Assessment of the 5D2 by the BBC (Alan Roberts)

[David Heath]

Originally Posted by Don Miller

I noticed the beautiful footage but had to look for the aliasing.

This is really missing the point about aliasing. It's danger is not that it looks objectionable at first sight - it may be barely visible - but it could show up very badly after further compression, such as on broadcast transmission.

The original test report explains why:

Aliases in moving pictures are much more of a problem [than in still images] because, when the image moves, the aliased frequency content moves in the opposite direction to the image motion, causing a rippling effect on edges. Since motion-sensitive compressors such as MPEG2 and MPEG4 depend on the cleanliness of edges to measure motion, these aliases can cause the compressor to allot undue bit-rate to motion and/or result in excessive compression artefacts.

Steve Philips and Daniel have got it right - footage may look great when played straight to TV, or even through an entire NLE, but show unacceptable degradation because of aliasing when transmitted. A second camera may look identical on straight viewing, but lack of aliasing mean a far better image makes it to the viewer.

The only way to predict this in advance is by the use of test charts, and I agree with the BBC report - the 5D2 shows an extremely high aliasing level.

There's no doubt such as the BBC may use 5D2 footage if it was all that was available of a unique event, and to hell with the quality. But this test is more interested in evaluating cameras for planned and commissioned work, and there is no sense in adopting a camera whose use would involve having to increase channel bitrates to cope with camera aliasing.

[Brian Drysdale]

Originally Posted by David Heath

This is really missing the point about aliasing. It's danger is not that it looks objectionable at first sight - it may be barely visible - but it could show up very badly after further compression, such as on broadcast transmission.

I think is something many people forget about, digital material can also degrade as it goes down a few generations due to compression. Also, the different codecs used during the chain can create problems. TV programmes can go through a complex post production process and I don't think Canon were planning for this when making this camera for the news guys.

This is a first generation camera and I suspect there may be two approaches to the HD DSLR: using a codec which requires less processing power on basically a stills camera or a shooting stills on a camera which has the processing power to handle a codec for motion pictures without artefacts. RED seems to be going for the latter, but it appears to be more expensive and larger than a stills camera design.

A smaller sensor than FF35 for HD work does make a lot of sense. There are focusing problems with the larger sensor size and a S35 sized sensor allows you to also use cine lenses. I know some people have a shallow depth of field fetish, but you don't need a FF35 DOF to create great images. I was watching "I am Cuba" the other day and it's more cinematic than most of these shallow DOF films - they used wide angle lenses with a large DOF in many shots.

I expect the next generation of these hybrid cameras will be better.

[Pat Reddy]

I noticed major aliasing artifacts on a nationally broadcast football game yesterday. These were evident when they switched to the little POV cameras that fly around above the field. Artifacts on the white lines on the field were most evident in wide angle shots but went away when they zoomed in. I also noticed the same thing when the sports show this morning showed a high school football game shot with a cell phone camera. My skepticism about this being an issue is now gone. I still think that there is a place for HDV and cameras like the 5D II in broadcast TV. I've never noticed any problems, for example, with those Discovery Channel shows that are shot almost exclusively on HDV cameras.

Pat

[Daniel Browning]

Originally Posted by Brian Drysdale

A smaller sensor than FF35 for HD work does make a lot of sense. There are focusing problems with the larger sensor size...

FWIW, that was only true with film. In digital, you can stop down a large sensor, increase the gain, and you will get the same image as a small sensor. (Same DOF, brightness, noise, diffraction, etc.).

[Daniel Lipats]

Originally Posted by Martin Koch

Interesting, I looked at their website and saw four variants: 4.0, 5.6, 8.0 and 11.0.
Which one do you recommend for the 5DMKII?

Hi Martin,

We need something a little stronger. The lower the number, the higher strength of the filter. There is a 2.0 and a 1.0 that are not listed on the web page. I use the 2.0 myself, but testing the 1.0 too. I am in contact with someone who is using the 1.0 and I will try and see if they can comment on its performance.

To reduce the moire / aliasing we must filter out high spacial frequencies. The trick is not to blur everything all at once, just areas causing problems.

It is very rare that I use the filters. To be honest, this problem has not bothered me enough to invest a lot time finding a solution.

[Brian Drysdale]

Originally Posted by Daniel Browning

FWIW, that was only true with film. In digital, you can stop down a large sensor, increase the gain, and you will get the same image as a small sensor. (Same DOF, brightness, noise, diffraction, etc.).

Greater sensitivity has been one of the big advantages for the larger sensors (assuming a similar number of pixels), but in practical terms the lenses do start to become much larger. This applies more for zoom lenses than prime lenses, even 35mm film cameras become bulky once they're mounted onto the camera.

I suspect it would also depend on the sensors being compared if they would give the same image in all respects.

[Don Miller]

Its important to remember that the artifacts will be very much less in a year or two. If you don't do photography it's easy to forget that these are still cameras that would cost about the same without the video feature. There's apparently little added cost foMr video. Most buyers have no interest in video.
Canon, Sony, Nikon or someone else will release this type of device without these flaws. Like red it will be a video camera first. It would be great if Nikon did that. They don't have to have discussions with the managers of the traditional video lines. I wonder how Canon's video division feels about the 5DII.

[Martin Koch]

Originally Posted by Daniel Lipats

Hi Martin,

We need something a little stronger. The lower the number, the higher strength of the filter. There is a 2.0 and a 1.0 that are not listed on the web page. I use the 2.0 myself, but testing the 1.0 too. I am in contact with someone who is using the 1.0 and I will try and see if they can comment on its performance.

