The full frame mystery revisited

and the true reasons for a full frame camera

Nikon D800 (right) and a hypothetical more compact D800c full frame camera (left) built along the design principles of the beautiful Pentax K-5 APS-C SLR. The K-5 is smaller than the D800c depicted above.
-- please click to enlarge --

Two years ago, right before the Photokina 2010 trade show, I had a detailed look at a possible trend for full frame cameras:

• Photokina 2010, Pentax and the full frame mystery

At that time, full frame was a non issue and until recently, no new full frame camera was released indeed. Mirrorless system cameras (SLD) were the new kids on the block. However, I guessed that SLR camera makers, most notably Pentax, better do some serious homework in 2011 and develop a "24-35 MP full frame SLR with Exmor HD sensor". To be launched before Photokina 2012.

As it turns out, Nikon (and Canon) did exactly this: the remarkable Nikon D800 now takes the enthusiast market by storm. It was meant to be a 2011 release but it was then postponed due to the natural desasters in Japan. And what remains from the enthusiast market may well become victim of the Nikon D600 which is about to launch right before Photokina (Cologne, 2012, September 18 - 23). It is rumored to be priced right where the enthusiast market used to be a couple of years ago. OTOH, Pentax was busy to digest a change of ownership (Hoya to Ricoh) which means nothing but that they lost precious time again.

So, what does it all mean for 2012 and the years to come?

Well, before I start to share my guess work, I'd like to clarify why full frame is an interesting technical proposition at all.


The true reasons for a full frame camera

There is an amazing amount of false information floating around the internet when it comes to the benefits of form factors such as 35 mm full frame or APS-C. Typical examples include statements that full frame equals more shallow depth of field, less noise or unreasonably high sensor cost. Or that APS-C is better because it is good enough in a smaller and less expensive package. Unfortunately, such statements are too simple to be possibly true.

Full frame basically offers more choice or options which may or may not lead to better image quality or other benefits. It is necessary to look at each aspect in somewhat more detail. Therefore, I compiled a LumoLabs white paper listing the true reasons in favour of a full frame or APS-C camera:

• www.falklumo.com/lumolabs/articles/equivalence/ff.html 
• The true reasons for a full frame camera (the above as PDF)
• LumoLabs: Camera equivalence (white paper laying the foundation, to be read first)

Available interchangeable lens options (in 35-mm equivalent terms) for cameras with 35-mm or APS-C sensor, resp. Shown with an emphasis on Nikon. Fig. from the white paper "The true reasons for a full frame camera".
-- please click to enlarge --

In a nutshell and citing the paper's conclusion, full frame cameras, esp. full frame digital SLRs, are a good option to obtain premium image quality. I explained why there is a sweet spot of image quality where full frame cameras deliver the most cost-efficient solution today. And this is why their market impact must be increasing rapidly.

Cost vs. performance for various sensor formats. Fig. from the white paper "The true reasons for a full frame camera".
-- please click to enlarge --

I believe that the region where a 35 mm full frame sensor is the sweet spot may be expressed today as the region of images with between 20 and 50 clear mega pixels. At lower resolution requirements, I think APS-C still provides the better alternative and above it may be medium format. The Nikon D800 sits right in the middle of this region and this may explain why it is such a smash hit.

Moreover, I think that the region of premium image quality will remain the domain of SLRs for quite a while. Because lenses aren't that small anyway and the optical viewfinders are harder to beat (they are hard to beat anyway when it comes to low light and fast action). This means that every SLR maker will ultimately have to offer a compelling range of full frame cameras and lenses (in order to stay SLR maker).

Statements derived from the above white paper I am going to use here include:

• There is a level of maximum image quality where full frame offers no benefit over APS-C. At that level, images from full frame and APS-C cameras are basically indistinguishable. And at that level, the weight and price difference between both types of cameras is small (technically speaking).
• There is a level of image quality which corresponds to printout sizes of approx. DIN A2 or 16" x 24" where full frame cameras (today) offer the better price/performance ratio (technically speaking) or the only option (practically speaking).
• There are some niche applications (single image HDR, very low available light, fast and accurate focus, portrait/very shallow depth of field) where full frame cameras are clearly better.
• There are (fewer) niche applications (sports) where an APS-C or a low pixel count (or a fast crop mode) full frame camera still is a better choice.

