Sony Alpha 7S Review
Raw Dynamic Range: Real WorldBy Rishi Sanyal
The previous two pages demonstrated that while the a7S fares well next to its competitors with respect to dynamic range, especially when compared to Canon DSLRs, it isn't quite class-leading, falling behind what we've come to expect from Sony Exmor sensors.
It can sometimes be a bit hard to read about 'Dynamic Range' or see test data and translate it into real-world impact. Here we demonstrate the processing latitude offered by the Raw files of the Sony a7S and a7R, which illustrates the two cameras' respective base ISO dynamic ranges. We do this by exposing each camera for the highlights, and then assessing the noise levels of shadows when they're brought up to visible levels.
The Raw dynamic range of a camera is defined by the difference between the brightest tone a camera can capture and the darkest usable tone that is not swamped in noise. While DxO provides rigorous measurements that put a number on this attribute (they place the a7S and a7R about 1 EV apart in this regard), we visually show you what the difference in base ISO Raw dynamic range between these cameras looks like.
We shot a moderately high dynamic range sunset scene with both the a7S and the a7R, without filters of any kind. Our choice of exposures for this test parallel how a landscape shooter may have shot this scene, and requires a bit of elaboration.
The best way to capture a high dynamic range scene in a single exposure is to 'expose to the right' (ETTR). Using this method, you give the camera as much exposure as possible until the brightest tones in the scene you wish to capture are just short of clipping in the Raw file. Not only does this ensure that highlights are preserved, it also ensures that other tones - mainly shadows and midtones - have a fighting chance despite the shorter exposure required to protect highlights. The more light you collect, the cleaner your tones are because you (1) minimize the risk of darker tones running into the noise floor of the sensor from too short an exposure, and (2) minimize noise inherent in the light itself ('shot noise', due to the random arrival of photons), which decreases or 'averages out', in a sense, the more light you collect. Hence ETTR philosophy champions giving the sensor as much exposure as you can, but not so much that you clip bright portions of the scene you wish to preserve.
Typically, when you then pull an exposed-for-highlights Raw file into your favorite Raw processing software, the shadows and midtones will be dark. This is largely due to the low dynamic range and brightness of most of our monitors these days, requiring us to push shadows in Raws exposed for the highlights just to make them visible. A comparison of the noise levels in these pushed shadow regions then gives one an idea of the dynamic range capabilities of the camera.
Above, we've captured Raw files using exposures that map some of the *. That is, 1/3 EV longer exposures on either camera clip the green channels in these clouds. We decided not to try and retain detail in the sun because that is probably photographically irrelevant. We're essentially trying to 'fit' the dynamic range of the scene into the dynamic range of the camera by mapping the brightest tones we wish to preserve as close to clipping on the sensor as possible, but not further below it, for the reasons we gave above.in our scene - the clouds above the sun - to Raw values just short of clipping
In a nutshell? a7R, hands down. As you can see in theabove, where we've downscaled the a7R image to the a7S' 12MP resolution, the a7R offers more detail and cleaner shadow/midtone imagery compared to the a7S. Downscaling the a7R image also appears to have the added benefit of making any noise present look more fine grained; the a7S' noise looks .
So much for more pixels = more noise, a fallacy we've now debunked a number of times in this review.
If Sony should've been bragging about the dynamic range of any of its cameras, it should've been the a7R, not the a7S. Sony marketing claimed 15.3 EV dynamic range for the a7S, which appears to be approximately exaggerated by 2 EV according to DXO tests. The a7R appears to be 1 EV ahead of the a7S in those tests. To put this in perspective, though, both cameras are well ahead of offerings from Canon, but if you're looking for dynamic range for landscapes, or exposure latitude for flexibility in post-processing (or because you've simply mis-exposed a shot), the a7R is the winner here. Even in non-normalized, full-resolution comparisons, where the a7R continues to offer than the a7S.
An aside: Sony Raw compression
One thing we're going to call Sony out for is its continued use of compression in Raw - which can affect your ability to perform some of the edits we performed above. Because of the compression scheme Sony uses even in Raw files (no, you can't turn this off), high contrast edges in a scene are sometimes prone to posterization. While it's not uncommon to see manufacturers offer compressed Raw modes that allow for smaller file sizes with minimal cost to image quality, some implementations are better than others. Typically, these modes will take advantage of the fact that most recorded tones inherently have some fluctuations associated with them due to photon/shot noise (random fluctuations in incoherent light itself), and it's only important to accurately record the magnitude of these deviations. Recording finer variations in signals doesn't hurt, but just over-quantizes shot noise, and so is typically redundant. This is how Nikon offers 12-bit Raw files that encode larger ranges of dynamic range, for example.
Sony's compression scheme is two-step, however, and while the first step of compression (that takes advantage of the shot noise fluctuations described above) seems perfectly reasonable, it's in further spatial compression of that data where things go wrong, and gaps in retained information become visible. What results are posterization artifacts in transitions between light and dark tones. The problem extends to many Sony cameras, including all of the a7-series bodies. Have a look at the borders between the bright Space Needle buildings and the dark blue sky (which has been lifted only 1.5 EV in post) in the rollover below:
100% crop #1
100% crop #2
You can find the original Raw file here. It's important to note that - in thise case - we didn't even have to make a drastic edit to make the posterization visible; in fact, posterization was evident even in out-of-camera JPEGs that had 'DRO' set to 'Auto' (as this mode performs some shadow boosting to even out tones). We feel that Raw shooters looking for the best image quality could do without the potential pitfalls of Sony's compression methods, especially considering the competition offers significantly more 'lossless' Raw. Not to mention the price point of some of these bodies. We hope to see this fixed in future Sony cameras.
