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Old May 28th, 2016, 07:37 PM   #1
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Shutter speed 2x frame rate golden rule!

Abstract: Using the Sony FDR-AX100 consumer camcorder and recording 4k video, 30p frame-rate at 100mbps, under overcast to full sunlight conditions no visible differences were observed - the footage was viewed on a 27 inch 4k monitor - when the shutter speed was varied between 60th up to a 3000th of a second, exposure being kept constant by deploying the built in ND filters as required and gain locked at 0.

Under the conditions of the experiment which included various levels of subject motion - passing motor vehicles, water splashes and ocean waves of various sizes - it appears that the old shutter speed 2x frame rate golden rule does not apply.
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Old May 30th, 2016, 07:24 AM   #2
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Re: Shutter speed 2x frame rate golden rule!

John,

Could you give a little more explanation about why you say the "old shutter speed 2x frame rate golden rule" doesn't apply?

I'm not sure to what it doesn't apply. I always thought that it was not a rule, but a guideline. Different shutter speeds are useful for different effects and, on every camera I've ever used including the AX100, the effects are very different.

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Old May 30th, 2016, 12:46 PM   #3
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Re: Shutter speed 2x frame rate golden rule!

He is most likely referring to locking the shutter to correspond twice to the frame rate which in most cases produces less shudder/ shimmering and interline Twitter plus helps SOMEWHAT when panning.

24p. 1/48 shutter

30p. 1/60 shutter

60p. 1/120 shutter
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Old May 30th, 2016, 01:24 PM   #4
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Re: Shutter speed 2x frame rate golden rule!

Thanks, Lou., I understand that part, but I was a little unsure about why he said it "does not apply."
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Old May 30th, 2016, 03:53 PM   #5
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Re: Shutter speed 2x frame rate golden rule!

Rule or guideline; some say one - others say the other. I'm easy.

The reason I wrote 'does not apply' is because under the various conditions of the test I did not observe any differences when the shutter speed was changed; the range being between 60th and 3000th, all else being kept constant. I did not observe any 'different effects' whatsoever. To use other words shutter speed variations between a 60th and a 3000th did not produce any different effects under the conditions of the test.

I didn't pan or zoom while rolling, I seldom do, other than when following a moving target.

If one does a search on the Internet we learn that shutter speed variations do produce various effects. That is one of the first rule/guidelines I learned many years ago when I first picked up a movie camera. Many still speak of the 180 degrees setting as being optimal and deviating from that will cause the sky to fall in. Not so, at least with my AX100 set up as described.

And this begs the question why not just go with the built in ND filters and lock in shutter speed? The AX100 is capable of shooting very reasonable 20 megapixel photographs. One press on the very conveniently located button above the start/stop record button and one is in photo mode. If, as is usual, I have been shooting 4k 30p video the shutter speed is set to a 60th. Switching to photo mode a shutter speed of a 60th is seldom fast enough and I have been routinely resetting the shutter speed to around a 500th, and removing ND filtration accordingly. While this reset is a bit fiddly the benefits of one cam for video and stills makes this a viable option. During the heat of the battle there were times when I just went ahead and began recording without resetting the shutter speed to a 60th. No harm done.

I have always looked for new gear that has built in ND filters. While I also have a set of screw on ND's and various adapters when in the field setting that up is a bit of a pain therefore built in ND's was high on my list of required features.

I asked a fellow who tests many cams, especially smaller models where built in ND's are rarely possible, about his thoughts regarding using shutter speed to control exposure. He does it all the time with no ill effects, he told me (not his exact words).

Just to be clear I am not saying different effects can not be generated by varying shutter speed. I am saying that under the conditions of the test, which is how I routinely use the AX100, shutter speed variations did not produce a visible difference.

Built in ND filters is about to be removed from my list of important features, on a case-by-case approach, I should add.
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Old May 30th, 2016, 05:27 PM   #6
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Re: Shutter speed 2x frame rate golden rule!

