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RF100-500 Purple Dot Dead Center

Started 3 months ago | Discussions
nanciej New Member • Posts: 15
RF100-500 Purple Dot Dead Center
1

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.

some post adjustments and a close up.

Canon EOS R5 Canon EOS R6 Canon RF 100-500mm F4.5-7.1L IS USM
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Askeladden New Member • Posts: 24
Re: RF100-500 Purple Dot Dead Center
1

Looks like the same problem that is common with certain speedboosters so probably as you have already concluded an optical problem.

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Leigh A. Wax Senior Member • Posts: 1,621
Re: RF100-500 Purple Dot Dead Center
8

Perhaps it has self-corrected, or maybe it's an eye defect as I don't see a purple dot any of the three images?

Tazz93
Tazz93 Veteran Member • Posts: 3,473
Anyone else seeing this?

That is odd, do you have a second body to confirm it isn't specific to the camera? If it's not the body, it may very well be the design of the lens. Getting a new copy and seeing the same aberration at a very specific and uncommon focal range and aperture... it may have slipped past the QC.

Curious to see if others are seeing this on their copies.

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Ephemeris
Ephemeris Senior Member • Posts: 1,186
Re: Anyone else seeing this?

Tazz93 wrote:

That is odd, do you have a second body to confirm it isn't specific to the camera? If it's not the body, it may very well be the design of the lens. Getting a new copy and seeing the same aberration at a very specific and uncommon focal range and aperture... it may have slipped past the QC.

Curious to see if others are seeing this on their copies.

He said that the defect followed the lens to an R6.

Given the type of change to the image it would seem to be optical and that is only at certain focal lengths.

Sounds like a job for Canon to fix and also why a new lens is full of dust.

WildImages
WildImages Contributing Member • Posts: 741
Re: RF100-500 Purple Dot Dead Center
6

Leigh A. Wax wrote:

Perhaps it has self-corrected, or maybe it's an eye defect as I don't see a purple dot any of the three images?

For me it appears as a purple smear discoloration on the shoulder of the rhino and the trunk of the elephant on the right.

Do you by chance use a filter?

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John Sheehy Forum Pro • Posts: 26,688
Re: RF100-500 Purple Dot Dead Center
5

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.

some post adjustments and a close up.

It looks like some kind of flare. Are you using anything else in the optical path, like a filter?

That color is the color you get with near-infrared light, and some lenses are just not designed to manipulate near-IR light correctly. In some outdoor situations, there can be more near-infrared light than usual, relative to visible light.

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gimp_dad Senior Member • Posts: 2,692
Hmm
2

Crazy that it has followed you across two completely different lenses and 2 completely different bodies.

What editing SW are you using?  Could it be an issue with the lens correction of your photo editor?

drsnoopy Senior Member • Posts: 1,216
Re: RF100-500 Purple Dot Dead Center
7

Two lenses, two bodies. And it’s something that I don’t think anyone else has seen. So logically it seems likely to be something in common with your two situations, but not to do with camera or lens. This leaves two possibilities;

1. Filter - are you using one, and did you use the same one on both lenses?

2. Software. Assuming you’re shooting RAW, which converter are you using and was it the same both times? Can you retry with a different RAW converter? Also did you by any chance also shoot JPEGs at the same time? In which case, is the spot on the JPEGs too?

I don’t know anything about the above comment re near infra red. I have the same body and lens and have used for many 100s of images at all focal lengths in different lighting conditions (but not under African sun) and never seen such an artefact.

Very interesting though.

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Ephemeris
Ephemeris Senior Member • Posts: 1,186
Re: Hmm

gimp_dad wrote:

Crazy that it has followed you across two completely different lenses and 2 completely different bodies.

What editing SW are you using? Could it be an issue with the lens correction of your photo editor?

I missed the sending a new lens, oops.

2 bodies, 2 lenses, some canon cleaning, only certain focal lengths.

Filters, software - you could be right. Wierd one.

ZX11
ZX11 Veteran Member • Posts: 6,156
Re: RF100-500 Purple Dot Dead Center

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.

A perfect purple dot? Not really a dot or purple pixel.

The purple cast in the center of the frame is caused by dirt in the lens according to Canon. Since the same thing happened when the new lens was taken to Africa, and not before, Canon may be onto something. Full of dirt?  That is an extreme description.  How'd that happen?

Get someone other than Canon to clean it for a second opinion.

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Ephemeris
Ephemeris Senior Member • Posts: 1,186
Re: RF100-500 Purple Dot Dead Center

ZX11 wrote:

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.

A perfect purple dot? Not really a dot or purple pixel.

The purple cast in the center of the frame is caused by dirt in the lens according to Canon. Since the same thing happened when the new lens was taken to Africa, and not before, Canon may be onto something. Full of dirt? That is an extreme description. How'd that happen?

Get someone other than Canon to clean it for a second opinion.

