Using iPhone: Camera and Photo Comparisons: Part 1
August 7th, 2007
Daniel Eran Dilger
How does the iPhone’s integrated camera stack up? Compared to standalone point and shoot digital cameras, most cellphone cameras take very poor quality photos. They’re not designed to take the best pictures; they’re designed to be ready and available to grab a snapshot on occasions when there’s no good camera available.
The High Price of Features.
There are some exceptions, like Nokia’s $750 N95, which includes a 5.0 megapixel camera with LED flash and an autofocus lens. Its integrated camera compares well with standalone cameras, with a few exceptions. However, all features have their price. The N95 is not only $250 more than the 4 GB iPhone, but it lacks the iPhone’s 4 GB of Flash. Adding a 4 GB micro SD Flash card costs another $75.
That extra storage is important because a 5 megapixel photo, even when compressed by internal filtering, takes about 2 MB of space. On a phone that’s already starved for storage, the N95 really begs the user to set the camera to take photos at a more reasonable 3 megapixel setting.
Another example is the Nokia’s LED Flash; it’s only useful when taking photos where the subject to be illuminated is less than three feet away. An LED is no match for a flashbulb in a standalone camera, and a flashbulb makes little sense in a mobile because of the battery energy it consumes.
Another issue related to power management is a camera’s photo capture chip. Mobile phones like the N95 use CMOS sensor technology, where a camera designed solely to take good pictures would use a CCD chip, which at the cost of using more energy can take much better pictures.
An autofocus lens also sounds like a good idea, until you find yourself waiting for the lens to focus and miss your shot. Clearly, features that are great in a camera can’t always translate into a very different form factor without some significant tradeoffs. Simply comparing technical measurement numbers doesn’t provide an accurate representation of photo quality and suitability at a reasonable price point.
[Update: Several readers pointed out that CCD chips only offer an advantage when comparing against the low end of CMOS chips like those used in mobile phones.
Nick Fabry explained that the CCD advantage over CMOS “was true about 6 years ago, but since that time, primarily due to Canon, CMOS sensor chips have advanced and surpassed smaller CCD sensors in effective image quality - they were always better at dissipating less energy, and that remains true. Today, all of Canon's cameras use only CMOS sensors, including their top of the line 1Ds Mark II, a $7,000 camera, as does Nikon's top of the line SLR, the D2Xs, at $4,500.
”The only high quality, professional grade cameras that still use CCDs are the ultra high resolution, large sensor cameras (larger than 35 mm - think Hasselblad and lots more $$$), because large, high quality CCD sensors are easier to manufacture than large, high quality CMOS sensors, but it is probably just a matter of time before they switch as well.“
Eric Erickson added, ”Besides using less battery, CMOS also produces less noise artifacts when taking long exposures. I believe Nikon and Sony have also followed suit in using CMOS in their pricier cameras. At least I know Canon uses CMOS as it is in my Canon D20 SLR.“
The point remains that a 5.0 megapixel mobile phone camera is not equivalent to 5.0 megapixel dedicated use camera, for a variety of engineering reasons that relate to component cost, size, and battery use. There are more CCD vs CMOS comments in Using iPhone: Camera in Low Light Conditions: Part 2]
Mobile Phone Photos.
Cameras on most mobile phones are commonly 1.3 megapixel. That includes the Palm Treos and Samsung BlackJack, which runs Windows Mobile. I used each to take some comparison photos, along with a 5.0 megapixel Casio Exlim, the 1.3 megapixel camera built into the Mac Book Pro, and the iPhone’s 2.0 megapixel camera.
Megapixel ratings only indicate the number of dots of resolution in the captured image; they are not a raw measure of quality, particularly when comparing different technologies and implementations. As noted above, a CMOS camera capturing a 5 megapixel display with the aid of an LED flash and then heavily compressing it with image filtering is not the same as a 5 megapixel CCD camera with a real flash, which can save RAW data rather than a highly compressed JPEG image.
Color accuracy and detail depend on more than just the sensor used. After capturing a photo, all consumer digital cameras process the raw data, perform corrections, and heavily compress the photo file that is saved to Flash. The actual quality that results depends a lot upon the manufacturer’s photo technology. Among Windows Mobile phones, Samsung is at the top. Palm’s Treo is built by Windows Mobile maker HTC, not known for great photos.
Resolution in Megapixels.
A camera’s sensor resolution doesn’t necessarily match its output resolution. The Palm Treo, while using a 1.3 megapixel camera, actually captures photos at 640 x 480, which is only a 0.3 megapixel resolution.
The built-in iSight camera on Mac Books similarly captures at 640 x 480, despite being a 1.3 megapixel camera. The iPhone’s 2 megapixel camera actually captures a 1600 x 1200, 2.0 megapixel image, which is more than six times the resolution of the Treos.
