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-   -   Line skipping (https://www.dvinfo.net/forum/general-hd-720-1080-acquisition/526433-line-skipping.html)

David Heath January 15th, 2015 06:59 PM

Re: Line skipping

Originally Posted by John McCully (Post 1873698)
But I won't claim 'no line skipping', for now.

One last thing I would say is that if it did line skip, then from the reasoning of my previous post the max unaliased resolution can be no greater than 1/4 of the sensor dimensions.

We know that the hor photosite count is 5472, which predicts a max hor res of 1368 - which for 16:9 translates to about 770 lpph.

I'll say again I'd like to see definitive zone plates, but from what is available, the practical results seem to well exceed that before starting to alias. Which to me is pretty good evidence that whatever it's doing, it's not line skipping!

John McCully January 15th, 2015 07:16 PM

Re: Line skipping

Many thanks for taking the time to articulate line skipping so thoroughly here, most helpful and interesting. The 'so what' or as the Wicked Witch said 'who cares' is the bottom line of course. Line skipping is perhaps not the dirty word some would have us believe. Does the Bionz X processor eliminate line skipping? I just changed my position to 'possibly' :-)

And the technology continues to improve and our results with it. Long may it continue.


David Heath January 15th, 2015 07:51 PM

Re: Line skipping

Originally Posted by John McCully (Post 1873701)
Line skipping is perhaps not the dirty word some would have us believe.

It never should have been so regarded. It's yet another example of a curse that afflicts us where everything has to be seen as very good or very bad - nothing in between. Which is nonsense.

It started off simply as a way to get "liveview" for viewfinding, then someone thought if it could be made recordable it would just give added value to a still camera. And whilst the early ways of doing it were pretty crude (hence the association with coloured moire), it did get refined until what I described is probably about as good as it gets. For what it is now - a way to get pretty good video from a sensor not designed for such, and to do it quite simply and cheaply - it's pretty amazing. But it can't give the results that a 3 chip sensor gives, and admitting second best doesn't go in marketing.

Problem was the very term "line skipping" got associated with the early attempts - which did leave quite a bit to be desired. So when the technique became more refined, it was the marketing people who just wanted to avoid the term like the plague - and hence the BS you originally referred to. "No sir, our camera doesn't line skip!" just got seen by them as a bit of marketing. Of course, technical results were able to sometimes prove they were talking nonsense.

Mark Rosenzweig January 16th, 2015 07:55 AM

RX10 versus RX100 III
Just some more info from another source - slashcam.de. They compared the RX10 and the RX100 III. Here is the Google translation of what they said in reviewing the RX100 III:

"Of course, the question remains of questions, such as the sensor operates in video mode. Despite full sensor readout Sony seems to use a different downsampling algorithm than for the similar design RX10, which at that time could surprise us extremely positive.
Because in contrast to the almost perfect RX10 significant Moires in the test patterns are noted during RX100M3:

We have all modes (24p-60p) of the camera with and without image stabilization durchexerziert, but always with similar results. Why Sony is not used here the excellent downsampling the RX10, we are left with a puzzle. Finally, the signal processor and the sensor are likely similar, if not even be the same."

Here is the link to the full review in German. I posted the test charts above in an earlier post:

Test : Sony RX100 III Kompaktkamera -- großer Sensor, große Videoqualität?: Einleitung / Austtatung / Formate

So they are concluding it's all about superior downsampling, presumably not line skipping!

John McCully January 16th, 2015 01:51 PM

Re: Line skipping
Thanks Mark, that's interesting.

They are 'left with a puzzle'. Right!

One must ask how do they know there is 'full sensor readout'. They don't even know if the sensor and the processor are the same (RX10 and the RX100 III), it would appear. 'In video mode is now also no Lineskipping be used, but all Sensel of the sensor to the calculation of the video image will be consulted' (Google translation). How do they know that seems to me to be a reasonable question? I don't see anything helpful in that regard but perhaps it's lost in the translation.

