View Full Version : Strobing video


Kevin Herrin
December 21st, 2005, 08:34 AM
Hi all, like a lot of you I just started using the 100 and the pictures are great.

My problem is with "strobing" video. I just shot a bunch of interviews, the camera is locked down and when the guest is moving thier hands and heads it appears to strobe. I don't understand it! The camera is set at 720p30 with motion smooth on.

I am viewing this on a sony ntsc monitor, not sure if the progressive signal looks strange on an interlaced screen?? I just don't know. But I am afraid that I have a bunch of bad video. From reading the posts it seems that there are several issues with this camera, wondering if anyone else has experienced this.
Thanks
Kevin

side note: what is SSE stand for?
later

Manny Rodriguez
December 21st, 2005, 09:43 AM
what was your shutter running at? also try using component out to you monitors for best results. motion smooth is best used on fast action shots, sports etc. but it may have been your shutter

Greg Corke
December 21st, 2005, 10:28 AM
hi Kevin,

By strobing do you mean a kind of drag effect? I shot some footage today that had evidence of drag thought it might be down to the low light conditions. I did not have motion smooth on however.

Manny seems to think it may be shutter in which case what should our shutter speeds be a) for kevin 30p and b) for me 24p.

Thanks guys

Oh also do you guys know if it is okay to keep my idx 7s on my camera while i have it plugged into mains power?

Thanks again, Greg.

Andy Graham
December 21st, 2005, 11:49 AM
Hi guys,
The standard shutter speed when shooting 24p is 1/48th and when shooting 30p it is 1/60th so if during your interview Kevin the shutter was at say 1/30th you would get the strobing effect. with progressive cameras you will always get a bit of motion judder (shouldn't be much of a problem if the subject isn't moving and the camera is locked off though) when fast moving objects pass the lens i've found i have to be alot more carefull when composing and shooting a scene i.e keep the camera moving with the subject. As for the IDX question Gregg i don't have the battery solution for my camera yet so i don't know if it will damage it but i personaly remove the battery when plugged into the mains. Hope this helps.

Andy.

P.S Kevin SSE stands for split screen effect.

Kevin Herrin
December 21st, 2005, 11:57 AM
I guess that might be it. I thought that I was shooting at 1/60 but I know a few times I went to 1/30. The strange thing is that I didn't notice it on lcd camera monitor. I will do some testing to verify this. Thanks for the input. I did put some footage into FCP and it looks fine, the judder is diminished.
Thanks
Kevin

Shannon Rawls
December 21st, 2005, 12:09 PM
The strange thing is that I didn't notice it on lcd camera monitor. Kevin

Yes, I heard that this camera does not show you an example of what you're shooting in the on camera viewfiender or the montior. It seems to show you that the video is always smooth, even if you accidentally have the camera at strobby speeds that's being recorded to tape.

is this true? if so...that's not cool, and should be fixed.


*edit* I found where I read it: http://forums.creativecow.net/cgi-bin/new_read_post.cgi?forumid=162&postid=858694
2nd to last paragraph.

It's a simple fix. Just make sure the camera is set correctly each time before hitting the record button. Then you won't find out later after you get home that you ruined your footage.

- ShannonRawls.com

Manny Rodriguez
December 21st, 2005, 12:12 PM
Always make sure to overlight a bit, this way you'll have a bit more lead way in setting shutters and F-stops.

Kevin what where your settings in FCP to edit HDV 30/60 fps?

Kevin Herrin
December 21st, 2005, 12:56 PM
Manny,
I captured using the HDV codec and the sequence setup is 720p, square pixels, and the compressor is 720p30. I haven't done any editing yet.

Anyone have any tips for smoothing out the juddered video in post?
Kevin

Manny Rodriguez
December 21st, 2005, 02:17 PM
thanks Kevin, I'll try that, but I hope that FCP gets there codec together soon..

