vertical magenta lines - chromatic aberration?
 

I have sold my Sony FX1 and am about to buy the Canon A1. After watching a lot of A1 sample clips on this forum - thanks for sharing it! - I am a quite worried about the SIGNIFICANT (chromatic?) aberration I noticed in several shots: Vertical magenta lines on the right side of dark, vertical objects (e.g. trees), mostly in the left side of the frame.

Can anyone give me more detailed information / evaluation on that?

Thanks in advance, Michael Mann

It's the chroma undersampling effect, not chromatic aberration. It's caused by reduced chroma color bandwidth, which is a limitation of the HDV format. For an in-depth explanation, see this thread, specifically the posts from A.J. deLange: http://www.dvinfo.net/conf/showthread.php?t=71727

Thank you. I will study this thread. Best regards, Michael

All the cameras in this price range will occasionally show some purple fringing. It's not necessarily chromatic aberration. But it might be. If it's something that shows up on the edge of the frame but not in the center, then it may very well be C.A. If it's something that shows up against a blown-out/overexposed section of the frame, it's most likely not C.A. and is just blooming from the CCDs or some other artifact of overexposure.

Barry, the artifacts I was referring to are magenta/purple lines on the RIGHT side of dark, vertical objects (mostly trees) which I noticed on several A1 clips, and - that's strange! - ALWAYS on the left side of the frame. I never noticed such kind of artifacts on any of my Sony FX1 takes that I have been shooting during the last 2 years. Is there anyone with similar experience?

Thanks, Michael Mann

Hello, In Kaku Ito 24ftrpdpanoramaps9.m2t panoramic footage you can see the CA (might be a digital blooming/fringing from the CCD) in the tall buildings (Blue fringe on the right and red/magenta on the lefft corners.) I have shot with 35mm wide angle lenses (Wide angle lenses have this challenge) from Leica (15mm 2.8) and Canon (14mm 2.8L and 20mm 2.8) that have the same characteristics shooting digital color and just use Photoshop CS2 to eliminate CA in the RAW mode. I don't know if FCP has that capability to eliminate CA (fringing) in post. Possibly stopping down the aperture might help.

Both the FX1 and the A1 are built down to a 'domestic' price Michael. What this means is that corners are cut in an attempt to bring you the most mouth-watering specification sheet under the dollar deadline.

Both cameras are fine examples of the balancing act that manufacturers have to attempt. One feature is weighed against the others, such that you can have a better side-screen if you accept a 12x zoom. If you want a 20x zoom it'll have to be 1/4" chips I'm afraid, and so on.

So all the components are 'just good enough'. The colour fringing you spot will go un-noticed by many, and anyway, if your film is telling a good enough story, who the hell cares?

tom.

I agree that you get what you pay for, and you can get lenses for 2/3in CCD cameras that cost twice the price of the A1 and still display CA.

But as has been previously mentioned, this effect (which does seem quite pronounced on some shots) doesn't really look like CA. And I have my doubts about it being chroma undersampling in the codec (otherwise all HDV and DV footage would display this along vertical lines of strong contrast). So it must be something to do with the CCD... or possibly a combination of all three?

Does everyone see this? It seems most promenant on light shining directly into the lens (eg. silhouettes).

No more shooting into the sun?

no problem in normal life
 

If you pay attention you can see this in rare situations and before I saw it on the JVCHD100. But I don't see it as a problem. Besides, even in the small digital cam market you can find CA or sort alike if you take a search, but it is not bothering in 99 % of the cases. Actually, the lens has a sweet spot and you need to search for it, and use it. The image and the 20x lens are sharp.

I do not see "SIGNIFICANT (chromatic?) aberration" as Michael.

I sold my FX1 because I was - and still am - so impressed by the better sharpness of the A1. But these magenta lines parallel to the trees (i.e. beautiful Oregon clip of Devon Lyon) really jumped into my eyes. Yes, I'd call these artifacts significant - all the more I never noticed such artifacts in any of my several thousand FX1 takes, which were shot under all kind of lighting conditions. And that's what irritates me.

If it's in the sensor, then it's not CA. Fringing comes from a variety of causes, only one of which is chromatic aberration, and that's not even the most common cause.

I understand your frustration, and personally I think it would be great if just one of the camera manufacturers could produce a camera with no quirks...

Still, whatever tool you're using you have to work with the limitations of that tool - be it poor low-light performance, picture noise, CA, excessive coring, lens breathing, or (in this case) fringing on high contrast.

Does this effect every camera (I can't test mine 'cause it's at the menders)? Has anyone asked Canon service about it?

Michael you have had good luck or great skill in not seeing this with your FX1. A discussion of this problem with the FX1 can be found here: http://www.dvinfo.net/conf/showthrea...4&highlight=ca
and an example here:
http://www.moronthrottle.com/images/HDVwithcannon.jpg

I have examined the footage posted from ALL the 3-chip HDV cameras and they ALL show this problem to some degree. It is a bummer and it has delayed my plunge into HDV. However I would say that, like all other HDV cameras, the A1 shows the problem--but it does not seem to be one of the worst offenders, based on examples posted to this and other boards.

