GH3 Learning to Love ( or at least Like ) GH3 Focus Tracking...

T

TheDingo

Veteran
...Over the past couple of months I've been a little frustrated when shooting with my GH3 camera. The main issues for me have been:

Moire

Which pops up more often than it ever did with my GH2 camera. It's not as bad as other camera brands, but I guess I was spoiled by the GH2 lack of moire. The GH3 has made me more careful when it comes to watching out for moire creeping into a shot. ( I am hoping that the new Blackmagic Pocket Cine Camera has the GH2 level of moire, but maybe this is wishful thinking )

Focus

I own two beautiful sharp Panasonic zoom lenses ( 12-35mm f/2.8 and 35-100mm f/2.8 ), but neither of these lenses is parfocal so the focus will shift whenever I zoom in or out on my subject. This is fine if I treat these zooms as variable primes, but it's a pain that I can't adjust my framing while shooting by using the zoom controls without losing sharp focus. So I've realized that I am going to have to learn to like ( if not love ) the focus tracking features of the GH3 camera if I want to get the most out of these two excellent zoom lenses. Focus tracking definitely works, but I have to figure out when it's OK to use it.

This also makes me wonder about buying a Canon EF mount camera down the road, as it seems that Canon has the largest number of parfocal DSLR lenses on the market, and I can't afford to buy or rent real PL mount Cine lenses. ( right now an EF mount camera for me would be the Canon C100, the new BlackMagic 4K Production Camera, or the Speed Booster adapter with an EF mount which isn't going to happen for Micro 4/3 cameras this year )
 
I don't want to come across as a savage beast, but what about maintaining deeper focus throughout by stopping down a bit? Your post is very relevant to me, because I have a set of shots I need to do on my project where I will be zooming quite a bit (very slowly); lpowell already explained how there is inherent exposure flicker as you zoom that is inescapable with the GH3 - a major, major bummer; I am hoping to avoid the flicker because the zooms I need are very short and slow, so I'm hoping it won't trigger exposure changes over such a shot length (it's basically every stop or so). The focus issue you mention, I'm hoping to beat by simply increasing the depth of field - I realize it may not be the artistic choice for some, but it might be easier than an AF that hunts.
 
OldCorpse said:
...but what about maintaining deeper focus throughout by stopping down a bit?
Click to expand...

One of the reasons why I was willing to spend $2,800 on two Panasonic zoom lenses was to be able to shoot at f/2.8 and acheive a clean sharp 1080 HD image. If I'm going to stop down to f/4.0 and beyond I could have stayed with the less expensive Panasonic lenses. Keep in mind that f/2.8 on a GH3 is the same as f/5.6 on a Canon 5D Mk3, so f/2.8 is certainly usable DOF with a Micro 4/3 camera.

The GH3 focus-tracking is definitely usable, but I need to figure out when it's a good choice and when I should stick to manual focus. ( I am hesitant to rely on focus-tracking at the moment )

OldCorpse said:
lpowell already explained how there is inherent exposure flicker as you zoom that is inescapable with the GH3 - a major, major bummer
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This is a Panasonic 12-35mm f/2.8 zoom issue, and likely won't happen if you used something like a Tamron 17-50mm f/2.8 non-stabilized zoom. ( my sister owns this lens, so I will have to test it when I get a chance )

OldCorpse said:
The focus issue you mention, I'm hoping to beat by simply increasing the depth of field - I realize it may not be the artistic choice for some, but it might be easier than an AF that hunts.
Click to expand...

In good light with a contrasty subject the GH3's AF doesn't hunt, but this changes in dimmer light. I haven't spent enough time using the camera this way to figure out what works and what doesn't, so I'm being cautious.

