6: Image Quality & PerformanceNext
Do you need 41 megapixels? Our Nokia Lumia 1020 camera review
Peter M Ferenczi | Published: Aug 30, 2013 at 16:35 UTC368
Image Quality and Performance
With its dual-core Snapdragon processor and 2GB of RAM, the 1020 feels fast and smooth in general use. Windows Phone’s bold tiles glide nicely around the screen.
That’s the good news. The bad news is that when it comes to camera operation, the 1020 is sluggish compared to the competition. Whether using Nokia Pro Cam or the standard Windows Phone camera app, shot-to-shot time hovers around a glacial four seconds, long enough to leave many users frustrated. It’s fair to guess that this lag represents the enormous amount of sensor data the 1020 has to crunch for each shot, but that’s an explanation, not an excuse.
The fact that the 1020 can take a burst of 10 shots at a reasonable clip with the Smart Cam app hints at a possibility for better performance, but it’s likely that in that case the image data is dumped into an enormous buffer and then processed when the burst is complete. If the phone can’t chew while it’s cutting its next bite, there’s bound to be some lag that could only be addressed by intense computing horsepower.
So, you have to wait between shots. Unfortunately the Pro Cam isn’t too quick on the initial draw either, taking four to five seconds to launch (cold start or warm). Here, the standard Windows Phone app does better, kicking over in about two seconds.
Once you’ve got a capture app fired up, focus acquisition is competitive but not as snappy as the best. As usual, it’s a bit slower in low light, but accuracy is good: focus errors are very rare. In really low light (tripod territory) setting the manual focus to infinity is a good idea.
Daylight, Low ISO
It’s a little hard to know how to judge the 1020’s image quality. To be clear, pixel peeping a 38-megapixel phone camera image is insane. At 300 dpi, it would print 24 inches (60 cm) wide. At the pixel density of a 40-inch HD TV, you’d need a screen nearly 11 feet wide (2.5 meters) to display the whole image at native resolution. Pixel-peeping a 38MP image is going to tell you something, but it won’t have much to do with real-world image quality. Of course, that won’t stop us from doing it.
Then there’s the 5MP downsampled images. Is it fair to say that they contain less detail than the output of something like Samsung’s 13MP S4 when they’re really the distilled goodness of so much image data?
Despite concerns about fair apples-to-apples comparisons, it’s indisputable that the 1020 captures a phenomenal amount of detail in good light at low ISOs. Even at a 100% view on a screen, there’s a lot of usable detail at maximum resolution. The unzoomed, downsampled 5MP versions, while obviously containing less detail, look better than phone camera output studied at native resolution on screen usually does. Details are clean, clear and present, even in darker, low contrast areas that look smeary at the pixel level on most competitors. Nokia appears to apply a firm but judicious amount of sharpening to the 5MP file so that edges are crisp, but not overly so.
Noise is well controlled, even in the full-res files. What little appears there gets largely averaged out in the 5MP output, which is of course the point. Even in areas of smooth, darker tone, the 1020 delivers an impressive performance.
Colors are fairly accurate, though Nokia juices up saturation a bit to give photos that extra “pop” that we’ve come to expect from phone cam images (a saturation control would be a nice addition to Pro Cam). Automatic white balance accuracy is good, though it runs a little cool in the shade.
While the 1020’s combination of high resolution and larger sensor make great strides in some image quality metrics, dynamic range does not appear to be much better than the competition. From a technical perspective this makes sense. It’s the size of the individual photosites, rather than that of the sensor as a whole, that has the biggest impact on the ability to record wide dynamic range (the difference between the brightest and darkest parts of the scene). Because of the 1020’s high pixel count, the photosites are no bigger than on most phones. As that fact predicts, the 1020 appears to blow out highlights about as much anything else on the market. It’s worth noting that because of the 1020’s low noise output, you can get away with underexposing more to protect highlights and then brightening dark areas in postprocessing.
The 1020’s lens is sharp across most of the frame, but the unforgiving resolution showcases some poor corner sharpness. This is still visible, though less insulting, in the 5MP files.
Low Light, High ISO
With its big sensor and fast, image stabilized lens, the 1020 does very well in low light conditions: it’s currently the best phone for low-light photography on the market.
The 1020’s optical image stabilization means that you can avoid shake-induced blur at much lower shutter speeds than on most phones. For most competitors, speeds at or below 1/15 sec are flirting with blur, and speeds below 1/6 sec or so pretty much guarantee it. The 1020’s image stabilized lens soaks up hand movement to make 1/6 sec routinely usable and speeds as low as a 1/2 sec give good results with a solid shooting position, at least when shooting static scenes. This lets you keep ISO lower for better image quality (for a given phone, a scene that requires a 1/15 sec exposure at ISO 800 could be shot at ISO 100 at 1/2 sec), or simply shoot in lower light conditions than would otherwise be possible.
Image stabilization helps with hand shake, but not subject movement. For that, only higher shutter speeds will do, and that means higher ISOs. The 1020 will usually have you covered, with a manual ISO range that spans from 100 to 3200 (on auto, it hits a stratospheric 4000). Such rarified sensitivities aren’t unusual in phones today, but on the 1020, ISO 3200 is actually usable for web resolution output. At 1600 and below, the 1020 turns in a remarkable performance.
Zoom Image Quality
Nokia takes advantage of its big, high-res sensor to offer a true novelty: a digital zoom that doesn’t suck. A “digital zoom” traditionally means cropping the image and then upsampling it to the camera’s native resolution. Since you can’t create image data from thin air, heavy upsampling results in the soft, detail-impoverished images we’ve come to expect from digital zooming. The 1020’s high native resolution means that even with some cropping (zoom) applied, the image is still downsampled through most of the zoom range. You get a 2.7X zoom ratio (a 74mm equivalent in 4:3 mode) before the cropped image hits 5MP. The same digital zoom ratio on an 8MP camera results in a 1MP image being blown back up, with predictably underwhelming results.
In good light, quality drops off relatively little when zooming, thanks to the 1020’s solid low ISO performance. With a moderate zoom setting, the loss is negligible. At full zoom, when you’re getting un-oversampled output from the sensor, the quality remains good but noise is definitely more present.
At higher ISOs, image quality drops more as the 1020 doesn’t get to average out noise in the downsampling process. That said, at ISO 800, even at full zoom, image quality remains quite steady at screen resolutions: you have to get down to pixel level to see how more noise is cutting down on detail.
Our verdict is that while the zoom isn’t quite “lossless,” we wouldn’t hesitate to use it under most any lighting condition. Plus, if you’re saving the full-res file as well, you can always get back to the original, unzoomed image.
The 1020 is one of very few phones with a xenon strobe flash similar to what you’d find on a dedicated camera. Compared to the LED flashes on most phones, the 1020’s strobe is a powerhouse, providing bright, even lighting for relatively close subjects. If you take a lot of flash-lit people-shots at bars and parties, you’ll be impressed with how much the 1020’s output looks like that of a “real camera.” Because of the brief light pulse a xenon flash delivers, it can also help freeze action at lower shutter speeds.
While the flash is excellent by phone standards, it’s doesn’t have the oomph to light more distant group shots, and certainly not whole rooms. In addition to full auto mode, you can disable the flash and focus light entirely, or just kill the flash, leaving the focus light (an LED) active. Exposure compensation in Pro Cam doesn’t seem to impact flash exposure.