Sony a9: more speed, less dynamic range
The Sony a9 is a powerhouse of technology, particularly when it comes to speed and autofocus. But does its image quality stack up? We've taken an initial look at Raw and JPEG image quality and have come away impressed, but how does the a9 stack up in terms of dynamic range?
At the recent launch in New York City, I had a chance to shoot our standard ISO-invariance test but on a real-world scene (our studio scene isn't so portable...). Have a look at the performance below.
It's immediately obvious the a9 is not ISO-invariant (what is 'ISO-invariance'?). This means the camera is adding a fair amount of read noise that results in noisy shadows, limiting dynamic range at base ISO. That's why, for the same focal plane exposure, performing analog amplification by increasing ISO in-camera gets you a cleaner image than performing that amplification (or brightening) in post-processing.
It's not the typical performance we've come to expect from Sony sensors and we suspect the higher readout speed is leading to greater noise. In other words, it appears this sensor was likely optimized for speed at the expense of low ISO dynamic range.
Ultimately, this limits the exposure latitude of a9 Raws, so you'll have some limited ability to expose high contrast scenes for the highlights, then tonemap* (raise) shadows in post. You can check the effect of changing the Drive mode in the widget (EFCS = electronic first curtain, S = single, C = continuous), but there's not much difference between them.
Effect of Drive mode
|There is little to no difference in base ISO dynamic range in different drive modes. So the good news is that the drop to 12-bit in continuous drive comes at no cost. The bad news is that the 14-bit Raws aren't any better than the 12-bit ones. Click here to load the above as a widget.|
As we mentioned above, there's no difference in shadow noise as you change Drive mode. This is particularly interesting because all Single drive modes, including fully electronic, support full 14-bit Raw (we shot uncompressed). The Continuous drive modes, however, switch the sensor into a 12-bit** readout mode which, by definition, means files with no more than 12 - 12.5 stops of dynamic range.
This indicates that even the 14-bit Raws have at most ~12 EV of dynamic range at the pixel level, placing our estimates of base ISO dynamic range almost a full stop behind the a7R II at equivalent viewing size (normalized), if not more (since we're basing this off an upper limit estimate for the a9). For comparison, have a look at how much better the a7R II's 14-bit Raws look compared to its 12-bit Raws.
'Dual Gain' helps improve high ISO dynamic range
In our widget up top, you may have noticed that noise suddenly starts increasing once you fall below ISO 640 (how's that for sounding completely back-to-front?). Below you'll see this more clearly: shadow noise dramatically clears up as you go from an ISO 500 image (with a 3.7 EV push) to an ISO 640 image (with 3.3 EV push):
Things clean up at ISO 640 (as with the a7R II) because of the sensor's 'dual gain' architecture, where the camera increases the conversion gain (effectively amplification) at the pixel-level during readout, helping overcome the camera's relatively high (for a Sony design) read noise.
Above ISO 640, the camera is fairly ISO-invariant, since it's overcome most of its downstream read noise, but there's still some benefit to increasing ISO to keep noise levels low if your scene demands it. Below ISO 640, the lower conversion gain means that you'll start to see read noise if you push shadows.
The good news is that those worried about the camera dropping to 12-bit readout in continuous shooting needn't worry: there's no decrease in quality, since a 12 bit file can contain all its dynamic range. The bad news is that this is because the a9 doesn't appear to have more than roughly 12 EV pixel-level dynamic range to begin with, putting its base ISO dynamic range behind that of the a7R II by at least 1 EV in our estimation. By high ISO, general image quality catches up as the higher downstream read noise is overcome by the sensor's (similar to the a7R II) dual gain architecture. Take a look at this ISO 51,200 comparison with the a7R II:
|ISO 51,200 comparison of a7R II vs a9. Not much difference, though the a7R II does slightly edge out the a9. Normalized signal:noise ratio (SNR) measurements place the two neck-to-neck: 1.82 vs. 1.48 for the a7R II and a9 at the dark patches here, respectively. At ISO 25,600, the normalized SNR is exactly the same. Please click on image for proper 1:1 comparison|
This means that if you're shooting in conditions demanding high ISO, for any given focal plane exposure you may wish to at least increase in-camera amplification to ISO 640 to get most tones above the noise floor, if your scene demands the extra amplification to get a usable image. Dropping below ISO 640 to preserve highlights, and then raising shadows afterwards, will come at a greater noise cost than, say, Sony's own a7R II.
Interestingly, this means there's little advantage to those large (47MB) uncompressed 14-bit Raw files, save for the lack of compression artifacts. In a perfect world, Sony would have offered a 12-bit Raw mode with an effectively lossless compression curve (without that second stage of localized compression that leads to edge artifacts) for smaller file sizes with no visual loss in quality.
* There's a very specific reason I like to use the word 'tonemap' instead of 'raise the shadows'. We're forced to raise shadows of high contrast Raw files exposed for the highlights today because of the limited brightness of most current displays. Future displays capable of far higher brightnesses (perhaps even ten-fold) will need less shadow pushing, or tone-mapping, to make visible what you currently see as 'shadows' in such traditionally underexposed Raw files. For example, shadows you currently push +4 EV will likely be visible without any pushing at all on a 4,000 nit-capable display.
