Tuesday, 2 October 2007

Fast Track Journal?

Details changed to protect the guilty. The academic publishing business is undergoing a glacial process of shifting from dead tree products to on-line delivery of journal articles. Nowadays, at least for the journals to which I tend to submit, I as the author end up doing most of the work of writing the text, creating figures and graphs, setting out the layout, editing, spell checking and uploading all the electronic documents directly to the publisher's servers. This saves publishers lots of money and effort since they get near publishable quality (in layout if not research itself) without having to lift a finger.

The journal editors send out the submissions to referees (other authors typically, so I get to referee lots of papers myself) who have to read through each submission carefully and decide whether it is of sufficient quality and interest for the journal in question to publish. Usually a few constructive suggestions are made to improve the readability or point out a few things which could be usefully noted or expanded. Very rarely I referee a paper which needs nothing changed. Sometimes I get papers to referee which aren't worth the electrons/photons used to convey them. There may be a bit of to-ing and fro-ing between referee and author (via the editors who act as glorified messengers) before the editors have a clear cut decision to publish or reject. In all of this, the authors and referees (the same body of people) are contributing their research, effort and expertise for free.

In the end, the journal pays nothing to authors or referees in order for them to do the work for the journal, which then sells off access to the research (and all the layout, figures etc. that the author created) to universities and other academic instituions (who paid the researchers in the first place to do the research). There are some journals which operate on the open access model, where published research is free to download, but the costs of running the journal and online archives is met by the authors. This is somewhat better than the traditional model but still suffers from the problem that authors give up their copyright to their own work, as well as paying the people to whom you gave up your work.

It's not an easy problem to solve, to balance the desire for quality control (I think some form of peer review is necessary, hence the costs associated with running this) and the universal access that the internet provides. The arXiv is an invaluable service for scientists but it does not confer any amount of validation of the worth of the research published. An economic model which respects the rights of scientists to the fruits of their labours yet promotes the advancement of knowledge for all needs to be discovered.

The screenshot at the top of the entry shows you how a supposedly fast-track, electronic only journal handles a submission, they advertise that you get a reply within 33 days of submission. I've refereed for this journal and they expect a referee report within 7 days. It looks as if the editorial board couldn't get their act together and come up with a decision in a timely manner. In the end, luckily they decided to accept the paper so I won't complain too loudly :-).

Saturday, 8 September 2007

Live View: Why Not?

The claws are out over the absence of Live View in the Alpha 700. Personally, it would have been a nice feature which may have the occasional use but not a terribly important ability in a DSLR as it is currently implemented. There are several plausible reasons why Sony decided not to follow the herd.

Marginal Utility: Without a swivel screen, the shooting position is still confined to an arc directly behind the camera. Possibly to reduce sensor heating, the frame rate on the D300 is only 15Hz which is quite jerky. The 40D supposedly has a refresh rate of 30Hz but the screen is only 320x240. The 40D does not have contrast detection AF but relies on flipping down the mirror to take AF readings. The D300 does have contrast detect AF but Nikon say it's only really for tripod work. All of these concerns can be addressed as the system is developed but as it stands, Live View has serious drawbacks in its operation.

Added Cost and Mass: Implementing Live View is not simply a matter of reading out the information from the sensor in realtime. The mirror has to be flipped up and the shutter left open for extended periods of time, similar to bulb mode. This will increase power consumption and may require new mechanisms to deal with the different operating mode. To make Live View useful, Canon have used two separate motors to flip the mirror and cock the shutter independently allowing the shutter to operate without the mirror flipping. This means added mechanical complexity, weight and cost, engineering effort which could be applied elsewhere instead. To make Live View really worthwhile, an articulated LCD is required which also would increase complexity, weight and cost.

Integration: Sony will not want to implement a feature without it being polished enough to match the rest of the camera. Live View, in the opinion of Sony it has been reported, currently is not in the proper state for prime time integration with DSLRs, though I'm sure they are working hard at making it work to the best of its potential.

Thus the question of having or not having Live View does not have such a clear cut answer. There are many engineering issues as well as the all important marketing angle and it seems Sony, for the present, has allowed engineering principles to take precedence.


It's been nearly 2 days since Sony officially unveiled the new Alpha 700, and reaction has typically focused on a differences, rather than similarities, with the other two recently unveiled DSLRs aimed at the same segment, the D300 and 40D. The main difference between the the A700 and the others is the presence or absence of Live View, a comparatively new feature on DSLRs. In the forums of various photo web sites, fanboys of various ilks have been parading their colours but fail to see the wood from the trees. It's a matter of a tool fulfilling a function and if a tool does well what it is meant to do, then it is a good tool and maybe worth its asking price.

