Does the AF-100 Line skip?
 

Need to know more before considering a purchase.

Why does that matter if the output is good?

It does not appear to. But neither do the GH1 or GH2.

From what I've seen so far my Sony EX1 seems to make a better picture. My suspicion is line skipping and some have mentioned that it does. For me it's about quality in gives you a chance for quality out.

Some say the GH1 and GH2 do line skip?

We see none of the aliasing and moire usually associated with line skipping in the AF100 footage. Looks pretty darn good to me.

there is no line skipping being used. It uses an optical low-pass filter to resolve the aliasing and moire that is typical from high count imagers.

Best,

Jan

Thanks Jan. Could you also confirm the size of the sensor IE a 16:9 slice taken from a 17.3 x 13mm sensor?

Cheers

Mark

Actually the 4/3's sensor is a little larger than 17.3mm but what is used in the still cameras is that size, 17.3 X 13mm. When the engineers designed the AF100, they decided to use a little wider on the chip to maximize the height measurement as well, so the image size of the AF100 is 17.8 X 10mm. This gives approximately 12.4 million pixels to work with.

Best,

Jan

Thanks Jan

All questions answerd Sounds really good now!

Mark

Perfect Jan.

Thank you

Grazie

My understanding is that the OLPF is arranged to cut off the detail at around the detail level of an HD image - far less than the finer detail of the native chip.

There is no question that the OLPF will largely resolve the issues of moire/aliasing (it will), but this is quite independent of whether the chip is read in total or via line or pixel skipping. Saying that it uses an OLPF, and has little evident moire/aliasing, says little about how the chip is read.

The AF101 is reckoned to have about the same native sensitivity as a 1/2" 3 chip camera, with comparable technology. If every photosite was being read, every frame, the expectation would be that the sensitivity would be (should be) much higher. Technically, the AF101 results are in line with not every photosite being read or used in every frame readout - line skipping or pixel skipping.

If what is basically a still camera sensor is used, the alternative to line or pixel skipping is to read out the entire sensor (all 12.4 million pixels) every frame, deBayer, then downresolve with software filtering. The technical challenge of doing such in terms of complexity, power requirements, heat dissipation etc shouldn't be underestimated, and it is extremely difficult to see how they are overcome in a camera of this price, consuming relatively little power? From a designers point of view, far easier, sensible and more cost effective to pixel skip and deal with the aliasing with an OLPF.

If "line skipping" isn't used, what about other forms of pixel skipping, such as in blocks of four? It would be interesting to point the GH2 at a zone plate in 40fps burst mode, and see what the patterns reveal. That mode restricts resolution to 4 megapixels, and is likely to use the same principles that the AF101 does - but since the GH2 doesn't have the OLPF of the AF101, the alias patterns should be unaffected and tell us more about exactly what's going on.

So it's clear now it does line skip.... Difficult to see how a camera like this wouldn't.... I have to wonder now about other decisions made in its construction and design and possibly if this was why it has an 8 instead of 10 bit out and how image quality is affected if a Ki Pro is used, and then undergoes a lot of post colour correction for example.

David

Panasonic GH2 1:1 Mode Revealed

ETC Which shows you don't need to line skip?

Wide angle for GH2 in Video Mode?
 

Sorry, I'm a bit lost! Which micro 4:3 (m4/3) focal length should one have to achieve a wide angle view on a GH2, in video mode? By 'wide angle' I mean an angle of acceptance similar to that of a 35mm or 28mm lens on full frame stills 35mm.
In fact I'm so confused that maybe this post should have gone in the GH2 thread; except I want to use the GH2 I just ordered, alongside the AF 100/1 that I have just ordered. (Rush of blood to head.)

And is my old Nikkor 50mm only good for C.U.s of the Sea of Tranquillity? (On the Moon.)

To compare to full frame is a 2X multiplier.

So:
14mm MFT= 28mm 35FF
17mm MFT= 34mm 35FF
50mm MFT=100mm 35FF

This is comparing angle of view, not DOF. F-stop stays the same.

