Recording Format Opinions

[Gary Griffiths]

I know there probably isn't an answer to the question "What's the best recording format to use with the NX5U?", or at least the answer would have to be something like "depends on what you're doing". But I thought I'd try to solicit a few opinions, and see if there are any strong arguments one way or the other on the multitude on format combinations available on the NXCAM. I edit on FCP 7, and have just been leaving the camera on the default HD 1080/60i FX setting. I do event video and some talking head type web commercials, so I deliver DVD and web. I've never been a fan of interlace, but I've been working with it so long I'm used to it.

So how 'bout it - What's the best recording format for the NX5U?

Thanks for your opinion,
Gary

[Felix van Oost]

I'd say go progressive. Either 1080p/30 or 720p/60 would be a good choice for most situations.

[Perrone Ford]

Originally Posted by Gary Griffiths

I know there probably isn't an answer to the question "What's the best recording format to use with the NX5U?", or at least the answer would have to be something like "depends on what you're doing". But I thought I'd try to solicit a few opinions, and see if there are any strong arguments one way or the other on the multitude on format combinations available on the NXCAM. I edit on FCP 7, and have just been leaving the camera on the default HD 1080/60i FX setting. I do event video and some talking head type web commercials, so I deliver DVD and web. I've never been a fan of interlace, but I've been working with it so long I'm used to it.

So how 'bout it - What's the best recording format for the NX5U?

Thanks for your opinion,
Gary

Well, considering "the web" doesn't display interlaced video, I'd say that's an obvious incorrect choice for delivery to that medium.

However, 60i has some advantages for event video. It should be a full stop brighter than progressive, and it will certainly impart a more "video" or "TV" look to your footage if that's what you're after.

So choose accordingly.

[Joe Goldsberry]

If you're shooting for the web, progressive is definitely the best way to go. Computer and mobile devices are all progressive displays. Also if you shoot at 24p your file size will be smaller, better for web delivery.

Joe

[Adam Gold]

Originally Posted by Perrone Ford

...60i has some advantages for event video. It should be a full stop brighter than progressive...

Really? Can that be right? Everything I've ever heard says 30p would give you a full stop more than 60i, as you could use 1/30th rather than 1/60th. Glad to be corrected, but are you sure?

[Perrone Ford]

Originally Posted by Adam Gold

Really? Can that be right? Everything I've ever heard says 30p would give you a full stop more than 60i, as you could use 1/30th rather than 1/60th. Glad to be corrected, but are you sure?

Well two things...

I am COMPETELY unsure why you'd use 1/30th on 30p footage. I don't normally use a 360 degree shutter. I use a 180 degree shutter which would put me a 1/60 for 30p (and 60i since are both drawing the same frame over the same period of time).

And the sensitivity increase I should caveat by saying that's how it works on MY camera. Other cameras may well be different.

[Gary Griffiths]

Hey, thanks for the responses. It's great to get different perspectives. I would prefer to shoot progressive, but I want to make sure there aren't any issues I'm not aware of. I've never heard that interlace could be brighter. That's the kinda stuff looking for. I'll definitely have to test that.

[Adam Gold]

Originally Posted by Perrone Ford

Well two things...

I am COMPLETELY unsure why you'd use 1/30th on 30p footage. I don't normally use a 360 degree shutter. I use a 180 degree shutter which would put me a 1/60 for 30p (and 60i since are both drawing the same frame over the same period of time).

And the sensitivity increase I should caveat by saying that's how it works on MY camera. Other cameras may well be different.

Okay, still confused. I was just talking about the defaults, not a creative choice. At 60i my Z5s default to 1/60th and at 30p they default to 1/30th. And while 30p and 60i are drawing the same total frame over the same time period, they don't take each individual picture the same way; 60i is, as you know, 60 separate pictures per second at half res, not 30 pictures each split into two fields.

But my question remains, even if you're using 1/60th for both 60i and 30p -- as I would -- how could 60i give you a "brighter" picture?

[Perrone Ford]

Originally Posted by Adam Gold

Okay, still confused. I was just talking about the defaults, not a creative choice. At 60i my Z5s default to 1/60th and at 30p they default to 1/30th. And while 30p and 60i are drawing the same total frame over the same time period, they don't take each individual picture the same way; 60i is, as you know, 60 separate pictures per second at half res, not 30 pictures each split into two fields.

Hmm, ok. My camera doesn't default that way, but I don't have an NX5. I think you can set up the EX1's to do that, but when you set a 180 degree shutter, it properly adjusts the shutter speed regardless of the format you select.