I confine my consideration to APS-C vs. full frame. The reason is simple: other formats don't share the same mount. And larger or smaller formats currently slightly lack in terms of implementation. E.g., you may look at the current score board leaders at dxomark.com , using tscore = dxoscore + 30 x log_2(crop-factor) as format-independend technology index (the DxO score increases by 15 per EV stop of performance):

• Medium format (Phase One IQ180, Pentax 645D): tscore = 72
• Full Frame (Nikon D800E): tscore = 96
• APS-C (Pentax K-5): tscore = 100
• FourThirds (Panasonic Lumix DMC GH2): tscore = 90

Therefore, APS-C and full frame cameras perform almost equal when using equivalent lenses (with a possible difference in effective resolution). Other formats (or Canon) currently perform a bit lesser, when compared to cameras equipped with the Sony Exmor column-parallel ADC sensors.


Photokina 2012 and the full frame mystery

By "full frame mystery" I describe the fact that the APS-C dSLR was originally introduced (in 1998/DCS520 $12,000) as a temporary technical compromise in order to make a digital SLR feasible at all. And 35 mm full frame was introduced when that was feasible then (in 2000/Contax-ND $6,500, and Photokina 2002/Canon-1Ds $8,000/Kodak-14n $4,000).

But for no known reason, the market separation between entry-level SLR (APS-C) and pro-level SLR (full frame) has become a non-moving barrier. Around 2008 (3 years after the 5D) it should have reached and moved out of the $1,500 enthusiast camera segment. As described in the white paper above, there are no good technical reasons to explain why it did not happen. Including the manufacturing price differences which faded away, compared to what they have been initially. Today, the manufacturing price difference shouldn't be more than a few hundred $ (own research, would be the topic of a different blog article).

I assume two reasons which are responsible for this mysterious phenomenon:

1. Market separation: Spreading information (sometimes misleading, esp. from Canon), how expensive it would be to make a full frame sensor, vendors have been able to sell cheap APS-C cameras w/o cannibalizing their revenue from expensive pro gear. Customers trusting such statements never "asked" for more, or accepted a premium price for full frame.
2. The differences between APS-C and full frame (other than missing equivalent lens options) may not have been significant between about 10 and 20 MP. Therefore, the "good enough" argument applies to some extent.

Therefore, I claim (and actually already claimed in my 2010 article) that by 2012 there is an artificial separation between the APS-C and full frame markets. Artificial because less people still believe that full frame must be expensive. And artificial because image qualities beyond an effective resolution of 20 MP may simply require full frame. The new offers from Nikon (D800 and D600) therefore directly address this and may accelerate the disappearence of the artificial market separation. This is known as "supercriticality": the market ought to offer uncrippled, full frame enthusiast cameras in the $1,500 segment but offers APS-C cameras instead. Supercritical systems "fall" into their preferred state after only small perturbations occur. Once this happens, a D800 type camera will be in the $1,500 segment.

I believe we're going to see things unfold now:

While Photokina 2010 was dominated by the event of mirrorless (SLD) cameras, Photokina 2012 may start a trend for dSLRs to be full frame (only). This assumes that the entry level below $1,000 can't be defended by APS-C SLRs: the competition from SLDs (1" to APS-C) and large sensor compacts (1" etc.) may become too intense and the accuracy problems of APS-C phase-AF beyond 20 MP may start to become a problem.

On the other hand, I don't expect SLRs to disappear any time soon. A good optical viewfinder is almost impossible to beat in the next couple of years and hybrid viewfinders may bring some of the benefits of SLDs to SLRs.

Therefore, I speculate that four things are going to happen until Photokina 2014:

1. Full frame SLRs become mainstream above $1,000, in a more compact form factor.
2. Hybrid viewfinders combine the best of two worlds in high end SLRs.
3. Mirrorless SLDs and large sensor compact cameras dominate the segment between $500 and $1,000, mobile phones below.
4. Full frame SLDs emerge.

