Question about the Nano Flash and my EX1
 

I will be doing nature/wilderness related shooting with my EX1. One thing I've noticed about my EX1 is that even when I do a very slow pan on a dolly, such as using a deep DOF including foreground grasses/flowers and scenic background, as soon as I move the camera it loses sharpness on the foreground objects. I've done a lot of practice footage with my EX1 but I'm new to videography and have never seen how other codex renders motion like this... is it just "video" in general, or is it the Long GOP codex? If it's Long GOP, will using the Nano Flash completely eliminate this issue? Does it matter if I shoot Long GOP or I-Frame, or is the less compression the main factor so either would be fine? Thank you!

Hi Buck-

It's difficult to determine if this is caused by the camera sensor or the compression. The best test is to view the live video out the HD-SDI port and see if the problem is still present. This live view will eliminate any CODEC issues as the video is taken directly off the CMOS sensors. Ideally, if you can capture this uncompressed stream, you can examine on a frame by frame basis.

If it looks good in uncompressed form, then it will likely look good captured at 100 Mbps using the XDR/nano box, as this high data-rate works well even with lots of motion (in our experience).

Hi Buck, in addition to Mike's comments about the codec, be sure and check your shutter settings. First, is your EX1 shutter set to "off"? If so, this can effectively double the blurring you see in any motion scenario, as the shutter duration is the maximum possible for your frame rate (i.e. 1/24th sec for 24fps, 1/30th sec for 30fps).

For "normal" motion blurring you want 1/48th sec for 24fps; 1/60th sec for 30fps.

Regards,

Jim Arthurs

Buck,

I am wondering the same myself.

I don't have an EX-1, but this is a known issue with the EX-1 compression, and higher bitrates might help.

But and I-frame setting would solve the issue as each frame gets processed like you are shooting a still.

I noticed some of this during the olympic coverage this summer.

I don't know what exact cameras or codec was being used, but when the camera moved, everything got a bit soft until the camera stopped, then everything got sharp again.

This is with slight movements, not fast, beat the shutter speed type of movements.

Panasonic provided more than 100 HD cameras (HPX3000, HPX2000)
Sony had 78 cameras (28 PDW-700s, 42 HDC-1400s, HDC3300 (slo-mo cameras), 4 PMW-EX1s)
Thompson Grass Valley provided 550 cameras (LDK 8000 Mk2, LDK-6000, LDK-8300 super-slomo,


Codec were: DVCProHD, XDCam HD, XDCam EX, JPEG2000 (TGV)

So, if you saw motion breakup, you were seeing it with some of the best hardware money can currently buy right now.

Source: HDVideoPro October 2008, pp. 46-51

Dear Tim,

How were you watching the Olympic coverage?

For example, was it via cable or live over the air HD broadcast?

The cameras could have been perfect, but by the time you saw it, it could have been highly compressed for transmission to your television.

I was watching over DirecTV HD on a Panasonic 1080p Plasma.

The area where I noticed the out of focus on movement was during the gymnastic coverage.

For example, when gymnasts were stationary waiting for there results, a camera often on a steadicam would move over to them.

When the camera was in motion or even if there was a slight adjustment, the frame would go a bit soft.

When the motion stopped, a definite return to clarity happened.

I may be wrong, but I thought Sony equipment was being used in the gymnastic coverage and Panasonic was used in the swimming/diving and anchor desk.

I think I saw Sony looking camera bodies in the gymnastic area.

Anyway, the Panasonic folks say this is a big drawback of the EX-1 family of cameras as the codec needs a lot of bandwidth to not eat away at the scene.

Not rip on any camera, but I did notice this exact effect during the olympic coverage.

The bitrate in the EX1 is fixed, however, the compression rate is variable. How can this be, a curious mind may ask? The long GOP compression uses whatever level of compression it needs to meet the 35mbps rate. When the cam is held still and motion within frame is small, practically the entire 35mbps rate is available for GOP's . When you pan the camera and the frames see "drastic" motion, a lot "I" frames are needed and more of the bandwidth used for GOP compression is used for I frames. The result you see is a slight blurring of the image. not blocks or pixelation, but blur...looks a lot like motion blur.

Caveat: My use of the IGOP nomenclature is metaphoric. It's the best way I can describe how the Sony HQ codec works.

Thank you for the comments/suggestions. I haven't messed with the shutter, not even sure if it's on or off, so I'll have to play around with various scenarios and combinations to see if I can solve the issue. If the Nano Flash will solve it, they've got my moolah right here and now. But admittedly I don't wouldn't know a bit rate if it came up and bit me. I learned photography on my own shooting gazillions of rolls of film, and it's paid me well once I figured it out. With video I guess I better actually crank open some manuals and learn this stuff, it's a lot more techy than stills. I could eventually learn on my own like I did with photography, but by then all this new gear I've bought will be outdated, so I need to expedite my learning curve with studying. But all this video tech stuff is like learning an el foreign-o language-o to me-o.

Buck, if I remember right, the camera ships with the shutter on/off switch in "off". Check the front of the camera, below the lens for the location of the switch. Turn it on, verify in the menu that the shutter is appropriate for your frame rate as outlined in my previous post and compare the results.

Regards,

Jim Arthurs

Gracias, Jim, I will do that for sure!

Okay, I tried various settings (and my shutter is on). I tried 1080/60i/30p/24p and 720/60p/30p at the default shutter speed (such as 60 for 30p, etc.) and I tried 1080/30p at a faster shutter speed (250).

I used a row of books on a bookshelf as my test and slowly horizontally panned slowly across the book spines. The motion breaks up the sharpness noticeably. The best in my unscientific test was 720/60p, but it still wasn't good. Once I stop the camera everything is razor sharp... once I slowly pan it immediately loses sharpness. I viewed this on my 30" Apple Cinema Display... I haven't had time to determine if it's the monitor refresh rate and maybe the motion would stay sharp after going to blu-ray or whatever, but I'm not confident about that.

Are there any plans soon to test "motion" with the Nano Flash? Just basically doing a quick and simple EX1 pan with and without the Nano Flash (or XDR)? Motion on static subjects is my only concern here. I'm happy with the color and sharpness of stills (or even following a moving subject), but the visions I have in my mind of what I want to create on video defintely requires sharp rendering of motion on static foreground scenes. El periodo.

I dont think codec
 

has much to do with what your referring to here, sure you get codec breakup etc, but any pan will smooth things out so I'm not sure why your looking for sharp detail under these circumstances? you can up the shutter speed quite high to improve this.
Or maybe I'm just missing the whole jist of what's being discussed here? Which as Perrone said the bit rate won't help change this fact.

Sorry if I've missed it??

Adam

OK, I'll say this as simply as I can. What you're seeing is n-o-r-m-a-l for 35mbps encoding with the EX1. Maybe going to a higher bitrate(like 100mbps), will help this out. At least, I'm hoping so, but since I don't have my nanoflash yet, I don't know for sure. Since the EX1 is limited to 35mbps in HQ mode, recording on nanoflash via the HD-SDI port is one way to get higher bitrate recording. Shutter speed won't help this, frame rate or format will help only to the extent that certain frame rate and format settings (like 720p24) ease the compression crunch. But then again, panning in 24fps has other issues. What would help the most is to stop panning.

Hey Doc, it only hurts when I laugh.

see this post:http://www.dvinfo.net/conf/convergen...ke-schell.html

I think the main thrust of this thread is wondering if a higher bitrate will diminish or take this effect away.

But the nice thing about the Flash XDR is that it also has an I-Frame option which will definately take this away.

Which is what I will be using for shots with a lot of motion or panning etc...