Kevin Herrin
December 21st, 2005, 02:26 PM
No kidding, it is a mess tryiing to capture and put something on a timeline.
Kevin

Tim Dashwood
December 21st, 2005, 03:45 PM
Kevin,

Back to your original questions:

You should have the shutter set to "off" unless you need it to be something other than 1/48, 1/50 or 1/60 (depending on your frame rate it will default to the correct shutter speed when set to "off")

The "live" output of the camera is always "double clocked." So if you are shooting in 720P30, you will actually be seeing 720P60 on the live output. If shooting 720P24, you will see 720P48 on the live output. This can be confusing, but has its advantages.

IMHO, you should never have motion smooth turned on. Frankly, to me, it just reminds me of the XL1's FRAME MODE. You will never have one complete isolated frame. It works by superimposing the image from 2 60fps frame samples and combining them into one 30P frame.

Greg Corke
December 22nd, 2005, 03:58 AM
Hi Guys,

I think my shutter was correct, although I was talking about a kind of lag as i move the camera. Is this the same as strobing or is this something different e.g I did not notice it on other test footage so i'm wondering if it is down to the low light. Additionaly can any of you guys give me some guidance on how to use a light meter with camera as I don't understand what film speed to dial in or is it done differently with digi?

Thanks again, Greg.

P.S. can anyone recommend a good light meter to use with this camera?

Marc Colemont
December 22nd, 2005, 05:09 AM
I use the HDV-rack software to see exactly what's been recorded through firewire to my laptop. You see what will be recorded on tape.
Together with the waveform/vector scope and harddisk recording possibility from the software, this is the perfect tool for me to carry with me.

Steve Mullen
December 22nd, 2005, 07:40 AM
Kevin, It works by superimposing the image from 2 60fps frame samples and combining them into one 30P frame.

Actually looking carefully at stills -- it is more sophisticated. It uses a 3-point smoothing filter.

The output frame is a mix of the current frame at 50% plus the previous frame at 100% and the final frame of the last pair of frames at 50%.

Each of these frames has its own bit of motion blur. So you can see three not two images. One -- the middle in time -- is quite solid. There is one faint leading image and one faint trailing image.

While I agree that experienced filmmakers will want the filter OFF -- the filter should be ON for those doing ENG shooting as it eliminates "foreground strobing" from 30p. This makes it much like shooting 720p60. However, it's possible that with very low motion scenes -- a camera pan -- the filter could create a lagging blur.

Good tip to just leave the shutter at it's default.

Steve Mullen
December 22nd, 2005, 07:51 AM
Hi Guys,

I think my shutter was correct, although I was talking about a kind of lag as i move the camera. Is this the same as strobing or is this something different e.g I did not notice it on other test footage so i'm wondering if it is down to the low light. Additionaly can any of you guys give me some guidance on how to use a light meter with camera as I don't understand what film speed to dial in or is it done differently with digi?

The motion filter could cause LAGGING BLUR -- see my description of how it works -- and if so, then I'd have say you should turn off the filter when there will be very little motion.

Try an ASA of 200 at your selected shutter-speed. Please let us know how this works for you! An Incident meter measures the light while a Reflective measues the illuminated scene. Many, Gossen for example, have a little white dome that slides into place to get an Incident reading. Tim is the one to really answer the pros/cons of each. The cheapest you can find should be fine!

Greg Corke
December 22nd, 2005, 09:26 AM
Hi Steve,

Thanks for the input. I have some more questions but I'm going to consult the old book of knowledge first as I imagine a lot of the answers to my questions are going to be in there. Give me a couple of days to get my head round it. Truth is I'm being a bit lazy posting questions when I haven't exhausted my other resources. Anyway, until then amigos.

Regards, Greg.

Kevin Herrin
December 26th, 2005, 08:53 AM
Good tip to just leave the shutter at it's default.
Are you saying the default shutter is off?
Thanks for the info
Kevin