XDcamEX vs JVC GY HD250
 

Big can of worms.
I too do lots of hand held work and can't hold a DVX100, Z1U, etc. steady for very long without some form of support. I never used to have problems like that with my BetaCam or DV500. Frankly, the extra weight was a small price to pay for a steady shot.
I like the specs on the XDcamEX very much but wonder how the image will stack up next to the HD250. The firestore of course is an option for the JVC vs cards on the XDcamEX. The solid state of the XDcamEX does seem to be the way of the future. I'm still at a loss however about the JVC 720P 20mbs vs 1080i 25mbs/ 35mbs Sony aside. I guess the proof will be when a side by side shoot out is possible.

I too do lots of hand held work and can't hold a DVX100, Z1U, etc. steady for very long without some form of support. I never used to have problems like that with my BetaCam or DV500. Frankly, the extra weight was a small price to pay for a steady shot.

Its called practice, and yes, you CAN get stable, if not more superior camera motion results with smaller cameras. In fact, i sold of my DSR570 because of the bulk, and I've never looked back. Yes I miss the big imager and the wow factor of the camera, but for the majority of my work (weddings) I think its the best decision ive made. faster compositions, unrestricted movement due to weight, battery power, tape price.... there are many reasons why smaller units are superior to ENG type cameras (and of course vice versa)

I like the specs on the XDcamEX very much but wonder how the image will stack up next to the HD250.

IMO it will rule over anything in this price range.. but thats judging from what I've seen of the codec already running off 1/2 imagers... (F350) considering the imager size, and codecs, to me its a not a contest, its an obvious difference)

The Firestore of course is an option for the JVC vs cards on the XDcamEX.

The solid state of the XDcamEX does seem to be the way of the future. I'm still at a loss however about the JVC 720P 20mbs vs 1080i 25mbs/ 35mbs Sony aside.

The difference is that the JVC is using short GOP structure, vs MPG2 long GOP structure of XDCam. motion differential isnt all that bad though considering the bitrates in question. There's also the issue of XDCam uncompressed audio.. and for me THAT is one of the biggest issues (I also do a lot of concerts so audio isn't compromised

I guess the proof will be when a side by side shoot out is possible. Don't forget the XDCam is also about one year younger than then the JVC.. in turn, technologies evolve...

I seem to recall seeing on a JVC leaflet that solid state was in their planning "for the future" - whenever that may be, and whatever form it will take. I agree that the form factor of the JVC series is far better than the HVX200 and the Z1 etc, and would love to see a camera like the 250 with a SxS or CF slot built in, ideally in addition to the tape deck. (But maybe with the option for higher bitrate recording?)

Comparision EX v/s Gy 200 series
 

Hello guys this is my first messege after months off reading, searching and investigating in the forum. I need a little help in my future camera choice. I ended in this thread because one off my choices is the Jvc Gy-201E (by the way Im chilean but I live in sweden), now after all the publicity and discution in the forum, the another choice is the Sony EX. I know that the comparison between them is only theoretic but I will read some opinions, the image quality comparison, lens, work in NLE system, etc. (I know is all in theory).
If it´s important I need the camera for diverse works like shortfilms, documetaries, maybe publicity, etc.
Help me with my choice.

Greetings to all of you in the forum, and sorry for my english!!

There is world of difference in these cameras.

EX:
Fixed lens
1/2 in. chips
full 1080 hd chips
solid state media
consumer form factor batteries
Small form factor

JVC:
Upgradable lens
1/3 in. chips
720 HD only
HDV Tape based
Pro batteries available
Shoulder mount

But the question is what is your style and what do you feel comfortable with.

