Focus problem

[johnmeyer]

I have taken thousands of hours of video, starting in 1981. When autofocus was added to camcorders in the late 1980s one of the first things I did was turn it off unless I was doing "run and gun" video where the focus is constantly changing. Auto-focus "hunting" is really evil and totally avoidable. It is particularly a problem when the camera is focused at or near infinity. In these circumstances you should never have autofocus enabled.

So, with a drone, if I was following someone at a close distance (like a walk through a forest), I'd turn on auto focus.

For everything else, turn it off!!

As for getting proper focus, one of the first things I did with my M2P was to assign focus and exposure shortcuts to two of the controller buttons. I now have a routine that I follow every time I fly:

1. Ascend straight up to at least 25 feet in order to calibrate the vision sensor for auto landing and return to home. I seldom use either, but if I ever really need them, I want them to work.

2. I orient the drone to point the camera at something in the distance and first press the button to which I assigned exposure (this works even if in video mode), and then press the button to which I assigned focus.

3. I then adjust the EV compensation, using the dial control, to make sure I don't have zebras (over-exposure indicator on the screen) over any object that should be correctly exposed. Specular highlights (e.g., reflections off water) are OK to blow out, but not white shirts, etc.

 

[GadgetGuy]

I have taken thousands of hours of video, starting in 1981. When autofocus was added to camcorders in the late 1980s one of the first things I did was turn it off unless I was doing "run and gun" video where the focus is constantly changing. Auto-focus "hunting" is really evil and totally avoidable. It is particularly a problem when the camera is focused at or near infinity. In these circumstances you should never have autofocus enabled.

So, with a drone, if I was following someone at a close distance (like a walk through a forest), I'd turn on auto focus.

For everything else, turn it off!!

As for getting proper focus, one of the first things I did with my M2P was to assign focus and exposure shortcuts to two of the controller buttons. I now have a routine that I follow every time I fly:

1. Ascend straight up to at least 25 feet in order to calibrate the vision sensor for auto landing and return to home. I seldom use either, but if I ever really need them, I want them to work.

2. I orient the drone to point the camera at something in the distance and first press the button to which I assigned exposure (this works even if in video mode), and then press the button to which I assigned focus.

3. I then adjust the EV compensation, using the dial control, to make sure I don't have zebras (over-exposure indicator on the screen) over any object that should be correctly exposed. Specular highlights (e.g., reflections off water) are OK to blow out, but not white shirts, etc.

How far away do you prefer your focus target to be during the initial focus setting?

 

[johnmeyer]

How far away do you prefer your focus target to be during the initial focus setting?

That depends on how far away the thing I'm filming is going to be. Remember that, unless you have a big drone with a DSLR camera, the little cameras on the drones we all use have extremely wide-angle lenses. With these lenses, even at the wide aperture recommended to avoid diffraction issues, the depth of field is enormous. So, unless you are recording objects that are under thirty feet away, you can focus at infinity and be in fine shape.

I suspect that the focus problem reported by the OP was caused by focusing while the drone was still on the ground thereby setting the focus to the closest possible distance. In that case, everything at thirty feet to infinity will be blurred.

Finally, as I said in my earlier post, if I were doing a "follow me" type video where the drone was tracking a thing or person from twenty feet or less, I'd probably use auto focus because the occasional "pop" in and out of focus when it hunts, would be more than offset by having the rest of the video perfectly in focus as the distance relationships constantly changed.

 

[GadgetGuy]

That depends on how far away the thing I'm filming is going to be. Remember that, unless you have a big drone with a DSLR camera, the little cameras on the drones we all use have extremely wide-angle lenses. With these lenses, even at the wide aperture recommended to avoid diffraction issues, the depth of field is enormous. So, unless you are recording objects that are under thirty feet away, you can focus at infinity and be in fine shape.

I suspect that the focus problem reported by the OP was caused by focusing while the drone was still on the ground thereby setting the focus to the closest possible distance. In that case, everything at thirty feet to infinity will be blurred.

