comparison, since I, the OP, mentioned that lens as a possible option for my trip - the goal being a decent (or better), lightweight, inexpensive lens I could leave in the trunk of my car or otherwise beat on.

Fotoguy20d · Jul 31, 2009

andrewkirkby said:
Incorrect.
I have seen lenses a lot worse that perform quite well. Certainly not useless!

As i have recommended to the OP: Test before you buy!

Andrew Kirkby
Canon Australia

I tested the lens quite thoroughly under a variety of conditions before agreeing to buy it. And, IMHO, from the limited sample I've seen thus far, it's performing quite well. The lens got a good workout (with and without a 1.4x TC) at Rocky Mountain National Park over the past week - I'm glad I had a long lens along with me and that I felt comfortable leaving it in the trunk of the car at times. As an aside, there was a good program by a visiting ranger from Australia on the national parks in Australia's Alps - interesting and informative.

I called my local canon service center and the front lens element (which seems to be just a protective "filter") will cost me $30. Depending on labor cost I'll either let them change it out or do it myself. I can find no evidence of fungus internally but just to be safe I'll let it sit on a windowsill for a while. What would be the downside to a more intensive UV exposure via an artificial UV light source?

Dan

Canon Lens Coating Issue

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