** We confirmed that continuous modes were in fact 12-bit, while single modes were in fact 14-bit, by comparing histograms of respective Raw files. The 14-bit single drive files do, in fact, have 14-bits of data compared to the 12-bit files (the histogram shows the latter missing levels 1, 2, and 3, in between 0 and 4, but the 14-bit files do have pixels with these values).
Jul 24, 2017
Jun 29, 2017
Jun 14, 2017
Jun 24, 2017
Images have appeared which claim to show Nikon's forthcoming D850 DSLR, the development of which was announced this week. If genuine, the pictures indicate that the D850 will offer illuminated controls and a tilting LCD screen, but no built-in flash.
To celebrate the Daguerreotype Achromat 2.9/64 lens' successful Kickstarter campaign, Lomography has announced a chrome-plated version of the lens in Nikon and Canon DSLR mounts.
Nikon just released four new firmware updates, adding features and fixing bugs in the D600, D610, D750 and the KeyMission 80.
It probably hasn't made your landscape photography bucket list just yet, but there's a good reason to visit Idaho. Here are 9 must-visit locations in this beautiful state.
Oops... Adobe accidentally leaked their unfinished Lightroom-powered cloud-based photo editor 'Project Nimbus' to some Creative Cloud users yesterday.
Storm chaser and award-winning photographer Mike Oblinski just released his latest time-lapse, and it is absolutely stunning.
Looking to level up your video capture capabilities without buying a whole new camera? Blackmagic's Video Assist 4K is well worth considering, despite a few flaws and its lack of 4K/60p support.
We're big fans of Fujifilm's fast-growing GFX system, and the GF 110mm F2 lens is no exception. Positioned as the system's classic portrait lens, its optics are just as impressive with non-human subjects as well.
Nikon turns 100 years old today, and the company is celebrating with a wacky music video, some tributes to its history, and a new vision presented by president Kazuo Ushida.
Phottix just released the Premio Parabolic Umbrellas series, replacing their Para-Pro line with a stronger, deeper and better made set of parabolic umbrellas.
The Moto Z2 is Motorola's first dual-camera smartphone and, compared to its predecessor, comes with a number of improvements and new camera features.
Researchers at Stanford have revealed a new '4D camera system' built for robots. The system is based on the same light field tech that allowed Lytro cameras to refocus images after they were taken.
If you want 'beautiful rendition' from your lenses, follow this simple rule: only buy classic low-element prime lenses with lead glass elements—everything else is junk.
In an interview with CNBC, Leica Chairman Andreas Kaufmann said he dreams of a 'true Leica phone,' and hinted at what's next for the Leica and Huawei partnership.
Wildlife and nature photographer Peter Mather tells the story behind this exceptional shot of a mama grizzly and her cub searching for salmon in Yukon, Canada.
Popular YouTube channel TastyTuts has put together this 33-video Beginner's Guide to Adobe Photoshop—a godsend for anybody who wants to learn Photoshop from scratch.
The long anticipated replacement for the popular Rode VideoMic Pro is almost ready for shipping. The price of the upgraded VideoMic Pro+ will be £290/$300 when it goes on sale in mid-August.
A new iOS app called Explorest wants to help you find new locations to shoot. It's limited to Singapore for now, but the app is packed full of useful location scouting features.
Nikon's D850 development announcement is extremely light on details, so we assembled a wish list of upgrades and features we'd love to see.
Nikon has announced the development of the long-awaited replacement to its full-frame D810: the D850. Nikon says that the D850 will build on the strengths of its predecessor and offer 'new technologies, features and performance enhancements.'
Lens manufacturer Voigtlander has introduced a 65mm F2 macro lens for Sony E-mount that it says "rates as one of the finest in the history of Voigtländer."
The UK released a preview of their upcoming drone safety regulations, and it looks like drone pilots will have to both register their device and pass safety awareness tests.
National Geographic photographer Bob Holmes talks about light, and why you need to learn how to 'see' and not just 'look' at your subject.
Photographer Alessandro Barteletti shares the story behind his National Geographic Italia cover, shot with a 10-year-old DSLR and an iPhone flashlight.
Fashion catalog photographers in China have some next-level models to work with. In this video, you see one model hitting 30 poses in 15 seconds as the photographer snaps away.
Photographer Paul Adshead breaks down 11 photography-related smartphone apps he couldn't live without—from a pocket light meter to a lighting diagram app.
Fast-growing Chinese flash brand Godox is teasing a brand new flash trigger... for smartphones. The Godox A1 is a 'phone flash system' that can act as both flash and 2.4GHz trigger.
On July 12, Canon opened its newest Technology and Support Center, designed to serve the motion picture industry, in Burbank, CA. DPReview got a sneak peak and takes you behind the scenes.
The Sigma 14mm F1.8 Art is truly one-of-a-kind. It offers the fastest aperture of any lens that shares its focal length, produces beautiful sunstars and is incredibly sharp to boot. If you're in the market for a fast ultrawide prime, this looks to be the one to get.
In this article, expert macro photographer Thomas Shahan shares advice for successful closeup photography of bugs, insects and small animals.