I would add my experience to this; I have owned the JVC HD100 and I also owned in the past (or worked with) a number of Sony cameras from prosumer to professional (VX3, VX1000, DSR-500, Z1U, F900, etc.). Based on my personal experience, I would state the following (in addition to what has been said already):

SONY EX (either we already know or I assume as very likely):
-'consumer-style batteries' but they last a long time and they are light
-uncompressed audio
-1080p/1080i/720p at various frame rates
-file-based, no moving parts = fewer problems
-great LCD (even in daylight)
-35 mbs VBR sounds like a very good codec
-built-in workflow via XDCAM disks
-if other Sony cameras are any indication, the EX should be robust and reliable

JVC:
-very unreliable, many issues from SSE to TC (check the boards)
-plastic feel, easy damage to the VF, LCD and other parts
-better form factor - shoulder mount
-as Chris mentioned, only 720p
-'pro batteries' but they don't necessary last longer than the 'consumer-style' Sony variety and are heavy
-tape-based, moving parts = problems (TC, dropouts, tape selections - yes, there are endless threads on 'which tape' to use with the JVC as it is very finicky)
-poor LCD and VF (really bad colour rendition and LCD completely useless in daylight)
-25 mbs and compressed audio
-to this day somewhat limited NLE support

The JVC has an interchangeable lens but to get a really good glass one has to spend another $8-10k. The stock lens isn't very wide at all and it exhibits a lot of CA. And there aren't that many lenses to chose from anyway. If I am not mistaken, the EX1 has a function to minimize CA through its internal circuitry.

I personally think that the SONY is a far better choice and if it proves to be reliable then it will beat the JVC in many respects.

I'd also add that there's many ways to turn a handheld camera into a shoulder mount and run it off brick batteries. I've yet to see anyway to go the other way.
Add rods, matte box, FF, shoulder mount extension out the back and hang a brick battery out there to power the camera and a decent on camera light and I think the most fickle client will think you're a pro.

If you want to shoot 50p or 60p then the JVC has a GOP pretty darn close or equal to that of the mpeg2 from the EX1.

18mbits/s for 60p 12 frame GOP (only the lower framerates use the 6 frame GOP)
35mbits/s for 60p 12 or 15 frame GOP or somewhere in between.
Think of this as the difference between a DVD at 4.5mbits and one at 9mbits.
The Sony may also use different GOP lengths for 720p recording. I don't think anybody knows yet exactly how the GOP structure will be for 720p so we will have to wait but for 60p the playing field should be pretty even.

It doesn't take much to see that the EX1 will offer 720p mpeg2 encoding at double the bitrate of the JVC 250.

If 720p is what you want then the EX1 should blow away th JVC cameras just with the optics, chip size, native resoltuion and bitrate of the codec. About the only thing you could make better on the JVC is the optics but to get a new higher quality lens for the JVC you are looking to spend almost as much as the cost for a whole EX1.

The EX1 then takes it one step further by allowing you to shoot 1080i or 1080p if you ever need to. This is something you just cannot do at all with the JVC.

I would test out the EX1 on some type of support system to see how you like it.

Thanks guys for the answers! Chris I need the camera for diverse works like shortfilms, documetaries, maybe publicity, etc. and I like the shoulder mount ergonomics, but I kan use a handycam form factor anyway.

A few more questions, what about the Cmos sensors v/s the Ccd´s in terms of image quality? any diference?

How can i solve the issue that you can´t transfer the higher quality from the Ex through firewire cable? It´s that true? If I don´t have the expresscard reader, have I others options to transfer all the images to the pc and work for example with APPcs3 or avid express?

I also like the handycam form factor for certain things, but not for others. As you can see from the posts after mine all of these things are personal preference. In the end which is going to give you a usable image?

Both of them. But usable for what. I personally don't want to be tied to a 720HD
image I would rather have full HD. But Full HD doesn't mean anything if you are uprezzing chips, because you can do that in post.

I love the EX and everything it is on paper. I already have one ordered. But what it will be when it gets out in the wild still remains to be seen.

As far as CMOS vs. CCD that argument is the same as the camera argument. They both produce great images and have strengths and weakness. In a few years there will be no argument it seems because all of the camera manufactures are heading for CMOS or thus it appears.

I believe you can transfer the file information over firewire but not as a video stream. So it is like a removable hard drive not a DV camera. But there are card readers right now for that memory stick form factor, that will get faster transfer speed. It is just a beefed up express card manufactured by Sandisk.

ok, the mention of an "upgradable" lens was made, but in al honesty, how many lenses with this size (native mount) has fujinon actually made?
Lets face it.. take a look at the XL2 and XLh1... of the EF lens options available, not many people would even consider changing the lens, let alone actually invest in higher grade or prime lenses.