Of course, this means that the cameras with a full frame mount but a half frame sensor become what they meant to be: a curiosity of the past. The full frame mystery will eventually be obsolete. Let's check back before Photokina 2014 ;)


And Pentax ? ... ;)

Long time followers of my blog know that I have quite some sympathy for Pentax. Pentax, 10x smaller than Nikon or Canon but with products challenging the most popular cameras of the big two. E.g., I consider the Pentax K-5 to be a better camera than the Nikon D7000: similiar, but more beautiful, more ergonomic and more fun to use. This is why I would be very disappointed to see Pentax and their K mount continue to fade away as it did in the past since the arrival of the K10D.

Pentax, now having lost half of their enthusiast user base, cannot wait until Photokina 2014 to join what then will be the full frame SLR bandwagon. Their remaining enthusiast users can't wait: the jump in image quality from, say a K-5 to say, a D800 is too dramatic to be ignored. I cannot imagine that Ricoh has bold plans for the K mount but then doesn't come to the same conclusion. Therefore, I assume Pentax to at least "leak" information around Photokina 2012 wrt their own plans. Speculation goes they release a full frame SLR with the Sony A99 sensor in 2013. They better do. The K mount has no future as APS-C only. Esp. as the mirrorless K mount bodies (K-0x) make much more sense with full frame.

CU @ PK12 :)

The iCamera (Nokia 808 Pureview) Part I

Why "The iCamera"?

Because in my opinion, this term would best describe what this camera is all about. Camera? Yes, I consider the Nokia 808 Pureview to be a camera (which happens to have an embedded phone), not the other way round. Nokia may not like this perspective. Not yet. Further down, I am going to explain why it is such a great revolutionary camera. But first, let me explain why I call it the iCamera. And no, I will not say anything about the iCamera's embedded phone function. Please, refer to Nokia for further details about the phone.

Remember the iPhone back in 2007? The year the 808 project was started? "It is an iPod, a phone, and an internet communications device". Some laughed at it, but it became the blueprint for almost every smartphone made since. And a big success. And what matters most: it came from a company who never did a phone before! Launched after years of hidden development.

Now, you have "a camera, a phone, and an internet communications device". Some laugh at it, but it may become the blueprint for almost every compact camera going to be made. It comes from a company who never did a camera before! Launched after years of hidden development.

Nokia may not realize what they did and actually may still screw it up. But if they play their cards right, they can create an entirely new market and rule it! A photography market. Just let's forget for a second that the 808 is also a phone. The iPhone is also an iPod. So what?

And so I call it the iCamera.


Why is it revolutionary?

A product becomes revolutionary if it combines existing technologies in a way that the result leapfrogs several generations of competing products and seems to contradict common wisdom. The 808 does this. Let me explain in detail now.

First, let me classify the iCamera. You need to read my paper about camera equivalence though. You'll find it here:

• falklumo.blogspot.com/2012/02/camera-equivalence.html

It explains how to correctly compare cameras when they have different sensor sizes. The 808 is two different cameras at the wideangle and the long tele end. And another different camera in video mode. I give three 35mm equivalent cameras at both ends now (ISO are the minimum equivalent values), followed by 5 other cameras serving as a reference:

• Wide iCamera:      28mm/8 iso640 (38MP, 169g)
  exact: 38.4 MP (4:3), 27.7 mm, F8.3, ISO 690 (crop 3.45)
• Long iCamera:      77mm/22 iso6400 (5MP, 169g)
  exact: 5.0 MP (4:3), 76.6 mm, F22.9, ISO 5300 (crop 9.55)
• Wide video iCamera:      26mm/8 iso640 (HD, 169g)
  exact: 2.1 MP (16:9), 25.7mm, F7.7, ISO 590 (crop 3.2 wrt 4:3)
• Apple iPhone 4:      29mm/22 iso4800 (5MP, 137g)
• Wide Olympus E-P3 + 14-42/3.5-5.6II:      28mm/7 iso400 (12MP, 481g)
• Long Olympus E-P3 + 14-42/3.5-5.6II:      84mm/11 iso400 (12MP, 481g)
• Wide Nikon D800 + 24-70/2.8G:      24mm/2.8 iso50 (36MP, 1800g)
• Long Nikon D800 + 24-70/2.8G:      70mm/2.8 iso50 (36MP, 1800g)

Please, refer to the Nokia White Paper for the 808 specification and further details.