Personally, I can see where Live View may be useful but it's absence will not be a big handicap for the shooting that normally like doing. Macro and underwater photographers may feel the lack more severely but since I do not do either on a regular basis, these applications are not driving my photographic needs. Fans of competing systems who do have Live View seem to believe that theirs is the One True Way and if Sony have chosen not to implement the flavour of the month, then we (Alpha Mount shooters) are all doomed by our choice.

But looking at a camera as a whole, instead of simply a sum of its specifications, we should really evaluate a camera as means to an end. As stated above, if your end is high magnification macro or underwater photography, a D300 may be a better tool with its contrast detection AF. However, if you are in the mainstream and looking for a camera that fits well in the hand, has a comprehensive and ergonomic control system (including vertical grip for some), most probably comparable AF performance and image quality, and the bonus of in-body image stabilization, then one cannot fault the A700.

I take photos because it's enjoyable, and a key to that is the process and tactility of handling the camera to take the shot. The main difference between a compact camera and an SLR is the degree of control one has over the picture making process. With a compact camera, usually one can only point it in a particular direction, perhaps change zoom to crop the scene, and press the shutter. The camera decides where to focus, what aperture to use and hence the depth of field (which is usually the whole scene for small sensor cameras), the shutter speed, exposure, whether to use flash, colour balance, and then recording a processed JPEG which has limited post-processing potential. Where manual controls are available, they are slow and unwieldy to use. With an enthusiast DSLR, the interface and ability to set the shooting parameters quickly and efficiently are the key features which sets it apart.

The Alpha 700 looks to retain the old Minolta spirit pioneered with the 600si, refined in the 7, and then carried through with the 7D. Though one may lament the loss of a knob and dial, it looks as if Sony have further refined the camera interface. The placement of the key buttons on the read of the body have been retained. The AF, AEL, AE mode dial and directional selector are still in their well placed positions. The vertical grip replicates the controls almost exactly meaning that shooting in portrait position should be as easy as in landscape. The replacement of the drive dial with a button press and control wheel is a main change, one that needs to be tried before a definite opinion can be formed. The change of the ISO button to the top is also another thing that has to be tested. But overall, the interface matches or exceeds that of its forebears.

The one thing that may prove to be a consumer gain over the 40D is the rear LCD. This is a 640x480 X-Fine dual mode LCD. This means that it can operate in transmissive or reflective mode so that it should be viewable both indoors and out. Reviewers have generally been effusive over the clarity of the display (apparantly shared with the D300). The extrememly fine pixel pitch (267 ppi) means that images look extremely good and that reviewing sharpness is improved.

So to compare with the 40D, we have Live View on one hand and the high resolution LCD on the other. The screen will be a feature that every shooter can appreciate whereas Live View may only be of practical use to a few. This may prove to be a deciding factor for buyers coming from the existing Sony consumer market which Sony hope to tap into, many of these will see cameras as a way of instantly sharing photos to others at social occasions and so the better screen will be a strong selling point. Due to the lack of AF in Live View mode on the 40D, this feature is not going to be useful to users who come from a compact camera background.

The D300 has Live View and a high resolution 3" screen so there is no advantage to the Alpha 700 on this front. The anticipated comparatively large step in price from the Alpha 700 to D300 (as opposed to the delta between the 40D and A700) may be a potential draw for the Alpha, but at this level, perceived brand values may play more of a role.

The lightness of the A700 may indicate that Sony is focusing on the female photographic market. It has fairly compact dimensions compared to the other two making it more friendly to smaller hands. On the other hand, the addition of the vertical grip makes for a formidable camera, especially wedded to a tele zoom like the 70-200mm SSM. So stylistically, Sony seems not to give anything away to its competitors.

On the lens front, the provision of the 18-250mm and 16-105mm lenses makes for a compelling package for first time DSLR buyers. Zeiss lenses in the line up offer upgrade potential. For the majority of buyers, the Sony lens line up is perfectly adequate, with the newly announced lenses offering a combination of convenience but also acceptable quality.

So looking at the bigger picture picture, the Alpha 700 is an attractive offering for newcomers not blinded by brand loyalty or gimicky fashion. All three competing cameras are good photographic tools and it will boil down to an individual tactile dialogue which camera suits them best. I think Sony have done a good job and I look forward to the time I can mount my own lenses to an Alpha 700.

Wednesday, 5 September 2007

Sony Alpha 700: Breaking News

18:03 BST 5/9/2007
Just noticed that the Alpha 700 has a 16:9 shooting mode, for fitting on HDTVs more easily I guess. Sony claim a 1/2 stop increase in the effectiveness of SSS, especially on tele lenses. I hope that they also fixed the low frequency drift which can sometimes make wide angle long exposures tricky.