My scepticism kicking in again :-)

David Heath January 16th, 2015 05:40 PM

Re: Line skipping

Originally Posted by John McCully (Post 1873775)
One must ask how do they know there is 'full sensor readout'. They don't even know if the sensor and the processor are the same (RX10 and the RX100 III), it would appear.

I'll go back to a previous answer where I said:

Originally Posted by David Heath
It does seem to be giving full 1080 resolution from a 20Mp chip (which it wouldn't if it was line skipping). But there is aliasing above at very high frequencies. I suppose that's the real problem of trying to build a camera for both still and video use. If it was solely for video the aliasing could be greatly minimised with an OLPF - but that would make it a very soft stills camera! :-)

But it does seem as if Sony have got away from line-skipping, which is a big step forward.

and the important bit is "seem to be giving full 1080 resolution from a 20Mp chip".

It's not possible to *KNOW* for certain neither the RX10 or RX100 derive their output without line-skipping, but for the reasons I gave earlier I do think it's reasonable to deduce that IF they WERE line-skipping, the unaliased resolution would max at about 770lpph. It seems to be far better than that - so I consider it logical to therefore reason that line-skipping isn't taking place.

Of course, the assumption is that any line skipping would be of the type I described earlier (which is the best form I'm aware of) so max resolution is 1/4 of sensor resolution. Maybe they have developed a better system - but it's hard to think what geometry it could use. And at the end of the day, does it matter? Does it matter whether any camera line-skips or not if it delivers full 1080 resolution, as the RX10 and RX100 do seem to? In the past "line-skipping" almost automatically did mean performance well below par compared to a 3 1920x1080 chip camera - if that was not to be the case any more, then why worry about it?

On balance of probabilities, I think it far more likely that both these cameras DO read the full sensor. But that's not the end of it as there is downconversion and downconversion! (As people making SD DVDs from HD original matter have found out!) GOOD downconversion will digitally low pass filter the intermediate (20Mp) image before the actual downconversion to HD - but it's difficult to do well. It doesn't surprise me at all if the downconversion in what is, after all, primarily a stills camera, is not as good as a dedicated box costing thousands of pounds in a broadcast chain!

I've said before, and will say again, that the real breakthrough in terms of a hybrid stills/video camera will come with a sensor of (2x3840)x(2x2160) - which is about 33Mp for 16:9. That will be more than good enough for high quality stills, and is easily directly read with simple processing (no downconversions) for both 4k (2x2 Bayer blocks) and HD (4x4 Bayer blocks).

John McCully January 16th, 2015 06:53 PM

Re: Line skipping
Indeed David, another great elucidation but of course my post above, my question 'how do they know...' is rhetorical and not grammatical in nature. In other words I am pointing out the shakiness of the foundation upon which their conclusions are based which undermines their credibility, that's all. As with lots of so-called technical websites that we take as presenting the truth on closer examination turn out to be highly questionable and little more than gossip purveyors. In particular I recall one such website that Chris Hurd in his wisdom quite some time ago refused to permit links to here. I'm not saying Slashcam.de falls into that category but it might, it seems. At least they were honest and upfront enough to inform us they are puzzled.

Pushing misinformation either deliberately or in ignorance is not a crime but websites that purport to be providing solid technical information that cannot withstand critical examination...then going back to my allergy they fall into the BS category, the sub-subject of this thread.

Reader beware! Keep the salt handy.

The internet is a wonderful place, that's for sure; there are bucketfuls of great information out there. There is a huge amount of misinformation out there too and determining the difference is sometimes something of a challenge. Sometimes it makes little difference and sometimes it makes a huge difference.

May I suggest one read with a mindset of healthy scepticism, particularly if one's read might result in one plonking down a fair chunk of change!

And when the real breakthrough camera you described above becomes available I shall be an early adopter, if I can afford it!

Dave Blackhurst January 16th, 2015 08:30 PM

Re: Line skipping
I thought I made a mistake once, but I was wrong...

