Video with A7 cameras - thoughts from those who use

[pilsburypie]

Hi all

 

Very close to ditching my Canon stills setup and video camera in favour of a do it all A7x (most likely A7rii/A7s or maybe A7sii when it surfaces). Just a few questions.

 

1. If stopped down (f8 - f11) how well does the autofocus work? I know I'll have a bit of DOF to play with at these smaller appertures, but was still wondering if the video autofocus is any use.

2. How well do the native lenses perform (not the 28-135 video lens)? Was thinking of the new batis lenses, but have seen no video footage as yet from them. The Sony 55 is tack sharp for stills, how does that perform for video?

3. Is decent depth of field a problem with FF? My Panasonic Sd900 seems to always have most things in focus due to its small sensor. Sure it is nice to have shallow DOF on occasion, but this for me could be more of a burden filming kids running around. Does stopping down help this? What is a decent f stop for general videography?

 

[trorvik]

Unlike the mayority of people on these forums i rely on autofocus 80% of the time. This is because I do news-shooting with steadicam where there is no possibility for a focus puller. So for me autofocus performance is my main concern when choosing cameras. I would have liked to choose the a7s since that is the one that is made with focus on video, but i chose the a7ii because of two things. The autofocus is better and it has in camera image stabilization that will also give you stabilization on prime lenses that usually dont have this built into the lens. The 20% of the time i don't use a steadicam i shoot handheld and then image stabilization is a must-have. For your needs I would not have bought the a7s. The new a7r ii however has all the improvements the a7ii has and probably even better autofocus. But at double the cost. The upcoming a7s ii hopefully will be placed between the two in price and be the ideal solution. 

 

Regarding AF performance while recording video almost everything you read on the net talks about AF-performance when you do photography. The camera itself can AF really really fast and accurately. Almost instantly if it needs to. But my experience is that Sony has taken a different approach than others in implementing AF in video. I came from using a GH4 which is extremly fast in AF during video. This is in some ways a nice thing, but has its problems. If you try to use it while filming an interview, using face detect, the AF will be constantly working making small adjustments. But sometimes it sees something in the background that it thinks is more interesting (particularly things that move) and it will change focus to the background in a millisecond. Then continue to hunt until it again takes interest in the person in front. This happens much too often.

 

Sonys approach is more of a "wait and see". It does autofocus more like you would do it yourself with a slow and nice transition and does not hunt back and forth all the time. During an interview this is really nice since it almost never hunts for focus. But if you move fast towards something it will not be able to keep up with the motion since it always want to do smooth transitions. Face detection works a bit different. If it recognizes a face that is closer to the camera it will change focus to this superfast. So i am pretty sure Sony could have made the AF just as fast as the GH4, but prioritizes smooth transitions to avoid focushunting. In my case Sonys approach is the best but i wished you could adjust how fast it reacts to changes like I have seen the Samsung NX1 can. 

 

The face recognition is the best I have seen but has two weaknesses. It does not like people wearing glasses and people with caps or hats. In these cases the AF hunts a bit. But people without headwear or glasses you can trust the AF 98% of the time. 

 

If you havent tried working with full frame i suggest you try before you buy. Coming from a 43-sensor on the GH4 I knew there would be a difference in DOF but was shocked how big it was in reality. In this way 43-sensors are a good compromise. You can use a 0.95 lens and get all the shallow DOF you need. Or you could step down to f16 and focus about 50cm from the camera and have everything be in focus (using hyperfocal distance techniques etc).  On full frame the DOF is so shallow all the way through that you would have to use stops event higher than that to achive the same. At F8 to F11 you would have few problems with AF on things that are a few meters from the camera. But if you move closer you will not get a good result with the AF when shooting things like running children. Then you would have to rely on being good at manual focus.

 

So if your main use is filming things like running children using AF then I would not have chosen a full frame camera at all. Even with the best AF in the world this would not work really well. The safest is using you old camcorder with its small sensor where almost everything is in focus at all times (making the job of the AF on it really simple).

 

It would also be pretty safe to move up to the Sony RX10 (the old cheap one or the new one with 4K). I have that one as well. With its 1 inch sensor it can at least have a little bit of shallow DOF if you use the zoom and max aperture. Particularly with very close objects (it can focus extremly close). At the same time the sensor is small enough to give you a huge amount of DOF. If you leave it in full AF you will have very few problems with focus even on running children. It has fast AF and great face recognition. Really love this camera if you want the comfort of shooting with an iPhone and not having to worry about anything. But with the quality of a real camera. And it does great stills too and has a good zoom range. This is the closest to an all in one camera I have found. The only downside to it is that the powerzoom does not move totally smooth. Zooming in it is smooth enough. But zooming out it makes a small jump/shake midway. I thought this was a fault on mine, but tried another that did the same. But I am used to powerzooms on 30 000$ lenses so am probably expecting too much of a 600$ camera.

 

If you want to be more creative with more shallow depth of field I would have tried the GH4. This can to a degree do "running children", at least in OK light and particularly with the 12-35mm lens (and to a degree the new 14-140mm). And at the same time give you all the shallow depth of field you want with the Voigtlander 0.95. It also will give you lots and lots of long-zoom with affordable and small lenses.  But it will never give you the dynamic range and low light performance of full frame.

 

I guess there really is no camera that will give you everything. You will have to prioritise what is most import to you (or carry multiple cameras. Good luck :-)         

[pilsburypie]

Thanks for your excellent reply. I think your last statement says it all. There is no camera that will give me everything! 2 cameras is not an option..... Just got to weigh up my needs and get the best fit.

 

Cheers

[boojoo007]

I've got the a7s with 55mm 1.8. I don't use auto focus that much either. It seems to do fairly well when at f8-f11 when using autofocus.

I depends on what your shooting but overall it does a great job.