Purple outline on background objects

[Brian Rhodes]

Starting to edit my first shoot done with the V1u in 24p mode. I noticed a purple outline on people standing in the background and next to the windows on the Boat. Also a purple outline around the window. Whats causing this is it my Iris setting?

[Lee Berger]

I believe it's chromatic aberration. I also noticed in this scene shot in 30P on some of the pine trees (full wide focal length). It's a bit more subtle than your example, but there none the less.
http://leebergermedia.com/images/rxburn.jpg

But not in this telephoto shot
http://leebergermedia.com/images/rxburn6.jpg

[Piotr Wozniacki]

Brian, if you can, ask your dealer for a replacement. The Canon A1 is said to suffer from CA/color fringing more than the V1, but I must say I never saw it that bad, even at the zoom/aperture limits. Not to mention that the V1 I had before (or HC1 for that matter) showed an almost unnoticeable CA.

[Tony Tremble]

It is a chromatic aberration but I don't think is what we generally term chromatic aberration. I have seen the purple fringe on bright light objects shot with the v1. I have also seen this in footage from the XH-A1 but is less so because there is CCD smear that covers over the problem.

With cameras and lenses at these prices there will be aberrations of several types and it is best not too get hung up on them. I doubt whether your customers will notice them as they'll be far more interested in the content.

If anyone asks just say it is a lens flare!! :)

TT

[Lee Berger]

I notice that it appears more in wide shots, but not telephoto.

[Alex Leith]

Both the A1 and the V1 have fair amounts fringing. The amount varies from unit to unit.

Like Tony says, it's best not to get too hung up about it. Unless you have 10,000 to spend on a lens, you're unlikely NOT to see CA.

[Alex Leith]

Oh yes... to minimise CA, reduce the iris to mid levels, avoid the extreme ends of the lens, and avoid high contrast edges - especially with back lighting.

And then thank the Lord you don't have to contend with the JVC HD-100's standard lens.

[Piotr Wozniacki]

Originally Posted by Alex Leith

Both the A1 and the V1 have fair amounts fringing. The amount varies from unit to unit.

Exactly, and this is why I advised Brian to try and replace his unit. Didn't want to upset you, Brian!

[Brian Rhodes]

Originally Posted by Piotr Wozniacki

Exactly, and this is why I advised Brian to try and replace his unit. Didn't want to upset you, Brian!

Thanks for the quick response guys.
Could my UV FILTER have caused the chromatic aberration to be more noticeable?

I started work on a short film last week just down loaded some of the footage it has the chromatic aberration also. I will call my dealer Monday and ask for a replacement unit. I never notice this on my Z1,FX1 OR A1U.

Alex there was another cameraman at the shot using a JVC GY-HD100U I will try to get some footage and compare.

[Alex Leith]

It's very unlikely (but not impossible) that a flat glass UV filter could cause fringing.

However, UV filters can cause ghosting, flare, and loss of contrast.

And strong lighting (such as the light coming in through the windows) can be a challenge for any video camera (even with CMOS).

[Zsolt Gordos]

Is it that we talked too much about oil paint effect - I can also see it apart from the color fringes.
On certain patterns of the clothings and in the kitchen in the sink. Anyone else see it?

[Alex Leith]

I agree Zsolt. It's mild, but I can see it too!

[Chris Hurd]

Originally Posted by Tony Tremble

It is a chromatic aberration but I don't think is what we generally term chromatic aberration.

Much more accurate to say it is fringing but not what we generally term chromatic aberration. Not all fringing is chromatic abberation (which is only one of many causes of fringing). In this case, most likely it is the chroma subsampling effect (color bandwidth limitation), as previously described by A.J. deLange in our Canon XL H1 forum: see http://www.dvinfo.net/conf/showpost....5&postcount=40 and the rest of that thread for more details.

Nevertheless, it is not what we generally term chromatic aberration.

[Stephen van Vuuren]

This is a non issue for me as it's a common artifact of high contrast edges over an overexposed background with electronic sensors. I remember when this surfaced on the first DVX100 clips and people freaked out. A gamma setting without a knee or much knee will increase this happening - with a DVX Cinegamma or similar setting on another camera, you must avoid any overexposure at all costs otherwise you will get this issue or similar ones.

It does not appear to be lens based CA which generally you need motion clips instead of screenshots to properly diagnose as changing focus/zoom should alter the amount of lens CA.

In this lighting situation, you need to either drop the exposure way down or get lots of fill or use a gamma/knee setting with lots of rolloff into highlights.