You're correct that one should ALWAYS have the "BS filter" engaged, even more critical on the internet, the new "marketplace of ideas". It occurs to me that 10,000 monkeys might be behind the whole entire thing! Can someone please pass a banana...

The bottom line is that the RX10 performs above what you might expect. The RX100M3 is supposed to be the same underlying tech, but isn't quite as good... different engineering team, probably different firmware tweaks, and definitely different lens, in a much smaller camera. It does what it does well enough, but if the RX10 had the 4K firmware update that arguably it is well capable of, I'd prefer it overall, and aside from not fitting in your pocket, it's a "better" (and more expensive) camera.

When Sony made their product announcements for CES, the FDR-AX33 specs ON THE SONY SITE said it had the 1" sensor on the BOSS system (likely physically impossible). Many people who are qualified to comment have concluded it is far more likely that it has a 1/2.3" sensor... which is likely due to the physics and the economics of a $1K camera (pricing also was quoted at both $999 and $1099 in various "official" releases).

What I'm gettin at is that when the MANUFACTURER can't even get the critical specs right... you have to give a LITTLE slack to the sites who are on a fast "reporting" cycle trying to "scoop" the "hot new thing".

Sites like DVi provide a venue to discuss "real world" product experience, and a pretty good base of technical savvy (and we all still probably make a mistake sometimes!) to discuss the details of what we can deduce about the "toys" we buy....

John McCully January 16th, 2015 10:13 PM

Re: Line skipping
Thanks for your thoughts Dave. That's correct (or is that incorrect), I have read a lot of your posts here and you have never been wrong ha ha. It's enough to drive anyone bananas!

In my opinion you are certainly not wrong about the RX10. I don't believe I have owned and operated a more satisfying camera. It's not perfect of course. Now and again I wish it had more reach. I would sacrifice the constant f/2.8 for that as I rarely shoot in low light but right now I would not walk out the door without that thing hanging around my neck. And the truth is whether it line skips or not hardy matters as the video I bring home is invariably clean and delightful (well, almost always).

I noticed the screw up regarding the AX33. I certainly had an adrenaline rush when I noted the 1" sensor but no, too good to be true in such a tiny body I reckon. Another huge disappointment that kinda made me happy was the observation reported by Cinema5d that 'Almost after very time of pulling the the EVF out, new eye focusing adjustment need to be done.' (The couple of typos there are in the text on the website which is a bit sloppy but we can overlook.) The reason that sort of made me happy is that exactly the same problem occurs with my CX700v and I never got around to sending it away for repairs. I guess that is inherent in the design, would you believe, and not repairable, probably. I worry a bit about Sony these days. It's one thing to cut corners and use existing designs for new products as seems they have done with the AX33 but not with a sub par design such as this seems to be.

Whatever, it is OK for me to make a mistake from time to time but that's no excuse for you ha ha.

Thanks for the input and I trust you are enjoying the winter-less Apple Valley these days.


Dave Blackhurst January 17th, 2015 04:53 PM

Re: Line skipping
Well, we do get a little snow, which you can then go out in shorts and t-shirt to enjoy... a desert pair-o-dice!

Yeah, that was a big excitement... let down on the AX33... a smaller AX100 with magic eyeball would have been nice, not so sure about the small sensor! Gotten spoiled by the performance from the "1" class" Sony devices...

Still hoping for a 4K firmware for the RX10's, I'm afraid that Sony will (as they so often do) lose something when they release a "new improved" model. They got so much right with the RX10 and AX100 (and for the most part the RX100 series), I'm worried that "tinkering" won't be good for the products!

John McCully January 17th, 2015 07:53 PM

Re: Line skipping
Snow you say? But not never-ending days of frigidity! I do enjoy a desert climate but oh! I do like to be beside the seaside, I do like to be beside the sea!