All this talk about lenses etc and over 95% of users stick with the stock unit.. totally defeats the purpose

I am not arguing for the JVC. But B&H offers three different stock Fujinon lenses to package with this camera. These are broadcast lenses not hampered by the limitations of adapting a 35 mm still lens to an application it wasn't designed for. No disrespect to Canon. They make some of the finest video lens out there. Just not for the XLH1.

I agree that the original lens for the HD100 series was inadequate. Most are that come in a package. Which is why past a certain price point camera bodies don't come with a lens. You have to buy it separate.

The original HD100 series batteries were also woefully underpowered. Lasting only 30 to 40 min. But they offered a work around kit for that with larger, longer lasting, IDX and AB batteries.

I hope the EX batteries do better. But the kind of juice required to power a camera lens combo like this is considerable. I still want one though.

Sometimes I wonder...

How many people actually know that 720p50 is far superior to 1080i50? Or how many even know that 1080i is NOT full HD? And yet - it is just a matter of the easiest mathematics:

50 x 1280 x 720 pps or 50 x 1440 x 540 pps is kinda obvious. (and that's not even taking into account the interlaced filter you need to keep the image from being jittery)

Not to mention all HD screens nowadays are progressive, so you can not watch 1080i optimally.

choosing 1080i and 720p might be difficult, but not as an aquisition format: you can aquire 720p and make perfect slow motions and whatever you want to do and then convert it to 1080i if a client asks for 1080i. If you would choose 1080i as an aquisition format, you can't make any serious slow motions (they'll have almost half the resolution and just half the temporal definition) or any other effect that uses deinterlacing. Furthermore, you cannot supply a client with seriously good looking 720p. Pretty simple if you ask me. But some people will be holding on to 1080i, and as a mathematician and image processing expert, I can only say: I suppose they're let by the fact that 1080 sounds larger then 720 ... ?

Anyhow. That's not even taking into account that the MPEG2 compression scheme has no higher order for interlaced images, thus losing efficiency in 1080i. 1080i in MPEG2 at 35 Mbps can't be compressed better then 720p at MPEG2 at 20 Mbps. I'm not especially promoting JVC here (although I know they have the better product here), but I cannot agree to Sony for what they are doing: They are making XDCAM look like it is a higher end format, but any scientist (as I am) know they are marketing HDV on a different format: it is also 420 - 18 and 25 Mbps is HDV. 35 Mbps is just SLIGHTLY superior standard Z1 HDV. It is obviously all long GOP. XDCAM HD is HDV in 18 and 25 Mbps mode and it is just very slightly better in 35 Mbps, while retaining all disadvantages for it not to be a high end format: long GOP mpeg2, interlaced, just 35Mbps in interlaced, 4:2:0, ....

Quality of the camera and lens, we'll have to see. If the EX wanders onto my desk, and I want to get the best out of it, I'm recording in 720p. Needless to say - that's what I do with the Panasonic HPX-500 that I have as well and with the JVC GY-HD201 (athough, there I have no choice).

Well, not 95% but a lot, indeed. And I think that's probably because of the price point of the HD100/HD200. The fuyinon 16x5.5 isn't all that bad, but the problem is you need to pay in between 8.500 euro and 12.800 euro for a lens that's better. And for some people shopping at this camera price point, that's too much. That said, we have sold a few 13x lenses, but more because of the wide angle possibility, rather then the improved quality (the wide angle is more important to broadcasters).

Werner,

The EX1 shoots 1080p as well. While it doesn't shoot p50/p60 in that mode (it does shoot 720p60), it does shoot 1080p30, 1080p25, 1080p24. Also the EX1, in 35mbps, records FULL 1920x1080 from chips of the same size, even though other XDCAM HD cameras only record 1440x1080.

35mbps is more that "slightly" better than 25mbps. 25mbps is CBR and 35mbps is VBR. Fast moving images are allocated more bits making the codec MUCH HARDER TO BREAK than HDV.

