Thursday, November 6, 2014

iPhone 6 Camera Review

This is a user review of the iPhone 6's camera, with an emphasis on its usage for candid photos.  This post will only talk about iPhone 6's photos but not its video, which I will have to discuss another time.  Note: the iPhone 6 Plus has the same camera as the iPhone 6, but adds optical image stabilization. My comments apply to the 6 Plus as well unless otherwise noted.

First, I will discuss the significant features.  Second, I will discuss the characteristics of the iPhone 6 as a camera.


Phase Detection Autofocus ("Focus Pixels")
One of the iPhone 6's new features is the phase detection autofocus which Apple calls "Focus Pixels".  Here is a description of it.  Apple promises that it will enable to iPhone 6 to focus faster.  It does indeed focus much faster than other phones I've used, including the iPhone 5s.  However, it is nowhere near as fast as a DSLR even though they both use phase detection to autofocus.  I would say it is about as fast as a decent compact camera.  I suspect that the iPhone 6 uses a hybrid autofocus, because when I tap on a subject it still focuses forward and backward.

I haven't found myself complaining about autofocus speed except in very dark conditions, or where the subject is strongly backlit.  In those situations, the camera takes longer to focus and can focus on the wrong part of the scene.

Burst mode
The iPhone 6 can shoot at a very fast 10 fps.  In practice, the burst mode is useful not just for fast action but to get sharper shots.  You don't need to switch to a different drive mode.  Instead, holding down the shutter (or volume button) will automatically shoot a burst.  Fortunately, shooting in a burst will not tie up the iPhone 6's cache.  It's ready for the next shot as soon as you finish the burst.

When you examine the shot, the shots from the burst are automatically stacked into one photo.  You can then select which of the photos you want to keep.  By default, the camera will automatically select what it thinks is the best shot from the burst, based on blur and other variables.  After you choose which photo(s) to keep, the camera gives you an option to delete the others.

HDR mode
The HDR mode is an old feature but I note it here because it improves the usability of the iPhone 6 as a camera.  It extends highlight range and allows you to capture highlight details that would otherwise have been lost.  The HDR mode works by taking quick shots in succession at differing exposures and automatically combines them.  You can choose whether to keep both the HDR and non-HDR shots, or just the HDR shot.  I choose to keep both because the HDR shot can appear less sharp if there is movement in the scene.

Thankfully, the result does not at all look like typical garish HDR shots, and instead looks quite natural.  It is useful not only for scenes with wide dynamic range but also for making the highlight rolloff smoother.  In the shots below, note not just the additional detail in the clouds, but also the smoother highlight rolloff in the floating spheres.


Slow motion
This is more of a video feature so I'll discuss it another time.

iOS 8 adds time-lapse to the iPhone 6 and on some older phones such as the 5s.  The settings cannot be changed.  Instead, the phone will adjust the frequency of shots and the speed of the video based on the duration of the shoot.  With a longer time lapse shot, it will take fewer images and the video will be faster.


Focal length
The iPhone has a focal length with a field of view equivalent to 29mm on a full frame camera, which is slightly wide angle.  Composing on wide and ultrawide is more challenging than on a normal or telephoto lens, and requires careful consideration of the entire frame, as well as the foreground and background.

Depth of field
One of the ways I find the iPhone useful is for its deep depth of field.  A lot of amateurs (myself included) typically like using a shallow depth of field.  However, a deep depth of field is very useful as well, if you compose for it.

Costco on a Saturday

I find that the iPhone's exposure is pretty good considering its limited dynamic range (due to its small sensor).  If there is a large area that has highlight detail, the iPhone makes some effort not to blow those highlights, even if it's slightly underexposed.

In the shot below, if the camera had exposed for the subject (the dancers) then parts of the buildings in the background would have been blown out.  Instead, the camera chose an exposure that preserved the highlight detail in the background (and even some of the clouds).  In post, I raised the exposure of the shaded area to normalize the exposure of the subject:

Here is the original shot:

Very bright highlights, however, tend to be sacrificed, as in the parts of the background below, which were directly illuminated by halogen lights.

With respect to the camera's chosen exposure, the aperture is fixed at f/2.2.  The ISO range is supposed to be from 32 to 2500, although the highest ISO I've seen it use is 2000.  The shutter speed is as slow as 1/2 sec. to as high as 1/8000 sec.  It appears that it slows the shutter speed down to as low as 1/30 under normal conditions in order to try to keep the ISO low.  In dark conditions, the shutter slows down to 1/15 before starting to increase the ISO.  A shutter speed of 1/30 usually is too slow for all but stationary subjects.  It is here where the burst mode comes in handy.