[Dave F. Nelson]

Originally Posted by Stephen van Vuuren

This is a non issue for me as it's a common artifact of high contrast edges over an overexposed background with electronic sensors. I remember when this surfaced on the first DVX100 clips and people freaked out. A gamma setting without a knee or much knee will increase this happening - with a DVX Cinegamma or similar setting on another camera, you must avoid any overexposure at all costs otherwise you will get this issue or similar ones.

It does not appear to be lens based CA which generally you need motion clips instead of screenshots to properly diagnose as changing focus/zoom should alter the amount of lens CA.

In this lighting situation, you need to either drop the exposure way down or get lots of fill or use a gamma/knee setting with lots of rolloff into highlights.

I don't agree with you that this fringing problem is a non-issue, but it can be worked around quite successfully. I don't own a V1U, but I have owned a Canon XL-H1 for quite some time now. The red and green fringing issue to which many here refer to as CA, occurs most often in overexposed, high-contrast shots, especially where sharp edges are shot against a high contrast background such as trees against the sky, especially at the outer edges of the frame.

Most of the footage I have seen here exhibits this fringing problem too, but not to the same extent that my XL-H1 does. Also, most of the shots I have seen here, with the exception of Steve Mullens work, tend to be overexposed. I think new shooters, or those new to a camera like the V1U tend to rely on the auto mode which overexposes most scenes.

This fringing problem can be reduced to a minimun by avoiding the long and wide ends of the zoom range of your lens and avoiding overexposing your shots, especially very high-contrast scenes. Brian's stills at the top of this thread are perfect examples of overexposed, high-contrast material. Use of the ND filter, and reducing the exposure should minimize or eliminate the fringing in these shots.

The example 24p V1N footage shot by Jung Kyu is a great example of the use of the ND filter to minimize the problems of fringing associated with overexposure. These shots are great and exhibit very little fringing. This footage was well shot from an exposure point of view.

See this link to view Jung Kyu's clip: http://www.dvinfo.net/conf/showthread.php?t=84987

However, I don't agree with the statement that you "need motion clips instead of screenshots to properly diagnose... the amount of lens CA." In fact, it is very easy to analyze lens problems associated with CA in a still photo. CA problems are predominantly at the edges of the lens and not in the center. When you see stills with fringing at the outer edges of the frame only, the probablity that the fringing is CA is very high.

Problems with the chroma subsampling effect (color bandwidth limitation) of electronic sensors, can and will occur anywhere in the frame, while CA occurs at the edges of the frame, more so on the left and right of the frame than the top and bottom because the left and right sides of the frame are the extreme edges of the lens in a 16x9 frame. If this were a chroma subsampling problem, you could see the fringing anywhere within the frame.

If you take a look at the stills Brian provided, you will notice that they are all wide shots (bad area of the lens for CA). You will also notice that they are all very high-contrast, overexposed, and the fringing is on the left and right as well as top and bottom of the frame, but not in the center. This is not a chroma subsampling problem. It is CA. CA isn't a problem at the center of the lens, only at the lens's extremes.

This problem could be reduced to a minimum by turning Auto OFF, setting IRE to 70, using an ND filter and lowering the exposure level. Setting IRE to 70 allows you to see overexposure peaks before there is a problem and gives you plenty of headroom to work with when adjusting your exposure in high-contrast scenes.

There is also the possibility that Brian's camera does have a problem. I have looked at a lot of footage with fringing problems, since I have been on a mission to understand this fringing problem so as to erradicate from all of my shots, but this is probably the worst case I have seen. The problem is that the shots are so overexposed and blown out that it is difficult to determine whether it is definitely CA or a camera problem.

CA is usually both green and magenta on the left and right sides of sharp objects and these stills have mainly magenta fringes, although PDVD_009.jpg does show signs of green fringing on the door of the refrigerator. Magenta only fringing is not characteristic of CA. I would certainly have the camera looked at if you can't get decent shots, since the camera is under warranty. But I would first try to shoot a similar scene with the camera set to Manual mode with IRE set to 70, using the ND filter, and reducing the exposure level. If you get a fairly fringe-free shot, It is probably not a problem with the camera.

Canon has written quite a bit about CA and other lens issues. To read Canon's FAQ on chromatic aberration (CA), visit this link: http://www.canon.com/bctv/faq/chrab.html

Canon offers a great deal of information on this and other issues on their website, but this article is a good starting point.