I see this fringing everywhere on sample footage and it bugs me silly but if my audiences ever see it I certainly have not done my job in setting up shots (keeping the edge contrast reasonable) and telling a compelling story.

I hope post solutions become more common for dealing with the HDV fringing problem.

Alex and Bill, thanks for your evaluations and for the link. Michael

Well, that might well explain what was going on - after all I think the fringing is most evident on very contrasty edges.

Well that's something to try. Also, I wonder what the knee settings were for the shots that display the fringing, given that fringing in the DVX was caused by an unknee'd cinegamma.

The problem seems to happen with all cameras in this price range. For a direct comparison between the A1 and the FX7, please check Wolfgang's HDV blog on http://www.fxsupport.de/14.html and download the following pictures:

http://www.fxsupport.de/pic/06/12/09/fx7_02.jpg
and
http://www.fxsupport.de/pic/06/12/09/a1_01.jpg

look at the bottom "V" of the tree. Don't you see similar green/purple fringing on both cameras?

Now look at
http://www.fxsupport.de/pic/06/12/09/fx7_01.jpg
and
http://www.fxsupport.de/pic/06/12/09/a1_02.jpg
and check the trees on the left hand side of the picture. Don't you see similar green/purple fringing on both cameras again?

As far as I know, the chromatic aberration is almost unavoidable with zooms, and is noticeable on still cameras as well. One way to minimize it is to close the iris or to zoom in a bit, but this may not always be possible of course.


Übrigens: vielen Dank an Wolfgang Winne für seine sehr informative Web-Seiten!

Jerome, this site is a real treasure chest! Good example of German thoroughness :)
Danke an Wolfgang Winne auch von mir!

The fringing seems slightly more obvious on the A1 in that it doesn't fall off so softly... It's like a solid magenta outline rather than a gradient.

However, it's definately there on both cameras - using different types of sensor. And CMOS aren't supposed to bloom, so it may not be a sensor problem after all?

Whatever's going on, I never saw this sort of fringing with the FX1/Z1 in a way that made me draw breath through my teeth (although I accept that these cameras do display fringing too).

comparison
 

If i understand the site correctly, it looks like the pictures listed above are

1. Still snaphots from memory stick, not video capture
2. the A1 photo was resized using photoshop

the resizing may explain why the A1 halo looks different?

Anyone have a source for V1(release quality) vs A1 video comaprison?

the canon is overexposed. not a fair comparison.

I'd say not only is the Canon over exposed, but the sharpness appears set substantially higher than the Sony's. Neither of those attributes are likely to reduce fringing issues...

Not a comparison to the A1, But Douglass Spotted Eagle has a still and some clips of the Sony at:

http://www.sundancemediagroup.com/ar..._camcorder.htm

You can see some fringing in those. Note the purple cords on the parachute (among the white ones) in the still or video. It's minor, but it is still there.

I'm really beginning to believe that these four thousand dollar camcorders simply don't offer the optical and compression quality of seventy thousand dollar camcorders with forty thousand dollar lenses.

The pictures shown above (Wolfgang blog) from the A1 are 'straight out the box' he did nothing to get the best picture. That is what he is telling on his blog.
If you buy the 70.000 cam you need to work on the picture too, so I say ' I want it all done at the highest quality in the automatic mode'.

Wolfgang's pictures are from the memory card, not the tape but were not otherwise tweaked. Still: I did not post them for people to compare which of the two cameras has the worst CA (you can't really use them for that), but to show that two modern, competing cameras in the same price range exhibit CA.

If you want to compare the two cameras, you would need pictures from tape and a set of pictures at various zoom length and iris settings, exposed and sharpened in the same manner.

For anyone who's having problems, River Rock Studios have a $9.99 plugin for FCP that can (apparently) fix CA.

http://www.riverrockstudios.com/rive...cheapLens.html

It's actually designed to simulate CA, but the sliders also go into negative values :).

That's interesting! Is there a similar plugin for Vegas?

Sorry, I don't know of any that do the same for Vegas.

The slightly ($485) more expensive 55mm plugin (which includes a CA fix) from Digital Film Tools supports FCP, Adobe AE and Avid.

But I haven't come across anything for Vegas...

In theory, it should work but I don't think that this plug-in will be usable to minimize CA in real life. Similar plugins are integrated in the raw converters of SLRs. From personal experience I can tell than using them is very tedious. Using them for video will be excrutiatingly tedious, because CA has to be adjusted for each focal length. So each time you zoom in and out, you will have to continuously readjust everything.

Now, if one had a plugin which did that automatically (they exist for SLRs from dxo labs), I'd be telling another story.

Once again... fringing has many causes. Please stop calling it CA; that's misleading.

Sorry... I was just suggesting a fix for any element of the fringing that may be caused by CA.

Although we all know that we shouldn't be zooming in-vision, and I would guess it's only going to be a handful of shots that might display the phenomenon. So it might be useful for saving the odd shot?