"If one does a search on the Internet" one can learn all sorts of things, not necessarily correct. The 2x frame rate (180 degree) shutter rule is a reasonable rule of thumb - it was never golden. If you shoot with a shutter around 180 degrees, say between 145 and 270, motion blur from action and pans matches most movie film. Over 145 with action you're likely to notice strobing, especially with 24-25-30p video. Doesn't seem to bother a lot of TV footage. Good on you John for doing some experimenting and passing on your results rather than blindly accepting convention.
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Old May 30th, 2016, 05:33 PM   #7
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Re: Shutter speed 2x frame rate golden rule!

Dang - accidentally double posted earlier edit to remove "spurious". John, very sorry - didn't mean to suggest your results were in any way false or misleading, just worthy of further study

Last edited by Rainer Listing; May 31st, 2016 at 05:01 PM.
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Old May 30th, 2016, 08:44 PM   #8
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Re: Shutter speed 2x frame rate golden rule!

Spurious is a big word (rhetorically speaking) therefore I checked Merriam-Webster. We are informed '...the more common meaning is "false" (a sense introduced to spurious in Late Latin).'

Here again, in a nutshell, let me repeat, is the result of the test I conducted:

'...under the conditions of the test...shutter speed variations did not produce a visible difference.'

In what way is the result 'a bit spurious' (false)?

Please understand my reference to 180 degrees was to historically contextualize the test. Please also pardon me for the possible confusion; this test is not about traditional film (celluloid) movie cameras but the Sony FDR-AX100 digital 4k capable consumer camcorder. Shutter degrees is not mentioned in the AX100 online help guide.

I do appreciate your thanks for sharing the results and while I am tempted to bask in your mild praise for not blindly accepting convention I must in all honesty emphasize that was not the driver. As described above this test was driven by error and then pragmatism, that's all. Having said that I do subscribe, tongue in cheek that is, to the maxim attributed to the Postmodernists 'question authority and ignore the answers', but that's a bit off topic :-).
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Old May 31st, 2016, 04:07 AM   #9
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Re: Shutter speed 2x frame rate golden rule!

Shooting stills and video thru the same lens at the same time has been at least for me a holy grail quest and I've tried pulling it off over the years with an HC1, FX7, cx550v, a5100 and ax100
During a recent figureskating competition and using ax100 indoors arena with full spectrum florescent overhead lighting which provide far fewer lumens than sunshine, in fact 12-15 db of gain is often required and using f5.6 - 8 in order to achieve a decent dof to keep the fast moving figureskater in focus it is then a tricky matter to use shuttter speeds faster than 1/60. Of course the shutter needs to be 1/250 to stop motion but there is insufficent light so the iso goes up and the images get grainy. There is also a perceptual loss of colour depth or something which is hard to describe plus and this sounds weird but there's almost a cumulative effect where the video catches up to the frames
as always plenty of light is better than slightly insufficient light.
I find that the ax100 takes forever to write a photo file and doubly long to write a photo file while recording video so extracting 4k stills works for me but does take some time after the fact
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Old May 31st, 2016, 03:25 PM   #10
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Re: Shutter speed 2x frame rate golden rule!

This was discussed at least peripherally in the never ending AX100 thread when the cam first came out.

I initially let the camera run "auto", including shutter speed - the results were horrible, with strobing or "shimmer" on all detail with any motion at all. The "effect" was that of a series of very sharp stills (sort of like a "flip book"), and it was jarring....

Once I started riding the shutter speed and keeping it closer to the FR, I got much more pleasing results, as there was now motion blur to help smooth out the overly sharp "stills". I fiddled with up to around 125 shutter with still decent results, so the "rule" is bendable to SOME degree, depending on one's tolerance for the video becoming "jumpy" or strobing/shimmering.

Of course if one is pulling stills from 4K clips, or shooting stills, motion blur may not be desirable (and higher/faster shutter speeds ARE), so it becomes a balancing act depending on the motion and detail in the scene....

Funny how shooting the latest greatest 4K requires one to go back to the old school fundamentals of photography and cinema shooting guidelines! I actually enjoy shooting more though, as I have to "think" a bit more about what I'm wanting the camera to do, rather than relying on the camera being "smarter" than I am.... it's probably still smarter, but at least I get to tell it what to do to get closer to what I want!
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Old May 31st, 2016, 03:50 PM   #11
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Re: Shutter speed 2x frame rate golden rule!