...Last week I was shooting a live training assignment, which 4 people at a table and a discussion facilitator, so I was trying to gently zoom in to frame the facilitator and a trainee when they were talking one-on-one, and then pull back to a wider shot when it was a group discussion. This was using the 12-35mm zoom ( the room wasn't huge, so I needed the wider lens ), and it was p*ssing me off that the focus kept shifting as I zoomed. If I knew what I was shooting in advance I would have practiced with the GH3 focus-tracking, because I think it would have completely solved my focus shift problem. ( I can live with a little bit of exposure flicker as long as things remain sharply focused )
 
OK, I slightly misremembered what lpowell said. This is the actual quote:

Lpowell said:
The iris flicker that occurs when you zoom an electronic Panasonic or Olympus lens is due to the camera making a step adjustment to the iris to keep the aperture setting relatively constant as you zoom. The points in the zoom range where these clicks occur vary with each lens, its f-stop setting, and the M/43 camera model you use it with.

With the Olympus 14-35mm f2.0, there is no iris flicker when used on an AF100 at f2.0. At any f-stop above f2.0, there is a single iris click very near the wide end of the zoom range. On the GH2, this single iris click occurs at all aperture settings, near the wide end of the zoom range. The closest the click gets to 14mm is when the aperture is set to f2.0. I don't know whether the GH3 will behave like the GH2.

Just as you did with vintage mechanical zooms, it's best to set focus at the narrow end of the zoom range. As you zoom out to wider focal lengths, the DOF will naturally expand and help keep your subject in focus. Once you set focus at the narrow end, you can freely zoom in and out from either end of the range.
Click to expand...
 
God I hate these modern 'advanced' electronic lenses.

Screw autofocus. Screw having not having an aperture ring. Screw having a focus ring that spins forever with no end and no feel. I feel so detached when I have to fly by wire with these lenses. What crap.
 
TheDingo said:
so I was trying to gently zoom in to frame the facilitator and a trainee when they were talking one-on-one,
Click to expand...

Zooming even on high end video cams looks pretty 70's. On dslr it looks like a mistake. I suggest shooting docu-style; snap zoom to frame and auto focus on the shot you want then hold shot until you want a change of value or angle. Swish pan to next shot, snap zoom and do the same. Zooms are an editors worst nightmare :lipsrseal I'm finding that the GH3 has very good auto focus response even at very low light levels. It surprised me actually. The focus tracking works pretty well in good light with contrasty edges but fails miserably in low light I'm finding. Just my 2 cents.
 
Balagan said:
Zooming even on high end video cams looks pretty 70's.
Click to expand...

This video was shot for corporate training purposes and they generally like subtlety in the final product, so I'm not sure a snap-zoom would be appropriate. If I had time and budget, I would rather have a few cameras going so I could cut back and forth between a wide and close-up shots and not have to bother with the zoom at all.
 
Steve Kahn said:
God I hate these modern 'advanced' electronic lenses.

Screw autofocus. Screw having not having an aperture ring. Screw having a focus ring that spins forever with no end and no feel. I feel so detached when I have to fly by wire with these lenses. What crap.
Click to expand...

I couldn't agree less... I suppose you're still using a rotary dial phone...
 
Never used a rotary phone so wouldn't know how good they are.

Give me the most advanced sensor with the most mechanical optics please.
 
toxotis70 said:
Can you tell us , what fast (f/2.8) parfocal lenses Canon has ?
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Digging around on the web, here is a list of lenses that are supposed to be parfocal. Some of the older lenses went through manufacturing changes over the years, so there is no guarantee that the lens you get will be parfocal, but at least this is a starting point...


Canon Parfocal (EF)