I agree, the RX10 is a hard act to follow and given the financial challenges facing Sony right now I do hope they are up to the task of doing even better, but I'm not holding my breath. Notwithstanding the enthusiasm of some of our friends, in particular the prodigious excellent output from Mark Rosenzweig, the originals of which he very kindly makes available for download, I'm not about to make the leap into 4k, at least not for now.

But I do absolutely NEED a new piece of kit. See, that word is NEED and not Want.

I am having a ball shooting the wildlife, the sailboats, the cruise ships and so on here and in as much as I have yet to master the art of walking on water I must get closer by other means and I have concluded that means new glass, probably.

So I don my reading glasses and head out on the Internet. I quickly learn that the recently deployed Bionz X processor is the greatest thing since sliced bread, in fact is a must have as it does away with that dreadful line skipping business. And of course with David Heath's most helpful input here in this thread we now have that processor properly put in its place.

One wise fellow made the point that first select the lens that will do what you want and then select a camera to fit it onto. He went on to recommend the Sony 70-400mm f/4-5.6 G2 Telephoto Zoom Lens and to mount that thing on a A7s body. Right! The good news is that that lens gets me half-way there and with the A7s I can do it at night. The not so good news is the total cost of that setup. Ouch!

On the other hand Stephen McDonald, who absolutely knows a thing or two, speaking about the Sony HX400v which has a zoom which reaches out to 1200 mm (equiv.) says it '...is probably the most underrated camera of its type.' And the whole kit and caboodle for about the price of the lens cap on the big Sony zoom above, almost.

And somewhere in between I could go with the Sony a6000 and see if I can fit the Tamron 150-600 onto it. Won't have the reach of the HX400v but nice video output with that combo, I believe. Under good to excellent lighting which we mostly have here I'm not sure the video would be that much better than that delivered by the HX400v and at least 3x the price, perhaps more.

So that's what got me seeking to understand one element of the puzzle; the Bionz X processor, which all three options have inside, by the way.

I'm getting there, slowly. Suggestions most welcome...

Dave Blackhurst January 19th, 2015 07:00 PM

Re: Line skipping
Well, there's one possible advantage to 4K, should it ever grace the RX10 through a firmware update, or perhaps a replacement that hopefully will not be a step backwards... you can zoom and crop surprisingly effectively. A few of use are using the AX100 that way, same sensor and processor, as far as anyone has been able to determine. May be worth a few moments of consideration.

I've got the HX300 for those "long shots", tried the 400 briefly, and felt the stills went backwards a bit (one of those aforementioned "Sony backwards steps"). I can shoot video with it, but the AVCHD even at 60p is starting to look and feel very "dated"... worse when put up against XAVCS 4K/30p or 1080/60P at higher bitrates (and another update is supposed to be coming for even higher bitrates in March). BUT, you do get raw lens reach, with a small sensor, and a workable image capture. Bang /buck ratio for a used HX300 is pretty hard to argue with, and if you don't pixel peep TOO hard, you probably will be thrilled. The HX400 has a few nice feature upgrades, and if you can find one at the right price, again, good bang/buck ratio, and the stills are not "bad" or anything, I just felt they were a little worse than the 300...

I've tried the "NEX", series, now rechristened "Alpha", just somehow didn't hit me, and I've got A-mount glass I couldn't afford to replace... but A-mount is definitely lagging behind in R&D... so I continue to consider getting on board the A7 train (after robbing a couple banks). An A7SII with in body stabilization, with a few adapters maybe...

The challenge of a really LONG lens and getting a stable shot with it is a tough one, no doubt, and to get high image quality with long range, is going to bust your budget anyway you slice it.... you could probably just get nice small boat or jet ski and improve your "optical zoom" distance! One thing I've found with "long shots" is that the atmospheric "effects" start to really mess with image quality as well!, doesn't matter HOW good your glass is! So now you can justify buying a boat! Not sure if that's helpful or not.... I think the "boat hobby" is more investment intensive than the "camera hobby"...

