With the growing popularity of cameraphones, we’re increasingly leaving our cameras at home. In this article, we look at whether picture quality on smartphones has matched that on dedicated cameras. We’ll also look at the key differences between cameraphones and separate standalone cameras.
Sensor Size & Low-Light Performance
Digital cameras make use of a sensor to convert particles of light (photons) into an electrical signal. The sensor is divided up into a grid of pixels. When a photograph is taken, your camera measures the amount of light landing on each pixel. It then combines the data from all of the individual pixels to produce a photograph.
If you’re taking photos in low-light conditions, sensor size can be an important consideration. If there’s not enough light landing on the sensor, photos will lack detail and will look noisy or grainy. With a larger sensor, this becomes less of a problem as more light can be collected. When taking photos on an overcast day, at night or indoors, it can be particularly beneficial to have a standalone camera with a bigger sensor.
On a cameraphone, the sensor size is approximately half of that on a typical point-and-shoot. The following diagram shows a to-scale comparison of the sensor size on smartphones and point-and-shoot cameras:
When compared to the sensor size of an SLR camera, the differences are even more striking:
Comparison of sensor sizes on digital cameras (to scale). Professional cameras have a much larger sensor. This makes them a much better choice for low-light photography.
Digital cameras make use of several techniques to take better photos in low-light conditions:
Using Flash
Cameras have traditionally used a xenon-powered flash but most modern cameraphones now use an LED-powered flash.
Xenon flash is typically used in professional photography. Compared to LED bulbs, xenon bulbs can produce a burst of light that’s brighter and faster. Xenon emits 1,000 times more light in well under 1 millisecond. As it’s brighter, you’ll capture better photos especially when the subject is further away. Due to the speed, there’ll also be less blurring in the image. Subjects are essentially “frozen in time” by the quick flash. In contrast, an LED flash lasts for about 100ms giving plenty of opportunity for people to move.
Longer Exposure Time
Increasing the exposure time is another way to take photos in low-light conditions. By allowing more time for light to collect on the sensor, the signal-to-noise ratio can be improved. This gives photos with more detail and with less grainy noise.
Long exposure times can also be problematic. This is because it’s often difficult to hold your camera still: small movements and camera shake will lead to blurring in the image. Most standalone cameras feature optical image stabilisation which can correct for shaking. In contrast, cameraphones usually lack this feature (though it’s recently appeared on the Nokia Lumia 920 and the HTC One). Standalone cameras can also be attached to a tripod. This helps when taking long-exposure shots.
Larger Pixels
Rather than using a bigger sensor to collects more light (and subsequently taking up more space within the phone), it’s possible to increase the size of individual pixels on the sensor. This comes at the cost of having fewer pixels. With bigger pixels, each pixel can collect more light. This can give better quality photos in low-light conditions. The HTC One has taken this approach.
Pixel size compares as follows across different types of digital cameras:
|
Handset |
Sensor Size |
Megapixels |
Pixel Size |
|
Entry-Level Smartphone |
9.6 mm2 |
5 megapixels |
1.9 µm2 |
|
High-End Smartphone |
15.5 mm2 |
8 megapixels |
1.9 µm2 |
|
17.5 mm2 |
4 megapixels |
4.0 µm2 |
|
|
Point & Shoot Camera |
28.5 mm2 |
12 megapixels |
2.4 µm2 |
|
Consumer SLR Camera |
384 mm2 |
16 megapixels |
24.0 µm2 |
|
Professional SLR Camera |
864 mm2 |
16 megapixels |
54.0 µm2 |
Comparison of pixel size on sensor for different types of digital cameras.
Depth of Field
When taking photos on a dedicated camera (in particular, SLRs), it’s possible to take photos with a shallower depth of field. This isolates the subject from the background which would otherwise compete for attention. Due to the small sensors found on cameraphones, the photos that are taken will always have an extended depth of field. The entire image will be in focus.
When images are taken with a large depth of field (left), the background can compete for attention with the subject of the photograph. When a smaller depth of field is used (right), the subject can be isolated from the background. Photos taken on a smartphone will usually have a large depth of field as seen on the left. Images by Fir0002/Flagstaffotos [1, 2]. Used under the GFDL License.
Digital Zoom VS Optical Zoom
As cameraphones lack a zoom lens, the only way to enlarge part of the image is through digital zoom. As digital zoom will simply crop and enlarge part of the image, no further detail can be gained.
A standalone camera with optical zoom will give much better picture quality when zoomed in.
Comparison of a photo that is digitally zoomed (left) and optically zoomed (right). CC-licensed photo by Hustvedt from Wikipedia [3].
Connectivity & Apps
One area where smartphones excel is in connectivity.
With cameraphones, connectivity has always been central to the experience. Smartphones have both 3G and wi-fi connectivity: this makes it much easier to share photos online. As soon as a photo is taken, it’s possible to upload it straight away to social networks such as Facebook, Twitter and Instagram. Applications can also be used to back up your photos in the cloud (e.g. iCloud and Dropbox).
Cameraphones can also be connected to your TV to review photos. You can also use GPS to geo-tag your photos with a location.
Megapixels
The latest cameraphones can capture images at up to 13 megapixels. With standalone cameras, the latest models can usually capture up to 16 megapixels. In reality, this is unlikely to make any practical difference.
The following table shows the number of megapixels required to print a good quality photograph:
|
Number of Megapixels |
Size of Printed Photograph (in inches) |
|
2 megapixels |
4” x 6” (standard photograph size) |
|
5 megapixels |
5” x 7” |
|
8 megapixels |
8” x 10” (approx. A4 size) |
An 8 megapixel photo should already be sufficient for a good-quality A4 print. For this reason, there is probably little benefit from saving your photos at a higher resolution.
Storage
With a smartphone, things are not always as simple. Whilst some smartphones have a slot for micro-SD cards (e.g. Samsung Galaxy S4 and Sony Xperia Z), others do not (e.g. iPhone 5, HTC One and Nexus 4).
Frequent photographers may prefer a standalone camera for storage reasons. Alternatively, a cameraphone that supports micro-SD cards can do the job.
Your Thoughts…
In this article, we’ve compared cameraphones and dedicated cameras. Without a doubt, dedicated cameras still rule the roost in terms of picture quality. However, cameraphones rate highly on convenience, connectivity and choice of apps.
Has your cameraphone replaced your camera? Are cameraphone photos now “good enough”? Would you use your cameraphone or a dedicated camera when on holiday? We’d love to hear your thoughts… please drop us a comment below and let us know what you think!
Ken Lo writes about mobile technology and the mobile industry at Ken's Tech Tips.