Even though the tele effect (Long iCamera) is achieved via simple cropping, it is equivalent to a different camera. Very much like a zoom lens which yields different focal lengths and apertures at both ends. Equivalent means you should expect the same indistinguishable image quality from a full frame 35mm camera with the given specification. Please feel invited to read the paper above to understand the details (applies to Nokia employees too: please understand why your way to zoom via crop is not equivalent to a constant aperture zoom).

In a nutshell: the above list allows for a direct, quick and no-nonsense comparison of available products.

And it shows that the iCamera is physically very close to a mobile smart phone (actually, Nokia says it is one) but its optical performance is rather close to a mirrorless system camera, only significantly bettered by a big full frame SLR with a fast lens.

So, in optical performance, the iCamera leapfrogs all mobile phone and P&S cameras, while in resolution, it additionally leapfrogs all mirrorless system cameras and even APS-C SLRs.

Of course, in order to make this claim, we have to check if the 808's lens is up to the task. So, let's refer to some sample images which have been published already

Image taken with the Nokia 808 Pureview (the iCamera). © 2012 Nokia (click to access original)

The above image is taken with the Nokia 808 Pureview (the iCamera). The image is mildly post-processed by me in a way typical for other photo cameras in JPG mode (the image is a bit sharpened and noise-reduced) to provide an easier reference for a direct comparison (the 808 seems to apply no or almost no post-processing to its results which is a good thing for photo enthusiasts).

The above image is an example of good image quality for a mobile phone or almost acceptable image quality one would expect from a system camera with a kit zoom. Most details are resolved but there remain a few sharpening/denoising artefacts.

So far, this is nothing spectacular or worth talking about.

But what if I tell you that the above is an 18x crop (1:1 or 100% crop) taken from the following image?

Image taken with the Nokia 808 Pureview (the iCamera). © 2012 Nokia (click to access original)

The above is the full and same image as shown above! Only resized to the typical web size. And now and immediately, you may understand why the iCamera is like no other camera before!


The Zeiss lens

Moreover, this example clearly shows that the lens is up to the task and able to resolve the incredible resolution of the sensor. Closer inspection of the original images reveals even the corner resolution is  good even if it doesn't fully resolve the sensor, still beating most other available cameras in the corner. A more complete analysis was done by Werner Ruotsalainen: Nokia 808 resolution tests. He concludes that even the smaller 5 MP images from the 808 beat 10 MP images from a P&S in resolution! And there are reasons to believe this to be true.

But how can a mobile phone lens resolve such tiny detail? Good question. As I explain in my paper about camera equivalence, it becomes increasingly harder to resolve many pixels when shrinking the sensor size.

But famous lens maker Zeiss did an incredible job solving this problem: By glueing 5 lenses together into one group, all having aspherical surfaces and one using ED glass, they created a lens with unprecedented optical performance and very tight manufacturing tolerances. The problem is larger than it appears: The lens aperture is only 3.34mm while the image circle 8mm further down the optical axis is a whopping 12.5mm, almost 4x the aperture. If the aperture were as large as the image circle, this would be an f/0.6 lens! So, the lens elements nearer to the sensor are larger than they appear when looking at the camera front. Such a lens must be mounted to the sensor assembly on extremely tight tolerances or it is decentered. We have to keep in mind that the iCamera's lens is diffraction-limited at F2.4! Nokia uses a live manufacturing method where live view from the camera is used to fine calibrate the lens when assembling the sealed camera module. That's fairly innovative by itself and definitely virgin territory. This method won't work for an interchangeable lens camera. More on this below.