Finally, as I said in my earlier post, if I were doing a "follow me" type video where the drone was tracking a thing or person from twenty feet or less, I'd probably use auto focus because the occasional "pop" in and out of focus when it hunts, would be more than offset by having the rest of the video perfectly in focus as the distance relationships constantly changed.

Thanks for the clarification. I was just asking at what distance you would prefer your initial focus subject to be, for an ideal infinity landscape focus. I've read others suggest 75 feet, and others say anything beyond 25 feet. I prefer something with detail around 25-50 feet, while hovering. Agree about refocusing for closeup work. If I am slightly out of focus during the closeup hand-catch landing from 2 feet away, I know the video will be in focus. If I am sharp, the focus was screwed up! I set it at launch, like you and leave it, unless I am using the M2Z in 4x at 1080p close up on a bird nest. Had an osprey nest available for about a month, and got some incredible closeup video while the chicks grew up. Every time I was able to fly closer, I reset focus. The pop in and out during refocusing is annoying, but it makes sure what follows is as sharp as you can get it, and can easily be edited out in post.

 

[Bebopperoo]

Canada Drone and fellow droners, thanks, you have quite literally changed my view of the world. Very grateful indeed!

 

[CanadaDrone]

Thanks for the clarification. I was just asking at what distance you would prefer your initial focus subject to be, for an ideal infinity landscape focus. I've read others suggest 75 feet, and others say anything beyond 25 feet. I prefer something with detail around 25-50 feet, while hovering. Agree about refocusing for closeup work. If I am slightly out of focus during the closeup hand-catch landing from 2 feet away, I know the video will be in focus. If I am sharp, the focus was screwed up! I set it at launch, like you and leave it, unless I am using the M2Z in 4x at 1080p close up on a bird nest. Had an osprey nest available for about a month, and got some incredible closeup video while the chicks grew up. Every time I was able to fly closer, I reset focus. The pop in and out during refocusing is annoying, but it makes sure what follows is as sharp as you can get it, and can easily be edited out in post.

In practice, you can use a subject around 30-50ft away to set your focus and that should be good enough so you never had to touch it ever again because the focus increments on the M2P are extremely coarse - it's super easy to verify either way though with the focus peaking in case it needs a tweak. Just play with it for a couple seconds and you'll see what works.

Technically speaking, the hyperfocal distance on the M2P at F4 is 58.6ft. What that means is once you are ~60ft in the air, at F4, your depth of field is already covering everything from 30ft all the way to infinity, which covers the overwhelming majority of flying scenarios, and everything will always be in ideal focus within that range if you have set your manual focus properly to begin with. At F2.8 the hyperfocal distance is 82.8ft, but if you're anywhere near that, you'd never be able to tell the difference I don't think. Beyond F4, diffraction begins to degrade the image due to having such a tiny sensor with a relatively high MP count (1", 20MP).

 

[GadgetGuy]

In practice, you can use a subject around 30-50ft away to set your focus and that should be good enough so you never had to touch it ever again because the focus increments on the M2P are extremely coarse - it's super easy to verify either way though with the focus peaking in case it needs a tweak. Just play with it for a couple seconds and you'll see what works.

Technically speaking, the hyperfocal distance on the M2P at F4 is 58.6ft. What that means is once you are ~60ft in the air, at F4, your depth of field is already covering everything from 30ft all the way to infinity, which covers the overwhelming majority of flying scenarios, and everything will always be in ideal focus within that range if you have set your manual focus properly to begin with. At F2.8 the hyperfocal distance is 82.8ft, but if you're anywhere near that, you'd never be able to tell the difference I don't think. Beyond F4, diffraction begins to degrade the image due to having such a tiny sensor with a relatively high MP count (1", 20MP).

Thanks for sharing the actual numbers. That gives me much more confidence in the validity of my current method. I use the same method on the P4P with optimal results. Turning off AFC is the settings first is the key on both!

 

[globetrotterdrone]

I have experienced slight focus shifts if I tilt the camera up and down for the very same object at infinity. That's why I keep focusing after I rotate it. I normally find an object with resembles infinity, but nonetheless, the best result for me is always, always, always focus on the centre of the image with the SC with f2.8.