Thanks Olof
 

SIDEBAR. Since a Four Thirds sensor already produces a 2X field of view as compared to full frame 35mm, this means that in ETC video mode the focal length marked on the lens is actually 5.2X what it would be in full-frame 35mm terms. So the long end of the new 100-300mm zoom is equivalent to 1,560mm in Extra Tele Conv video mode. Wildlife cinematography anyone?

This is from the link on the post by David Mark Williams, who happens to live in the same county as me, maybe I should walk round to his place and ask him!

Regards - Godfrey

Hi Godfrey I'm a bit confused by your post as it wasn't about the crop factor or what the ETC mode does. So to clarify my position.. I'm interested in buying the camera. My previous post was trying to figure out what is being said here about line skipping and was addressed to David to try an offer an explanation as to why the camera may not skip lines. Jan gave a definitive answer that the AF100 doesn't line skip and Davids post that for the cost and other barriers it likely does.

So two opposite answers raise more questions. I searched the net trying to find more info and the ETC video mode link explains there is no line skipping pixel binning etc in this mode so I may not know what I'm talking about in the previous post but hope David or Jan may put me straight on exactly how or why the AF100 does or doesnt line skip.

No - this mode only uses the centre part of the sensor, the middle 2 megapixels of the 18 total. It's a perfectly valid thing to do, but (as the article makes clear) it results in a "zooming in" compared to a standard still. The article says you get a "free teleconvertor", which is great if you want one - but a dead loss if you want a wide angle lens!

It would also negate the whole reason behind such a camera as the AF101 (you want a large sensor, that's what gives the shallow dof). In this case, you'd be building the 4/3 sensor in - then only using the central part! Far better to just use something like a 1/2" sensor and use all of it.

It's pretty easy to tell this from measurements of angle of view at differing focal lengths - the AF101 is using the whole width of the chip, which translates to 12.4 million photosites available.

Does that help?

As far as "line skipping" itself goes, line skipping is a special case of pixel skipping - a camera can pixel skip, but not line skip. There's an (incorrect) widely held belief that pixel skipping necessarily means "nasties" such as moire, aliasing etc. The belief therefore goes that if no moire/aliasing - therefore it proves no line (pixel) skipping. That's completely untrue.

What IS true is that pixel skipping on a high photosite sensor WILL give aliasing IF - NO - OLPF - IS - USED. Use an OLPF, and the moire/aliasing etc problem is largely solved, even if some form of pixel skipping is still used in the chip readout. Pixel skipping shouldn't necessarily be thought of as a "bad thing" in itself - only when the OLPF isn't used.

The "good thing" about pixel skipping is that it enables decent video to be obtained from what are basically still camera sensors, at a sensible price, power consumption, etc.

You may then be wondering why, if they are such a good thing, why not fit OLPFs to DSLR sensors? Answer is easy - they greatly improve the video, but restrict the resolution of stills to only HD resolution (2 megapixel). Great in the AF101 - useless in a DSLR! :-)

Becoming clearer.....
 

Thanks Mark (Sorry I got your name wrong! - said I was confused) & David - So, the ETC (teleconvertor) is an additional feature of the camera, not something that happens when you switch it into Video Mode. For a nasty moment there I thought I was going to have to stand in Essex in order to do a 'head and shoulders' framing in Hertfordshire......

Not that I have got anything against Essex.... except the usual...

Hi David okay its just the article mentions no line skipping used as part of the ETC process and wondered if this might have been a way to avoid it in other areas of the Cameras capture process.. I can see I'm confusing two separate issues.

I really don't know any more now than I did when I first started only that the camera may or may not line skip and my personal opinion would be if it line skips DON'T BUY because of the fear of problems in post with colour correction picture quality and green screen. Obviously if line skipping was an option Jim Jannard would be using it in his cameras.

My thoughts being a bit cynical are just my personal opinion based on the ruthlessnes of much of big business..
My suspicion was the Sony EX1 was an answer to Reds foray. Jim was an advocate for the ripped off consumer while major brands every year bought out slight improvements so everyone went out and bought a new model. But although Red has certainly stirred up the markets is now establishing itself as no longer a threat to the consumer market IE Price and the Scarlet is only going to be two thirds.