UPDATE 2012, March 5:
Today more information about the lens was made available by Nokia and Zeiss.

Zeiss 808 8mm/2.4 lens
source: http://conversations.nokia.com/2012/03/05/nokia-808-pureview-carl-zeiss-science-of-making-the-perfect-lens/

The lens is depicted in the image above and as it said in the source, it is made from a special plastics rather than glass. This is only possible for small lenses like the one in the 808 but has the advantage that much more complex surfaces can be made to precision. That seems to be part of the recipe how to achieve the high optical performance despite the small footprint. END OF UPDATE.

So, we conclude that the optical performance figures are hard to believe but they seem to be real.

But this isn't everything yet. We saw that the wide iCamera is equivalent to a camera with rather low ISO setting. So, it should have good dynamic range. And indeed, this seems to be true. I treated the above image in an HDR manner and came up with the following result:

Image taken with the Nokia 808 Pureview (the iCamera). © 2012 Nokia (click to access original)

The above is is still the same image as shown above! But now we used the iCamera's dynamic range to heavily boost shadows to illuminate the black regions of the original image. That's not normally possible with images from mobile phones.

The reason why this works is that the iCamera has a large sensor, much larger than mobile phones or P&S cameras. It is almost as large as the sensor in the mirrorless Nikon 1 system cameras. The equivalent camera parameters express this as an equivalent ISO value of 640 which is known to be good enough to have enough headroom for extending an image's dynamic range (like I did above).

I hope that all the text above answered the question why the iCamera is indeed revolutionary.


One more thing ...

It wouldn't be The iCamera if there wouldn't be one more thing ... :)

All still photo cameras have the problem that the sensor has many more pixels than there are in HD video. But it is hard to read out all pixels of a still image (10 MP or more) 24, 25, 30 or even 60 times a second. Therefore, still cameras only read a small fraction of its pixels to make the video stream, known as subsampling or line skipping. The effect is a significant degradation of image quality in video mode: there is noise, line flicker, color moiré and the result is no match for HD content produced with so called 4k cameras or cameras with supersampling such as the Canon C300. Such cameras cost $15,000 or more (a notworthy exception is the Panasonic GH2 though which made it the camera of choice for serious video work on a budget).

And what shall I say? The iCamera does it too, not supersampling 8MP (C300) or 16MP (GH2) but supersampling all 33,593,616 pixels (16:9) 30 times every second! That's one billion pixels the iCamera processes every second. In a mobile phone. This is crazy!

As a consequence, the wide iCamera could have the same good low light capabilities in video mode as the legendary Canon 5DmkII which does line skipping, but without the Moiré and line flicker problems.

And because no graphics processor (GPU) obviously can handle this data rate (otherwise, HDSLRs would be able to do it too), Nokia designed a special chip (the scaling processor) which sits in the camera module between the sensor and the GPU. And Toshiba managed to make a sensor which can output the equivalent of 8 GBit/s. So, there is a large CMOS sensor, a scaling processor, a graphics processor and the ARM CPU chewing each others output to get the job done.


The people behind

Nokia was kind enough to emphasize the role of three persons in this project:

Eero Salmelin and Juha Alakarhu (Nokia "pureview inventors")
Source: http://conversations.nokia.com/2012/02/29/zooming-in-on-nokia-pureview/

Damian Dinning (Nokia "imaging guru")
Source: http://conversations.nokia.com/2012/03/01/nokia-pureview-qa-with-damian-dinning

I believe that the creation of the iCamera was driven by opportunity rather than strategic planning. Nokia decided to give engineering green light to pursue the project and see where it leads to. And I guess they are still watching. The Nokia press conference only "mentioned" the 808. And that's the real difference between the iCamera and the iPhone: the iCamera isn't top-level driven, it is not born out of vision from the leaders. It is born out of engineering vision and often, this is not enough.

So, here is my humble advice to Nokia managers who are only watching the 808:


Implications

The iCamera is such a groundbreaking device that Nokia must no longer consider themselves a phone maker.

The iCamera is such a groundbreaking device that Nokia must no longer consider themselves a phone maker.