If I put the focus more to the right or left, parts of the image are differently sharp. The focus follows a certain curvature and I guess with this small sensor and wide angle lense, some deviations cannot be fully avoided.

That said, focus can shift too with temperature (and altered focal length which the M2P certainly does not support), but I guess, that's minimal considering the sensor size.

 

[CanadaDrone]

I have experienced slight focus shifts if I tilt the camera up and down for the very same object at infinity. That's why I keep focusing after I rotate it. I normally find an object with resembles infinity, but nonetheless, the best result for me is always, always, always focus on the centre of the image with the SC with f2.8.

If I put the focus more to the right or left, parts of the image are differently sharp. The focus follows a certain curvature and I guess with this small sensor and wide angle lense, some deviations cannot be fully avoided.

That said, focus can shift too with temperature (and altered focal length which the M2P certainly does not support), but I guess, that's minimal considering the sensor size.

You're probably seeing imperfections in the lens, because the focus is not going to have any kind of curvature to it if you are more than about 30 feet in the air and manually focused properly - everything is going to be in focus across the board, and that isn't specific to the M2P, it is something you can calculate. The image will naturally get softer as you approach the corners, but if you can notice anything significant or asymmetrical then there is probably something else going on. My M2P does not exhibit what you describe, assuming I am understanding you properly.

 

[globetrotterdrone]

Well yes @CanadaDrone I get you.
It is not something what I've experienced in SLR times, but still it happens with my drone.

The curvature should be quite small and may only affect focussing in the very near distance. You are certainly right when saying, that past 10 meters, the field curvature is gone.
I guess these are imperfections to the lens, but luckily, just refocussing to the centre will do the trick (it's my 2nd M2P, the first had soft spots no matter where focussing was put to).

 

[rbtmckny]

I just had this out of focus issue yesterday. I have experienced it before, not often. When it happened before I was either just flying around not filming or noticed right away and fixed it by tapping in the screen. Yesterday I did not notice and wasted my second full battery filming out of focus. It was early in the morning and the first battery was good, but then clouds moved in and it got darker out. I had an ND 16 on and I should have changed to an ND8, but was lazy and figured I would fix it in post production if needed. After I took off with my third battery i saw that my focus was bad and I tapped my SM screen and it was fixed. I have noticed that AFC does not always work if my ND Filter is too strong. A friend and I drove for over an hour to film a beach and resort we had never been to. My best shots were on battery #2.

 

[CanadaDrone]

I have noticed that AFC does not always work if my ND Filter is too strong.

I would suggest always being locked in Manual Focus - it would have likely solved any problems you had that day. Regarding autofocus, it needs light and contrast to work, neither of which it can see if the ND filter is too strong (this applies to any camera not just the M2P). With traditional photography, after about a ND6 (and depending how sensitive that particular camera's AF is), you need to either manually focus or remove the filter, focus, and reinstall the filter - again issues you shouldn't run into with the M2P if manual focus is locked in before hand.

 

[rbtmckny]

I would suggest always being locked in Manual Focus - it would have likely solved any problems you had that day. Regarding autofocus, it needs light and contrast to work, neither of which it can see if the ND filter is too strong (this applies to any camera not just the M2P). With traditional photography, after about a ND6 (and depending how sensitive that particular camera's AF is), you need to either manually focus or remove the filter, focus, and reinstall the filter - again issues you shouldn't run into with the M2P if manual focus is locked in before hand.

Thanks for the comment. I also see where johnmeyer above talked about the Drone focusing on what was on the ground before take off being a problem. That was also a factor with me I think. Before take off everything looks good, then when I get in the air the subjects more than a few of meters away are fuzzy. Then with the incorrect ND Filter the AFC did not adjust.

 

[GadgetGuy]

Thanks for the comment. I also see where johnmeyer above talked about the Drone focusing on what was on the ground before take off being a problem. That was also a factor with me I think. Before take off everything looks good, then when I get in the air the subjects more than a few of meters away are fuzzy. Then with the incorrect ND Filter the AFC did not adjust.

Just make it a point to find a well lit object with detail some 30-50 feet away to set focus upon, immediately after take off. That's the first thing I do!