The AF101 potentially takes a lot of those consumers who hoped scarlet would be what AF100 appears to be. When in fact the AF100 won't be accepted as professional or useful in a professional capacity due to line skipping. So keeping the status quo of consumer and professional market apart.

At this moment in time I think it may be prudent to watch. The EX1/3 May turn out to be a very good and lasting buy even if using a Letus adapter.

You have had the categoric assurance that this camera does not line skip from the Panasonic US Product Manager so I am not sure why you persist in this confusion.

I'm not sure why the EX1/3 series should be compared to RED, they're very different cameras and extremely successful. Most productions actaully don't need a larger sensor, sure there's a lot of talk on forums, but the 2/3" and smaller are out in much larger numbers.

Given that DSLRs are being accepted on on professional productions in spite of a number of issues, I can't see why the AF100 shouldn't be. It remains to be seen if HD broadcasters will accept it recording onto a Nanoflash etc, but that just one professional sector and the chances are pretty good that they will accept it for quite a few types of production. Until the camera gets tested they can't make a judgement.

I agree Brian but I suspect many will buy the AF100 Thinking it is professional when it may not be which is what I'm trying to ascertain.

Actually its not me that is persisting in the confusion. Maybe you should read David Heaths post who clearly shows the Camera is likely to line skip. His explanation sounds right and technical. Are you saying that David has got it wrong and Jan is right and if so can you present a technical reason as to how the camera does away with Line skipping? Clearly this is something Red would love to be able to do Are you saying the Panasonic has beaten red to the post with this?.

No disrespect to David but I think to prefer the speculations of some contributor on an Internet forum over an assurance from a representative of the manufacturer is an odd choice. I don't need to give a technical reason as I am quite prepared to take on trust that the engineers at Panasonic who really know about this stuff (unlike us forum contributors) did whatever was necessary to accomplish their magic.

I can't speak for other internet message boards (thankfully), but as
far as DV Info Net is concerned, the input from the product manager
usually trumps everybody else.

I would like to hear a further technical explanation how this problem is avoided after all there may be another way similar to line skipping and if so would like to here the pros and cons. Maybe the issue is fully resolved and if so how? I'm not asking for full details trade secrets etc Just an acknowledgement there was a problem that was resolved and a brief summing up of how and why.

This way I and others will be able to make a determination on whether this meets our needs

Chris I agree that Jan is right I hope you don't mind though if I pursue more information re this.

Mark, I think the proof is in the footage. Soon there will be all kinds of footage available. I should have my camera soon. And I will be doing a bunch of comparisons to other cameras.

From what I have seen so far Pany has done an excellent job of downsampling without any hint of stair stepping or moire. I did see and handle the AF100 in Boston a while ago and I saw the SDI out on a large screen from 6' away, even in low light the picture was very good. Jan explained that there was a lot of proprietary "magic" in how the downsampling is done. That may be as technical an explanation as we will get in the near future.

If you have any doubts about ordering this camera I would suggest you rent one and do your own testing, soon there will be lots of them available, I am sure.

I think one of the huge things to remember about this camera is that it is not a Varicam, F3 or F35, and it is not trying to be. It is a $4,800.00 camera (v/o lens), and for that price it is quite remarkable. It is 8 bit with 422 SDI out. The native codec looks good for a lot of purposes as well. It certainly rivals the Canon DSLR and EXcam 35mb codecs.

It is the first of this kind of camera and I for one really like what I have seen so far.

Merry X-mas to all, and congratulations to Jan and the whole Pany team.

Olof

I don't know as I would call it remarkable I would say progressive but it is a camera without a lens. What I would call remarkable is the fact you can buy a new car for not much more.

We have a deal here.. Consumers buy. Manufacturers make products to make a profit and not because they are doing us a favour they are after all businesses.

Manufacturers DO not do consumers favours they SELL.

Marketing hype advertising and commercialism is I'm sure a concept we are all familiar with all I'm trying to do is get an answer to what I am purchasing. If some are happy with the explanation of magic and secrets fine that's consumer choice too. I though prefer to understand what I may be buying into.