True it's 4:2:0, to card, but as a "studio" camera it's uncompressed 4:2:2 (both SD and HD) out of HD-SDI before the MPEG2 codec touches it.

If you're talking about XDCAM HD in general, Sony will have a XDCAM MPEG2 4:2:2 50mbps format out soon in the highest end XDCAM HD.

You can ask people using the F355 if they're happy with the image and workflow. It works well.

I'd like to shoot 720p60 especially when I'm shooting fast action or material that may lend itself to slo-mo. I like having the option of shooting 1080p30 or 1080p24 though.

Werner,
from our tests and the comments of others 1080i produces much better slomo than 1080p or 720p for that matter and that makes perfect sense scientifically. 1080i has double the temporal resolution to start with.

I agree to that, but I have seen in the last year or so that lots of people don't have the skills to be shooting in 25p (here in Europe). They keep insisting it is bad, which it isn't, but they can't produce anything in such a low temporal definition because of their camera techniques etc.

We'll also have to see if the CCD's are progressive 1080 CCD's - that hasn't always been the case. I believe the verical resolution of the Z1 was 1080 as well, but those CCD's weren't able of true progressive readout (ergo the 'frame' mode).

Actually I'm not saying anything on the quality of the SONY, I am merely reacting to some people that have never gotten the right info on p and i. the sony and the JVC aren't very comparible if you ask me. They are both designed for a segment in the market. The 16mm and 35mm adapters for the JVC go well e.g. and there's no substitute for that with this sony. Furthermore - JVC offers no handheld option. I personally think this sony model, just as the HVX200, is way to big and bulky for a handheld type camera, but nevertheless, sony and panasonic offer the option and some people like it.

Sorry bob, 1080i50 and 720p50 have the same temporal resolution. 1080i needs deinterlacing before producing slow motion, therefore dropping in temporal resolution over 720p50 due to field removal. Obviously, spacial resolution drops too dus to field removal. (you are probably comparing to 720p25, which makes it still not true, as the higher temporal resolution of 1080i goes out the window as soon as you deinterlace. And you can't slow anything down without deintercaling first).

Don't believe what you hear - just really test it if you don't believe the numbers:

1/2 speed:
720p50 > 720p25
1080i50 > 540p12,5
(advanced deinterlacing techniques can make this a bit better, perhaps +/- 600p12,5 so to speak)


if you test it:
take 1080p50 fotage,
render it to 1080i50 and to 720p50,
then slow down both files,
compare

Shooting in 24p or 25p requires a different (improved?) set of skills due to the motion. Too many people think it's "flip a switch" and you can move the camera as before.

The EX1 is CMOS, not CCD BTW. The chips and the processing are Progressive coming from 1920x1080 (but there are various shooting modes).

For me, I need to shoot hand held frequently so I like the form factor. I've used shoulder mount and have found that awkward in some circumstances.
I don't think either is inherently "better." I think it's a matter of shooting style and technique. It looks like the EX1 rotating control grip should help wrist fatigue a bit.

Actually for 25p it's not really an issue. 24p is a challenge to work with because pull-down makes movement stutter.

I've been working with 25p for years with barely any special consideration. It would be just like going from 60i to 30p... It practically looks the same (only a little better IMHO)!

Not all 24p involves pulldown. Both the HVX200 and EX1 have modes that record 24p (23.98) natively to cards. It's one of the advantages of a card (solid state) based workflow.

One can certainly work from acquisition to master without using 29.97. Of course if you're heading for NTSC broadast the pulldown is going to happen at some point though.

I agree it is a lot more. I just wanted to point out though that VBR isn't instant magic.

VBR just means it can adjust the bitrate depending on how complex the scene is. VBR 35 mbits will look just as good if you had CBR 35 mbits. VBR was more of a space saver then a quality booster. The only time the quality gets better is when you have to lower the bitrate. For example a DVD at 4.5 VBR will mostly still look as good as 4.5 CBR. It is just when it needs it it will bump the bitrate up to help.

