Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Canon DSLR with Lens - what is this artifact?

  • Please log in to reply
6 replies to this topic

#1 Dan Crowson

Dan Crowson

    Vanguard

  • *****
  • Moderators
  • topic starter
  • Posts: 2186
  • Joined: 08 Oct 2010
  • Loc: Dardenne Prairie, MO

Posted 23 August 2019 - 10:41 AM

I've been imaging for a lot of years and head up our local club's AP SIG. We had someone come in that is getting some strange artifacts using a stock Canon EOS 6D Mark II with a Canon lens (don't know the model). The user took some pictures of lightning in JPG (I know...) and the results have some small black circles with white crosses in them. These are in different places on different images and I ruled out a software issue by looking at them on other machines. I've never seen anything like this. Here's a couple of examples along with links to the original, out of the camera jpgs:

 

IMG_4211_crop.jpg

 

Link to full image - https://www.crowson....CK/IMG_4211.jpg

 

 

IMG_4220_crop.jpg

 

Link to full image - https://www.crowson....CK/IMG_4220.jpg

 

Any ideas?

Dan



#2 james7ca

james7ca

    Fly Me to the Moon

  • *****
  • Posts: 7338
  • Joined: 21 May 2011
  • Loc: San Diego, CA

Posted 23 August 2019 - 11:01 AM

Could be simple bright pixel defects that have been distorted by the JPEG compression. If you look around on the image you can see that they vary in size, some may result from a single pixel defect, others from when there are two or more defects that are close to each other. Bright pixel defects can come and go or vary in strength, so that would cause them to change between each image.

 

But, I'm kind of guessing as to their cause and I don't know for sure.

 

You can also get strange looking backscatter from rain drops, particularly if a flash was use (or maybe from a flash of lightning).



#3 Boom

Boom

    Messenger

  • *****
  • Posts: 421
  • Joined: 11 Jan 2008

Posted 23 August 2019 - 11:25 AM

I found this bit interesting:

 

https://photo.stacke...his-a-hot-pixel



#4 Dan Crowson

Dan Crowson

    Vanguard

  • *****
  • Moderators
  • topic starter
  • Posts: 2186
  • Joined: 08 Oct 2010
  • Loc: Dardenne Prairie, MO

Posted 23 August 2019 - 01:04 PM

Could be simple bright pixel defects that have been distorted by the JPEG compression.

I was thinking about something like this as well.

 

Thanks,

 

Dan



#5 Dan Crowson

Dan Crowson

    Vanguard

  • *****
  • Moderators
  • topic starter
  • Posts: 2186
  • Joined: 08 Oct 2010
  • Loc: Dardenne Prairie, MO

Posted 23 August 2019 - 01:06 PM

I found this bit interesting:

 

https://photo.stacke...his-a-hot-pixel

Thanks! I was looking for something like this but could not find correct terms to google.

 

Dan



#6 Dan Crowson

Dan Crowson

    Vanguard

  • *****
  • Moderators
  • topic starter
  • Posts: 2186
  • Joined: 08 Oct 2010
  • Loc: Dardenne Prairie, MO

Posted 24 August 2019 - 09:23 AM

I had the user take some exposures with the lens cap on. The images have the same kind of issues and evidently, the problems are in the same places in each image - something I hadn't seen with the couple I copied from him before. I had him take RAW+JPG and he's still getting to the RAWs but, even if a jpg compression issue causing the cross and black around them, it would make the camera a real challenge for everyday use.
 
Dan



#7 Dan Crowson

Dan Crowson

    Vanguard

  • *****
  • Moderators
  • topic starter
  • Posts: 2186
  • Joined: 08 Oct 2010
  • Loc: Dardenne Prairie, MO

Posted 24 August 2019 - 10:11 AM

Raws with the issue here. I can't read these files on my machine.
 
https://www.crowson....ensor Issue.zip
 
Dan




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics