Focus Tracking GH4 with NA-GH4 Manta Ray Nusa Penida

Hi all..

Sorry to make a new subject regarding Focus Tracking on GH4, but I think my situation is a bit different.

A bit of background: I'm fairly new for video. I'm using GH4 on nauticam housing with Pana 7-14 and Nauticam glass dome. No zoom or focus gear just yet, so I've set the lens at 7mm and focus set on auto (AFS/AFF).

I though I got it nailed, the Manta was coming toward me and the sun ray was just perfect. But after checking the clip on bigger screen I found that the focus was just jumping around. Especially if there were smaller fish came between me and the Manta.

Any suggestion what should I do next in this kind of scenario?

1. Manual focus with added focus gear and peaking?

2. Or keep in auto but with what setting?

3. Any other suggestion?

The following is the clip -> https://youtu.be/r9fAHRIUTco

Also any other comments/critics regarding the clip not related to the focus are always welcome!

Thanks in advance!

Bona

With what you have at present,try using the backbutton set to Autofocus Lock. Set aperture to 8 or a larger number to get greater depth of field. Frame the subject, with the cross hairs on it. Press autofocus lock.

Set your focus switch to AFS. Set the AF/AE lock button in the menus to lock focus. Set to one-area focus and make the box fairly big in the centre of the display. Aim at something roughly the range of your subject, or a bit closer. If there's no reef etc. there then aim at your fin. Press the AF/AE lock button to lock the focus on that subject. Then most of what you shoot should then be in focus, but you can re-focus again later in the dive if you're filming stuff that is closer or further away. After setting the focus that way you can also switch to manual focus, which should keep the same focal distance. Switch peaking on. Then you can either fine tune the focus manually with the focus knob, or you can move the camera to keep the subject within the focus range indicated by the peaking.

The other alternative is to start in manual focus mode and lock focus with the AF/AE lock button. I currently prefer the first way though as I can make the focus box smaller, which is better for some situations such as focusing on an eye.

Don't be scared of going to a larger aperture than F8 rather than increasing the ISO or slowing the shutter. With that lens/port you should still get a reasonable depth of field. Test it!

Thanks Nick and recd..

Still learning with the GH4, I'm moving from the RX100M2 and there are lots to learn and so little time to test it! As a matter of fact I just returned from the dive trip and just found about this "jumping focus" when I saw the result in my mac at home and my next dive trip still months away

I'll make sure I use smaller aperture (bigger number) next time to get more depth of field. Hopefully I still can get enough shutter speed or ISO to be able to capture the sun ray.

As to Auto Focus I learnt that the GH4 will switch to the closest subject it can focus, I think I can try to make the focus box much bigger next time but it will not smart enough to know which subject I want to focus correct?

Regards,

Bona

The AFS/AFC switch on the back of the camera does not work (as you would think) in Creative Movie Mode.

Selecting AFS or AFC has no bearing on it continuously autofocusing while recording.

The option you need to deselect is within the Motion Picture menu and is called 'Continuous AF'

What I normally do, is use the AE/AF Lock button and set the AF switch to MF. Before shooting point camera at something 1-1.5m away and hit the AE/AF Lock button to focus on it. Then with a small aperture of f5.6 or greater you have almost everything in focus (due to hyper focal distance)

Hi Richard,

Thanks, yes that'll work. With f5.6 and smaller top side with GH4 the hyperfocal is about 80 cm. I guess underwater all object in 1-1.5m and further should be in focus.

And with the "Continuous AF" deselected the camera will not switch focus to say some fish that incidentally swim between you and the object at closer distance of the hyperfocal.

Regards,

Bona

What I normally do, is use the AE/AF Lock button and set the AF switch to MF. Before shooting point camera at something 1-1.5m away and hit the AE/AF Lock button to focus on it. Then with a small aperture of f5.6 or greater you have almost everything in focus (due to hyper focal distance)

One more thing, I can't use the AE/AF Lock to focus when I switched to MF. But it work when switched to AFS/AFF. Am I missing something here?

Thanks in advance!

Bona,

Program the AE/AF button to "AF-On". If you use MF, it doesn't matter if "Continuous ON" is off or not because the camera will never do AF by itself. I leave my "Continuous ON" on the whole time as it's useful for closeup subject.

Moses

Bona,

 

Program the AE/AF button to "AF-On". If you use MF, it doesn't matter if "Continuous ON" is off or not because the camera will never do AF by itself. I leave my "Continuous ON" on the whole time as it's useful for closeup subject.

 

Moses

Ah.. Got it!

Thanks Moses..

I think "Continuous ON" will be helpful for closeup subject but for wide angle shoot disable it make more sense, right?

Bona

Can someone please confirm this, in case I'm spreading misinformation.

In manual focus, with 1-area set as the AF mode, the smallest focus box you can get (in preparation for doing a temporary autofocus with the "AF/AE lock" button) is this, and you can't move it to the edges of the display:

However in AFS mode, you can get a focus box this small, and not limited to the centre part of the display.

Right?

 

Right?

Yup.. Tried it just now. Both the size of the focus box and its coverage area. In AFS the focus box can be made smaller and cover the entire display area.

Ok, it's getting a bit more complex now. I'm using LX100, but the concept should be the same. I only use my GH4 on land. Anyway, for wide angle, turning OFF "Continuous AF" should be the way to go. In another discussion, there is this talk about setting to F5.6, then focus something in within 2ft using AFS and leave it there, so essentially relying on the hyperfocus distance of the lens to hope that anything beyond 2ft will be in focus. I'm not fully understand the "hyperfocus distance" concept. Personally I haven't tried this as I haven't come across any real opportunity for wide angle shot with big creature. I did swim by coral and school of fish, and I have been using manual focus with the AF-On to set initial focus, and so far it works for me.

 

Ah.. Got it!

 

Thanks Moses..

 

I think "Continuous ON" will be helpful for closeup subject but for wide angle shoot disable it make more sense, right?

 

Bona

I'm not fully understand the "hyperfocus distance" concept. Personally I haven't tried this as I haven't come across any real opportunity for wide angle shot with big creature. I did swim by coral and school of fish, and I have been using manual focus with the AF-On to set initial focus, and so far it works for me.

 

CMIIW.. But I think what you mean is "hyperfocal distance". Is basically a point at certain distance from the camera where from that point to infinity will be in focus.

I'm using this iPhone app "DoFViewer" where you can calculate the Hyperfocal Distance based on sensor size (camera type/model), focal length of the lens and your aperture setting.

So for example if you use 8mm lens on GH4 at f/4 you will get a Hyperfocal Distance of 1.07 m. That means from 1.07 m from the camera to infinity is in focus. Bear in mind this is for topside photography not underwater. I assume for UW the Hyperfocal Distance will be closer but please don't quote me on that.

Hope that helps.

With extreme wide angles lenses, hyperfocal distance ranges 1/3 in front and 2/3 behind the focal point. At f8 and smaller, focus on your fin and you'll lose focus only when the fish kisses your port. Divers way in the distance may be a bit soft, but viewers will discount that. On the GH4, that holds true for the 8mm fisheye and the 7-14mm rectilinear lenses.

With extreme wide angles lenses, hyperfocal distance ranges 1/3 in front and 2/3 behind the focal point. At f8 and smaller, focus on your fin and you'll lose focus only when the fish kisses your port. Divers way in the distance may be a bit soft, but viewers will discount that. On the GH4, that holds true for the 8mm fisheye and the 7-14mm rectilinear lenses.