( I said it twice on purpose.) Like the iPhone made Apple drop the "Computer" in "Apple Computer", Nokia may consider to drop the "Phone" in their brain. They may continue building great phones just like Apple continues to build great computers. But now, they have to become a camera maker and whatever this leads to. Nokia engineers may have understood it already: They provide a tripod mount and a decent camera user interface.

It is useful to consider what the iCamera could be in another form factor (less phone like) and to remember that interchangeable lenses wouldn't necessarily deliver (cf. above). The "lens module" concept then comes to mind. Where a lens module is exactly what the camera module is in the 808: A sealed module containing lens and sensor. And therefore, a system camera would become:

A mirrorless interchangeable module camera (MIMC).

Nokia wouldn't be first (Pentax Ricoh Imaging with their GXR line is first). But an 808-based MIMC would be the first camera where this concept actually makes sense: Because it delivers a level of performance not possible otherwise. And at an attractive price point considering the Nokia 808 minus the phone isn't more expensive than a system camera's lens.

Nokia could create the future and dominant kind of camera market between the phone and 35mm full frame system cameras. And they could reestablish a European camera industry just like Apple revitalized a dying US phone industry. There are good cooperation partners to the task, like Zeiss or Leica. Nokia may even consider to make a GXR module to test the waters.

Anyway, personally I plan to release more parts to this article after I got the chance to run some laboratory tests. It will be exciting to see what all of this leads to.

Enjoy your iCamera.

LumoLabs: Camera equivalence

Various parameters, or variables of a real camera or a reference camera are depicted above

In preparation of an article discussing the advantages and disadvantages of various sensor sizes for a given camera performance, I try to set a common ground for such discussions.

I have prepared a white paper which dives much deeper into the topic than is possible in this short blog article. You may find it here:

• PDF version (recommended)
• HTML transcript of white paper

The short version is this: An image contains no information whatsoever about the size of the sensor within the camera which was used to capture it. None. Nothing. Nada. (except EXIF of course ;) ) The proof is beyond the scope of this blog article and the article only gives some clues. But this is a fact, trust me.

Therefore, all cameras which could have captured a given image create a so-called equivalence class: they are all equivalent, producing indistinguishable images. And they have different sized sensors! By camera, I mean a camera with all the parameters defined it used to capture an image, such as the variables shown in the title image. Changing any variable "creates" a different camera. The exposure time used to capture an image is defined implicitely too: the one giving correct exposure (and it is a constant of course for indistinguishable images).

The following image shows an equivalent camera where the sensor has only half the size of the first or reference camera, i.e., an equivalent crop-2 camera:

The camera's lens has the same absolute diameter but it's focal length is shorter to maintain a common field of view. The equivalent crop-2 camera has a different F-stop and ISO sensitivity.


Main claim:

Any discussion about the impact of varying sensor sizes must be based on cameras made equivalent first. Otherwise, any comparison will just reveal the inequivalence of parameters the respective cameras have been set to and nothing else. And such a result would be trivial, known and not worth a further discussion.

Such trivial results are that a larger sensor produces a more shallow depth of field or less image noise. This is not true! Because it just means that the cameras were used with non-equivalent settings, e.g., with lenses of different diameter d which means with lenses of different weight and cost. Another example are ISO comparisons between cameras with different sized sensors but ISO kept the same. Such comparisons are pointless! Instead, compare a FourThirds camera at ISO 100 with a full frame camera at ISO 400 because only then they are equivalent. Not doing so just compares the size of lenses which a ruler can do just as well.


Secondary claim:

Once equivalent cameras are compared, results start to become interesting. Because now any deviation is due to deviations with respect to an ideal camera. Such like a lens with aberrations, production or design tolerances or compromises in a CMOS production process. The white paper explains that such deviations are generally expected to be larger with smaller sized sensors. Of course, one such deviation is obvious: when an equivalent camera doesn't exist for a sensor size, e.g., because an f/0.1 aperture is unfeasible.


I will follow up this article with a more complete article of the impact of sensor size on image quality.

Stay tuned and enjoy your read :)