Panasonic have traditionally been rather slow in disclosing certain information, but it does come out in the end.

In the short term, for a user, the important thing is if it does what they need and, in reality, the only way to find out is to test it, regardless of the methodology or claims used by a camera manufacturer.

In the past, tests have also revealed the processes used.

Brian

Yes looking forward to Olof and others testing the camera.

Happy Xmas everyone!

Mark,
I'm also interested in making sure that the AF100 is all that Panasonic is saying it is before I purchase one also, but I wanted to clarify one of your statements:

Jan Crittenden Livingston clearly states above: "there is no line skipping being used."

You responded after an initial post: "Thanks, Jan. All questions answered. Sounds real good now!"

David Heath then provides some great input and possible alternatives that Panasonic may be using in lieu of line skipping, and your next statement is: "so it's clear now that it does line skip." In David's statement, he never ended with the perspective that the AF100 was line skipping. David actually states in a later comment in this post, "a camera can pixel skip, but not line skip." How did you come away with the position that the AF100 is definitely line skipping from his statement (on 12-22-10 @ 5:38 am)?I'd be interested to see if it can be clarified if the AF100 is pixel skipping instead.

I think quite a few people really need to CAREFULLY reread EXACTLY what has previously been written, and then they may see there is not necessarily any conflict between what I've put and Jans statement. In particular:
So I'm not directly contradicting anything Jan wrote - she said it doesn't line skip, NOT that it doesn't pixel skip. They are NOT the same thing. Though the terms are sometimes (wrongly) used interchangeably.

The other statement she made was that the use of an OLPF means it doesn't suffer the aliasing problems that a DSLR does. There is no question that is anything other than absolutely true.

Maybe, to avoid any ambiguity whatsoever, the original question posed should be reworded to something like "can it be categorically stated that the AF101 reads out all 12.4 million photosites each frame, forms the image from all of them, then downresolves the result to form the final 1080 image"?

As it is, the confusion centres more around nomenclature than what is happening technically.

Brian - yes, tests will eventually independently confirm exactly what is going on - but the process shouldn't be underestimated. It needs proper test cards, not just evaluation of real world footage. As far as "real world" results, then again I repeat what was previously said:
I think some people need to write that out 100 times. Pixel skipping doesn't necessarily mean aliasing/moire. It's only in the absence of a suitable OLPF that the two really are linked.

Yes, testing with charts would be a part of the process.

I apologise for my mixing up of line skipping with Pixel skipping.

So the real question is HOW does it do its magic OR another word for possibly something along the lines of does the camera pixel skip use blocks of four etc as clearly that statement and Jans statement regarding the use of the OLPF intertwined with her statement that it doesn't pixel skip leaves more questions.

I can see pixel skipping as being possibly equated with some form of compression.

One thing that seems clear to me is that the magic that is happening is removing something from the original image and replacing it with a new clever algorythmn of some kind. Something I think that a professional camera like the Sony EX1 doesn't do.

If I get any of the above wrong I am not an expert Just a seeker of the truth to enable me to decide whether or not to purchase the AF101.

With single sensor cameras you need some algorithms, it just comes down to how invisible they are in the final image.

Yes I managed to work that out. It did initially confuse me as I thought the answer that there was no line skipping meant no other type of algorthmn either like pixel skipping because I took for granted and would have expected that to have been helpfully offered as part of an answer. It's what your not told and wording that you have to be careful of I can see that now.

Mark,

You're overly concerned about something you'll never have to deal with in real-world usage. "Line skipping"? Trust me, that's something only measurebators concern themselves with when looking at a technical specs between camera models. You will never, ever see any aspects of line-skipping from the AF100. And how can I say this with such certainty?

Going back to the days far before AVCHD was even a speck of electrons in a engineers' brain, Panasonic has always been an engineering company, first and foremost. What that means is that when they research a new product they work the *science* behind the product first, then they work out the feature details and human interfacing. This is quite different from Sony or Canon who's methodology is always to address features and aesthetics first, then bring in the technology behind it. Which is exactly why both Sony and Canon products have always had a slightly more clean-aesthetic appearance where Panny products often look more... industrial in comparison.

