How to manual focus in video ?

[wolf33d]

Hello, 

I cannot properly focus my RX100IV. When I put focus to infinity, infinity is in focus but very far (more than 10 meters, anything closer is OOF) at 24mm. 
Even with the aperture at F8 (which should give me a ridiculously big DoF considering sensor size) I cannot have everything in focus between lets say 1m and infinity. If I set the hyperfocal then anything far from me is OOF.
I noticed the same thing on my A7RII at 15mm. hyperfocal rule says everything should be in focus if I set it at 0.xxm, but even set at 5 meters far objects are OOF. I need to set it purely on infinity to have far buildings and objects in focus, but then anything close to me (even 2 meters from me) is OOF. Hyperfocal does not work at all for me, and especially what is written on the lens itself (voigtlander 15mm). I did this test at F11.

How do you do? Do you adjust focus all the time, or do you accept a part of the frame is not in focus when viewed at 100% ? 

[Don Kotlos]

One thing that we have to do with high resolution digital sensors is forget about the hyperfocal distances. They exist from the film days where print sizes depended on film size and should not be used today when critical focus is important. Just focus on the object that you want very sharp and adjust your aperture to extend the acceptably sharp objects. 

Here is a nice article:

http://www.northlight-images.co.uk/article_pages/hyperfocal_distance.html

[wolf33d]

Thanks. Interesting article!
My goal with the RX100 is to put it on my new Pilotfly gimbal. I would like to set the focus one time and be fine at 24mm, assuming a small aperture.
I am afraid diffraction is too strong at lowest aperture. Does someone found the sweet spot on this camera? 
Continuous focus seems too hazardous. 

[richg101]

One thing that we have to do with high resolution digital sensors is forget about the hyperfocal distances. They exist from the film days where print sizes depended on film size and should not be used today when critical focus is important. Just focus on the object that you want very sharp and adjust your aperture to extend the acceptably sharp objects. 

Here is a nice article:

http://www.northlight-images.co.uk/article_pages/hyperfocal_distance.html

I disagree.  learning and having an idea of hyperfocal distance is very important to camera users - particularly for documentary and observational/fly on the wall film making.  there's in focus, and there is 'acceptably sharp'.  I'd much rather get a shot that's acceptably sharp over the required field, than not get the shot at all due to messing around backing and fourthing to get one aspect perfectly sharp, by that time the subject has clocked they're being captured and the shot is ruined.

Our eyes don;t like seeing everything in focus anyway.  it looks nasty.  at f8 on the widest setting on the rx100, i'm certain focusing at 2m will mean everything from 1m-infinity is 'acceptably' sharp.  it'll only be bang on at 2m, but the rolloff should be slow enough to make the entire frame usable in regards to illustrating what you're trying to show.

 

[Don Kotlos]

I disagree.  learning and having an idea of hyperfocal distance is very important to camera users - particularly for documentary and observational/fly on the wall film making.  there's in focus, and there is 'acceptably sharp'.  I'd much rather get a shot that's acceptably sharp over the required field, than not get the shot at all due to messing around backing and fourthing to get one aspect perfectly sharp, by that time the subject has clocked they're being captured and the shot is ruined.

Our eyes don;t like seeing everything in focus anyway.  it looks nasty.  at f8 on the widest setting on the rx100, i'm certain focusing at 2m will mean everything from 1m-infinity is 'acceptably' sharp.  it'll only be bang on at 2m, but the rolloff should be slow enough to make the entire frame usable in regards to illustrating what you're trying to show.

Rich the problem is, and I learned it the hard way as did Wolf, that you will end up with things not in focus and not acceptably sharp in both near focus and far focus distances. And it will ruin shoots. 

You can still use hyperfocal distances but you have to do the tests yourself in order to find them out because other than the sensor size they will be different for 1080p, 4K, and of course different resolution sensors for stills. There are some calculators that you can adjust the circle of confusion to match for what you find in your test and go on from there. But in my personal experience its very very hard thing to do when you want to get a shoot or grab an image. The technique that I have found works the best for large DoF is to place the focus at the distances that my objects are and close the aperture as far as light allows. 

Of course we have to understand focus distances and use them effectively and cleverly. So let's talk about your example. In the case that you have a subject that moves and you don't want to "not get the shot at all due to messing around backing and fourthing to get one aspect perfectly sharp, by that time the subject has clocked they're being captured and the shot is ruined." and you can't have a sufficiently large DoF or you don't want:  "Our eyes don;t like seeing everything in focus anyway.  it looks nasty." . What do you do? What do I do: Focus at the point where the person. Estimate if possible the range of distances that he is going to cover and adjust your aperture accordingly. As the person is  moving adjust the distance while knowing that the DoF extends about 2/3 to the back of the focus point and 1/3 to the front. 

For a gimbal shoot I would set the focus at the thing that the gimbal is most probably going to be looking at. Let's say it is a face that is moving. What is the distance that this person is going to be at most of the time? 3m? What is the maximum and minimum distances that you expect him to be? 10-1m? Focus at 3m and adjust the aperture until objects from 1-10m are "acceptably sharp". Either have a very sharp monitor or use the focus peaking for that. 

[thefactory]

Thanks. Interesting article!
My goal with the RX100 is to put it on my new Pilotfly gimbal. I would like to set the focus one time and be fine at 24mm, assuming a small aperture.
I am afraid diffraction is too strong at lowest aperture. Does someone found the sweet spot on this camera? 
Continuous focus seems too hazardous. 

I have used the rx100 on the pilot fly and love that combo. So much easier to balance and I was happy with the results. I had not had time to test it so I used auto focus and was prepared to throw away the footage if it did not work as it was b-roll nice to have stuff. As it turns out it worked really well. although next time I will use manual focus as I think I got lucky! 

[M Carter]

Thanks. Interesting article!
My goal with the RX100 is to put it on my new Pilotfly gimbal. I would like to set the focus one time and be fine at 24mm, assuming a small aperture.
I am afraid diffraction is too strong at lowest aperture. Does someone found the sweet spot on this camera? 
Continuous focus seems too hazardous. 

Why not run some tests yourself? Why ask someone about the "sweet spot" for a lens between wide open and diffraction when you can find out for yourself in a matter of minutes? Don't you want to know how your lens performs across the aperture range? If someone tells you "F32, man" you'd be happy with that? Even if the lens only goes to F22?

Test test test.