EF 17-35mm f/2.8L USM ( discontinued )
EF 16-35mm f/2.8L USM
EF 17-40mm f/4L USM
EF 20-35mm f/2.8L ( discontinued )
EF 24-70mm f/2.8L USM ( Mark II is not parfocal )
EF 24-105mm f/4L IS ( discontinued )
EF 28-70mm f/2.8L USM ( discontinued )
EF 28-80mm f/2.8-4L USM ( discontinued )
EF 50-200mm f/3.5-4.5 USM ( discontinued )
EF 50-200mm f/3.5-4.5 ( discontinued )
EF 70-200mm f/2.8L USM
EF 70-200mm f/2.8L IS USM
EF 70-200mm f/4L USM
EF 70-200mm f/4L IS USM
EF 70-210mm f/4 ( discontinued )
EF 75-300mm f/4-5.6 IS USM
EF 75-300mm f/4-5.6 III USM
EF 75-300mm f/4-5.6 III
EF 75-300mm f/4-5.6 II USM ( discontinued )
EF 75-300mm f/4-5.6 II ( discontinued )
EF 75-300mm f/4-5.6 USM ( discontinued )
EF 75-300mm f/4-5.6 ( discontinued )
EF 80-200mm f/2.8L ( discontinued )
EF 90-300mm f/4.5-5.6 USM
EF 90-300mm f/4.5-5.6
EF 75-300mm f/4-5.6 IS USM
EF 75-300mm f/4-5.6 III USM
EF 75-300mm f/4-5.6 III
EF 90-300mm f/4.5-5.6 USM
EF 90-300mm f/4.5-5.6
EF 100-300mm f/5.6L ( discontinued )
EF 100-300mm f/5.6 ( discontinued )


Nikon Parfocal

17-35mm f/2.8
24-70mm f/2.8 AF-S
70-200mm f/2.8 VR Mark I ( Mark II is not parfocal )


Olympus Parfocal

11-22mm f/2.8-3.5 ( 4/3 mount )
35-70mm f/4.0 ( OM mount )
75-150mm f/4.0 ( OM mount )
85-250mm f/5.0 ( OM mount )


Panasonic Parfocal

7-14mm f/4.0
14-140mm f/4-5.6
45-175mm f/4.0-5.6


Pentax Parfocal

Pentax M 28-50mm f/3.5-4.5
Pentax M 80-200mm f/4.5 ( push-pull )
Pentax F 100-300mm f/4.5-5.6
Pentax DA 16-45mm f/4.0
Pentax A 35-105mm f/3.5
Pentax FA 24-90mm f/3.5-4.5
Pentax F 28-80mm f/3.5-4.5
Pentax DA 50-200mm f/4-5.6 WR
Pentax F 80-200mm f/4.7-5.6
Pentax FA 100-300mm f/4.5-5.6


Tamron Parfocal

17-50mm f/2.8
28-75mm f/2.8


Tokina Parfocal

11-16mm f/2.8
16-50mm f/2.8


LensRentals.com : Photo Lenses for Video

Doug Chinnery Photography

Ben Edwards

( I also culled bits and pieces from many forum threads that seemed to know what they were talking about )
 
TheDingo said:
This video was shot for corporate training purposes and they generally like subtlety in the final product, so I'm not sure a snap-zoom would be appropriate. If I had time and budget, I would rather have a few cameras going so I could cut back and forth between a wide and close-up shots and not have to bother with the zoom at all.
Click to expand...

I didn't mean to include the snap zoom or swish pan in your edit. I meant its best to get to your next shot quickly and edit out the zooms completely. Cover your reframes, pans and zooms with B-roll, silent reaction shots, process shots, graphics... whatever. Even with one camera rolling you can always ask the "talent" to give you a few pick-ups of them listening or performing some task, after you've covered your principal action. Better to rent a slider, jib or steadicam and do smooth push ins or pulls if you want to do the Orson Welles stuff, or as you said have a second cam covering either one character or a locked-off wide shot. I've edited a number of broadcast documentary shows and zooms are a major PITA for timing. You always cut out the middle anyway.

On another note, I'm finding the GH3 a fantastic camera. Just hope that VK and his gang can hack it soon and find a way to integrate zebras and peaking. The footage coming from this little cam is so much nicer than the 100mbs stuff from the older Panny beasts that cost upwards of $50,000.00 just a few long years ago. Just need to find a faster solution to the "pink" tint when there's not enough turn around for proper grading. So far Andrew's (EOSHD) Portrait recipe seems to do a btter job than Natural, but I haven't done enough testing to be sure.
 
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