Saturday, November 2, 2013

Low Light Photography with your Mobile Device

Smartphone photography is evolving and it is evolving fast. Apple may be in the spotlight but are there enough photography apps out there to support more demanding photographers? Most of the complaint so far has been Apple's reluctance to allow more control over the device camera, and with the iOS 7 update, long exposure is limited to just 1 second. Max. 

For anything requiring extended exposure time, the Joby GripTight proved to be a valuable tool and none of the exposure methods listed below would work without it. Please do not attempt any of these without having some form of grip to hold your device steady. 

One of the rules to allow hand holding any DSLR steady is...weight. The heavier it is, the easier it is to hold it rigid but with mobile devices, hand holding is at best a gamble. The anti-shake mechanism advertised in some apps are not true stabilizers. These apps make use of the in-built gyroscope to detect movement and the shutter only fires when it detects that exposure/shutter speed requirements are met. It is true that wider focal lengths (27mm and below) allow you to shoot at a much lower shutter speed when hand holding but the majority of smartphones are in the ballpark of 30mm. (The iPhone has an equivalent 33mm lens in full frame speak). This means that shooting at 1/30 of a second, hand held at a fixed f/2.2 or f/2.4 aperture, is possible.  

Long Exposure

ISO 32 @ 1/120 seconds

ISO 32 @ 1/3 seconds using Night Cap App
Night Cap for iOS do their best to capture a scene but the onus is on you if you don't have something like the GripTight GorrillaPod as hand-holding the device is virtually impossible at longer exposures. In DSLRs you have the P or Program mode, this is essentially what the iOS app does, turn your device into a P mode camera. This gives you some form of shutter control over the automatic exposure one normally gets from a device. In situations where the aperture is fixed (iPhone and iPod devices are between f/2.4 and f/2.2) camera apps rely on changing the ISO and Shutter Speed to meet any long exposure requirements.

Time Exposure app for iOS has five buit in presets that allow for greater control without going fully manual while Night Cap allows for the maximum 1 sec exposure while saving files in TIFF. 

ISO 64 @ 1/2 second exposure with Night Cap app
Night Mode and Night Cap apps even tells you the ISO used at the longest possible exposure setting, giving you some idea on what it takes to have low noise images at night. I manage to get this down to ISO32 for some night shots on a iPod Touch 5G. If you are curious about such apps used to capture "light painting" or light trails, well, it can but the results are less than satisfactory on iOS devices. To circumvent around the 1 sec iOS 7 restrictions, apps work around this by taking multiple exposures to capture light trails and merging them into a single image later. This technique is not perfect as the noise levels in the image gets excessive. I suspect the main cause of this is the JPEG compression that isn't optimized for such type of shooting.

Light Trails or Light Painting Apps don't work well on the iOS7

Time Lapse

Joby's own iOS app allows for this with a limited preset. Lapse it for Android offers far more controls over the duration of capture and produces a much larger file in the process. This can drain your battery so you have been forewarned. To produce those beautiful time lapse of day to night will require you to have you device plugged in for the whole duration and this is not something many of you would do for the sake of photography but the results are a joy to behold. 

In places where four seasons is the norm, the shorter night to day duration is ideal for such time lapse imagery but there is another thing you should watch out for, that is when the device is overheating. Apple's iPhone and iPod Touch devices are built with a heat sensor. Once you start taking Time Lapse photos, there is a good chance you'd be leaving the device running for hours. In cold climates, this may not pose a problem but in warmer places, your device will shut down automatically once heat is excessive. This is applicable to some Android smartphones as well. 

Aside from this, you probably need heaps of patience to get the desired results. Setting up a Time Lapse Cam and leaving it running for hours on end may not seem like a good idea if you're expecting calls and emails.

Multi Frame HDR and Exposure Stacking

Having tried apps on both iOS 7 and Android Jellybean, I must say that the only real benefit you get from using apps like Average Camera Pro for iOS7 and A Better Camera for Android, is skewered more towards ISO noise control rather than offering more Dynamic Range. These apps allow you to capture several frames and merge them into a low noise image with no apparent improvement on dynamic range.

Mutli exposures for stacking or HDR has its limitations due to device firmware. For example, the shots made with the Galaxy Note 2 shown here is a prime example. The device has a exposure limitation as it will not go below 1/17 sec for any one frame. This is inbuilt into the firmware. Therefore in low light conditions, the amount of detail you can claw back from a stacked exposure process is just marginally  better. 

ISO 800 @ 1/33 sec with camera app

Stacked exposure HDR, five frames.
Large sensor cameras tend to have better dynamic range than small sensors and it shows. The BSI sensors used in both iOS and Android device are designed to address noise issue rather than dynamic range. The average smartphone BSI sensor probably has in the ballpark of between 6 to 7 EVs. Unfortunately DXO mark does not publish Dynamic range profiles on mobile device sensors so this is my best guess for such devices. Compact cameras and mirrorless cameras have between 9 and 11 EVs while full frame DSLR sensors can hit the 15 EV mark. For now, the only way for Android phones to squeeze just a little more Dynamic range is to use exposure stacking. This is built into the new LG Nexus 5 camera app but you still need a Joby GripTight to hold it steady as hand held use is not encouraged.

Conclusion... What's the Best Option?

In mobile devices, the Lumia Nokia 1020 and Lumia 1520 carry the largest sensors and theoretically speaking, these could capture up to 9 EV of Dynamic range. Coupled with the fact that the Lumia also offers much better control, long exposures are limited to just 4 seconds a frame, making it the de-facto king of mobile photography. The only caveat is that it lacks the variety of apps that make photography fun. 

The iOS universe doesn't quite match up on paper but it does offer you a plethora of apps to play with. Manual controls are hard to come by but iOS does offer more long exposure possibilities than Android. the current crop of Galaxy Note 3 and S4 cameras are limited to 1/17 sec exposure times. This should be in the ballpark of all other manufacturers who use the same 8 megapixel sensor module. Large sensors and not more megapixels are the way forward if you wish to take your mobile photography to another notch and unfortunately at this time, there isn't much of a market for such devices. Nokia may well be creating a niche for itself and should they ever put a Lumia 1020 on Android, it could change the entire mobile photography landscape. 


Post a Comment