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The Frame Rate Dilemma

frame rate shutter speed neutral density filter film look 25 fps overexposed

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#1 Arrigo Verderosa

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Posted 24 March 2013 - 06:31 AM

Hi guys,

 

so I'm going to shoot a movie for university, and I want to use 25 fps, in order to give the famous "film-look" to the image... my problem is that in some shots I'd like to obtain a depth of field as shallow as possible. 

 

So here's my dilemma: they say when you're shooting in 25 fps, the maximum quality of image results in using 50 shutter speed (fps * 2); but if I use 50 shutter speed, then the aperture would be affected: and as you know, in order to obtain a shallow depth of field you should have the aperture all the way open, which in my case, with 50 shutter speed, could result sometime in having an overexposed image. My question is: if I got a good Neutral density filter, a better one than the camera already has, could I succeed in darken the image while using 50 sp and the aperture all the way open? 

 

Other tips and recommendations are very well accepted, thank you all for your time and effort in answering my question. 


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#2 Chris Millar

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Posted 24 March 2013 - 08:25 AM

Short answer:

Yes
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#3 Arrigo Verderosa

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Posted 24 March 2013 - 09:54 AM

Short answer:

Yes

 

thanks for your comment


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#4 Stuart Brereton

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Posted 24 March 2013 - 04:25 PM

Shooting at 50fps will result in slow motion when played back at 25fps, which it will be in the PAL world. 

 

If the only reason for shooting at 50fps is to be able to open up another stop on the lens, then ND filters are a far more sensible solution.


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#5 Chris Millar

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Posted 24 March 2013 - 04:37 PM

I think he's referring to a 1/50sec exposure via a 180deg shutter (at 25fps)
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#6 Arrigo Verderosa

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Posted 24 March 2013 - 08:23 PM

Shooting at 50fps will result in slow motion when played back at 25fps, which it will be in the PAL world. 

 

If the only reason for shooting at 50fps is to be able to open up another stop on the lens, then ND filters are a far more sensible solution.

 

Thanks for your comment... but as Chris Millar very punctually remarked, with "50" I wanted to mean the shutter speed, not the fps... the fps I want to keep it stable at 25... any recommendation you can give from you personal experience will be really appreciated


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#7 Adrian Sierkowski

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Posted 24 March 2013 - 10:18 PM

You would just ND the lens; simple as that. If you're say, at a F8 and you want to be at an F4 then you're put on a ND.6.

With digital, however, if you want to go waayyy down, and start throwing on NDs, you need to make sure you get NDIR filters to kill the IR pollution that a digital sensor will pick up. This really only applies when you start putting on ND1.2s and higher, but your mileage will vary depending on how sensitive your specific camera is to IR pollution.


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#8 Igor Trajkovski

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Posted 25 March 2013 - 09:26 AM

On the topic of IR polution when using strong ND filters
you can watch the informative video from ABELCINE EXPO:

ABELCINE EXPO: Filters for Digital Cinema

It practicaly demonstrates the IR polution and which filter brand

works best for witch of the popular s35 single chip cameras.

 

Best

 

Igor


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#9 Stuart Brereton

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Posted 25 March 2013 - 04:08 PM

I think he's referring to a 1/50sec exposure via a 180deg shutter (at 25fps)

 

Ah. Yeah, you're probably right.

 

This question should really be in the beginners section.


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#10 Arrigo Verderosa

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Posted 01 April 2013 - 09:43 AM

Shooting at 50fps will result in slow motion when played back at 25fps, which it will be in the PAL world. 

 

If the only reason for shooting at 50fps is to be able to open up another stop on the lens, then ND filters are a far more sensible solution.

 

thank you very much for your comment


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#11 Arrigo Verderosa

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Posted 01 April 2013 - 09:45 AM

Ah. Yeah, you're probably right.

 

This question should really be in the beginners section.

 

Thank you very much for your comment Stuart. As you rightly pointed out, I am a beginner, but in this particular case I just wanted to semplify the matter, so I didn't really pay attention about "1/50" or "50"... considering that english is not my native language, I always have to keep in mind lots of things to make myself clear... your remark was really appreciated though, and thank to you I won't make the same mistake again. Thanks


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