Originally Posted by Adam Gold

But my question remains, even if you're using 1/60th for both 60i and 30p -- as I would -- how could 60i give you a "brighter" picture?

It's called dual-row summation. Google that.

See the heading "Sensitivity" here: ProVideo Coalition.com: Camera Log by Adam Wilt | Founder | Pro Cameras, HDV Camera, HD Camera, Sony, Panasonic, JVC, RED, Video Camera Reviews

[Adam Gold]

Okay, thanks for the links -- I'll check them out.

But note that if you are using 1/60th in 60i, then you are not in fact simulating a 180 degree shutter at all -- you are in fact shooting with the equivalent of a 360 degree shutter. Unless you've found a way to defeat the time-space continuum.

Edit: interestingly the Google search of dual-row summation returned only links to the article referenced above, which doesn't explain what it is or how it works. There were a couple of other relevant hits, which lead to forums that link to the same article, but contain posts from users who say that there isn't really any increased sensitivity. Finally, this all seems to be exclusive to the EX1, so possibly not generalizable to the NX5. Granted, my comments pertain to the Z5, which also isn't an NX5, but it's a lot closer and I think reflects the behavior of most cams in this class.

Not trying to be argumentative but really want to understand this; when revolutionary counter-intuitive claims are made, I really like to understand what's behind them.

[Perrone Ford]

Originally Posted by Adam Gold

But note that if you are using 1/60th in 60i, then you are not in fact simulating a 180 degree shutter at all -- you are in fact shooting with the equivalent of a 360 degree shutter. Unless you've found a way to defeat the time-space continuum.

Not according to the EX1. I just took it out to check. When set to 1080/60i and set to a 180angle shutter, if I change over to shutter speed it shows 1/60. As I would expect it to.

At 60i the camera is still drawing the equivalent of a 30p frame, it's just doing it in two passes. Therefore, I wouldn't expect the shutter speed to be set any differently.

Assuming your way, if you set your camera to record a scene with fixed lighting, then setting it to 60i with a 1/30 shutter and 30p with a 1/60 shutter should show the same exposure values. Take out your camera and see if this holds.

[Perrone Ford]

Originally Posted by Adam Gold

Edit: interestingly the Google search of dual-row summation returned only links to the article referenced above, which doesn't explain what it is or how it works. There were a couple of other relevant hits, which lead to forums that link to the same article, but contain posts from users who say that there isn't really any increased sensitivity. Finally, this all seems to be exclusive to the EX1, so possibly not generalizable to the NX5. Granted, my comments pertain to the Z5, which also isn't an NX5, but it's a lot closer and I think reflects the behavior of most cams in this class.

Not trying to be argumentative but really want to understand this; when revolutionary counter-intuitive claims are made, I really like to understand what's behind them.

Well, I will tell you this. When I change my camera from 1080/30p in a setting with low light, to 1080/60i in the same setting, I can watch the histogram change drastically. Even with the shutter setting remaining exactly where it was, and the iris untouched. I've done exactly the same with my DVX100 and gotten the same result. Try it for yourself.

My understanding of what is happening, is that when shooting interlaced footage, the light gathered by the camera only has to excite half the number of photosites. Or alternately, two adjacent photosites can be summed, since the camera is only drawing half the picture each time. This would in effect, allow for an image to be twice as bright. Clearly this is an oversimplification, but my experience and that of other shooters seems to bear it out. As does my histogram, and my light meter.

[Adam Gold]

I'm just not following your math. If you take 60 different pictures a second -- albeit at half res -- then 1/60th is by definition a 360 degree shutter. If your cam doesn't show this then the display is wrong, but it doesn't change the physics.

And your last line doesn't make any sense to me at all, but obviously that's just me. The values are the same no matter what the frame rate. 30p at 1/30th causes the iris to close down one stop compared to 60i at 1/60th; at 1/60th for both, all the other values are identical as well. I can't imagine a scenario where 60i with 1/30th is even possible unless there's a buffer in the cam that could write the same picture to two consecutive fields -- the exposure time is double the amount of time each "field" is in front of the lens, to carry the film analogy further. But tweaking the shutter speed as you direct results in the iris stopping down as well, so they're not the same.

Actual Data on one of my Z5s looking out the window: With gain fixed at -3, 1/60th, regardless of 60i or 30p, reads iris as f4. At 1/30th, iris is f5.6, again at both 60i and 30p settings.