When I was a direct consultant to Panny during the P2 HD Tour of '07 I got to see their methodology put into action firsthand whilst they were developing more P2 products (HPX500/2000). The science behind DVCPRO and it's HD variant were technically amazing when compared to the other codecs available at the time, not to mention the industry-leading technology built into the P2 cards themselves. (Note I said built "into", not the physical cards).

The AF100 is in point of fact lock-step with Panny's tradition of "science first" design; they've taken both CMOS and AVCHD technology a few steps beyond the competition and provided a visibly superior output. And at the price-point it's being offered there's not even a close competitor both in output and feature-set.

If you want to be concerned about any aspect of using the AF100 - or any other CMOS-based, AVCHD-type camera for that matter - which really does impact image quality/usability, it's rolling shutter. And unfortunately about 90% of all "video" cameras made today use a rolling shutter. That's the real headache today, not the sensor, not the codec and certainly not the price!

Happy Holidays to All!

Thanks Robert.

Taken on board what you have said!

Happy hols to you too.

Mark

Well, in one respect, I have to fully agree with that. I posted a long time ago in this thread (and later restated) "There's an (incorrect) widely held belief that pixel skipping necessarily means "nasties" such as moire, aliasing etc." So no, I fully agree, pixel-skipping does not necessarily mean bad pictures - not as long as a good OLPF is used. (And I'm sure in the AF100 it is.)

But in another respect pixel-skipping can be of concern to all users. It's not "just for measurebators". The theory doesn't just predict the possibility of moire etc (if no OLPF is used), but also much lower than expected sensitivity. And to turn things around, it's the (relatively) poorer than expected measured sensitivity that is one of the main reasons for currently supposing that this camera DOES pixel shift!

You'd expect it to be about 2 stops better than something like an EX1 with this size of chip if some sort of pixel skipping wasn't happening. (Three stops better due to 8x chip area, then lose about a stop as one chip versus three.) In practice, the stories I'm hearing are about equivalent to an EX1.

I posed the open question before Christmas: "can it be categorically stated that the AF101 reads out all 12.4 million photosites each frame, forms the image from all of them, then downresolves the result to form the final 1080 image"? If Panasonic were to give a categoric "YES" to that question, it still leaves the question about sensitivity wide open. As it is, pixel skipping ties a lot of (observed) technical points up very neatly.

Does it matter though? The EX1 is seen as pretty good in low light anyway, isn't it?

If the AF100 is used with fast primes, that argument holds pretty true most of the time. But use solely with primes can be very limiting, and it's using a camera like this with zooms when the sensitivity issue starts to matter. If the sensitivity was 2 stops up on the EX, it becomes possible to use apertures of about f3.5 and maintain usage parity in low light with an EX. And f3.5 zooms for such large format sensors are likely to be reasonably affordable.

But use an f3.5 lens on an AF101, and it will be trounced in low light by the f1.8 of the EX1.
I'm sure that's exactly the Panasonic party line, but in truth, if their policy really was "science first", they'd have developed a purpose designed large sensor of more like 4 megapixel, not adapted what is first and foremost a still imager. I fully accept their approach has led to a product which is far cheaper than it otherwise would have been, and (by virtue of the OLPF) should give moire/alias free video. But it shouldn't be seen as equal to a "designed for" sensor.

At the moment, you're probably right that it is in a space of it's own. The F3 has many features the same, is unquestionably better in other respects - but is a lot more expensive.

But surely it's the future, and the NXCAM little brother of the F3 that Panasonic must be really worrying about? Price reckoned to be about the same as the AF100, same native codec, many other features similar - but having the same purpose designed sensor as the F3?

If I wanted a large sensor dedicated video camera NOW, I'd get the F3 if I could afford it, and the AF100 if I couldn't. But if there was no pressing need, surely it must be better to at least wait until NAB and see exactly what the F3 little brother will consist of? Latest rumours are of far better ergonomics than the AF100 (or the F3, for that matter!), let alone the far better sensor.