With XDCAM the 35 VBR is the max so most of the time you might end up with bitrates lower then 35 mbits such as 25 or 30. So yes it looks better but not just because of VBR it looks better mainly for the reason it can go up to 35. 35 at CBR would look just as good but it would have been a waste of space because not all scenes would need 35 mbits. That is the key to VBR. Easy scenes can use lower bitrates. HDV isn't bad because it uses CBR. It is bad because sometimes 25 just isn't enough and it needs a little extra umphf.

With that said another thing I would like to point out is that with 35bmits on the EX1 it has to encode 1920x1080 instead of 1440x1080. It still uses a better quality encoder chip (I hope) but I think the 35mbit mode is going to look compression wise more like the 25mbit mode on the higher end XDCAM HD cameras. 1920x1080 has 1.33x more data to deal with so that almost cancels out the extra 1.4x worth of bits. Of course it isn't an exact science so it will still look better then 25 mbit HDV because most of the time a 1920x1080 image isn't going to have 100% unique pixels. My whole point is that 35mbits on the EX1 does have to work harder then 35mbits on other XDCAM HD cameras so do not expect a 1:1 quality compression between those cameras. Sure the EX1 is nicer because it is 1920x1080 but it will be slightly more compressed.

And that is why I may prefer shooting 720p with the EX1. Some of you may have seen my thread on 720p 24p and how awesome it is going to look on the EX1. Well even 60p or 50p is going to look great. Progressive is much easier to compress and 35mbits is about double of that of normal 720p broadcasts or what the JVC cameras use for their bitrates.

Werner I totally agree with you. People just cannot seem to get out of the mind set that 720p 60p or 50p is just as good as 1440x1080 6oi or 50i. Sure they are both good but they have different types of good. with interlaced if you have a perfectly still scene sure it may look like it has more detail but as soon as things move a little bit you loose a lot of that detail. 720p offers a clean compression with a consistant look no matter what type of scene you have. Good viewing of 1080i also depends on how good of a HDTV you have. Some just bob the interlaced video while others try to smart bob the video. Soem really advanced HDTVs will try to fill in the missing lines. Again we have inconsistant viewing experiences depending on who watches the video. With 720p everything looks clean all the time.

One thing people forget about interlaced video is that it has to low pass filter the video so there isn't any interlace flickering. So yes you may have 1080 lines but those 1080 lines are slightly softened to the point where they only have a tiny tiny bit of extra detail in still scenes. Like you pointed out most 1080 video even from HDCAM tape is 1440 which isn't all that much higher then 1280. Although to be fair until there was HDV 720p tape only used 960x720 pixels which is why some people may notice a lack of detail in some 720p shows. True 720p however is just as good if not better then normal 1080i video. Sure 1920x1080 may have a little bit of an edge over 1440x1080 but it is still interlaced and it still has a low pass filter. Even shooting progressive with a 1080i camera you have to be carefull. Sure the video may be progressive but a lot of HDTV's and a lot of HDV formats will still play this back as 1080i. 1080p material still has to have low pass filters or as soon as you watch it as 1080i you will get flickering. Again why 1080i or 1080p can give a lot of inconsistant results.

I like to think of HD in terms of a sliding scale. On one end you have dirty detail and the other end you have clean softness. It kind of depends on what you like but to me quality equals clean video with as few of artifacts as possible.

I didn't hear a lot of people complaining about the World Series which was on FOX which uses 720p. In fact it looked pretty darn good.

Your numbers don't make sense - both formats start with 50 samples a second. Cut that in half, and both formats now have 25 samples a second.

What your numbers describe is de-interlacing first to produce a progressive frame and then slowing it down - but that's simply a bad workflow, not a limitation of interlaced video. The deinterlacing should occur naturally as part of the process of slowing it down. Drop 50i/60i footage into AE, tell it to separate fields and conform to 50/60fps in the interpret footage dialogue and each field will be scaled to a progressive frame, retaining your full temporal resolution at the expense of up to half of your spatial resolution (depending on motion levels).

Now you're back to comparing 50x1280x720 to 50x1440x540, which is a 15% difference - certainly significant but close enough that the I'd argue the deciding factor in which looks better comes down more to the lens and imaging system of the cameras than the format.

