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Backfocus Question

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Matt Orfalea
Backfocus Question
on May 14, 2014 at 10:08:32 pm

I'm using a Sony EX-1 with up to date firmware.

And have my iris all the way open at f 1.9 (w shutterspeed on @ 1/125) No ND filters

My lens is all the way wide (infinity)

And the background goes out of focus.

I have fixed my back focus many times (following sony's own steps)

But the background remains out of focus with my iris all the way open. Is this a result of the iris being all the way open or a result of poor back focus (ie the backfocusing I'm doing is not really working)?

Thanks in advance!

Matt
http://www.youtube.com/orf


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Todd Terry
Re: Backfocus Question
on May 14, 2014 at 10:27:57 pm
Last Edited By Todd Terry on May 14, 2014 at 10:29:03 pm

One question, you say the background is out of focus... but do you mean that your foreground subject is still correctly in sharp focus?

If so, sounds like your camera is behaving perfectly normally... as it should be, and as you would want it to.

With the lens wide open like that your depth of field is at its very shallowest. So if the point that the camera is actually focusing on is sharp, it's doing what it is supposed to. If you want a deeper depth of field, you'll need to shoot with a higher f-stop.

If indeed both the background (and foreground) and your focal point are all soft, then yes you likely have a backfocus issue.



And not that you asked, but assuming you are shooting something with motion (which you may or may not be) and assuming you are wanting natural and normal-looking motion (which you might not) and assuming you are not shooting a higher-than-usual fps... why are you shooting with a 1/125th shutter speed? That's way high, and will give you that annoying strobby staccato "narrow shutter" look if you have any motion going on.

I realize I'm butting in and mentioning something that you didn't ask about (and something that has nothing to do with backfocus or DoF), and you probably are using that high shutter speed for a specific reason.... but I just had to ask.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Matt Orfalea
Re: Backfocus Question
on May 14, 2014 at 11:06:21 pm

My foreground subject (10 ft away) is also soft. The further a subject goes in the background the more soft it gets. So it sounds like a backfocus problem. BUT when I lower the shutterspeed and close the iris, focus is crisp. So is it back focus prob or just iris? I'm still not sure.

my frame rate is 24p

The video has a lot of firing water pistols and I didn't want those bursts of water to be blurry so I thought an increased shutter speed would help. Is my thinking right?

Thanks in advance!

Matt
http://www.youtube.com/orf


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Todd Terry
Re: Backfocus Question
on May 15, 2014 at 1:42:16 am

Hmmm... sounds like you do indeed have a backfocus problem then. If you keep adjusting it but the settings don't "stick," then sounds like some camera service might be in order.



[Matt Orfalea] " I didn't want those bursts of water to be blurry so I thought an increased shutter speed would help."

Well, yes and no. This gets slightly complicated. Yes, indeed the higher shutter speed will make the water bursts less blurry... if that's what you really want (which it might be).

Unless there are special circumstances, usually a "normal" shutter speed is desirable... normal being the equivalent of a 180° shutter in a film camera. Translating to the video world the math is easy... "one over twice the frame rate." Ergo, when shooting 24fps, a "normal" shutter would be 1/48th of a second.

Some people might think "won't such a slow shutter speed make motion blurry?" Yep... and that's the whole idea. Your brain needs that motion blur in order to interpret that series of still photos as smooth motion. If you shoot with a higher shutter speed, the motion gets very choppy and staccato because each frame is sharp and your eyes/brain gets no motion blur to make everything look smooth. A higher shutter than that will give that "narrow shutter" look that some cinematographers use to purposely make action movies look more "actiony." It's a very slippery slope though and must be done judiciously. See "Saving Private Ryan" to see it used very carefully and to good effect. See "Gladiator" or a zillion other action movies to see it waaaaaaay overdone to the point of annoyance.

So... if you want that choppy strobby look (which might indeed be desired, depending on what aesthetic look you are going for), then yes your 1/125th shutter (or even higher) is the way to go. If however you want things to look smooth with much more natural fluid motion, then stick to something closer to 1/48th.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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