In the shot below, the robot below kept moving, so it was hard to capture at 1/15.  I took a few bursts and picked out the best one.

The iPhone 6 Plus has optical image stabilization, which reduces blur from handshake.  I haven't tried the 6 Plus except at store demos, but my understanding is that the exposure is even more biased toward slower shutter speeds to take advantage of its OIS.  While the OIS helps blur from handshake, it doesn't do anything for motion blur.  As it is, I find it hard enough to capture a non-stationary subject at 1/15 or 1/30, so for my purposes, it would be nice to have OIS, but being able to shoot at slower shutter speeds is not that big of a deal.

Macro capabilities
The iPhone 6 can shoot fairly close at 3.5 inches.  It doesn't let you shoot macro images per se, but this close focusing ability allows closeup images of small objects.

The wheel shown here has a 77mm diameter

The interior diameter of these bearings is 8mm.

The iPhone is susceptible to flare.  When it reduces the contrast, I adjust the black point to recover some of the contrast:

This was the original shot:

Sometimes, the flare can also be used for effect:

(through a net)

Improved interface
iOS 8 improved the iPhone's camera controls.  You tap on the screen to select the area where you want to focus.  You can then adjust the exposure (similar to exposure compensation) by dragging up or down anywhere on the screen.  You can lock the autofocus and exposure by tapping on your target and holding your finger their for a couple of seconds.  You'll see "AE / AF lock".  You can further adjust the exposure by dragging up or down.

Strictly speaking, the improved interface is a feature of iOS 8, not the iPhone 6 per se.  Nonetheless, I note it here because it is a significant improvement and makes the camera much easier to control.

In iOS 8, Apple also now allows third-party apps to have more control over exposure variables such as ISO and shutter speed.

Image quality
I find that the image quality of the iPhone is quite good as long as you are viewing at laptop screen sizes or smaller, especially when there is ample light.  I also really like the way the iPhone 6 renders colors, which look natural and realistic.

When viewed at 100%, the image has little detail, and looks impressionistic, so it won't appeal to pixel peepers.  But I don't think camera phones were designed for that audience anyway. :)

How does the image quality compare to that of a compact camera?  It's not entirely fair to compare the iPhone 6 to a dedicated camera because they have different uses -- you can bring the iPhone with you everywhere, whereas that's not always true for cameras.  Nonetheless, I found a couple of similar shots that can give you an idea of the difference between the iPhone 6 and the Stylus 1, which has an above-average size sensor:


In case you're wondering, the iPhone shot is the one below.  If the images are viewed at 100%, there is of course no comparison.  The iPhone has no detail at that level.  Without zooming in, the biggest differences between them (in my view) are the dynamic range and the tonal and color depth, as in the hair of "Elsa".  Nonetheless, I think the iPhone image quality is still quite good when viewed at laptop screen sizes.  A nonphotographer would probably have a hard time telling which is which.

High ISO
At 2000 ISO, the images in my opinion are still usable for casual shots at web-viewing sizes, and retain decent color and contrast, even in the shadow areas.

ISO 2000 rear camera (waiting at a movie theater; bluish overhead lights and mixed lighting from the movie screen)
Note: in low light, I use the rear camera even for selfies.  The front camera is nowhere near as good:

ISO 2000 front camera

The built-in photo editor is much improved, and vaguely reminds me of Lightroom.  There are three categories of edits: cropping (including rotation to any degree), filters, and levels.  Cropping and filters are self-explanatory.  Levels are somewhat similar to Lightroom controls. When you select it, you're given 3 major categories: Light, Color, and B&W.
  • Selecting Light allows you to change the exposure by dragging a slide at the bottom of the frame.  In addition, there is a small menu that you can select for finer controls.  In Light sub-menu, you can change: exposure, highlights, shadows, brightness, contrast, and black point.
  • Selecting Color allows you to change saturation.  Its sub-menu allows you to change saturation, color contrast, and cast (color temperature).
  • Selecting B&W converts the image the black and white, and by default controls intensity.  The sub-menu controls neutrals, tone, and grain.
I would say the built-in photo editor is very easy to use and is reasonably capable for editing shots.

Going home

The iPhone 6 works quite well as an everyday camera.  Its primary limitation for photography is not its image quality -- which is better than I expected -- but its focal length.  Either you like shooting wide or you don't.  If you don't, then a compact camera is a necessity.  A compact is also a better choice if you're taking a lot of shots in low light.  Otherwise, if you like a shooting with wider focal length and you're not shooting in low light, I think the iPhone 6 is pretty good for viewing at laptop screen sizes or smaller.

In my next post on the iPhone 6, I will discuss its video capabilities.  In the meantime, here are a few more sample images.


with handheld LED light

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