I'm obviously missing something, and I'm sorry I dragged this OT. I just feel bad for the poor guy who started this all off with a simple i vs p question. Let's just agree that our cams behave differently and leave it at that.

EDIT: Thanks for the explanation in your last post above. That was my initial guess but I couldn't possibly articulate it as well as you did. Appreciate it, and interesting info to know, even though it appears to apply to only some cams. I still stand in awe of your knowledge and experience, and always look forward to learning something new from you. This'll teach me to check the boards on a weekend when I should be editing....

[Perrone Ford]

Originally Posted by Adam Gold

I'm just not following your math. If you take 60 different pictures a second -- albeit at half res -- then 1/60th is by definition a 360 degree shutter. If your cam doesn't show this then the display is wrong, but it doesn't change the physics.

The problem is that you aren't taking 60 pictures per second. You're taking 60 *half* pictures per second. Those 60 half pictures add up to 30 whole pictures. This is why 60i and 30p share the same shutter speed for equivalent exposure.

Originally Posted by Adam Gold

And your last line doesn't make any sense to me at all, but obviously that's just me. The values are the same no matter what the frame rate. 30p at 1/30th causes the iris to close down one stop compared to 60i at 1/60th; at 1/60th for both, all the other values are identical as well. I can't imagine a scenario where 60i with 1/30th is even possible unless there's a buffer in the cam that could write the same picture to two consecutive fields -- the exposure time is double the amount of time each "field" is in front of the lens, to carry the film analogy further. But tweaking the shutter speed as you direct results in the iris stopping down as well, so they're not the same.

I don't understand what you're saying here, because the iris moves independently of either shutter or frame rate. The thing is, in a video camera (unlike film) the entire sensor is exposed to light for the entire duration of time the "shutter" is open. How that get's written or used is simply different when progressive scanning or interlaced scanning is selected. What happens when you shoot 720p in your camera. Does the camera merely shut off the extra photosites? Or does the camera read the entire sensor just as it did before and simply interpolate what it needs based on what you asked for?

Originally Posted by Adam Gold

Actual Data on one of my Z5s looking out the window: With gain fixed at -3, 1/60th, regardless of 60i or 30p, reads iris as f4. At 1/30th, iris is f5.6, again at both 60i and 30p settings.

So you have your iris set to auto. Ok. so changing your shutter speed by a stop registers a full stop in iris change. That's normal and expected. It also indicates that your camera is not doing dual-row summation. And that may well be unique to EX cameras. What is interesting here, is this information based on your earlier statements. You just shot 60i at 1/30th which you started off telling me I couldn't do. Your words:

"I can't imagine a scenario where 60i with 1/30th is even possible..."

Not only is it possible, but you just did it and got the expected results. 60i is equivalent to 30p in terms of exposure ASSUMING there is no dual row summation happening at the sensor. Therefore, 30p with a 1/30th shutter = a 360 shutter, and 60i with a 1/30th shutter = 360 degree shutter.

Originally Posted by Adam Gold

I'm obviously missing something, and I'm sorry I dragged this OT. I just feel bad for the poor guy who started this all off with a simple i vs p question. Let's just agree that our cams behave differently and leave it at that.

EDIT: Thanks for the explanation in your last post above. That was my initial guess but I couldn't possibly articulate it as well as you did. Appreciate is, and interesting info to know, even though it appears to only some cams.

I think this is an important topic to discuss, and I'm quite glad we went down this road.

[Adam Gold]

I agree it's an important topic, but not here, and right now my head hurts and I need to take a nap...

It's interesting to us but possibly no one else, and at this point we are merely debating semantics. Yes, you are in fact taking 60 separate and distinct pictures per second in 60i, regardless of resolution, taken at 60 different points in time, and completely unrelated to one another. They are only half pictures compared to how sharp they appear when blended, but they are in fact 60 unique images.

And anyone who owns a Sony knows that just because the LCD says something doesn't mean it's true. Sure, you could take a picture at 1/30th of a second and have the cams split the single pic into two fields and technically end up with 1/30th at 60i, but it isn't really 60i. You can't fit a quart of milk into a pint jar, no matter how much you think you can. You need two pint jars to do it. So we're possibly saying the same thing. But by duplicating the same image onto two fields (albeit with alternating scan lines) you are essentially using a "720 degree" shutter, because your theoretical exposure is twice as long as your field interval.

But I trust you and it's good to get a lesson on how the EX1 works. Very valuable if I ever upgrade.

Okay, now I'm going to go take a nap...