17:30 BST 5/9/2007
Looks like there is a british site still open. A few things in english:
3 memories for settings
Manual flash control of inbuilt flash
Shutter 100,000 actuations
Silicon seals
3-layer optical low pass filter for less moire (how this impacts on resolution will be interesting)
Selectable additional High, Medium, Low levels of noise reduction at High EI
DRO optimization for RAW
Striped pixel array 3" 921K dot LCD. AR coated. RGB Histogram
Pentaprism,, L or M interchangeble screens
Supplied remote commander (for HDMI output) doubles as remote release (yay)
11 point AF and 11 lines (?). New AF motor. Macro focus f/2.8 sensor, AF Illunimator (Yay)
17 RAW buffer minimum, 5fps or 3fps selectable
0.9x 95% Pentaprism (not mirror), 25mm eye relief
141.7x104.8x79.7mm, 690g w/o battery
NP-FM500H 11.8Whr 1650mAh 78g

New Lenses:
DT 16-105mm/3.5-5.6 15 elements in 11 groups, 1 ED and 2 Asph elements
DT 18-250mm/3.5-6.3 16 elements in 13 groups
DT 55-200mm/4-5.6 13 elements in 9 groups

17:26 BST 5/9/2007
Looks like the leaks are being plugged. The flash ads are back to the Alpha 100 ones, and the Romanian site is not showing the Alpha 700 details anymore. Guess we'll have to wait till tomorrow for the official official word.

17:05 5/9/2007
A few random thoughts. I think the Alpha 700 will be for me. I don't think the image quality will be much different from the D300 as they both use the same type of sensor, the exception is that Nikon may have specified 14 bit ADCs and implemented live view which should not make a whole lot of difference. The ergonomics are growing on me but I'll have to handle one make sure. The vertical grip seems to be near perfect, I will definitely have to put that on the accessary list. Magnesium construction for body and grip is very good, much better than the VC-7D. The duplication of the controls is great. We'll see about the viewfinder, I will definitely have to have the ML screen installed, just like the one on my 7D. They'll be moaning that it's "only" 5fps compared to the 40D and D300, but it's not an issue for me at all. I don't care much for the HDTV out. It might make a nice feature in studios where yo can instantly show clients fairly hi-res previews of shots. All in all, I think it's a great package which will handle well and won't give an inch on the image quality front.

16:43 BST 5/9/2007
Looking at the Romanian flash site for the Alpha 700, it seems to confirm the more credible rumours: 12.24MP CMOS sensor EI100-3200 (6400 with boost), 3" 921K (dot) LCD, Al-Mg frame, some weather sealing, Interchangeable screens (M or L), Dual CF/MS slot, 11 point AF, 1/8000th top shutter speed, 1/250 or 1/200 flash sync (SSS off/on), 5fps continuous shooting speed, VG-C70AM magnesium vertical grip, InfoLithium battery NP-FM500H.

16:35 BST 5/9/2007
The Romanian Sony site has a flash animation of the new camera.
New features include a 3" hybrid X-Fine LCD. May have OLED technology?

16:22 BST 5/9/2007
It's official, the name of the new Sony DSLR is the Alpha 700. It has appeared on Sony websites. I will update this page as more information is released.

Wednesday, 29 August 2007

The Beta Mount?

The trend in consumer camera sensors seems to be heading towards greater on-chip processing and capabilities due to CMOS active pixel sensor (APS) architecture. This has now filtered upstream to DSLRs in the form of Live View, the ability to see a video frame-rate output from the sensor before final image capture. Sony have been pushing hard recently with parallel column ADC in order to increase readout rate and simultaneously lower readout noise. It is not inconceivable that in the near future, an interchangeable lens camera based on the alpha mount and lenses will be developed which omits the reflex mirror of a DSLR, replacing framing, AF and AE functions by Live View and a suitable electronic viewfinder (EVF).

For this to happen, several things need to be improved. The video refresh rate should be 60 fps or higher to allow accurate tracking and to avoid the feeling of lag. The power consumption should be low, comparable or lower than the power consumed by AF and AE. The EVF needs to have sufficiently high resolution to allow for manual focusing. To reproduce the viewfinder size and magnification of the Dynax 7, for example, may require something on the order of 2MP, roughly HDTV resolution. The technology is getting there, the same technology which is going into HDTV projectors could be adapted for EVF displays. The parallel column ADC approach allows greater flexibility in readout modes.

There are several advantages from a manufacturing point of view, by forgoing the reflex mirror and pentaprism, considerable bulk, mass and mechanical complexity can be eliminated leading to cheaper, lighter, and potentially more reliable cameras. Electronic shuttering would allow flash sync at all shutter speeds, viewfinder blackout would be reduced, and the frame rate would not be limited by mechanical parts. Noise and vibration would also be reduced leading to quieter and sharper operation. Live view would improve exposure and allow detailed manual focusing. Of course, there will be reluctance from traditionalists, perhaps sceptical about the clarity and responsiveness of EVFs, but the time may come where these objections may be overcome by improvements in electro-optics.

