topic Re: RF 50mm F1.2 - Smudges on glass won't go away in EF & RF Lenses

RF 50mm F1.2 - Smudges on glass won't go away

SarVinci — Sat, 07 Oct 2023 15:51:43 GMT

Hello Canon Community,

I recently noticed micro particles I wanted to remove and couldn't on my Canon RF 50mm F1.2 lens, I found a glass cleaner I realized I shouldn't have used because it had dust on it too. I used 70% alcohol that contains purified water, ALSO I am talking about the back part of the lens glass near the sensor when attached to camera body. There are still some smudges on there I tried removing, no luck 100%. I bought a K&F Concept kit with a spray bottle, is that a good way to clean it? Was there any lens coating damaged I may have caused on the back glass? Is it possible to remove the smudge and smears with a cleaner microfiber cloth and the solution from K&F?

Re: RF 50mm F1.2 - Smudges on glass won't go away

Peter — Sat, 07 Oct 2023 16:46:52 GMT

I use isopropanol and a microfibre cloth to clean my EF lenses. No damaged coating.

RF 28-70/2 on the other hand is a lens I have seen many samples of destroyed lens coating, so I wouldn't dare to clean that one. Perhaps UV filter would be an easy solution for the front lens and only microfibre cloth without alcohol for the rear element?

You have different RF lens than 28-70. If you are unsure if you damaged the coating or not I would say that you will notice if it went bad.

Re: RF 50mm F1.2 - Smudges on glass won't go away

SarVinci — Sat, 07 Oct 2023 15:56:52 GMT

I really hope I didn't destroy the expensive lens with the alcohol solution. I have not heard if the back part of the lens has coating, but I have heard it's the front part of the lens glass that has coating. Can you tell if the lens coating is destroyed? What do images look like?

Re: RF 50mm F1.2 - Smudges on glass won't go away

Peter — Sat, 07 Oct 2023 16:03:06 GMT

Damaged lens coating will shift colour/shape, see Meyer-Optik Orestor 135mm f/2.8 http://japb.net/gear/general-articles-on-gear/lensdefects6-surface-defects/

Re: RF 50mm F1.2 - Smudges on glass won't go away

Anonymous — Sat, 07 Oct 2023 18:18:03 GMT

Lenses have coatings on the rear element of the lens also.

Re: RF 50mm F1.2 - Smudges on glass won't go away

SarVinci — Sat, 07 Oct 2023 19:42:16 GMT

Oh I see. So are you saying that one or two isopropyl alcohol 70% applications with lens cloth removed the coating or does it take more?

Re: RF 50mm F1.2 - Smudges on glass won't go away

Anonymous — Sat, 07 Oct 2023 19:52:34 GMT

No, I wasn't implying that. I was answering your question about rear lens elements being coated.

Isopropyl alcohol shouldn't damage lens coatings, but you should use a blower to blow off dust and loose dirt before using a cloth or lens tissue moistened with lens cleaner or alcohol. You should keep your lenses capped when not mounted or being used.

Can you post a photo of the rear lens element showing what you are seeing?

Re: RF 50mm F1.2 - Smudges on glass won't go away

SarVinci — Sun, 08 Oct 2023 12:55:01 GMT

I will send photos here soon. However, I want to say that I saw some pictures of damaged coating, it looks like pieces of the glass is damaged and chipping, mine doesn't reflect such a damage. I do use the blower to remove bigger dust or debris that might scratch the lens glass, but what I had issues with was super small particles that would not get removed with blower, so I bought K&F Concept lens cleaning kit, I hope the liquid spray used with the microfiber would be safe to apply to the lens glass to make it cleaner. I will use the brush as well, since it seems that the brush works well to remove stubborn debris. Lastly, there are some minor smears and smudges on the rear glass of my 50mm. f1.2 RF lens, I want to use the kit to make it crystal clear, then I won't touch that part of the lens to avoid grinding.

Re: RF 50mm F1.2 - Smudges on glass won't go away

ebiggs1 — Wed, 11 Oct 2023 14:35:46 GMT

There are several brands of cleaner you can buy that are designed for camera lens cleaning. I would opt for a lens cleaning cloth like the ones your eye doctor has. Not a micro-fiber cloth. Mine gives them to me for free. Secondly I would buy a high quality B+W protecto filter so I never have to clean that expensive lens again.

I doubt you damaged the lens coating if you did this just once and did not drench the lens with the alcohol but do not repeat it again. If the lens coating is damaged it is not possible to replace the coating or repair it. It is a lens element replacement job. It is a very thin layer applied to the lens's front and back surface. The coating on the front element is basically an antireflective, antiglare or anti-reflection coating. It improves the efficiency since less light is lost due to reflection which makes the lens transmit more light. A typical lens may transmit 95% of the light without any coating but transmit 99.5% with it. So you see it can be very important. Get a protecto filter today.

Re: RF 50mm F1.2 - Smudges on glass won't go away

SarVinci — Wed, 11 Oct 2023 14:39:59 GMT

Hi! I have protector filter for the front part of the lens but the back part doesn’t. I doubt there are any for the back part glass. Right?

Re: RF 50mm F1.2 - Smudges on glass won't go away

ebiggs1 — Wed, 11 Oct 2023 15:06:48 GMT

OK, sorry, I thought you were cleaning the front element. Although a very expensive lens like yours will have coating on the rear element all lenses do not have that. In my nearly 6 decades of photography I don't ever remember cleaning the rear element beyond using a Rocket blower.

Here is my advice, if it is not impacting your photos I would ignore it. Leave it alone! As it most likely doesn't hurt anything. However, if it does and you are concerned about it, you need to send it to Canon for service. You can only make it worse.

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