Frames per second
 

In tv, av or manual modes fps rate can be manipulated, but I'm not sure of the pros and cons.

Someone (Don DesJardin, I think) once said that shooting bird-flight at 50fps (rather than the usual 25fps) allows the application in post of duration lengthening (slo-mo) without the result being too jagged (especially if the background is moving). That has made sense and worked out well the few times I tried it.

Question: If my XM2 (GL2) was on a sturdy tripod (& the IS turned off) would I get better image quality from using 50fps or higher fps? Any comments on the upside and downsides of increasing/decreasing fps very welcome, please? I'm trying to optimize the quality of footage I get when a rare opportunity presents itself.

Hi Brendan,

As far as I understand the higher the frame rate the better for slow motion. Ideally if you were making a film with a reasonable budget you would have access (hire or purchase) to a high speed camera that can fire up to 2000 fps.

Given that these cameras are an expensive luxury, we have to find ways of creating relatively decent slow motion footage on the cheap. If you want the best possible slow motion you need to shoot in 'progressive scan' and use specialist software such as 'After Effects' or 'Realviz Retimer' to create the extra frames for you.

Progressive scan is better because the footage is a series of still frames (like film), where as interlaced (normal video mode) is a series of 50 frames that mix together to get one frame (50i = 25fps).

I use Premiere for editing - but it is rubbish at slow motion, to add the extra frames it just blurrs the images to create those extra frames. So I use Vegas for slow motion - because Vegas will actually interpret the existing images to create the additional images - I believe it's called interpolation. Using this method you get a much smoother, less blurry slow motion.

I then import this footage into Premiere for editing with the rest of the project.

So if your GL2 can shoot progressive at 25fps (pal) then this is the best for creating slow motion. If it only shoots interlaced then you can de-interlace in your edit suite prior to adding the slow motion effect - just make sure that you use software that uses interpolation to figure out the extra frames (like vegas).

Lastly, there are some hardware solutions from Canopus & Matrox that say their hardware encoders can do realtime slow motion - but I haven't any experience of these.

Hope this helps

Cheers
Pete

www.petermcmurdie.co.uk

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Brendan, back in 2004 I was asking for almost the same as your are, view the thread here:
http://www.dvinfo.net/conf/showthrea...ght=slowmotion

Some of the new camcorders today have something called variable frame rate. Most of them goes from 4-60 fps. I have not tried any of them yet but as I'm told, when using 60 fps, slowing them down in post to 25 fps gives you some nice slowmotion.

Is it this you are asking for Brendan?

Thank you Pete. Your advice makes sense.
I can't find progressive scan on GL2 so I'm not sure of my options other than using 50fps or higher. And now I am confusing fps with shutter speeds; are they different and if so how do they differ? Fast shutter speeds must need better light. Do faster fps also need better light? Have you ever used higher shutter speeds and with what results?


Per Johan, thank you
Back in 2004 in response to your question Rob Lohman said ...

I would shoot at interlaced with a high as shutter speed as you
can (given the light), this should give you the least amount of
motion blur and the highest resolution both temporal (ie 50
samples per second instead of 25).

... This answer seems to make sense to me. I'm sure your XLH1 is much more sophisticated than the equipment of 2004 (& so is the software for post). But apart from that, given that my XM2 is now old-fashioned, would you say Rob's advice would answer my question? Or what would you suggest for slowmotion?

My original objective remains, as above ...

I'm trying to optimize the quality of footage I get when a rare opportunity presents itself. I suppose I must face the fact that it's not easy to optimize my footage when my cam does not have interchangeable lens, progressive scan or HD. But all suggestions are welcome.

Hi Brendan,

As far as I'm aware the XM2 can only shoot 25 frames per second - This is equal to 50i ( i for interlaced) - they are the same thing. when shooting in interlaced - 2 interlaced fields make up 1 frame i.e. 50i = 25fps. It's confusing I know - why camera manufacturers have suddenly started specifying cameras like this is anybodies guess. It's probably because the newer HDV cams can shoot in so many different modes i.e. 25p 50i 720p 1080i 24p etc. (and that's just the pal models).

Shutter speed is something different - but can be helpful for slow motion - a faster (higher number) shutter speed will give you a clearer image per frame and generally speaking is better for slow motion - and yes you will need better lighting conditions and will probably need to adjust your exposure settings, but that shouldn't be a problem as long as it isn't really dark.

But, here's the trade off - if you set your shutter speed to say 500 and you are shooting a deer walking - the footage may look a bit kind of jumpy or edgy (sometimes you can shoot like this on purpose to get an edgy look), slower shutter speeds will be more fluid and smooth in the transition between frames (really slow shutter speeds will blur the footage i.e. 6 or 12).

The best thing you can do is run some tests - have a play with high and low shutter speeds for normal filming and see the affects. Film (not shoot tehe) the cat with a high shutter and low and test the slow motion on your NLE - don't forget to de-interlace the clip before applying the slow motion filter. Running these tests will give you an understanding of the affects of shutter speeds and the capabilities of the XM2 and put you in a better position to get the best out of the camera.

