Infinite focus on Samsung S9 not working (trying to use for time lapse)

[WolfStock]

Greetings - any help on this would be appreciated. I love doing time lapse videos on my S9, however am having a problem trying to sunrise and sunset, because the manual infinite focus in pro mode is not working right - it's blurry. Infinite focus works right in auto-focus, however this does not work well in low light, so I'd like to use manual.

Some details in Samsung forums are here. I haven't gotten any help there yet though. If anyone knows a solution it would be most appreciated!

https://us.community.samsung.com/t5/Galaxy-S9/S9-camera-in-Pro-mode-will-not-focus-properly-on-infinity/m-p/1188237#M38074

 

[Mooncatt]

Infinite focus on many lenses can throw everything out of focus. Even on something like a DSLR doing astro-photography, you may have to go a step below infinite focus.

What I would do is set your phone up as usual, but do so in the daytime. Manually set your focus on a distant object (like a tree on the horizon) and find which focus setting gives you the sharpest image. Make a note of that, then use it for the time lapse recording.

 

[WolfStock]

Infinite focus on many lenses can throw everything out of focus. Even on something like a DSLR doing astro-photography, you may have to go a step below infinite focus.

What I would do is set your phone up as usual, but do so in the daytime. Manually set your focus on a distant object (like a tree on the horizon) and find which focus setting gives you the sharpest image. Make a note of that, then use it for the time lapse recording.

Thanks - though unfortunately this won't work. It's not that the "infinity" setting (end of the range) goes too far - it's that it doesn't go far enough. So there isn't any setting in the range that works.

I try looking at the pictures' metadata, but apparently Samsung doesn't store a lot of the metadata correctly. It always shows 4.3mm for the focal length, regardless of what the actual focal length is.

 

[WolfStock]

P.S. I'm guessing this is a low-level command thing in the camera's API, rather than an app thing, since it's broken both in the Samsumg Photo app as well as the LapseIt Pro timelapse app. Presumably they are both telling the camera controller "focus on infinity", but the camera controller software doesn't correctly understand what infinity is.

However it works in auto-focus. This presumably is because the focus feedback mechanism in the camera software doesn't use this same API - the sensor that senses the how well the camera is currently focused feeds back directly into the camera's focusing driver, rather than using the API that's exposed for external apps.

(This is conjecture on my part, but would explain why the camera can focus on infinity when doing auto-focus, but not when an app tells it to focus on infinity)

 

[Mooncatt]

I try looking at the pictures' metadata, but apparently Samsung doesn't store a lot of the metadata correctly. It always shows 4.3mm for the focal length, regardless of what the actual focal length is.

Focal length is independent of focus. Focal length only changes when you optically zoom in or out (not digital zoom), or change lenses, so it will remain 4.3mm until you switch to the other lens on the phone.

As to why it seems to work in auto-focus, but not manual, I have no idea without being able to get my hands on the phone itself.

 

[lucianus_luciferus]

If you tap on the screen does it focus properly?
If so then you can enable tracking auto focus in camera settings and the camera will keep the focus on the object you tap on.

 

[WolfStock]

Focal length is independent of focus. Focal length only changes when you optically zoom in or out (not digital zoom), or change lenses, so it will remain 4.3mm until you switch to the other lens on the phone.

As to why it seems to work in auto-focus, but not manual, I have no idea without being able to get my hands on the phone itself.

OK pardon my ignorance on this subject. I mistakenly thought "focal length" was literally the distance between the camera and the subject being focused on, but I see (as a bell rings) that it's the distance between the lens and the sensor. What I was really referring to was focal *distance* - the distance between the camera and the subject being focused on. I guess that's not in the metadata (?) - at least I don't see that listed. However I think can be calculated from the other data - e.g. ApertureValue and such (?).

Not sure if you know much about such things, but here's a comparison of the meta-data for good vs bad:

Good (taken in auto mode):

https://drive.google.com/open?id=1WOkg2EiyNJWjlkqP9LAbswosb2aqbVM2

Bad (taken in pro mode - "inifinite" focus):

https://drive.google.com/open?id=1Z0MSsdV_SyycbfvgTmVfrxpufeSVr2eu

I'll play around with it some later to see how the different settings work, and see if I can get Pro mode to as-close-as-possible approximate the auto mode settings, to try to figure out what the "x factor" is.

 

[WolfStock]

If you tap on the screen does it focus properly?
If so then you can enable tracking auto focus in camera settings and the camera will keep the focus on the object you tap on.

When in auto mode - yes it will focus properly, but only in good-light conditions. In low light (e.g. late dusk) it has trouble auto-focusing*, which is why I want to use manual focus.

*This is natural I believe - since cameras use contrast in their focusing algorithms, and there's less contrast in low-light conditions.

