# What is the role of aperture in video recording?



## blabus (Nov 5, 2010)

So I just recently bought a NEX-5, and since they don't currently offer a f/1.8 E-mount lens for it, I bought the LA-EA1 lens adapter and the Sony A-mount 35mm f/1.8. So far I'm absolutely loving the photos I'm getting with it, the only downside being that I have to focus manually (they did release an updated firmware that adds autofocusing, but it's so slow as to be unusable). I'm getting fairly good at focusing after practicing a bit, so that's not a concern.

However, where I am having some trouble is with video- the lens will not autofocus at all with video, and trying to focus manually while recording has proven difficult- a lot of the video you can clearly see me hunting for the focus and things go blurry and sharp constantly.

So, I'm thinking about buying an E-mount lens to use for video recording. My question is, what effect does the aperture have on video recording/quality? For example, I shoot video right now with my f/1.8 wide open, and I love the shallow depth of field and low-light performance. Does the f/2.8 on the E-mount do as well in low-light for video? I sort of had the notion that aperture is more important with still photos, when the blades are snapping open and closed very fast, as opposed to when they're constantly open for video- but is that correct?

Basically my question is, would the E-mount f/2.8 be close to the video performance of my f/1.8? And what about the 18-55 zoom? Would that be similar in quality under low-light or no? Given the choice between low-light capability or zoom capability, I'd prefer low-light, but if the f/2.8 and zoom are similar enough, obviously I'd then opt for the zoom capability.

Thanks for any help!


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## Garbz (Nov 5, 2010)

But are they always open? Aperture serves the same purpose in video as film. As a controller of light through the lens.


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## blabus (Nov 6, 2010)

Garbz said:


> But are they always open? Aperture serves the same purpose in video as film. As a controller of light through the lens.



Well I believe in a digital camera they are open constantly, at least to a specified size obviously based on the set aperture. I assume the individual photos that make up the frames of the video are generated digitally by the sensor, not with a physical actuation of the aperture and other components as when you take a still photograph. Otherwise you'd have a good bit of loud noise hearing the aperture open and close 30 times a second.


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## chito beach (Nov 6, 2010)

blabus said:


> Garbz said:
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> 
> > But are they always open? Aperture serves the same purpose in video as film. As a controller of light through the lens.
> ...




In the Sony nex and A33 and A55 you have full manual control

that being said I would leave the ISO on auto as well as other functions.  Most video cameras dont come close to a 1.8 lens but more in the 4.0 range, Ive shot HD video with the my 2.8 Tokina without issue.  The only time the lens speed is really relevant in the video mode is under very poor lighting conditions or after dark.


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## blabus (Nov 6, 2010)

chito beach said:


> In the Sony nex and A33 and A55 you have full manual control
> 
> that being said I would leave the ISO on auto as well as other functions.  Most video cameras dont come close to a 1.8 lens but more in the 4.0 range, Ive shot HD video with the my 2.8 Tokina without issue.  The only time the lens speed is really relevant in the video mode is under very poor lighting conditions or after dark.



Yeah that's sort of what I was thinking. So in moderate to low light would you see much of a difference between f/2.8 on the prime and f/3.5 on the wide end of the zoom? I'm thinking maybe I should just get the zoom if there's not a whole lot of difference there, cause the zoom would be pretty convenient.


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## chito beach (Nov 6, 2010)

blabus said:


> chito beach said:
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> > In the Sony nex and A33 and A55 you have full manual control
> ...



the zoom can be a godsend when video taping


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## KmH (Nov 6, 2010)

blabus said:


> Garbz said:
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> > But are they always open? Aperture serves the same purpose in video as film. As a controller of light through the lens.
> ...


Actually, top-of-the-line DSLR's open and close the aperture at the same frame rate the camera is operating:


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## chito beach (Nov 6, 2010)

KmH said:


> blabus said:
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> > Garbz said:
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the NEX  shoots at 30FPS


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## KmH (Nov 6, 2010)

chito beach said:


> KmH said:
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> > blabus said:
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Yes! Well, that is the video fps, and irrelevant to my post which was about what I have highlighted above.


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## chito beach (Nov 6, 2010)

KmH said:


> chito beach said:
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> > KmH said:
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Ah well yes then why post it in a video thread??


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## blabus (Nov 6, 2010)

Yeah, that video is in reference to when you're using the continuous shooting mode for still photos. I don't know of any camera that has a continuous mode of 30 fps.  Although even at 11 that's still impressive that that much mechanical action is performed so rapidly.


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## chito beach (Nov 6, 2010)

blabus said:


> Yeah, that video is in reference to when you're using the continuous shooting mode for still photos. I don't know of any camera that has a continuous mode of 30 fps.  Although even at 11 that's still impressive that that much mechanical action is performed so rapidly.



Mine only shoots at 10 FPS at Fine Jpeg :mrgreen:


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