Cleaning a lens - have I messed up?

I was out an about taking photos today and had a couple of lens swaps. When I got back, I gave my kit a check over, blowing most of the dust etc off with a rocket blower.

Now the painful part. On the rear element of my 24-105 there was a spot that would not go away, a bit like a water mark or something. I got out my brand new (unused) microfibre cloth and rubbed it fairly hard from one side to the other... only to notice a large streak across the lens. A bit more gentle rubbing with clean faces of the cloth has got rid of said mark and streak but it has resulted in what looks me rubbing off a film/ coating off the lens! This is only visible in direct sunlight though and not under a normal desktop light.

So, the questions:

1) Has anybody done this before?
2) Is there some sort of film on the rear element of a lens?
2) How do I fix it?
3) Does it matter anyway if I cannot see any trace of it on my photos?

Thanks for any input. I am hoping to hear that I am not as much of a cretin as I now feel.

Before deciding that I had done something wrong I would wet clean the lens element in question. I normally keep Zeiss premoistened lens cloths in my camera bag for this but any good lens cleaning liquid and lens tissue is as good (although less convenient)

Wayne

WMS wrote in post #5684129
Before deciding that I had done something wrong I would wet clean the lens element in question. I normally keep Zeiss premoistened lens cloths in my camera bag for this but any good lens cleaning liquid and lens tissue is as good (although less convenient)

Wayne

good suggestion. i'd think you'd have to be using some serious elbow grease to remove lens coatings with a micro fiber cloth .

ed rader

Thanks both. I will buy some lens cloths and give it a shot.

let us know the result

WMS wrote in post #5684129
Before deciding that I had done something wrong I would wet clean the lens element in question. I normally keep Zeiss premoistened lens cloths in my camera bag for this but any good lens cleaning liquid and lens tissue is as good (although less convenient)

Wayne

I also use this product for cleaning, and keep a few in the bag just in case. They're not cheap, but they work well.

Andy_Cam wrote in post #5684089
A bit more gentle rubbing with clean faces of the cloth has got rid of said mark and streak but it has resulted in what looks me rubbing off a film/ coating off the lens! This is only visible in direct sunlight though and not under a normal desktop light.

It sounds like you removed the multi-coating on the rear element of your lens. Multi-coating is designed to prevent reflections, improve contrast, and improve light transmission. Since this is the back of the rear element the improved light transmission from the coating is very minor, but the the anti-reflective property is fairly important. Without the coating you may end up with a reflection of the sensor appearing in your images. This is probably the only thing that you will notice from the loss of the coating. You most likely wont see any signs of this is most images, but it might happen once in a while.

As for fixing it, applying multi-coating is a very precise job as the thickness of the coating needs to be nearly identical across the element. I'm sure if you sent it into canon they could fix it, but I have no idea how much it would cost, but I doubt it would be very cheep.


When cleaning lenses in the future it is best to wait until you are at home, and can work under a bright light. Unless the element is filthy theres a good chance that any dust or crud that a rocket blower wont remove wont even show up in any images. Also you should never rub with lots of pressure, if anything the amount of pressure should be as little as possible, ideally just the weight of the lens cleaning tissue, the trick is to just use more tissues. Just remember a dirty lens will generally perform better than a poorly cleaned lens.

It sounds to me like some oily residue on the rear element since you can smear it.
But before using a microfiber, I'd recommend blowing on the lens or better yet moistening a microfiber with a bit of a lens cleaning solution, use that to initially clean the lens and then drying it off with a dry part of the micro fiber.

I doubt you did any damage, but dry cleaning a lens which may potentially have something on it with a microfiber is not a good idea. Also, you generally should clean lightly with the fiber to prevent accidentally scratching the lens.

Good luck.

Marnault wrote in post #5689010
It sounds .... Without the coating you may end up with a reflection of the sensor appearing in your images. ....

You could just as well end up with a reflection of Elvis. Have you ever documented a reflection of the sensor? I would honestly like to see this one verified.

The reflections the coatings minimize don't make a ghost image show up on the sensor. Those reflections, just like those inside a lens, cause a general reduction in contrast and color saturation.

Never dry rub a lens with anything IMHO. At a minimum, fog it with your breath first. And only do that after a blower or brush treatment first to remove any surface debris.

MichSt wrote in post #5688460
I also use this product for cleaning, and keep a few in the bag just in case. They're not cheap, but they work well.

I've also been using the disposeable zeiss cleaning cloths and never looked back. I've found them as cheap as $7 for a 21 pack.

The biggest problem with those micro fiber cloths is they're exposed, so any dust or crap thats on them that you dont know about can get wiped on or scratch up your element.

tryandcatchme wrote in post #5690574
I've also been using the disposeable zeiss cleaning cloths and never looked back. I've found them as cheap as $7 for a 21 pack.

The biggest problem with those micro fiber cloths is they're exposed, so any dust or crap thats on them that you dont know about can get wiped on or scratch up your element.

i just paid $10.90 delivered for a box of 90 from evil bay . these look like they will work great.

ed rader

You can get the zeiss cloths from walmart for fairly cheap.

bryank930 wrote in post #5690898
You can get the zeiss cloths from walmart for fairly cheap.

What department do they carry them in??

Order a Lenspen while you're at it!