Image Quality & Performance

The iPhone 6 Plus is powered by Apple's latest processor, the A8, and feels very responsive and snappy in general use. The camera opens and is ready to shoot from both home and lock screen in approximately one second. 

Shot-to-shot times are impressively fast in bright conditions at around 5.5 frames per second, at least that was the fastest I could tap on the on-screen shutter button. However, as soon as the scene gets a little darker shot-to-to shot times are slowed down, presumably due to the autofocus system, to a more pedestrian 0.9 frames per second. If that's not fast enough, pressing and holding the shutter button triggers the iPhone's burst mode at a staggering 10 frames per seconds. Images are saved as bursts in the Photos app but you can select and extract your favorite single frames.

The addition of on-sensor phase detection to the AF system has noticeable improved performance. In bright conditions the AF locks pretty much instantly. In lower light it  slows down to approximately 1.5 sec in very dark scenes but is consistently quicker than the competition across all light levels. We were also impressed with the device's battery life. We easily got through a day even with heavy use and managed two entire days of moderate use without recharging. 

Daylight, Low ISO

In good light the iPhone 6 delivers images that show excellent exposure and white balance. Color is a little less saturated than on many competitors which gives the Apple output a pleasantly natural touch. In terms of dynamic range the 6 Plus is on a similar level as most competitors with small sensors and struggles with high-contrast scenes. However, the camera usually finds a decent compromise between maintaining shadow and highlight detail.

The lens of our iPhone 6 Plus is sharp across the frame and, despite the for a high-end phone low nominal resolution, the camera captures excellent detail. There is less smearing of fine detail through noise reduction than on most competitors and in combination with just the right amount of sharpening this results in 8MP images that show a touch more detail than even some of the 13MP competitors. 

The low-level noise reduction means that at a 100% view there is some luminance noise visible even at base ISO. However, its fine grain makes it much less intrusive than the clumped and smeared noise we often see on many devices with higher-resolution camera sensors. Chromatic aberrations are very well controlled as well and we could not find any other artifacts in the iPhone 6 Plus image output. Overall the Apple device performs very well in good light and in terms of detail makes the most out of its 8MP 1/3-inch sensor, capturing better resolution than many smartphone cameras with higher pixel counts.

ISO 32, 1/1647 sec
Good exposure and detail, natural colors
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ISO 32, 1/430 sec
Highlight clipping in high-contrast scenes
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ISO 32, 1/1364 sec
Natural skin tones
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ISO 32, 1/3300 sec
Some luminance noise even at base ISO
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ISO 32, 1/1014 sec
The new AF system keeps even fast moving subjects in focus. 
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ISO 32, 1/1319 sec
Good exposure, color and tonality
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Low light, high ISO

The iPhone 6 Plus is the first Apple smartphone to feature an optical image stabilization system and in our testing we found the system to work very efficiently, leaving us with a smaller than usual proportion of blurred low light images.That said, it appears that at least at the very slowest shutter speeds Apple is using some kind of multi-frame mode to reduce blurring through subject motion and keep the ISO down simultaneously. There is no way of knowing how this mode exactly works but at shutter speeds as low as 1/4 sec we would usually expect stronger subject blurring than we can see in our samples. 

ISO 320, 1/4 sec
Shutter speed for this sample is reported as 1/4 sec in the EXIF-data. However, looking at the people walking through the scene at the bottom of the frame subject blurring is less pronounced than we would expect at such slow shutter speeds.
On the other hand noise reduction appears to be stronger on the moving subjects than the rest of the frame which leads us to suspect that Apple has come up with a multi-shot method that in very low light captures two or more frames and blends them to create the final exposure.

During our tests we hardly ever saw the camera push the ISO higher than 500 but we have a few night samples for which the camera selected ISOs as high as 2000 and faster shutter speeds. Despite plenty of low-light shooting it is not quite clear under which circumstances the iPhone opts for the higher ISO values.

Exposure and color are generally decent across the ISO range but night scenes would sometimes benefit from a slightly brighter exposure. With the new manual control in iOS you can easily dial in some exposure compensation though. The iPhone 6 Plus does a good job in terms of detail capture in low light as well. As you would expect, noise increases as the ISO goes up but even in ISO 500 exposures of very dark scenes it is still finely grained and the images show good edge detail. Chroma noise is very well under control as well. Things get a little more ugly in images captured at ISO 1000 and higher but as mentioned above this is only a small fraction of low light images.

Depending on your personal preferences you might occasionally want to apply some positive exposure compensation but overall the the iPhone 6 Plus performs very well in low light.

ISO 80, 1/30 sec
Good detail in this ISO 80 shot
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ISO 125, 1/10 sec
Good edge detail and little noise
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ISO 250, 1/17 sec
Edge detail is well maintained but some softness is noticeable in this shot.
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ISO 400, 1/4 sec
Noise is finely grained, exposure could be a little brighter in this night shot.
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ISO 500, 1/4 sec
Even for this very dark scene the camera set ISO only to 500.
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ISO 2000, 1/17 sec
Occasionally the camera picks ISOs up to 2000 for night shots which results in noticeably reduced detail.
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Flash

Like in low light shooting the iPhone 6 Plus keeps the ISO very low when using the flash. For close-up portraits like the first sample below which was shot in very low light, ISO is usually kept under 100. As you move further away from your subject sensitivity will increase but the camera keeps shutter speed at a steady 1/16 sec. This is not fast enough to freeze any motion but usually does the job for human subjects who are capable of keeping still. 

Exposure tends to be good and avoids clipping on skin tones. Thanks to the two-tone LED flash unit the latter also look natural and not too cool as it often is the case on smartphone flash images. With the camera capturing images at relatively low ISOs image detail is still good, even in very dark scenes. Overall the iPhone 6 Plus flash cannot match the Xenon units in compact cameras or in the Nokia Lumia 1020 but it performs very well for a smartphone camera.

ISO 80, 1/16 sec
Good detail and natural skin tones in this shot captured in very low light.
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ISO 160, 1/16 sec
The flash white balance tends to deal well with mixed light situations.
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