Sunday, February 8, 2015

Canon EOS 5DS and 5DS R Launch Review



In time for the 2015 CP+ Japanese tradeshow, Canon announced the 50mp EOS 5DS and the 5DS R variant. The internet is naturally abuzz, proving that "big number" product marketing isn't dead in the camera industry. What has changed since the 5D Mark III:

  • New 50.2MP Canon-designed sensor 
  • 150k pixels exposure meter (RGB+IR, like 7DmII
  • Reinforced tripod mount
  • Electronic first curtain shutter option in Live View
  • Dual Digic 6 processors
  • Artificial light flicker reduction (like 7D Mark II)
  • New mirror mechanism (like 7D Mark II)

What hasn't changed:

  • 61-point AF module, 41 cross-type, 5 double-cross type
  • 1080/30p video (7DmII can do 60p)

What's worse:

  • No headhone jack
  • No clean HDMI output
  • Battery life slightly worse

The end result is a mixture of ultra-high resolution feature set combined with features that seem curiously...crippled. The exposure meter is upgraded from the 5D Mark III, which is synergistic with the increased resolution. Though the 5D Mark III autofocus system is good, a (theoretically) better unit now exists in the 7D Mark II. The fact that video hasn't changed at all and is arguably worse than the 5DmIII indicates that Canon is being more single-minded about the EOS 5DS' mission than it was with the general-purpose predecessors.


Sensor

 

Resolution


The difference between the 50mp 5DS the 36mp Nikon D810 is equal to an 18% increase in linear resolution. Though 50mp is a big number, this is just under the difference in linear resolution between the Nikon  D810 and the 5D Mark III. To put the increase into perspective, at 300 DPI, you can produce detailed prints with a 5D Mark III at 13" x 19", the largest size that the home-oriented Canon Pixma Pro-100 can accomplish.

Inevitably, the question arises: do you need all of this resolution? The answer is: if you have to ask, then the answer is no. The longer answer is much more nuanced, of course. If you are doing large prints more resolution is a better thing. However, many people don't notice/pay attention to the colour detail lost to the Bayer array. This is why more pixels is always better if there aren't any downsides. If the 5DS can create a more detailed image than the 5D Mark III without a noise or dynamic range penalty, then it is a better sensor by virtue of the fact that it is sample more image data. Put another way; you don't have to use all 50mp to get the benefit of more pixels; the 5DS image down-sampled to 5D Mark III dimension will appear crisper and sharper. You can see this with the Nikon D810; when you down-sample its images, you still get better visual acuity than with smaller sensors at native resolution.

Optical Low-pass Filter


Like the D800/D800e, the 5DS is split between the regular version and the "R" version which uses a cancelled-out optical low-pass filter. The reason why the anti-aliasing filter isn't removed completely is because the optical system at the microscopic level has some depth to it; in order to produce both cameras on the same production line, the dimensions of the sensor stack assembly have to be kept the same to maintain manufacturing tolerances.

A more interesting questions is why Canon decided to bifurcate the 5DS line at a time when Nikon consolidated the D800/D800e into the D810. Nikon made the decision that the upside (better resolution) was greater than the downside (moire and false colour patterns)  for the majority of their users. Real-world use shows that unless you are shooting at tight repeating patterns (fabrics), moire is not a significant issue with the D810... and that's with a camera that has a lower pixel density than the 5DS. As pixel density climbs, the ability of the camera to discriminate high frequency detail goes up. The Sony-sourced medium format sensors used on the Pentax 645Z and the Hasselblad H5D-50c don't use anti-aliasing filters either. In this regards, the 5DS is out of step with the rest of the industry. It's a curious move considering that the real-world difference between the D800 and D800e was equivalent to a very modest amount of sharpening in post-processing, and that the D800e itself sold in very few numbers relative to the D800.

Product Marketing


Some of this might come down to Canon's following with wedding and fashion photographers, but there is another reason to split the line-up, and it has nothing to do with the capability of the camera itself. It comes back to the dreaded phenomenon of "shelf-stuffing", the practice of filling out a product line-up with the hopes of crowding out other competitors in terms of retail space and mind-share. The problem is that Nikon got there first and have a more varied full-frame line-up. Until now, the Canon EF-body line-up was very stark: you were either a consumer level shooter (EOS 6D), a semi-pro (5D Mark III) or a professional sports shooter (1Dx). There are big jumps in price and capability between those three cameras. While that made it easier for Canon shooters to figure out where they fit in, the Nikon line-up made people stop and think longer about which camera (D610, D750, Df, D810, D4s) suited them. Therein lies the rub; if you are spending more time thinking through one brand with a larger line-up, you are spending less time concentrating on the competing brand with the smaller line-up.