 

[lucianus_luciferus]

this is why i have suggested to enable tracking auto focus. that way you can tap on the screen to focus and the focus will be locked on to that and when dusk comes it will not try to auto focus again.

 

[Mooncatt]

OK pardon my ignorance on this subject. I mistakenly thought "focal length" was literally the distance between the camera and the subject being focused on, but I see (as a bell rings) that it's the distance between the lens and the sensor. What I was really referring to was focal *distance* - the distance between the camera and the subject being focused on. I guess that's not in the metadata (?) - at least I don't see that listed. However I think can be calculated from the other data - e.g. ApertureValue and such (?).

Not sure if you know much about such things, but here's a comparison of the meta-data for good vs bad:

Good (taken in auto mode):

https://drive.google.com/open?id=1WOkg2EiyNJWjlkqP9LAbswosb2aqbVM2

Bad (taken in pro mode - "inifinite" focus):

https://drive.google.com/open?id=1Z0MSsdV_SyycbfvgTmVfrxpufeSVr2eu

I'll play around with it some later to see how the different settings work, and see if I can get Pro mode to as-close-as-possible approximate the auto mode settings, to try to figure out what the "x factor" is.

What sticks out most to me between those two data sets is the aperture value. The good one had a smaller aperture value than the bad. They labeled things a bit odd, so I'll give a little explanation in case it's not clear for you.

Aperture is how "open" the lens is. The larger the opening, the more light is let in, which is great for low light photography and why you see phones advertised with wide apertures. The aperture is defined as an f-stop number, and is an inverse ratio of focal length to aperture diameter. So in the good example, your aperture is 1:2.52. In common vernacular, it would be labeled f2.52 (because it's always 1/x, thus the 1 is understood as constant), or sometimes just 2.52 as in your examples. The larger the number, the smaller the diameter of the opening.

For a typical phone user, this doesn't matter because most phones have a fixed aperture on the lenses. Yours happens to have a variable aperture, so is something to understand when using manual mode. The downside you should be aware of is that the aperture also plays a part in the depth of field. A wider aperture will have a more shallow DoF than a narrow aperture. When you focus on a spot, a certain amount of the scene in front and behind that spot will also be in focus. The wider the aperture, the less distance from the focal point will be in focus and vice versa. The further away you set the focus point, the larger the DoF, and vice versa again.

You may now see what I'm getting to. If possible, try again using the narrow aperture. I've seen complaints that Samsung will override manual settings in low light, so it may prevent you from switching the aperture. Try both at infinite focus and a step or two back from that as in my initial suggestion. Because this causes less light into the sensor, you will need to bump or the ISO, and/or increase the shutter time to compensate.

As for calculating the focal distance from the metadata, I've never seen that done. I doubt it is even possible, nor have I ever seen a photographer mention it when posting details of a photo. In full fledged cameras, the focus adjustment ring on the lens isn't even labeled with setting amounts.

 

[WolfStock]

Thanks for the help guys. I've been doing a bit of messing around but am in a class this week so haven't had a chance to post. Will post some within the next couple of days. One thing I need to do is learn a little more about how this kind of camera does its focusing with the CMOS. I think it's more complicated than I realized. Still haven't gotten it to work even after messing around with all the shutter speed, F-stop, and ISO settings. I think it's due to the way it uses the modes - perhaps using a different (and ironically sometimes not as good) focusing mechanism in Pro mode vs Auto mode. Not sure though.

 

[WolfStock]

this is why i have suggested to enable tracking auto focus. that way you can tap on the screen to focus and the focus will be locked on to that and when dusk comes it will not try to auto focus again.

The problem with tracking mode is that it doesn't stay constant focus - it "tracks" whatever is in the frame that you point to, and continues refocusing on that, so it suffers from the same low-light problem that auto-focus does - if it doesn't have enough contrast (due to the low light) it has a problem focusing. I figured I'd give it a shot regardless - unfortunately the LapseItPro app doesn't have a "tracking" focus mode though. It does have a "Continuous" mode, which I think is supposed to be similar, and I tried that however it didn't work - once the light got dim it behaved similar to autofocus, and many of the pictures in the time lapse were very out of focus.

Thanks for the suggestion though.

 

[WolfStock]

OK well - I've messed around with every setting possible, and it's just not working. It's just not focusing well when in Pro mode, no matter what ISO, F-stop, or shutter speed I use.

So the question is - is the general Samsung S9 issue, or is it a problem with my phone specifically. If anyone happens to see this thread that has a S9, and is willing to do me a favor and try it out it would be appreciated! It's really easy to reproduce. (My brother has an Tab S10 and it doesn't have the problem) I'll probably start another thread and also try to get in touch with Samsung. Not sure if it's under warranty though probably not at this point.