To reduce the moire / aliasing we must filter out high spacial frequencies. The trick is not to blur everything all at once, just areas causing problems.

It is very rare that I use the filters. To be honest, this problem has not bothered me enough to invest a lot time finding a solution.

Thanks Daniel, this was the first time I heard of such filters.
I also had no real problems with aliasing so far but its always good to be prepared.

[David Heath]

Originally Posted by Pat Reddy

I still think that there is a place for HDV and cameras like the 5D II in broadcast TV. I've never noticed any problems, for example, with those Discovery Channel shows that are shot almost exclusively on HDV cameras.

Ah - but look at the test reports from the same source for the Z1 - http://thebrownings.name/WHP034/pdf/...VRZ1E-FX1E.pdf .

The Z1 is not up to the standard of true broadcast cameras, and does show an amount of aliasing - but nowhere near as much as the 5D2. What that means is that what emerges at the viewers screen after compression and transmission won't be as good as from a higher priced camera - but at least it won't be too different from what is seen during editing etc. And that's the real problem with the 5D2 for broadcast.

It's quite likely that at the TV station some 5D2 pictures may look significantly better than some from an HDV camera like a Z1. But also very likely that after compression/transmission the 5D2 pictures will degrade more than the Z1 pictures and end up looking significantly worse. Wecome to the wonderful world of aliasing and digital compression! This is why cameras can't be sensibly assessed for broadcast pictures simply by looking at pictures alone.

For many cameras, pre-filtering may improve aliasing a lot (at the expense of sharpness), but the 5D2 results show quite a lot of nasty things going on. The multiple centres to the alias rings and their coloured nature indicate many causes, not simply those associated with detail too sharp for the chip. As the report also says:

Also, since the alias patterns are highly coloured, there must be some doubt cast on the actual method of filtering. ........... One possible reason for the presence of the coloured aliases would be if the R G and B signals from the Bayer pattern were down-converted to a Bayer pattern at HDTV resolution using simple interpolation, before being decoded, instead of the eminently more sensible approach of decoding at high resolution and then down-converting the very high resolution signal using correct sub-sampling low-pass filtering.

In other words, soft filtration will be only of limited use in getting rid of aliasing for video with this camera. Many of the problems are caused not by the normal causes, but by the processing used to downsample the chip resolution to HDTV resolutions.

One day there may be a camera that will produce good stills and high quality video, but it's not here yet. And don't be misled by what the pictures look like straight from the camera, it's how they will stand up to further processing that is key. A user may think they are not troubled by aliasing - then get a phone call saying "that material you supplied us with yesterday...... yeah, looked good, didn't it......but, the funniest thing, I saw it at home and it looked really bad compared to what that other guy shot on his HDV camera......."

[Mike Demmers]

One thing I notice, reading through these various reports, is the pretty consistent recommendation that a diffusion filter that creates the optimal circle of confusion for that system be used.

While not so useful for the 5D, it seems to me that when these sensors are used in newer systems intended more for video use, it would be wise to include such a filter - selectable on or off for cases of soft lenses, or for still use - right in the stock system, much as ND filters are commonly included now to solve THAT consistent problem.

The manufacturer should be best positioned to pick the best option for this filter.

-MD

[Don Miller]

I've been watching Ken Burns new national park series in the U.S. I guess it won't be seen in the U.K., as technically it is quite a mess. Particularly with poor colors and softness. It's no 'Planet Earth'. About half the video would be dramatically better if it had been shot with a 5D.

This is what I find somewhat misleading about these technical assessments. When it comes down to what is actually aired it's pretty meaningless. For beauty shots I can't imagine an editor looking at well shot 5D footage and wishing it had been shot on a EX3. It's like Jennifer Garner with a pimple compared to Margaret Thatcher.

[Evan Donn]

Originally Posted by Don Miller

It's no 'Planet Earth'.

That's funny - it's exactly the same reaction I had when I saw it. I didn't realize what I was watching as it was on when I walked in the room, and once I realized what it was I thought something was off on my TV. I would be shocked if someone couldn't go out right now with a 5D and get footage that would look better, even after transmission, than his series does.

[Peter Burke]

Originally Posted by Don Miller

It's no 'Planet Earth'.

Funny you should say that. I bought the Planet Earth Blu-ray and was disappointed in the general softness of the picture. Over at AVSFORUM 'Planet Earth' is only ranked at 500th (or lower) on the PQ rankings thread. Link: The New PQ Tier Thread for Blu-Ray - Rankings - AVS Forum and is no-where close to the reference group.

Based on the 5D2 footage I have seen so far, I am absolutely confident that the 5D2 produces better images than seen on 'Planet Earth'.

[Don Miller]

The broadcast Planet Earth I saw looked good, although I was looking at the superb shots more than the technical quality.

[Brian Drysdale]

Originally Posted by Don Miller

This is what I find somewhat misleading about these technical assessments. When it comes down to what is actually aired it's pretty meaningless. For beauty shots I can't imagine an editor looking at well shot 5D footage and wishing it had been shot on a EX3. It's like Jennifer Garner with a pimple compared to Margaret Thatcher.

Doesn't what you said here confirm the technical assessment?

http://www.dvinfo.net/forum/canon-eo...l-footage.html

Having to shoot with a shallow DOF is pretty limiting and having more detail what you want, especially in the wide shots.