I keep an HX300 around just for that silly long zoom, and it's cheap enough you can't go too far wrong, FWIW... somehow I doubt that the BIONZ X in the 400 is using all the features, and honestly it would be wasted on AVCHD.... not sure if Sony plans to beef up their Cybershot line (or even keep it around?) with the better CODECS/higher bitrates, but that would add some potential image quality...

John McCully January 20th, 2015 01:01 AM

Re: Line skipping
Thanks for the input Dave, most interesting. I should get a boat, you say. Well, I did that a few months ago. I purchased a 31 ft cruiser/racer sailboat built here in New Zealand quite a few years ago. Most everyone knows that when it comes to designing and building sailboats the Kiwi's are world class. My Raven 31 is no exception. And let me hasten to advise you; in my instance the boat hobby (and that's what it is) is hugely more expensive than the camera hobby. It is not just the initial cost but the ongoing costs including marina fees, repairs and maintenance and so on. For some unknown reason anything to do with boating is twice as expensive, and more, than similar other products.

I'm not complaining - just today, perfect high summer day, I sailed up to Blumine Island and back, out there in Queen Charlotte Sound amongst the wildlife and loving it. Talk about unspoiled unexploited pristine nature at its abundant best - this is it.

When it comes to the task of shooting the birds and animals I really do need more reach than the RX10 delivers, more often than not. Today I used my HX200v. Better than nothing, for sure, but I would like to do better. I was hoping the HX400v would be a significant upgrade and some folks are certainly of that opinion. Your words discourage me somewhat from heading down that path. I am somewhat surprised as I would have thought that the latest greatest processor that Sony are deploying would have delivered superior results compared to their earlier versions.

I do know about the atmospheric interference problem, heat distortion and the mirage phenomenon. That certainly can be a problem over large distances particularly in desert climates but less so I believe over water. If I want to shoot a wild seal having breakfast I do need to keep a healthy distance even if that might only be 25 or 50 meters and a superzoom is the tool for the job (or a gigantic lens mounted on a A7 something costing almost as much as my sailboat and weighing in around the same :-).

While I do want to deliver the best quality I can afford, and is practical, I also remind myself that if that which I capture is sufficiently interesting then if it does not quite attain the quality of the latest 4k offerings folks will not mind too much. And while I wait for the perfect camera I remind myself that 'content is king'. Hackneyed perhaps but still true eh?

Thanks again Dave, I very much appreciate your thoughts.

Dave Blackhurst January 23rd, 2015 09:31 PM

Re: Line skipping
Yeah, I kinda figured boating was a tad more expensive - how's the old saying go? Something about a hole in the water you pour money into?

The HX200 was no slouch, really the entire HX "SLR style" series is pretty nice as small sensor cams go. It's just when you start to shoot a higher bitrate that you start to see the weaknesses. I really didn't test video much with the HX400 once I saw that the stills were not quite as good as the HX300, and stills are my main use for high zoom, I'm too wobbly to shoot video in that mode! I normally would have looked at the video more closely, but the AX100 and RX10 in XAVCS mode are my "go to" cameras for most things now, so normally wouldn't use an HX in that capacity.

I'm sure Sony COULD begin to add XAVCS and higher bitrates into "consumer" cameras, but there seems to be a reluctance, probably due to the need for faster memory cards, and the complaints they'd no doubt hear if low quality cards were used by someone not reading he "instructions" - they do have menu pop up warnings "in camera", but I'm thinking they are taking it a "bit" at a time as thy introduce higher resolutions and bitrates.

I don't know if Sony is even going to bother with the "consumer" camera market moving forward, but I wouldn't mind seeing the sensor in the AX33 in a future HX camera as a possible offering. With CES behind us, and not a single "Cybershot" announced, who knows where or when an upgrade will pop up!?
I would hate to see the "superzoom" niche disappear, for the things it does well. As long as the air is clear (always seems like it's foggy or misty when I want to shoot on the coast), a superzoom is a handy tool!

It's always the content, but it's hard to feel like a "tool" is holding you back (or making you look bad!)... and of course some tools work better for some things than other tools...

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