# 5D mk3 "Purple Amp Glow" Design flaw in BRHC of all high ISO images



## Edwardallen (Jul 9, 2014)

_*If you have the mk3 have you noticed the the purple thumb sized area that appears in the bottom right hand corner of all images shot at higher ISOs (say 12800 plus?)*_

I shoot quite a lot of motion based indoor events like concerts, sports etc, and spotted that there is a purple "thumb print" sized area that forms in the bottom right hand corner of *every* image shot at 12800+; on the LCD, in the RAW file and the JPEG file too. 

(To replicate the effect simply take a shot at say 12800 with the lens cap on with a slow exposure speed and you can see it on the LCD of the camera) you will see a black image speckled with a typical amount of noise, but in the BRHC you will a concentration of purple apparently called "Amp Glow"

I took this up months ago with Canon Canada & Canon USA, who have made every effort to avoid acknowledging the problem exists, and have repeatedly tried to tell me its a RAW image processing problem (in Lightroom, Rawdigger, you name it!) Off the record in phone calls with their tech staff however they admit its a design flaw, but prefer to call it a "characteristic"! 

I will provide a link here to an overview of the issue including images, as documented on the Adobe Forum site: http://feedback.photoshop.com/photoshop_family/topics/purple_fringing_in_bottom_rh_corner_of_images_from_canon_5d_mk3_could_it_be_the_lightroom_import_algorithm?utm_content=reply_link&utm_medium=email&utm_source=reply_notification#reply_13969775 

I also have 100s of shots and a raft of documentation to/from Canon I can share, but to cut a long story short, here's the facts: 
They have built the Mk3 with some heat generating components near the BRH corner of the image sensor, which at the higher ISOs create a purple distortion called "Amp Glow" in the BRHC of the sensor. It cannot be corrected in the model, as its a design flaw. Canon will not formally acknowledge its existence, presumable for fear of opening the flood gates to claims / recalls. 

Why does this matter? 

Practically speaking I bought the mk3 specifically for its low light capabilities, and its a real pain to be trying to edit out this mark on shot after shot. 

This product is advertised at having an ISO capability way above 12800 where the problem is apparent. This is (deliberately) misleading to us all. 

Canon have just been so deliberately evasive in all my communications with them, I find I now no longer trust them as a company, and would strongly advise others to be very careful when buying their products. 

We, as photographers should expect much better from an industry leader, and I think more photographers should be aware of this issue and Canon's practises when a genuine problem is identified. 

Personally I'm disgusted by their wriggling and distortions (no pun intended) and I'd really love to hear from other Mk3 users about their experience with this issue. Perhaps if enough of us complain they'll be forced to listen.


Thanks in advance.

Edward Allen
Sarnia, Ontario.


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## mackguyver (Jul 9, 2014)

Edward, with all due respect, I don't see this as a significant issue. Shooting at ISOs that high isn't going to give you great images anyways, and in the actual photos, the effect isn't exactly horrifying and seems like it would be easy to correct in PS. It seems like the solution would be to shoot at f/2.8 and lower the ISO vs. shooting at f/5 or 5.6 & ISO 12800, at least with the gear in the shots provided. You would also get better subject isolation and roughly double the shutter speed at ISO 6400.

I'm sorry to disagree, but I feel this is much ado about very little.


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## neuroanatomist (Jul 9, 2014)

mackguyver said:


> I'm sorry to disagree, but I feel this is much ado about very little.



Apparently, shooting images with the lens cap on is not a priority of yours. For those who value the highly prized "black frame image", this is a terrible travesty! Can you imagine the horror if such an image was pushed 4-5 stops in post? Our dear friend Aglet would probably vomit or soil his pants.


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## mackguyver (Jul 9, 2014)

neuroanatomist said:


> mackguyver said:
> 
> 
> > I'm sorry to disagree, but I feel this is much ado about very little.
> ...


Are you kidding, I shoot with the body cap on sometimes! Okay, it's just to test my CF card speeds, but still...


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## neuroanatomist (Jul 9, 2014)

I stand corrected. Ok, technically, I _sit_ corrected, with a glass of wine in one hand. 

Does the nap glow have a deleterious effect on your card speed tests? :-X


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## Mt Spokane Photography (Jul 9, 2014)

Edwardallen said:


> _*If you have the mk3 have you noticed the the purple thumb sized area that appears in the bottom right hand corner of all images shot at higher ISOs (say 12800 plus?)*_
> 
> I shoot quite a lot of motion based indoor events like concerts, sports etc, and spotted that there is a purple "thumb print" sized area that forms in the bottom right hand corner of *every* image shot at 12800+; on the LCD, in the RAW file and the JPEG file too.
> 
> ...


 
I tend to be forced to use ISO levels 12800 and higher with my 5D MK III. I use 25600 far too much, and any purple amp glow is the least of issues for images taken in the dark. I don't doubt that its there, its just not a factor for me. 

I literally have hundreds of them, and none were ruined by Purple AMP glow. But then, I tend to shoot without a lens cap on, the IQ is definitely better that way.

Here is a image taken at ISO 25600








Another at 25600






Yet another


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## philmoz (Jul 9, 2014)

In your first image (the 30 second exposure), did you put the cover over the viewfinder?

That looks more like light leaking in through the viewfinder, than amp glow (which is why Canon provide a cover to use for long exposures).

Phil.


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