Mavic Focus

[Butterpuff 6]

That means if you focus on infinity you get sharpness way beyond infinity. Wow!

No, I think it's only sharp to 12.7 meters beyond infinity.

 

[David_Cambridge]

You are only partly correct. The coc is in fact an optics calculation based on phuysical factors. It's existence however, as others have noted, and in its high level definition as well is to define what appears to be acceptably sharp to the human eye. At that level, the distance from the eye to the image, and the eye's basic resolution determine what most people consider acceptable. It was derived from early magazine and photographic printing processes. Many photographers, myself included, find that the formula allows for what we believe for the creation of unsharp images. Hence when evaluating setups requiring depth of focus for our desired output, we use a smaller coc as the standard.

This is all about human perception, and the average human's willingness to decide that an image is sharp

 

[DefaultIT]

With all due respect, I'm not sure human perception is anywhere near as simple to determine in this age of multi-use digital imagery; who knows where what parts of any given image will be used/filtered/composited and whichever device renders them to viewers at what distance. CoC size with respect to pixel density is, on the other hand, a pretty hard and fast calculation, with very demonstrable results. Details are either rendered at sub-pixel accuracy (sharp) or they're not. I don't think I can keep up with you guys regarding delineation methods for resolution limits, but it makes a lot of sense to me to consider the measurements with respect to the sensor itself.

 

[DarkEnergy]

You are only partly correct. The coc is in fact an optics calculation based on phuysical factors. It's existence however, as others have noted, and in its high level definition as well is to define what appears to be acceptably sharp to the human eye. At that level, the distance from the eye to the image, and the eye's basic resolution determine what most people consider acceptable. It was derived from early magazine and photographic printing processes. Many photographers, myself included, find that the formula allows for what we believe for the creation of unsharp images. Hence when evaluating setups requiring depth of focus for our desired output, we use a smaller coc as the standard.

This is all about human perception, and the average human's willingness to decide that an image is sharp

The human eye angular resolution is about 1 arc minute for 10/10 vision and is determined by the eye effective focal length and the median distance between cones in the center of the macula where the density is higher. If we leave side the quality of the optIt is exactly the same with any photographic dispositive. It is easier to quantify with digital detectors because of the uniformity of the distribution of pixels. According to the sampling theorem a resolution element has about 2.5 pixels size. As mentioned above by Peter Galbavy (17), with colour images depends on how the colour element is defined. With photographic emulsions was more complicated because the silver grains have a size range and therefore an "average" resolution has to be defined. The resolution of photographic emulsions was and is determined analizing under a microscope the negatives themselves and is given in resolved lines per mm.

 

[datincan]

The human eye angular resolution is about 1 arc minute for 10/10 vision and is determined by the eye effective focal length and the median distance between cones in the center of the macula where the density is higher. If we leave side the quality of the optIt is exactly the same with any photographic dispositive. It is easier to quantify with digital detectors because of the uniformity of the distribution of pixels. According to the sampling theorem a resolution element has about 2.5 pixels size. As mentioned above by Peter Galbavy (17), with colour images depends on how the colour element is defined. With photographic emulsions was more complicated because the silver grains have a size range and therefore an "average" resolution has to be defined. The resolution of photographic emulsions was and is determined analizing under a microscope the negatives themselves and is given in resolved lines per mm.

I have a ccc now from how this thread turned, so no one yet can say if the focus will stay locked on a subject if the M moves away from it?

 

[Mimoid]

No. Since the Mavic has not yet reached full production status, we just don't know. Personally, I am inclined to believe that the focus stays locked until your refocus, just like a DSLR where you press the shutter button halfway to lock the focus. But hopefully, DJI will implement an optional continuous autofocus mode.

/// Tom

 

[DefaultIT]

True we don't have them, but no one expects continuous autofocus on this bird. Take a look at the higher end X5 series and you'll see they work 2 ways: single-event tap to focus and manual rack via the [expensive] control wheels. Granted those are pro-targeted machines where continuous autofocus wouldn't be much use to ththe user base, but I wouldn't expect any difference in the Mavic initially. I also have my doubts about there being enough spare processing power to run CAF on board that tiny thing....DJI is relatively new to this game so they don't have sophisticated focusing algorithms laying around just yet

 

[pianoman011]

Can that be done with a firmware update?

 

[DefaultIT]

Can that be done with a firmware update?

I don't know if anyone but the R&D department at DJI can answer that; how the focus mechanism is controlled and what percentage of it is hard-coded vs firmware is anyone's guess... I'm not holding my breath, though

 

[Mimoid]

Can that be done with a firmware update?

I don't see why not. The whole function of the Mavic system is software based, so it should be possible, although I am not sure it is really necessary. Normally you wouldn't keep shifting the focus plane very often in a drone. Once you are more than 30-40 meters up in the air, everything is pretty much at the same focus plane.

/// Tom

 

[datincan]

I don't see why not. The whole function of the Mavic system is software based, so it should be possible, although I am not sure it is really necessary. Normally you wouldn't keep shifting the focus plane very often in a drone. Once you are more than 30-40 meters up in the air, everything is pretty much at the same focus plane.

/// Tom

True if you are 30-40m up it is all likely to be in focus at the infinity focus, but for shots where you fly to or away from a subject a close distance if they don't have focus lock on the subject, it's going to make it very difficult to get nice shots, especially when your reference to change focus is viewed on a small mobile phone screen. - So there are no beta testers on this forum I guess..

 

[len750]

Is the focus remaining fixed once it is locked onto a subject?

i.e. does it track the subject to maintain focus - or if the mavic moves away from a fixed subject will it loose focus?
for example, one of the demo shots on a review showed a pull away shot from the top of a small light house. - If the camera was first focused while close to the light house and as the mavic pulls up from it, will the light house and all subjects in similar focal plane become out of focus? ...or will the camera track the lighthouse and keep it in focus all the time?

Thanks guys, I now have a massive headache from all of this. Still waiting to get the Mavic though.

 

[rbarry12]

There's nothing more confusing than agreeing the circle of confusion. Can we safely say that if you get focus on an object 15 meters or so away then you will have near perfect focus clarity for anything further away from that distance, and say up to 10 meters in front of the lens. Any closer work will need a tap on the screen to make sure your close up work is near perfect. It can't be much easier than that can it?

 

[rmb]

Does anyone know if you can fix focus. I love that I can press a button and have the camera auto focus on an area, but as a cinematographer I have a concern that if you can't fix the focus then when you want to it could be a downfall of the Mavic.
I am imagining doing a slow descend past a bridge while focused in the distance. It would be a cinematic bummer if the camera decided to re-focus on the bridge as I pass it instead of remaining focused on the horizon.

 

[DefaultIT]

All indications are that it will refocus only when commanded by a screen tap or C-button (if set up for that)...and as such will remain fixed, shooting or not, until the next focus command. Craft aren't shipping and software and firmware have the potential to affect this, but from what we know now, your scenario shouldn't be a problem.

...also FWIW you'd have to get really close to that bridge to make it visibly soft anyway

 

[rbarry12]

Does anyone know if you can fix focus. I love that I can press a button and have the camera auto focus on an area, but as a cinematographer I have a concern that if you can't fix the focus then when you want to it could be a downfall of the Mavic.
I am imagining doing a slow descend past a bridge while focused in the distance. It would be a cinematic bummer if the camera decided to re-focus on the bridge as I pass it instead of remaining focused on the horizon.

As I understand, there is a high probability that it wont auto focus. For anything other than close up work, you wont need to refocus as infinity (or as close to infinity as matters) will be perfectly ok from a relatively close distance. The jury is still out as to what that distance is!