This is good  news for the consumer, but it's not good for the industry. During the boom years of the DSLR era, photographers generally lusted over one or two aspirational higher-end cameras. Now that the market is in a state of contraction and the pace of technological improvement is slowing down, it is taking the camera companies more time and effort to chase fewer sales. This means more variety to fill more niches. It's a headache for product planning and it's a headache for retailers who have to maintain multiple SKU's. However, the end result of the 5DS and 5DS R is that it potentially closes the sizable gap between the 6D and the true semi-pro portion of Canon's full-frame lineup. With the 5DS present, it allows the older 5D Mark III to drift downwards in price, closer in competition to the Nikon D750. This also makes opens up room for an possible 5D Mark IV to slot in below/beside the 5DS.

This last point carries with it some irony. When Nikon went from the D700 to the D800 some steadfastly refused to believe that the D800 was indeed the true successor, and that a more general-purpose camera with a more moderate megapixel count would surely come. That of course, never happened, not in the way that the Nikon faithful expected it to. Could history be repeating itself over on the Canon camp? Initial reception of the 5DS is like watching the introduction of the D800 all over again. Nikon got by because the D800 was a significantly better camera in almost all respects; the problem is that the same isn't true of the 5DS over the 5D Mark III.

Dynamic Range


One thing that is hard to avoid in current internet discussion is how much Canon has lagged behind the Sony sensor cameras (Nikon, Sony, Pentax et al) in terms of DxO scores. There are a lot of truths and half-truths about this, but it basically boils down to:

  • There is a practical difference in dynamic range between the 5D Mark III and the Nikon D810. This shows up especially in post-processing and with contrasty subject matter at low ISO
  • Be that as it may, the market share positions between Canon and Nikon have not changed appreciably over the past five years, so outright image quality is not the sole determinant of many Canon user's criteria for choosing the system. 

Lost in the jingoism of internet discussion is the fact that DxO publishes a composite score. The final "number" is a weighting of many different criteria, and the value of the score can be changed according to how the various components are weighted. The new Canon 5D moves forward with the move to 50mp, but the implication is that it has roughly the same dynamic range as the 5D Mark III. Considering that Canon hasn't announced any major changes in circuit manufacturing, this isn't surprising. If it's a case of more resolution but not as good exposure latitude as the D810, the DxO Mark score might still close up between the two cameras.. Given the past history of Canon and DxO, this alone would be considered a victory, but the specs give a clue to what's going on. The rated ISO range for the 5D Mark III is up to ISO 25,600 for native ISO; the 5DS cameras cap out at ISO 6400, two stops less than their predecessor. To put that into perspective, that's the same native ISO range as the EOS 70D.

The decrease in high ISO noise performance is understandable given the increased pixel density, but one that that is poorly understood is that the lagging low-ISO dynamic range is arises from the fundamental Canon image pipeline architecture. Canon sensors have used analog to digital converters (ADC’s) located outside off the image sensor itself. What is means is that a handful of ADC processors (with the 5D MarkIII, 8 are used) share data among all the columns on the sensor by multiplexing the analog signal out to the ADC board. Minor differences between these analog read-out channels produces patterns in the output signal which may be visible when the signal to noise ratio is low, as in the shadows. Because the analog pathway from sensor to ADC is longer than it is with the Sony chip's, the Canon chips tend to have more image noise at low ISO; the analog signal is vulnerable to picking up stray signals from the surrounding circuitry. The longer the signal stays in analogue form, the more chance of inducing extra noise. The difference tends to narrow at higher ISO.

Conversely, Sony chips use ADC's that are integrated into each pixel column on the sensor, and are run with a chip clock speed that is significantly lower rate than the Canon implementation. The signal fluctuations are still present but because there are thousands of built in ADC's running at lower speed instead of a handful running at high speed the signal variation is low and distributed more evenly across the the whole image readout. This results in less pattern noise, aka "read noise". This also improves the low ISO dynamic range compared to the recent Canon chips. Dynamic range is the difference between the saturation capacity of the light-well and the noise floor; because the Sony chips have such low read noise, the noise floor is lower. This has two implications for still images. The first is the idea of "ISO-less" shooting. The second is that it tends to inflate the DxOMark scores for sensors with on-chip ADC's, as the DxO composite scores are weighted to favour low ISO sensors.

However, even though the Sony method is better for still photography, that doesn't necessarily mean that it is the best architecture overall. With the ADC's located on-chip, heat generation can be an issue with higher frame rates, meaning that additional cooling considerations need to be factored into the design. The implications for continuing with an off-chip ADC go something like this:


Pros:


  • Lower power use on the sensor; less dark current. Good for video and astrophotography.
  • ADC can be designed independently of the image sensor

Cons:

  • Additional space taken up in the camera body by ADC mainboard.
  • Still image quality compromised at the benefit of improved video performance.