I wouldn't even bother with slow motion in Premiere - it really is rubbish - but as I said before Vegas does a decent job.

Hope I have explained this ok - if I haven't please feel free to ask for a better explanation.

All the best
Pete

Brendan, yep I think your getting confused between the two. FPS is set on 'most' video cameras, 25fps PAL 30fps NTSC. Some Panasonics have the variable frame are Per mentioned. Kevin Railsback is a big aficionado of 60 FPS....his slow shots are slick indeed, shooting at the 60fps in effect gives you 2xreal slow motion. Shutter speed however does have its part to play in slow mo shooting. The best way to demo this is to go and point your camera at some flowing water, a waterfall is great but a flowing tap will do. Shoot a few seconds at 1/50 and then a few seconds at 1/250. You will see that the 1/50th footage looks smooth while the 1/250th looks sharp and punchy. Its basically because of motion blur and because the speed at which your capturing the image. The shorter the exposure the less blur and if you think about slowing down fast moving footage it will look better with less blur.

I hope this helps and be sure to do that test, you will understand its effect much better I'm sure.

Brendan,

I do mostly bird work as you know.

I do not agree with some of the statements above.

1. Definitely shoot in frame/progressive with your gl2
2. If you shoot interlaced with fast shutter speeds you will assurely get wing flicker. I personally hate this.
3. for the slow mo to resemble that shot with film I have found shooting at 1/60th or 1/100th in frame will allow better straight video and slo mo in most editing programs.
Vegas with interpolation analysises the two frames and makes the frame in the middle. Twixtor does the same from what i have read. this will give you the best slo motion.
4. Premiere will be fine provided you do not stretch the frames to far as what they do is actually makes duplicate frames.

5. I thought the new sony cam corder that allows 240 frames per second would be the majic answer, but in discussion with those that have them they say the quality is not up to standard, what a shame!!!

6. have you looked into twixtor??
My goal is to actually make the footage closer to how my eyes would perceive it. Wings that move fast appear smooth because of the blur in the movements.

try this: set your camera to 1/1000 of a second shutter speed, shoot in interlaced and see how it looks.
Try 1/60th in frame and shoot under the same conditions.

See which one you like.

It is to late tonight but tomarrow I will post some goose footage fhot at 1/60 in progressive on an xl2 and some in 1/60th in frame on the gl2. See if you like it and tell me what you think.

Hi Dale

I'm new here and have spent a good few evenings reading various threads, and this one particularly caught my eye.

I took my new Canon XH A1 for it's first outing this weekend to the Wildfowl Trust reserve at Martin Mere , UK, to film the geese and swans. I'm well pleased with the results - considering the blustery winds - except for one thing. All of the in-flight shots are ruined by the birds apparently having two or three pairs of wings. Is this what you mean by wing flicker?

I was told a few years ago when I found the same thing on my XM2 that I should increase the shutter speed. Increasing the shutter speed on the XH A1 doesn't make any difference so I assume it is an interlacing problem.

You wrote that you would post some geese footage shot in progressive and interlaced modes, and I wondered if you had done this and where.

I probably won't get a chance to repeat shots of large birds in flight until February (if I am lucky) so I'm trying to learn before I forget and not leave the questions til the last minute as I usually do.

I'm trying to learn the same thing Annie. Welcome to the forum.

Your question is well put and answers from Dale, Per Johan, Peter, Mat, Don DesJardin and any one else would help me too. I'm still at XM2 level but I was hoping XHA1 & XLH1 had higher video shutter speeds to offer ...

Brendan,
I didn't say frames per second, it was the shutter speed at 1/50th of a second. With your XM 2, I don't think it's possible to change the frame rate.

Thank you Don, once again. I am a slow learner but this time I'm dragging it out in public. In fact my opening statement in this thread ...

<<< In tv, av or manual modes fps rate can be manipulated, but I'm not sure of the pros and cons >>>

..... is false. It's my shutter speed that can be manipulated.

Now will someone please tell me that a faster shutter speed will or will not facilitate a smoother slow-motion in post-production? Please forgive me if you have already answered this question.

Hi Brendan

Shutter speeds on the XH A1 go up to at least 1/1000 sec. It's a lot easier to choose a shutter speed (compared with the XM2) because you don't have to go through the menus to do it - in tv mode, you just turn a dial. You don't necessarily need very high light levels to get a faster shutter speed, it's a matter of balancing the aperture and shutter speed for the light conditions. Going for high shutter speeds may mean rather low apertures and therefore less depth of field/focus.

You're making that distinction at just the right time for me, Annie, thank you.
At least I understand it perfectly now. The next trick is to incorporate it into my working bible so that I remember it just before I need it ... perhaps a checklist is the way to go ... how do you cope with complexity?

Thirty years of stills photography means I know the theory, though it doesn't mean I remember to apply it! Like I don't always remember to check that the front lens is clear of dust (usually find out too late when shooting into the sun). Or to check the white balance, or to recharge the batteries! Guess I need a check-list too.