35MBS vbr vs. 25MBS cbr Question
 

Would someone exlpain the definition and diferrence between 25mbx CBR and 35mbs VBR terminology. Thanks.
Joel

Thomas,

Keep in mind that the EX uses only 2 channels of audio whereas the XDCAM HD uses 4. The 2 channel difference may help even the score you are talking about above.

Cheers,
G

And if XDCAM HD on the EX1 behaves anything like XDCAM on the F330/350/355, etc. then (according to a Sony Engineer who talked to Greg Boston) that the data rate can actually peak slightly above 35mbps.

CBR = constant bit rate, VBR = variable bit rate

25mbs CBR means every second of video consumes 25 megabits - no more, no less.
35mbs VBR means every second of video may consume up to 35 megabits, but no more.

VBR primarily affects recording capacity - a static talking head shot may not need the full 35mbs and therefore your recording time may increase.

The picture quality difference comes mostly from the increased total data - 35mbs is 40% more data per second than 25mbs. However, as others have noted, the EX's full raster (1920x1080) mode has 33% more pixels than 25mbs HDV - so the difference might seem like it's not that big.

However modern compression doesn't scale linearly with resolution - a big part of the compression is eliminating redundancy between frames. So your I frame (first frame in your group of pictures, GOP) may be 33% larger, but the differences in the remaining frames are not necessarily that much larger than the corresponding frames in an HDV-resolution file, so the net quality improvement may be higher than the numbers would indicate. That gets hard to estimate though because so much of it depends on variables in the image itself like image detail, detail movement, and camera movement - so we can guess all we like but until we have a lot of sample footage under a variety of shooting conditions we won't really know.

If what Alex mentioned is true about peaking it may be that 35mbs is really an average data rate, not the maximum, and that situations where a scene moves between static and motion shots may be able to 'bank' data not needed during the simpler portions and apply it to go above 35mbs where needed as long as the average data rate over a given period (probably a few seconds) doesn't exceed 35mbs.

The audio plays no part in that bitrate. In fact the audio is uncompressed and sits apart from the video bitrate. You could have 16 channels of audio and the video bitrate would still be the same.

yes peak slightly but not by a whole lot. Maybe 1 or 2 mbits/s is what I heard.

Specs are specs, but in the field myself, sometimes things can be somewhat different than a "black & white" description.
Without having the white paper or knowing the design engineers, looking at some specs is tough to call.

sure it is hard to calculate a value but if the redundant info helped that much then 1440x1080 wouldn't need that many more bits then 720x480. In fact you do need a lot more bits. Sure what you are saying is true that it isn't a 1:1 ratio but the encoder will have to work a lot harder. That is exactly why HDV and normal XDCAM HD is limited to 1440x1080. 1920x1080 would have pushed the 25mbits just a little too hard. There is also the fact that with 1920x1080 unique pixels your chances of redundant blocks of information is less because the overall image is sharper and more detailed. With the extra amount of pixels you have more blocks to deal with that could all be different. You end up with an opposite effect of how some encoders will apply a low pass filter to make the video compress easier. Well with more detail you make the compressor work harder.

I would say just giving a rough guess that 35 mbits from the EX1 will be about right in between 25 mbits HDV and 35 mbits XDCAM HD.

But - and a big but - all those examples you give assume 50 or 60Hz motion, which I agree is needed for such as sport. The argument may be valid for a pure sport channel, but most aren't, and too often the fact that nearly all drama and films are shot at 24/25fps gets totally overlooked.

In which case, the choice is 720p/25 or 1080p/25 (carried psf), and here the 720 system is at an undeniable disadvantage. Which is why I understand many channels are choosing the 1080 approach - they can be 1080p(psf)/25 for drama material, or 1080i for such as sport.

But hopefully the future is 1080p, with framerates from 24 to 60Hz as appropiate, and both interlace AND 720 can be consigned to history.

