Comments on: Izzy Video 139 – How to Focus an HD Camera

By: Marco

Marco — Mon, 04 Jan 2010 12:12:19 +0000

Hi Izzy, I am from Brazil and I am a new IzzyVideo member. Thank you for you videos. I am leraning a lot! I have a question about focus in a HD camcorder. Can you help me? I have a Sony Z7U HD Camcorder. When I shot one person in a “medium shot” (haf body) I can get e very good a sharp (detailed) focus, but when a I shot a “full shot” (full body) the face of the person get blured. Can you help me with this problem?

Thank you!

By: Michael C.

Michael C. — Thu, 17 Sep 2009 23:20:12 +0000

@Gregory:

“Actually changing your f-stop will never change your focus.” — who said that it does? But increasing aperture decreases DOF, and vice versa, it is a fact.

“yes, the bride’s dress may be blown out but her face will be properly exposed and 9 out of 10 times that faces are more important that dresses.” — James is wrong. When you zoom out aperture will not change if it was locked beforehand. When you zoom in aperture may decrease if your lens have variable speed.

By: Jerome T

Jerome T — Thu, 10 Sep 2009 04:50:11 +0000

Thanks for the info Izzy! Now I have to save some money.

Jerome

By: Izzy

Izzy — Mon, 07 Sep 2009 23:22:03 +0000

Hi, Jerome!

Thanks for the kind words. I usually shoot in TV mode with the HV20, but it sort of depends on what I’m trying to do. Sometimes I’ll use the Av mode because I want to control depth of field. But you’re right, usually it’s Tv.

And the second camera is my Sony PMW-EX1. It’s the camera I use to shoot all the tutorials.

I hope that helps!

By: Jerome T

Jerome T — Sun, 06 Sep 2009 14:44:59 +0000

Hi Izzy,
Your videos are great. Two questions. Do you prefer to shot your HV20 in TV mode? Also what was the second camcorder you used towards the end of the tutorial.

Thanks,
Jerome

By: Gregory

Gregory — Wed, 19 Aug 2009 08:07:29 +0000

Actually changing your f-stop will never change your focus. It will only change your depth of field. DOF and focus are entirely different things.
Focus refers to a point on the film plane where all light rays from the subject converge. By zooming in the way you suggest you will always set your lens to that point of convergence (or focus) on your film/sensor plane. If you change your aperture you are merely extended the distance in front of and behind that focus point (i.e. the Depth of Field). The effect is really an optical illusion as these other planes are not truly in focus, they are sharp enough to appear so to the human eye. So technically, a smaller aperture never gives you deeper focus because there can only ever be one point of convergence of the subject, however we say it is deeper focus because our eyes are fooled that those other planes are actually in focus.

@james: yes, the bride’s dress may be blown out but her face will be properly exposed and 9 out of 10 times that faces are more important that dresses. It all depends on the effect you are going for.

By: Michael C.

Michael C. — Wed, 05 Aug 2009 21:37:35 +0000

Gee, you are both right and wrong. Consumer camcorders, as well as many prosumer camcorders, have variable speed. This means, that at the widest lens the largest aperture can have smaller F-number than at the zoomed in lens. The HV20 Izzy used in his example, has speed F1.8-F3.0. This means that the camera can go as wide open as F1.8 at the wide lens, but only to F3.0 at full zoom. If you lock aperture to F1.8 at full wide and then will start zooming in, the camera will “ramp up” aperture, closing down the iris.

BUT: this all is true only for the largest aperture. If you don’t want to use the largest possible aperture, then you can simply stay numerically above the slowest speed and avoid the variable region. Say, if you set aperture to F3.0 or a larger number, then the camera will preserve it whatever you do, no ramping.

Now, where do I get my free membership?

By: james

james — Thu, 23 Jul 2009 21:19:43 +0000

Izzy – I was somewhat surprised at the level yes – it does seem very basic. But given that – setting the exposure the way you describe is bad practice. When you zoom in your maximum aperture is several stops lower than max aperture at the wide angle. I would strongly recommend you set your exposure once you have the framing where you want it.

Think of a bride in a white dress. You zoom in on her face set the exposure. Zoom out and her dress is blown out.

Whoops.

By: Izzy

Izzy — Thu, 23 Jul 2009 17:31:38 +0000

James,

You’re correct. They are basic because the vast majority of my audience consists of beginner to intermediate video people. While I try to throw in more advanced topics here and there, I need to make sure I’m creating content for my audience.

And yes, the tips could be summed up in a few sentences, but that would defeat the purpose of the video. I like to show examples and explain things while I’m doing them. This reduces the likelihood for confusion. There’s a lot to be said for seeing concepts in action.

Your last point is actually wrong if you follow my instructions in the video. You’ll notice that I said to zoom in and then “lock the exposure”. Most consumer video cameras I’ve used have the ability to lock the exposure, and this would prevent the aperture from changing. Of course, if you don’t lock the exposure, then you would be correct.

Even though the tone of your comment is quite abrupt, I assume that your intent was to be helpful, so I’ll thank you for it.

By: james

james — Thu, 23 Jul 2009 15:52:16 +0000

Really those tips for focus are very basic. All the info in this six minute video can be presernted in a couple of sentences.

FYI – when you zoom in and out with a small handicam in indoor lighting you will almost always change the aperture.