I get the impression that you and I, Bruce, are not the only ones always on the lookout for the perfect photo and video cam and while the AX100 is the best I have found to date it is far from perfect. For serious wildlife action, like a couple of days ago when I encountered a flock of Australiasian Gannets feeding, diving from 20 to 30 meters, then the AX100 just doesn't cut it and I reach for the Sony A6000 with a Sony FE 70-200mm F4 G OSS lens attached. That certainly did the trick.

I also find the photo mode on the AX100 slowish however when the amount of gear I can bring along is limited and the daylight is plentiful, as is usual here, then the AX100 does a half-decent job, especially now that I don't need to fiddle so much with the controls.

Yesterday, high cloud with a weak somewhat insipid sun trying to do its thing, I shot a bunch of clips with the ND filter off, gain locked in at zero, using the shutter to obtain correct exposure with speeds from 200 to 1000th and again absolutely no suggestion of shimmering or interline twitter or any other aberration for that matter in any of the clips.
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Old May 31st, 2016, 05:10 PM   #12
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Re: Shutter speed 2x frame rate golden rule!

Dave, using my AX100 under the conditions described above the rule is not just bendable; it is broken. To use less dramatic language let me say the 'rule' is N/A (non-applicable - does not apply).

I have no idea what I am doing 'wrong' to get such excellent results at such outrageously high shutter speeds (now including a 4000th). Maybe a firmware update or two, but there is no getting around it; what I am seeing on my 4k monitor is nothing but gorgeous looking-out-an-open-window seascapes and landscapes we know the AX100 is capable of delivering. And not the faintest suggestion of artifacts of any kind.

That'll do me!
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Old May 31st, 2016, 06:41 PM   #13
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Re: Shutter speed 2x frame rate golden rule!

daylight and lots of it is helping your shooting senario forsure
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Old May 31st, 2016, 07:17 PM   #14
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Re: Shutter speed 2x frame rate golden rule!

All my shoots are in the theatre. All cameras set at 1/60 shooting 60P on the AX100, AX53, NX30U and 60i of course on my now aging NX5U. For shows I even take stills, in post, from any of the 60P cameras and they are not bad !! I think the real issue with the "rule" was for slow frame/sample rates as any camera movement could cause artifacts like judder. Once you move to 60P camera movement is less of an issue and mainly goes away.One can then choose shutter speed for artistic reasons. Do you want blur or pin sharp image. If it is too sharp and high resolution one may need to go to an even higher frame rate too. We shall see what happens with 8K and HDR I expect a higher frame rate.

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Old May 31st, 2016, 08:47 PM   #15
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Re: Shutter speed 2x frame rate golden rule!

There's a definitel interaction between frame rate, shutter speed, and so on, along with the patterns and action in what you're shooting. Plus whether you want motion blur or super sharp individual frames. Lo resolution won't "cover up" any mistakes when you go to 4K!

I'd prefer to have 4K/60p, but for now 30p is what is available at an economic price both for format and for memory cards. It probably doesn't help that my big screen 4K display/playback is also 30Hz... but again, it is what it is for the price, and it still looks stunning.

If higher shutter speeds are working OK for you, that's good, I was just taken off guard at the shimmer I saw when I let the camera run the shutter speeds up. Now I'd push the ND filter into play to try to keep the shutter speed down, it's convenient with the AX100! The early problems were pretty much "out of the box" before I had time to figure out the camera, once past the learning curve it's been an outstanding camera that I don't think you can beat for the $$.


I'm sure you're aware of the RX10M3... aside from probably having to get external ND filters (dumb thing to leave that built in ND feature off, Sony!!), that may turn out to be the "best" dual mode camera... I've already been using the RX10 and the RX10M2 for my video purposes.... Still have the AX100 for what it does well, but the RX has been good to me... For multicam events, the AX100 and RX's are complementary for the most part, and all amazing cameras image wise.

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