I do not agree at all. watching a 24p movie on a 1080i channel is still 1080i which means the same reduction in detail I listed above. Sure maybe 720p 30p has a disadvantage to 1080i 60i but you are talking similar framerates. If framerates are the same then the same exact rules I gave above apply.

What about ABC? They are 720p and they have a lot of primetime drama shows. Ugly Betty, Pushing Daisies, Grey's Anatomy, Desperate House Wives, Brothers and Sisters and many other examples of highend 24p productions. Again not very many people complain about how those shows look and in fact they are some very popular shows. FOX has a lot of 24p based drama shows as well and some of those shows are very popular. I have never heard of anybody knocking the quality of any of those channels.

So why is 720 25p or 24p at a disadvantage? If it has the same framerate and the same lack of artifacts compared to 1080i 25p then I am sorry but I don't see how that is the case. 25p sitting inside of 50i still has to have a certain level of filtering and bad HDTV's will still bob the heck out of it. HDCAM, DVCPROHD and HDV cameras still shoot it at 1440x1080 pixels that are filtered so you only gain a small edge of detail. 1440 is not that was larger then 1280 and filtered 1080 isn't that much sharper then 720p. The same rules I gave for consistancy also apply to 25p or 24p. No matter what the image will look the same and what you see is what you get.

Of course it doesn't. Normal, un-supersampled slow mo (supersampling induces blur anyway) asks for deinterlacing first. Leaving 720p50 at 50fps, but making 1080i50 into 540p25. Slowed down that gives respectively 25 and 12,5 fps.

Depends on the receiver. Good ones should make use of the psf flag and resurrect the true p image, and keep the full resolution etc. Cheaper ones may not do such a good job, but at least the potential is there.
My comparison here was 720p/25 to 1080psf/25, and yes, they are the same framerates. The ones applicable to drama, films etc if not sport.
I can only say we are at the beginning of broadcast HDTV, and in the UK only one broadcaster is providing a general service, though that's likely to change next year. Most of the sets that have been available so far have had resolutions typically around the 1360x768 mark, but that is now changing rapidly with 1920x1080 fast becoming the norm.

Together with better electronics inside the sets, the bar is being raised, and the potential differences between 720p/25 and 1080psf/25 are increasingly likely to be evident to the viewer.
Resolution. 1280x720 pixels versus 1920x1080. Otherwise both the same - both 25fps, both progressive, but 1080p(psf)/25 potentially much sharper - dependent on receiver. And it's only now with 1920x1080 displays becoming the norm that it's really beginning to matter.

For the same reason 1080p/50 would be far superior to 720p/50, but the former is too much for most current technology. The same isn't true of 1080p(psf)/25.

Quite true. So it's waiting for a camcorder/system to come out with 1920x1080, 1080p50... A JVC HD400 or something? the GY-HD7000 perhaps? The Pana HPX3000 with AVC-intra is there, but still quite expensive.

Aren't we a little off topic?

Could we split to a thread of 1080 vs 720 because the argument of whether 1080 is worth it over 720 can be interesting.

Personally I'd prefer less compression and less resolution. Even SD on a 42" screen looks fine to me, as long as the compression is mild. In a perfect world, I'd go for 1080 every time, but it does require compromises elsewhere. I heard that testing with your average layman showed preference of 720p50 over 1080i50.

Agreed. Gentlemen, you have drifted off topic a bit.

Mike, your comment about SD looking good on a 42" looking good brings up another point that is often overlooked.

The PAL system has enjoyed superior vertical resolution to the NTSC system and I often hear Europeans comment that HD isn't that much better. I can see why. But in the world of NTSC with only 480 visible lines of resolution, the difference in SD to HD is quite apparent.

-gb-

It all depends on the screen size and viewing distance. 42" and smaller at a decent viewing distance 480p will still look very good. In fact a lot of consumers think they are watching HD when they watch a 480p DVD on their HDTV's. I bought my parents a 32" HDTV and when sitting on their couch 480p DVD's look just as good as HD channels. Of course the closer I get the more that changes but bumping up to 720p gives that little extra boost for when you are really close.

Resolution is not the only factor in quality.

How did we get in this debate anyway? I thought we were talking about shooting 720p with two different cameras?