Choosing a shutter speed - wedding-specific considerations

[Elliot Lee]

Hi all,

I've got a somewhat complex question that seems to have relevance to the video quality of wedding videos in particular - please bear with me.

As part of the process of gearing up to shoot a wedding in a couple of months, I got Final Cut Studio 2 installed today and ran some test footage through its "Smoothcam" optical flow feature. The footage was 1080/24F footage (i.e. pretty much 1080p/23.97), shot on my XH-A1 with a 1/48 shutter speed (trying to emulate "that cine look" :-)

One thing I noticed about the Smoothcam'd footage was how even though the Smoothcam filter took care of the jerkiness very well, the motion blur from the original jerkiness still is very noticeable. It's my guess that this type of problem would also be noticeable in slow-motion footage and any other shots where spatial resolution is especially important.

You can see my example clip at
http://www.jadebug.com/files/misc/smoothcam-blur.mov
(Quicktime H.264, 14M). The problem is most noticeable in the white area at the top end of the walkway - you can see every time a step lands, it blurs badly, even though Smoothcam has taken the actual shaking away.

Although I'm planning on shooting the upcoming wedding in 30p instead of 24p (which will help a little bit with slow-mo), getting sharp slow-motion footage is an important consideration for me, especially when I intend to overuse it as much as other inexperienced wedding videographers :) I also don't think the increase from 1/48 to 1/60 shutter speed will make a huge difference in really getting rid of the blur.

Any pointers on choosing the right shutter speed to balance the needs of special effects (smoothcam, slow-mo), capturing enough light without bumping up the gain, and getting good motion blur? The questions running through my mind are ones like:

1. If I record at a higher shutter speed to get good slow-mo & Smoothcam results, will adding the motion blur in post give pleasing results on the "cinematic motion blur" front?

2. For objects that are moving at people-speed (i.e. no pictures of revolving bicycle wheels here, just people waving), how relevant are the possible problems of strobing that come from using shutter speeds that are not multiple of the frames-per-second (e.g. in 30fps video, 1/60, 1/120, and 1/250 are the multiples that supposedly avoid strobing)? If motion blur in post will work, it'd be nice to be able to use as high a shutter speed as possible, even if it's not one of these multiples.

3. What other tips do you have on getting high-quality footage for slow-motion without overcranking, or setting exposure in general in the hectic environment of a live event?

Thanks,
-- Elliot

[Patrick Moreau]

Hi there,

I have the A1 as well and have found the best slow-motion footage to come from, by far, shooting in 60i at 1/60th. When I shoot in 24P, I don't notice much of a difference in slow motion as I change the shutter speeds as none of them compare to 60i. The best slow-motion in 24P I have gotten was done by doing my cam movements as slow as possible and slowing to 70% in post. Beyond that, even motion blur didn't seem to give the slow-mo a smooth look.

In regards to your questions about smoothcam, I would suggest concentrating on shooting stable footage and skipping that step all together. If you have longer clips, you would have to export and reimport to FCP to avoid it analyzing the whole clip and taking forever. In the end you lose much more time and quality as opposed to shooting the material right. As a last resort, when using smoothcam, I think the blurriness is standard and unavoidable as the shaky frames are often blurry themselves.

Here is a trash the dress video shot in 24P with an A1 and an HVX. Nothing compares to the overcranking of the HVX, but you can see some slo-mo from the A1 when she is in the fountain.


http://stillmotionblog.com/?p=128

Patrick

[Vito DeFilippo]

I would agree with Patrick in general. Smoothcam is no substitute for shooting stable footage from the get go. Use it to fix the odd shot when you have no alternative, but not as a general workflow choice. You will never get rid of the motion blur. And you lose resolution when the effect zooms in to fill the frame (necessary when stabilizing).

As for shutter speeds, you are agonizing over details that serve no purpose in the quick pace of a wedding day. If you know you will use lots of slow motion in your final video, stick to 60i. You'll get the best results. You're not going to think, "oh boy, I see people waving, should I switch frame rate and shutter speeds?"

You can use faster shutter speeds for a different look. When shooting fountains, for example, a faster shutter will let you see the individual drops in slow motion. Think the fight scenes in "Gladiator. But slowed down, it's not better than a standard shutter slowed down, it's just different."

[Elliot Lee]

Thanks for the replies guys... I admire the work I've seen both of you put out.

I agree that it's best to get it right whenever capturing whenever possible, which is why I'm working on things like smooth camera movement. In reality, though, I'm going to goof a few times, so I want to get my "insurance policy" in place. :)

I also agree that constantly switching shutter speeds is not feasible. However, some questions remain:
. If I go with a higher shutter speed, will adding motion blur in post-production give acceptable results?
. What are the problems with choosing odd shutter speeds that are not multiples of the fps?

Best,
-- Elliot

[Vito DeFilippo]

Hi Elliot

Originally Posted by Elliot Lee

. If I go with a higher shutter speed, will adding motion blur in post-production give acceptable results?

I'm not sure what you are getting at here. What would be the point of using a high shutter speed, then adding blur? Why not stick to the lower shutter speed and get the natural blur that comes with it?

What are the problems with choosing odd shutter speeds that are not multiples of the fps?

Makes no difference. You may be confusing the advice that some give to choose easily divisible fractions of the fps when using slow motion. That is, if shooting 30fps, then 15, or 10fps could make better slow mo than 13 or 17fps.

To be honest, however, I don't see any difference when I do slow mo in AVID Xpress whatever frame rate I choose. It renders slow mo very well. I don't know if it's a factor with Final Cut. Patrick may know, cause he uses it.

Though you know, half an hour of testing with short clips would give you the answer to your questions...

Cheers,
Vito

[Elliot Lee]

Vito asked "I'm not sure what you are getting at here. What would be the point of using a high shutter speed, then adding blur?"

The benefit would be the option of using the resulting footage for either crisper slow-motion output, or motion-blurred regular-speed output. Postponing that decision into post-production has value.

It does sound like there's no big consensus on the shutter speeds and I just need to get up and test it out. :)

Thanks for all the wisdom,
-- Elliot

[Vito DeFilippo]

Originally Posted by Elliot Lee

The benefit would be the option of using the resulting footage for either crisper slow-motion output, or motion-blurred regular-speed output. Postponing that decision into post-production has value.

Aha! I see your point now.

I suppose that depending on your location as the day progresses, you could shoot some high speed shutter material, then decide what you want to do with it in the video.

I do that already, but it never occurred to me that I might want to make the high shutter speed material look like it had been shot like the rest. The decision to use a high shutter has always been very specific, so I have zero experience with adding blur to such footage to change the look in post.

Have fun with your tests. Let us know what you find out if you have a moment.

Cheers,
Vito