Author Topic: Vertical Lines: is it a recognized problem? Can it ruin the photography?  (Read 14021 times)

Brawl

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Hello, I have noticed in RAW videos (n Vimeo, Youtube) ugly vertical lines in shadow and dark areas. I can post examples if you wish.
I saw those lines also on h264 footage (taken by me with a 7D). In very dark areas those vertical lines are there.

Is this a general problem of all canon DSLRs? Can it be fixed?

I wish to know if for cinematography this could be a serious problem.

Thanks.

1%

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #1 on: September 15, 2013, 11:07:45 PM »
Not fixable yet, problem on 7D + DigicV

a1ex

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #2 on: September 15, 2013, 11:10:57 PM »
What are you talking about?

CoresNZ

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #3 on: September 15, 2013, 11:17:11 PM »
I think he's referring to the vertical noise pattern in underexposed shadows..? It has been discussed many times before.

My fix is not to shoot in pitch black darkness..

And exposing to the right will clean your image up allot in the shadows in general.

Brawl

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #4 on: September 15, 2013, 11:21:14 PM »
I will try to post Images. But I'm almost sure that this problem is not only from 7D, I'll try to post something I hope I'm wrong. See you in a couple of days. Bye!

a1ex

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #5 on: September 15, 2013, 11:21:33 PM »
A dark frame should fix it. Look in the MLV thread, there are some tools that can subtract it.

Brawl

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #6 on: September 15, 2013, 11:50:19 PM »
A dark frame should fix it. Look in the MLV thread, there are some tools that can subtract it.
Thank you A1ex I'll search for it. Do you know if there are Canon DSLRs wich does not suffer from this problem? What cause this?

I have got a pic from a 600D footage to explain well.

image: http://postimg.org/image/4oyz83mub/full/
(I do not post image here because they are large)
video source:
I can see ugly vertical lines (more than my example) also on 7D RAW videos on Vimeo.  I do not know already about other models.

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #7 on: September 16, 2013, 02:07:28 AM »
It won't do anything to photos. For video I've seen them on EOSM/6D/7D. Not shooting in darkness is the only fix right now.

a1ex

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #8 on: September 16, 2013, 07:37:09 AM »
For photos, take the black correction algorithm from cr2hdr - it should help. If you upload some samples, I can try it.

Brawl

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #9 on: September 16, 2013, 02:46:50 PM »
For photos, take the black correction algorithm from cr2hdr - it should help. If you upload some samples, I can try it.
Thanks A1ex I'm writing a message to a friend who is a cinematographer and is also registered on this forum. He should have some original files of RAW data filmed at 1728x972 (no crop mode) with VAF filter. the takes come from a very nice short film, but I wish to listen him before posting anything about his work.
As soon as possible and thanks again for help,

Dan

dmilligan

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #10 on: September 16, 2013, 06:34:59 PM »
Thank you A1ex I'll search for it. Do you know if there are Canon DSLRs wich does not suffer from this problem? What cause this?

Fixed pattern noise, it's a fundamental problem of CMOS sensors (not just Canon, but any CMOS based camera will suffer this effect):
Quote
One of the major drawbacks of the three-pixel APS design is the relatively high level of an artifact known as fixed pattern noise (FPN). Variations in amplifier transistor gain and offset, which are a fundamental problem with CMOS technology process fluctuations during manufacture, produce a mismatch in transistor output performance across the entire array. The result is a noise pattern evident in captured images that is constant and reproducible from one image to another. In most cases, fixed pattern noise can be significantly reduced or eliminated by design tuning of analog signal processing circuitry located at the periphery of the array or by electronic subtraction of a dark image (flat-field correction).

Further reading (beware, some of these contain Maths):
https://classes.yale.edu/04-05/enas627b/lectures/EENG427l04bcds.pdf
http://www.cambridgeincolour.com/tutorials/image-noise.htm
http://en.wikipedia.org/wiki/Fixed-pattern_noise
http://micro.magnet.fsu.edu/primer/digitalimaging/cmosimagesensors.html

Rai2121

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #11 on: September 16, 2013, 08:38:37 PM »
For photos, take the black correction algorithm from cr2hdr - it should help. If you upload some samples, I can try it.

A1ex,

I unfortunately don't have the DNGs from this shoot anymore, but I have uploaded a clip to vimeo that shows off what we're talking about. Its barely noticeable in the compressed h.264 version, but if you download the original MOV, its pretty apparent in the dark grey shirt and on my face when I lean forward into a darker area.

I will make sure to hold onto to the DNGs in the future if it happens again to be able to share the originals with you.

Thanks again for all your hard work on the raw module.


RenatoPhoto

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Re: Vertical Lines: is it a recognized problem? Can it ruin the photography?
« Reply #12 on: December 14, 2013, 03:05:53 PM »
Please continue this discussion here:
http://www.magiclantern.fm/forum/index.php?topic=9564.0
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