They eventually replaced the lens.

I suppose it's possible they both have the same fault.

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OpticsEngineer Veteran Member • Posts: 7,822
My Purple Dot Dead Center
8

The last time I was fighting with a purple dot dead center was with a Canon SX260.  (a compact 20X camera)  The purple spot only appeared at certain zooms and focus distance.  I took quite a few pictures of my dog (Mister) when I was trying to figure it out.

I looked at the lens and to my professional eye, it looked clean.   I look at a lot of optics.  But then I thought, well, I should at least do what I tell my technicians to do at work.  Get some alcohol and clean the front lens element before chasing down anything else.   I was very surprised when the purple spot went away.  It certainly was not a lens "full of dirt"   Whatever it was I couldn't even see... maybe I should have looked harder with a bright flashlight... I was looking with overhead lights.   Problem with bright flashlights is you see so much that is not a problem.

With a lens there is the straight through light path that makes an image. But there are also lot of reflections off internal elements and some of them will focus on a sensor.  Some lens designs are known for a problem that if a surface becomes a light source, by scattering light off dirt, there will be some combination of multiple reflections inside the lens that happen to form hot spots on the sensor at certain zoom or focus settings.  When that happening, it is typical that small changes in zoom or focus will make the size of the spot get smaller or bigger on the sensor.    A lens hood sometimes eliminates the problem.   The spot is typically whatever color the AR coatings happen to reflect the most at, and that is typically some blue and some red, making purple.  Knowing that was what made me clean the lens even though it looked clean.

Not sure if that is relevant.  But that is my purple dot story.

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OP nanciej New Member • Posts: 15
Re: RF100-500 Purple Dot Dead Center
2

Thanks for all the replies. I do have a clear filter on the lens as I am often around flying pebbles. I just find it very odd this only occurs in a particular focal range. And always exactly in the middle. Canon is now suggesting it is lens flare? I have never experienced purple lens flare. Could be. But is lens flare that consistent with where it shows up and at what length?

OP nanciej New Member • Posts: 15
Re: RF100-500 Purple Dot Dead Center

-Perhaps it has self-corrected, or maybe it's an eye defect as I don't see a purple dot any of the three images?

What can I say. It’s there. Even Canon acknowledges it. 😊

OP nanciej New Member • Posts: 15
Re: RF100-500 Purple Dot Dead Center
1

Leigh A. Wax wrote:

Perhaps it has self-corrected, or maybe it's an eye defect as I don't see a purple dot any of the three images?

For me it appears as a purple smear discoloration on the shoulder of the rhino and the trunk of the elephant on the right.

Do you by chance use a filter?

It looks more circular on certain images-definitely as the fstop increases.

yes, I have a clear filter because there are often flying pebbles etc when I am working.

OP nanciej New Member • Posts: 15
Re: Anyone else seeing this?

Tazz93 wrote:

That is odd, do you have a second body to confirm it isn't specific to the camera? If it's not the body, it may very well be the design of the lens. Getting a new copy and seeing the same aberration at a very specific and uncommon focal range and aperture... it may have slipped past the QC.

Curious to see if others are seeing this on their copie

I also see it on the R6. It is bizarre.

OP nanciej New Member • Posts: 15
Re: Anyone else seeing this?

Ephemeris wrote:

Tazz93 wrote:

That is odd, do you have a second body to confirm it isn't specific to the camera? If it's not the body, it may very well be the design of the lens. Getting a new copy and seeing the same aberration at a very specific and uncommon focal range and aperture... it may have slipped past the QC.

Curious to see if others are seeing this on their copies.

He said that the defect followed the lens to an R6.

Given the type of change to the image it would seem to be optical and that is only at certain focal lengths.

Sounds like a job for Canon to fix and also why a new lens is full of dust.

the lens took one trip to Kenya and while there is dust, it was not crazy and  I cover the camera when not in use. So…after one trip if it was dusty that doesn’t bode well for the seal. My 100-400 was used on dozens of trips - when I had it serviced there was no mention of dust.  I found it odd…and odd that they would blame a dot like this on dust.

OP nanciej New Member • Posts: 15
Re: RF100-500 Purple Dot Dead Center

John Sheehy wrote:

It looks like some kind of flare. Are you using anything else in the optical path, like a filter?

That color is the color you get with near-infrared light, and some lenses are just not designed to manipulate near-IR light correctly. In some outdoor situations, there can be more near-infrared light than usual, relative to visible light.

-

I’m out of my depth with the the IR info. Thanks. I’ll read on that. But…would this still result in this issue always being dead center?

OP nanciej New Member • Posts: 15
Re: Hmm

gimp_dad wrote:

Crazy that it has followed you across two completely different lenses and 2 completely different bodies.

What editing SW are you using? Could it be an issue with the lens correction of your photo editor?

Lightroom. But you can see it on the lcd screen of the camera.

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