This doesn't mean that it is a case of either/or, though. The very video-focused Panasonic GH4 uses the on-chip ADC approach. If you look at the current trajectory of sensor design, it's very much in favour of using on-chip ADC's. The situation is similar to the CCD/CMOS "debate"; there basically is none, at least not for stills photography.

The final thought on this: if the 5D Mark III was more camera than you needed, then the narrow-ish dynamic range of these cameras don't matter from a technical stand point. Compared to a Nikon, you have to be more careful with how you shoot and you have less leeway to edit in post processing, but great photographers are using both systems. However.... for the amount of money that Canon charges for these cameras when they are new to the market, you would expect better.

Battery Life and Shutter


CIPA rated battery life is 700 shots with the LP-E6N battery.  For reference, the 5D Mark III was rated at 950 shots per charge. Quite frankly, this is disappointing for this class of camera for two reasons. The first is that this seems to be a trend, as the 7D Mark II rated battery life is also less than its predecessor. The second reason is that the competing Nikon D810 is rated at 1200 shots per charge under the CIPA testing protocols... and it should be remembered that the Nikon has a pop-up flash that must be used during the testing CIPA cycle.

One feature that might be a contributing factor to the decreased efficiency is with the new motor-driven mirror system. A conventional DSLR mirror is sprung to flip in one direction. The 5DS, however, shares the same mirror mechanism as the 7D Mark II, where the reciprocating action of the mirror (up-down) is articulated by a crank motor and connecting rod system. In action, the motion of the assembly resembles the way that the crankshaft and pistons articulate in an automotive engine:



The advantage to doing it is way is that the upwards motion of the mirror isn't just a straight linear acceleration followed by an abrupt stop; the motor housing has a brake lever that decelerates the upwards motion to soften the landing. Does this contribute to increased battery consumption compared to a conventional system? One can only speculate; there probably is an answer to to this... but it is worth noting that Nikon made a similar (and quite apparent) upgrade to the shutter mechanism with the D810 as well, but with no corresponding penalty to battery life.

No Dual-Pixel Autofocus


One conspicuously absence is the on-sensor phase detection ("Dual Pixel"). When it was first introduced on the 70D, it was hailed as Canon's way forward. On that camera, it certainly works well enough to think so, but it has only since been used on the 7D Mark II. Though Canon's engineers know better, one can speculate why they chose not to implement it on the new 5D. The Dual Pixel sensor technology uses twice the number of read-out wires that a conventional sensor does. This means that there is potentially a greater amount of innate electronic noise, and that each individual light well is more "crowded", letting in less light to the photo-gathering substrate. Here is where some perspective is required. If you simply scale up the 70D sensor to full frame size, you will get  50mp, meaning that a dual-pixel full frame sensor is already within the realms of possibility. The problem is that you would have a high resolution sensor with the image noise and dynamic range characteristics of a crop-frame sensor. That's a tough marketing sell; if you are going full frame, you want more and more on top of that.

Looking Ahead


Though there are some very obvious reasons why the 5DS and 5DS R were brought to market, there are also some things that don't add up. The benefit of increased resolution will be immediately usable for some, but without the corresponding bump in dynamic range the image quality won't truly have the "wow" factor to truly move it ahead of cameras like the D810 or Sony A7r. Though it is true that these cameras are starting to encroach into the territory that was once occupied by medium format, the EOS 5DS will likely not come as close. There is such a thing as the "medium format look" and it doesn't come simply from having more pixels. It's a combination of having many large pixels and the colour depth that can be achieved because of it. The 5DS only hits the resolution part of this equation; the acuity bite that comes from being able to use larger pixels and the deeper DR/colour depth isn't there. On paper, it's a better DSLR, but not a genre-breaking one.

In some way, the 5DS and its sibling seem as though Canon is testing the waters bit. The camera has the look of the broad-ranging workhorse 5D Mark III but is much more of a niche camera. This seems to echo what happened to the 7D Mark II; a better camera  than its predecessor, but less of an all-arounder in today's market and more of a niche segment. Again, we go back to the dreaded phenomenon of shelf-stuffing.

All in all, the EOS 5DS re-sets the cycle on the 5D series. Despite the lofty capabilities, this is a camera that will once again sell in larger numbers to amateurs and occasional professionals rather than full-time professions. The lure of that big number, 50mp, will be too hard for some to pass even if it is stratospherically more than what most people need. This is especially true for the growing markets were the newly wealthy are still going through the "bling" phase of economic development and are willing to snap up "the best" without hesitation.

Did you think that we are past the era of "more is more" and that we were now into "smarter pixels, not more pixels?" For the average photographer, the answer should be yes, but Canon is a deeply traditional camera company with a deeply traditional way of viewing the market. Hence, in the 5DS will have something that isn't going to the frontier of the camera market (connectivity, advanced video, etc) but instead aims for the peak of what we knew DSLR's to be all this time.


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