Author Topic: Artifact or a scratch on sensor?  (Read 3065 times)

PaulHarwood856

  • Senior
  • ****
  • Posts: 305
Artifact or a scratch on sensor?
« on: September 05, 2018, 05:38:33 PM »
Hello everyone,

    I have noticed something odd happening with my Canon 7D when shooting 60fps raw video with the VAF-7D filter. Lenses used are the Canon 100mm f2.8 USM and Nikkor 35mm f2 ai. This could be because the VAF-7D wasn't designed for 60fps in 720p, or the VAF-7D filter small scratches are showing, or the sensor is scratched (I wet cleaned once and while back. I now just stick with the rocket blower). I'm hoping you can look at a few photos and a video so I can pinpoint the issue.

Here are a few links:

Photos: https://drive.google.com/open?id=1LmvzCQ-Bi6sBGbgn2Z0Zut8ufz4fv2VM

Video:

           
The artifact can be seen in the video in the beginning where the kid is throwing candy from the back of the truck. The artifact is near her face.

As for the photos, I showed wide shots, and then zoomed in shots. It's a bit difficult to tell, but I did my best showing it. I'm hoping there is a way to remove it in batch_mlv_in-out. Sorry if this is vague, please let me know if there is more information needed, or more examples. Thank you.

- Paul Harwood

PaulHarwood856

  • Senior
  • ****
  • Posts: 305
Re: Artifact or a scratch on sensor?
« Reply #1 on: September 08, 2018, 08:44:58 AM »
Hello everyone,

    I found a solution. When using batch_mlv_in-out to convert MLV files to DNG sequences, I would hit R on my keyboard for Run. This includes all of the processing. For some reason, there are artifacts when shooting 59.94fps raw video in the DNGs. However, if I enter 3 on my keyboard, this enables "pass through original raw data without processing, it works for lossless or uncompressed raw" there are no artifacts. Here is a link to the files if anyone would like to view: https://drive.google.com/open?id=190chDIMC3lxG0FGZ6j1znpWGlwSi8lsI

- Paul

Danne

  • Developer
  • Hero Member
  • *****
  • Posts: 7367
Re: Artifact or a scratch on sensor?
« Reply #2 on: September 08, 2018, 09:15:42 AM »
My guess is that either vetical stripes fix or cold pixel fix is causing this. Luckily you could:
disable vertical stripes fixing or
do not fix cold pixels

Kharak

  • Hero Member
  • *****
  • Posts: 1022
Re: Artifact or a scratch on sensor?
« Reply #3 on: September 08, 2018, 04:43:11 PM »
I posted about a year ago in Batch mlv in out thread that cold pixel fix with darkframe subtraction can cause severe artifacts, looking like a faulty sensor. Disable cold pixel fix snd everything should be fine.
once you go raw you never go back

PaulHarwood856

  • Senior
  • ****
  • Posts: 305
Re: Artifact or a scratch on sensor?
« Reply #4 on: September 09, 2018, 04:20:14 PM »
Hey Danne and Kharak,

    Thank you for responding. I found disabling vertical stripes fix did not remove the artifacts, but disabling cold pixel fix did. Just to make sure, does the Canon 7D ever get cold pixels? I've gotten dead pixels and hot pixels, but I'm not familiar with cold pixels. Is cold pixels and dead pixels the same? I think Adobe Camera Raw removes hot pixels, not sure about dead pixels. Anyways, here is a link to the tests I did regarding your (Danne) recommendation: https://drive.google.com/open?id=19e4pcwYq-1h2h47jUFN8okjT53zNpVG-

     If anyone can tell me whether the 7D has cold pixels I would appreciate it. Thanks.

- Paul

Danne

  • Developer
  • Hero Member
  • *****
  • Posts: 7367
Re: Artifact or a scratch on sensor?
« Reply #5 on: September 09, 2018, 05:00:47 PM »
Actually, I would stay of the cold pixel function unless I would get a good reason to use it. Any cam could have a cold or hot pixel but only a few "lucky" brands have focus pixels. 7D is not among them.

PaulHarwood856

  • Senior
  • ****
  • Posts: 305
Re: Artifact or a scratch on sensor?
« Reply #6 on: September 09, 2018, 09:21:15 PM »
Hey Danne,

     Ok great. Thank you for the quick response.

- Paul

reddeercity

  • Contributor
  • Hero Member
  • *****
  • Posts: 2303
Re: Artifact or a scratch on sensor?
« Reply #7 on: September 10, 2018, 05:48:27 AM »
cold pixel fix is used on d4 cams when recording in 10 or 12 bit , if you want the real bitrate instead of upsampling  to 14 or 16bit .
Code: [Select]
mlv_dump --dng --no-fixcp your_file.MLVthis will give you 10 or 12 bit dng's (what ever you recorded at) , less file space but same quality of raw (e.g. 3.7MB 10bit 2880x1080 -- 6.3MB 14bit 2880x1080)

On the 7D you can still record 10bit in 3x crop_mode , with out losing any functionality in 14bit 1:1

Danne

  • Developer
  • Hero Member
  • *****
  • Posts: 7367
Re: Artifact or a scratch on sensor?
« Reply #8 on: September 10, 2018, 09:37:55 AM »
Or why not simply:
Code: [Select]
mlv_dump -b 10 Input.MLVCheck mlv_dump version in:
crop_rec_4k_mlv_snd branch.