The Samsung Blackjack captures a full 1.3 megapixel resolution of 1280 x 960 in the still photos it takes.
Rather than just compare resolution numbers, a more realistic goal is to compare useable functionality. A camera phone is designed primarily to capture casual photos, such as a friend’s portrait for their contact listing, or to grab shots at moments where carrying a real camera isn’t practical. Being able to frame and take photos rapidly is important, as is automatically coping with different lighting conditions.
The simple ability to get photos off of a camera phone and onto a computer for editing or posting into a blog is also important. Many phones from Verizon insist that that user send them–for a fee–as MMS picture messages rather than download them directly to their desktop. Seamless syncing is another advantage of the iPhone.
[Using iPhone: File Sync Via USB, Wireless, and Over the Air]
Photo Comparisons: Treo vs Blackjack vs iPhone vs a Standalone 5.0 Megapixel Camera.
This well lit scene was washed out for the Mac Book Pro’s camera (below left), which is designed primarily for indoor video conferencing. The Palm Treo’s camera (below right) is also low contrast and lacks detail. Both use a 1.3 megapixel sensor but record a 640 x 480 (0.3 megapixel) image.
The Samsung Blackjack’s photo (below left) is a considerable improvement over the Palm’s (above right), despite both using the same 1.3 megapixel sensor. But compared to the 2.0 megapixel iPhone photo (lower right), its colors look faint and it lacks detail and contrast overall.
A second iPhone image (lower left) I took of the same scene had softer focus. The iPhone’s fixed focus lens appears to provide a limited depth of field. While considerably better than other mobile phones’ cameras, the iPhone still lacks the detail of the sharper and more color accurate 5 camera megapixel image (lower right).
Blown up to native resolution, it’s even more obvious that the Blackjack (below top) and the iPhone (below middle) can’t compete with the camera image (underneath). Don’t throw away your stand alone camera just yet.
The iPhone Camera.
Despite having a competitive resolution for camera phones in its price range, the iPhone lacks any ability to record video, which is considered standard for most phones. The Treo and Blackjack record video at 320 x 240, a .07 megapixel resolution. These videos are nearly worthless, but some phones capture more usable video.
The iPhone’s camera is extremely basic, only offering to snap photos and then look at them. There’s no way to manually set shutter speed or exposure, making it particularly hard to capture pictures against a bright sky; the detail simply becomes a black outline.
A Software Button.
There’s and only one button and only one setting: fully automatic. The shutter button on the iPhone’s touch screen is a software button, so it doesn’t take a picture when you touch the button, but rather when you lift your finger. That’s useful to know when trying to capture a specific instant in a photo, or when trying to hold the iPhone steady to take a shot in low light, when the picture is most like to blur.
Without knowing that, it’s also tricky to include yourself in a photo. Since there’s no mirror on the back of the iPhone, it’s doubly hard to frame yourself in a shot: no way to aim, and no target button to hit sight unseen with your finger. There’s two tricks:
- first, it works best to touch the shutter button with your finger, aim the shot, and let go to take it.
- second, the Apple logo on the back of the iPhone is shiny enough to work as a mirror of sorts. To blindly frame yourself in the shot, line up your lips inside the Apple, and lift your finger to take the shot.
There’s little indication that a photo has been taken apart from the rather subtle click sound. With vibrate on, there’s no indication at all. Of course, that also makes it easy to take candid photos; some phones insist on playing a loud sound when taking a snapshot.
As the shutter snaps, the iPhone displays an animation of a closing aperture, which is somewhat oddly ironic. This also gives the impression that the photo is being taken during the moment or two that the shutter closes. It’s not; instead, it’s doing some image processing and saving the photo to flash RAM.
Blurring the Lines.
Once it’s ready to take the next shot, the captured photo slides down into a photo library icon, offering an intuitive hint as to where to view your captured photos. It takes a bit of trial and error to figure out how long the camera needs to stay steady after taking to photo in order to avoid blurring it.
This seems to depend a lot on how much light is available. In bright light, the camera is great for capturing portraits and good for taking landscape shots. In indirect lighting, photo quality falls down to fair; it appears prone to blur areas of the photo and wash out details. Any motion is blurred, particularly light sources.
I captured these trees on Market Street and Yerba Buena Lane, illuminated from below at 10:30 PM. Without keeping the camera steady, they turned into an impressionist smear:
Loss of detail in low light is most obvious only when the photos are blown up an examined in detail; photos typically look great on the iPhone’s high density screen. When it gets too dark, pictures start to get grainy fast. That doesn’t mean the iPhone is no good at all in low light conditions however. Part two will present more photos examples related to low light conditions: night photography, concerts, and indoors.
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