*To be precise: the brightest pixels have a 14-bit Raw value of 15,860 in the green channel, just short of the maximum 'clipped' signal of 15,988, as analyzed by RawDigger. Raw files are available for download for your own analysis.
Aug 8, 2017
Mar 2, 2015
Jun 28, 2016
Mar 15, 2016
|Fascia walkie talkie building London by ian herridge|
from Abstract Architecture
|Global Reach by cjf2|
Happy 2017 World Photo Day! We asked everyone on staff at DPReview to share one photo that they took within the last year that makes them jazzed on photography. Here's what we chose.
French President Emmanuel Macron has lodged a legal complaint against a paparazzo who snuck onto the president's private vacation property to take pictures.
Ever wonder what the difference is between compressed, uncompressed and lossless compressed Raw files? Photography Life's Nasim Mansurov breaks it down for you in this informative article.
The oldest known portrait of a US president was just discovered after over a century in storage. It's going up for auction in October, where it's expected to fetch between $150,000 and $250,000.
If you're using the popular Sigma 24-70mm F2.8 Art lens with Sigma's MC-11 converter, listen up: you'll want to update your lens and converter firmware ASAP.
If you've heard it once, you've probably heard it a thousand times: never check in your camera gear when flying. This shattered $11,000 lens is what can happen when you do.
Lensrentals just did its first Cine lens comparison, pitting five top-notch 35mm primes against each other: the Zeiss CP.2 35mm T2.1, Canon CN-E 35mm T1.5, Sigma 35mm T1.5 FF, Rokinon Xeen 35mm T1.5 and Schneider Xenon 35mm T2.1.
A team of Google researchers have found that slightly warping watermarks when embedding them into images can help prevent automatic removal.
You don't have to empty your savings account to take your photography to the next level. These cheap buys cost about $50 or less, and come with outsized benefits for your photography.
Joey L, Dani Diamond, Brandon Woelfel and Jessica Kobeissi go head-to-head in an episode of "4 photographers shoot the same model."
The latest flagship phone from Asus combines a 12MP 1/2.55" Sony IMX362 main sensor with a smaller Sony IMX351 chip for 2x zoom and a background-blurring portrait mode.
The company behind popular photo editor Picktorial 3 just released the X-Pack: a preset package that allows you to add Fuji's in-camera film simulation profiles to your RAF files in post.
Photoshop. GoPro. Every once in a while a product emerges that defines a category. And sometimes, it vanishes just as quickly as it arrived on the scene. This week's Throwback Thursday remembers the Flip, the pocket camcorder everyone had – until they didn't.
The Nokia 8's dual-cam combines the image data from a 13MP RGB sensor and a 13 monochrome chip for better detail, improved dynamic range and lower noise levels.
The company behind retail giant B&H Photo has agreed to pay out $3.2 million in monetary relief and back wages to settle a discrimination and harassment case from 2016.
After a popular Facebook teaser and some studio portrait samples, Godox has finally officially released the Godox A1 smartphone flash and flash trigger. Cheap, versatile and innovative, color us intrigued.
Canon’s EOS 5D Mk IV has won the European Imaging and Sound Association’s Professional DSLR of the Year award, making this the third year in a row that the brand has beaten Nikon to the top spot in the professional camera category.
A photograph and quote tweeted out by former president Barack Obama has officially become the most popular tweet of all time, receiving over 1.3 million retweets and 3.4 million likes.
Edward Weston was one of the most influential photographers of the 20th century, and in this episode of Advancing Your Photography we learn the extreme technique he used to capture one of his most famous still life photos.
Instagram just released a small update that will make a huge difference if you're active on the photo sharing app: threaded comment replies.
Venus Optics has announced the price and delivery date of the second lens to join its Zero-D line up: the 15mm F2 for Sony’s E mount. A lens they've dubbed, "the world's fastest 15mm rectilinear lens for full-frame."
Cinnac is a new social network for photographers that will help you separate your good photos from your great ones through a Tinder-like community-based rating system.
The Canon EF 35mm F2 IS USM is an understated jewel of a lens, and one that we've enjoyed on a variety of cameras since its release almost five years ago. Its relatively small size and image stabilization make it a versatile tool for a variety of photography - check out our sample gallery.
You don't need a fancy studio or tons of gear to capture the kind of classic product photography you see in magazines. In this video, Dustin Dolby shows you how to do it with just a couple of speedlights and some know-how.
The life-logging camera is trying to make a comeback. Say hello to FrontRow, a live-streaming enabled life-logging camera from Ubiquiti that hangs on a necklace like a pendant.
When a prospective client approaches you, don't just say "yes" right away. Here's a useful list of questions you should be asking before you decide to take the job and name your price.
Samsung just revealed a blazing-fast new Solid State Drive capable of data transfer speeds of up to 540MB/s.
DJI has developed a 'Local Data Mode' that lets pilots fly without being connected to the Internet. The mode should calm recent fears over data privacy and security when flying DJI drones.
After 1.7 million downloads on Apple computers since the launch in November 2015, Aurora HDR will be available for Windows PCs for the first time with the 2018 release.
The company behind the new Meyer Optik Goerlitz lens manufacturing business has formed a new brand to bring back the Biotar 75mm F1.5 that was made by Carl Zeiss Jena in the 1940s and 50s.