topic Re: EOS R8 Weird dark border + bright patches in EOS DSLR & Mirrorless Cameras

EOS R8 Weird dark border + bright patches

fisherman10 — Thu, 12 Mar 2026 12:02:55 GMT

Hi everyone, would anyone know what would be the cause of these issues. There is a dark band on the top and bottom edges (landscape) or left and right edges (portrait). There is also a bright patch/haze right after the dark band.

I can see the dark band in the viewfinder and the screen before taking the photo. All photos jpg straight out of camera. Using EFCS. NOT electronic shutter. First 3 photos with the lady taken with flash, last 2 photos of the white wall taken without flash.

Canon R8, Canon EF 100mm MACRO USM and Canon EF 24-105 F4, 3rd party EF-R adapter.

To add to that, I also see the same issue on the screen preview and viewfinder BEFORE taking the photo.

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Re: Weird dark border + bright patches

jrhoffman75 — Thu, 12 Mar 2026 10:09:07 GMT

Is the opening in your adapter rectangular? The one in my Canon brand adapter is. Maybe the sizing is not quite correct and there is an edge effect?

Re: Weird dark border + bright patches

kvbarkley — Thu, 12 Mar 2026 12:00:25 GMT

How long have you had the camera? I suggest you contact Canon. Do you have image corrections turned on?

Re: Weird dark border + bright patches

fisherman10 — Thu, 12 Mar 2026 13:50:12 GMT

Yup it looks rectangular to me

Re: Weird dark border + bright patches

fisherman10 — Thu, 12 Mar 2026 13:51:35 GMT

About a few months. Only realised it recently.

I need to check the settings but I don't think it's due to image corrections. I can see the black border at the top and bottom in the preview. Meaning I see it on-screen and in the viewfinder BEFORE I take the photo.

Re: EOS R8 Weird dark border + bright patches

kvbarkley — Thu, 12 Mar 2026 14:01:11 GMT

I believe the mirrorless cameras do on-the-fly corrections.

Re: EOS R8 Weird dark border + bright patches

stevet1 — Thu, 12 Mar 2026 14:20:14 GMT

fisherman10,

Maybe you could try a couple of suggestions while you're using your adapter for the time being:

1) You could try changing your composition a little to account for the border, an then do a little cropping; and/or,

2) switch to a 1:1 aspect ratio and only get what''s in the center of your frame instead of a rectangular 3:2.

Steve Thomas

Re: Weird dark border + bright patches

jrhoffman75 — Thu, 12 Mar 2026 14:23:29 GMT

Difficult to tell, but the opening in my Canon version appears larger. Does yours have anti-reflect ridges all the way to the RF side opening? Looks like a reflection right at the opening. You might be getting vignetting.

Re: EOS R8 Weird dark border + bright patches

ebiggs1 — Thu, 12 Mar 2026 14:38:38 GMT

"...3rd party EF-R adapter."

The oblivious, why don't you get a Canon adapter?

"You might be getting vignetting."

I have no doubt yours is vignetting the image.

Re: EOS R8 Weird dark border + bright patches

rs-eos — Thu, 12 Mar 2026 14:44:13 GMT

Since you're using a 3rd-party adapter, that may be the issue.

You could rent a Canon EF to RF adapter (at least at lensrentals, this is around $17 for a single day; taxes/insurance would raise that)

That way you'd know if this is your adapter or some other issue.

Re: EOS R8 Weird dark border + bright patches

SignifDigits — Sat, 21 Mar 2026 20:15:18 GMT

If you have access to any RF lens to put on the camera, even at a store, you can test narrow it down that way as well.

My Canon adapter opening is clearly larger than your third-party adapter. IMO it's not worth your time to rent one. Send yours third party adapter back for a refund and get a new or used Canon adapter from a reliable source. As of this writing Canon has them refurbished right now for $119 - https://www.usa.canon.com/shop/p/refurbished-mount-adapter-ef-eos-r

Re: EOS R8 Weird dark border + bright patches

fisherman10 — Mon, 23 Mar 2026 16:44:04 GMT

Thank you everyone for the replies and suggestions. It is indeed an issue with the 3rd party adapter.

I tried grinding the adapter (savagely 😂) and the issue seems to have resolved.

Re: EOS R8 Weird dark border + bright patches

SignifDigits — Mon, 23 Mar 2026 18:18:06 GMT

Bravo for inventiveness there! I would recommend being SURE you blow the heck out of it with a high-pressure air hose - you just made a gazillion pieces of microplastic to land on the back of your lens and your camera sensor. Wouldn't be worth the optical train risk for the savings to me, but I am a tightwad and totally get making what you have work. Again, please blow that thing out with high-pressure air for a long time, and every angle imaginable, and best of luck to you.

Re: EOS R8 Weird dark border + bright patches

jrhoffman75 — Mon, 23 Mar 2026 18:23:52 GMT

@fisherman10 wrote:

Thank you everyone for the replies and suggestions. It is indeed an issue with the 3rd party adapter.

I tried grinding the adapter (savagely 😂) and the issue seems to have resolved.

Another data point to counteract the contention "It's just an empty cylinder, why spend all the money for a Canon brand adapter" 😀

Re: EOS R8 Weird dark border + bright patches

SignifDigits — Mon, 23 Mar 2026 19:01:00 GMT

John, that is true but lost time and lost photos and aggravation are not great tradeoffs for some people. Fixing this one makes sense as long as no particles become an issue, and the adapter performs well long-term. I hope it does and applaud the inventiveness, and, all great and wonderful if it does. That said buying the Canon adapter would have avoided the time, energy and corrupted photos, so I'm still only comfortable recommending those.

Re: EOS R8 Weird dark border + bright patches

fisherman10 — Tue, 24 Mar 2026 05:15:37 GMT

Haha yes I did! I have a air compressor with filtered nozzle. I made sure to brush and blow a few times after trimming.

Re: EOS R8 Weird dark border + bright patches

ebiggs1 — Tue, 24 Mar 2026 14:16:30 GMT

"Another data point to counteract the contention "It's just an empty cylinder, why spend all the money for a Canon brand adapter""

Yes sir, it certainly is.