RF100-500 Purple Dot Dead Center

Leigh A. Wax wrote:

I noted the anomaly by rezzing the image up to 300%; but if that much area is considered to be a "dot", the Great Lakes should be described as puddles!

Maybe a waste of my time, Leigh, but I'll try to help you out a bit. Notice the red circles in the examples below. Now we know they're not as big as the Great Lakes 'cuz the birds are only Pinyon Jays after all...

But the flare, which exhibits itself as an irregular area covering almost the entire circles, is definitely there and is VERY obvious in the processing apps I use.

Notice, too, that it's in the same frame location as the OP's images.

Hopefully you won't need 300% to see the problem. If you do, perhaps you've got problems not at all related to the images.

The central hot spot (purple, blue, green, whatever depending upon the coating and the incident angle of the internal reflection) is common on cheaper telezoom lenses. Seen in some higher end lenses too.

Very often seen in cheap telescopes whith little or no light baffling.

The optical configuration of zoom lenses vary when zooming and the hot spot becomes more pronounced at certain focal ranges. The range mostly affected depends upon the lens, the optical configuration and coating.

nanciej wrote:

Hi

I am really hoping someone here may shine any light on this. About 16 months ago I bought the R5 and rf 100-500. Love them! I only photograph wildlife and I really only do it when I am in Africa. On the first trip with the kit, I noticed a purple dot, dead center. I only saw it on certain photos in the 140-170mm range. I sent the kit to Canon. They returned the R5 right away with a cleaned sensor. They said the brand new 100-500 was full of dirt and I would have to pay to get it cleaned. This was the issue. Every single Canon professional I had spoken to said dust would not form a perfect purple dot dead center. After some pushing and a rep from the store I do business with getting involved, Canon sent me a new 100-500.

November I found myself back in Africa and guess what? Purple dot. (images below) A couple of folks thought it might be the sensor...so I tired the lens on my R6. Same dot. It does not happen all the time. When it does, it is always between the 135-179mm range. I only ever see it at f14 or higher, which kind of makes sense. So two lenses and the issue is on two sensors.

Has anyone heard of this? Seen it? I am working once again with Canon support but the hoops!

Thanks for any thoughts.

Can I just ask if you are using the lens hood or not?

I did start reading through the thread but have not come across this question yet.

some post adjustments and a close up.

So far we have someone with the anomaly who is shooting through glass and the OP who was using a filter on the lens. Do we have any examples of the anomaly shot out in the open with no filter, no lens hood, no window glass? It is difficult to figure out what is going on without eliminating all the variables and just looking at the results of simply a camera + lens combination. By the way, my experience after some 15 or 16,000 images made with my RF 100-500 is that I have never noticed the issue.

birdbrain wrote:

I’ve gone through many of my 100-500 shots, and I can honestly say I’ve not seen any optical artefact’s in my images.

I always use the lens hood 100% of the time.

No filter used ever either.

I can only suggest you try without a filter and have the lens hood on.

Me also no probs at all, I never shoot at such small apertures either. Mostly wide open.

I have an old Sigma 15-30 that sometimes has lens flare the same color and shape as your purple dots. That makes me think your problem is caused by some sort of lens flare or internal reflection. You could talk Canon's tech support department and ask them to send you a link so you can upload a few sample photos to them. They may be able to help you confirm what is causing the problem.

Hello, I too have just recently observed the same issue—a purple hue circle in the dead center of my photos—with the rf100-500 on my R5 body.

Shooting cr3 raw using a neutral color profile and editing in light classic 2023.

Arboursabroad wrote:

Hello, I too have just recently observed the same issue—a purple hue circle in the dead center of my photos—with the rf100-500 on my R5 body.

Shooting cr3 raw using a neutral color profile and editing in light classic 2023.

Do you have a filter on the lens and are you using the lens hood ?

This is exactly what I am seeing, albeit at a different focal length! Thanks for posting. I have actually had a senior tech at Canon pick this up and we are in ongoing discussions. He was quick to eliminate the earlier “dirt in lens” dismissal. I will be passing this along to him as well.

Hi

i have been out of the country an unable to update. The opening on the lens hood has been closed-but good thing to note so thanks. As I commented on the previous post showing the same issue, the problem has been escalated at Canon. The senior technician now working on this certainly acknowledges the issue and has dismissed the previous “dirty lens” theory. He has not seen it before and first thoughts are possibly the filter. But I have also now sent over the link to the bird photos posted by Abbott - thanks for those-showing the same issue, with no filter on the lens, and occurring at a different focal length. It is an inconsistent issue to reproduce but trying to narrow it down. Thanks for all the interesting comments and apologies for the delay. I was not expecting to travel.

Lens hood is always on. Thanks.

Nancy, fyi I sent several Raw files illustrating the problem to CPS several weeks ago. They seem to be having trouble figuring out what's happening (I need to call them again). Their first response was that I needed a lens hood. However, when I described my shooting environment (standing well back from a window in an unlit room, with the sun totally blocked by the house) AND sent them photos shot from the same subject, same room, same camera position, but different natural light (same camera and 100-500 lens), they came up empty.

The interesting thing for me is that, all things being equal except lighting, the disc comes and goes (purplish disc under cloudy conditions, no disc under clear light).

Sadly, I got the phenomenon only twice, whereas I've shot the same thing dozens of times.

Have you seen the issue again?