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Don't use Auto Focus to speed up camera snaps

Jayziac

Jayziac

Well-Known Member
Apparently auto focus in a phone camera isn't all it's hyped up to be. To get faster performance (the time from pressing the shutter button to the picture being taken is usually slowed down by the camera trying to find focus in autofocus mode (and sometimes missing completely and giving up if the subject is dark or lack contrast).

I'm not sure about all Android phones, but my Acer Liquid has a focus setting either 'infinity' or 'auto'. From what what I understand about photography, on a small lens such as on a camera phone, the DOF (Depth of Field) is very large, and when the focus is set to the hyperfocal length (the 'infinity' setting), everything from infinity to about 2.5 ft is in focus. I confirmed this with my phone (set focus to infinity, see what the closest thing that's in focus).

So what this really means is for almost all regular picture-taking, it should be set to 'infinity' for faster performance, and only set to 'auto' when one needs to take pictures of objects closer than about 2.5 ft, like a 'macro' mode. So it would've actually made more sense if Android Camera app were to label the two settings '0-2.5 ft auto focus' and 2.5-infinity fixed focus'.

If your camera has this setting, give it a try and see if it's snappier.
 
This is a good post. I wasn't even aware our cameras had this setting. Now on Infinity and I even have an actual Macro mode (Droid) as well. So, of the three: Auto, Infinity and Macro it comes default on the one I will never use now that I know the other two exist. Thanks!
 
I imagine that just makes the aperture really small. Wouldn't that reduce low light performance? ...or am I giving phone cameras too much credit? :)
 
Phone cameras don't have variable apertures. Most are fixed at f2.8 (according to EXIF data), but because of the tiny sensor, has DOF like f8.0+ on an APS-C sensors. So basically letting in a decent amount of light, and still have large focus depth.

As for low light, my Acer has ISO 800 setting, which is equivalent to a regular compact camera's ISO 800, nothing too impressive, but can get some dim shots without motion blur.
 
Infinity isn't set to the hyperfocal distance. Infinity is typically the furthest point the lens can be focused to. With a regular camera, you would use this if you're focusing at something really far away, like more than a few hundred feet, or stars.
 
I haven't had too much time to test but it seems as though the infinity setting is just too much for most of my pictures and they aren't really focusing real well. Anyone else experiencing this?
 
Mormegil said:
Infinity isn't set to the hyperfocal distance. Infinity is typically the furthest point the lens can be focused to. With a regular camera, you would use this if you're focusing at something really far away, like more than a few hundred feet, or stars.
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The 'infinity' setting on the phone is just a label, hence why I put it in quotes. There's a minimum distance in which a lens with small aperture (camera phones) can focus on that gives it such a wide depth of field that it extends from a few feet closer than that hyperfocal distance and out to infinity. I'm not a camera designer, but given the limited space and trying to minimize the amount & distance of moving components, I would guess there's no point in actually focusing further than hyperfocal distance when it doesn't gain anything. Take a look at Hyperfocal Distance and Depth of Field Calculator - DOFMaster for explanation of this more.

I haven't had too much time to test but it seems as though the infinity setting is just too much for most of my pictures and they aren't really focusing real well. Anyone else experiencing this?
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I would suggest testing again in a outdoor daylight setting so camera shake blur is not an issue. In dark settings, the camera automatically reduces the shutter speed in order to get the proper exposure, which means it's more sensitive to hand motions. Better yet, lay down a tape measure on the ground, hold the camera about 1 ft above ground and take a picture of the other end of the tape, see where the tape starts to get blurry, this is the minimum cutoff distance for the 'infinity' setting on your camera. Mine is about 2.5 ft on the Acer Liquid.
 
Jayziac said:
I would suggest testing again in a outdoor daylight setting so camera shake blur is not an issue. In dark settings, the camera automatically reduces the shutter speed in order to get the proper exposure, which means it's more sensitive to hand motions. Better yet, lay down a tape measure on the ground, hold the camera about 1 ft above ground and take a picture of the other end of the tape, see where the tape starts to get blurry, this is the minimum cutoff distance for the 'infinity' setting on your camera. Mine is about 2.5 ft on the Acer Liquid.
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A lot of our pictures are taken in doors (dogs, items for sale...) so this doesn't really help me. I get what you are saying though and maybe out doors in good light it would be a benefit to set it to Infinity but for the rest I think leaving it on auto is going to have to do or Macro when up close. If nothing else I'm happy to learn that this phone has a Macro mode. Now I just wish that it would take photos half the quality of my Blackberry 8700 or Nokia E71. The Droid has more MP but there's MUCH more that goes into a decent photo and Android seems to have lost sight of that. The photos on my Droid have poor color and at times are grainy. I do get some blurring but I understand why that happens so I'm not faulting the phone entirely on that one although it does happen more often than the previous two phones mentioned.
 
Great tip this Jayziac! The camera is super fast now and close up shots just need a touch of the screen.
 
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