So presupposing sufficiently good EVFs and sensor performance, we can ask how best to adapt the Alpha mount to such a system. The absence of a mirror box means that the lens mount can be located much closer to the sensor. New lenses, especially wide angle lenses could take advantage of such geometry obviating the need for retrofocus design. However, the alpha mount and lenses are designed for a 44.5 mm distance between flange and sensor plane, meaning that these could not be directly used on such a short mount. The answer would be to design an adapter, basically an extension tube which would convey all the focusing and communication between body and lens. In this way, full compatibility could be maintained with existing lenses yet allow for optimised designs to take advantage of the reduced mount distance.

The new mount, for the purposes of this discussion called the Beta mount, could have a flange to sensor plane distance considerably shorter than the Alpha mount. Rangefinders have mount distances about half that of SLRs, 27.95mm (Leica M) vs 46.5mm (Nikon F). The Beta mount could have a mount distance even shorter, say 20mm, leaving enough room for adapters for all other mounts.

Beta mount lenses could follow EF lens design and have focusing and aperture electronically controlled by the body with power supplied by the body. This would further reduce the mechanical complexity of the body as well as simplifying the mechanical design of the mount. For alpha mount lenses attached via the adapter, focusing and aperture control could be retained by incorporating actuators within the adapter itself.

All of the above is speculation but could represent an avenue for Sony to make the best use of the advances in electro-optics yet maintain compatibility with legacy users.

Saturday, 25 August 2007

More Sony Speculations

Warning: Take the following with a large grain of salt. I do not think that this will have a very high chance of actually occurring but might just represent one possible avenue for Sony to develop their Alpha system.

I have already made a few predictions about what I expect and hope the Advanced Amateur camera will be like. I will make a few predictions about what the Flagship camera may be like when it is rumoured to come out some time next year, possibly at photokina. The primary focus will be on the sensor. I do not think that the sensor in the D3 will be used in a Sony body. The conventional readout using 12 high speed ADCs does not fit in with the sensors that Sony are developing. The coyness of Nikon to name the manufacturer also indicates that Sony has had very little input into the sensor.

If the size of the Flagship sensor is as expected (36mm x 24mm), I expect that it will be based upon the IMX021 and thus would be 28MP with a pixel pitch of 5.49 microns. It would have column parallel ADC readout giving 7fps if a suitable mechanism is found for AF and AE, either by a suitably beefed up reflex mirror or Live View. It may deliver 14 bit RAW files, not neccessarily because the DR warrants it but because of marketing concerns. Super Steady Shot will be included, the PMA presentation reinforced Sony's committment to providing this. There are no show-stopping problems in implementing this for a 135-sized sensor, merely a matter of mass, power, sufficient image circle (135-format lenses tend not to have a perfectly sharp-edged 43.3 mm image circle but have sufficient margin to allow for sensor movement) and control strategy.

Several shooting modes would be available, including a 7MP 14fps mode, either cropped to APS-C size or a subsampling of whole frame. These would be in Live View mode. A selectable 12/14 bit RAW file would also be provided. For single shot mode, a high precision sampling option would reduced frame rate but possibly justify the 14 bit RAW file. It's pretty safe to say that the image buffer will be large, possibly 1GB giving 20 RAW or 100 JPG shots. Sony may use a DNG file format, losslessly compressed. Other possible features are weather sealing, 100% viewfinder, interchangeable viewscreens, wireless transfer and control, and geotagging (GPS).

With the Flagship, Sony will want to make a strong statement. By providing the highest pixel count in a 35mm-style DSLR, Sony would signify its committment to the Alpha mount. Coupled with Zeiss optics, the combination would be a serious professional set-up.

Thursday, 23 August 2007

Nikon's D3 and D300: Implications for Sony?

Nikon shooters have had some very good news today, the long awaited and rumoured D3 and D300 have been unveiled to a rapturous audience. They both boast impressive specifications and many other sites have covered these in depth so I won't reproduce them here. I will speculate and point out some features of the new Nikons which may have some bearing on Sony's DSLR efforts. Given the long history between Nikon cameras and Sony sensors, hopefully the latest information on the new models will provide some insight into the machinations behind Sony's closed doors.

We'll start with the D3. From Rob Galbraith, Nikon says that the sensor is a 36mm x 23.9mm CMOS sensor with 8.45 micron square pixels and a 12 channel, 14bit readout giving at least 9 fps in full readout mode and 11 fps in cropped mode. It is stated that the sensor is an original Nikon design, though it is unknown who actually fabricates it.

From the above, we note a few things. The 12 channel readout is different from the parallel column ADC system used in the IMX021. This is the conventional way of reading out a focal plane array and uses a few high speed analogue to digital converters to quantize the photo-electron signal in each pixel. The 14-bit ADC is interesting, I am not sure whether it truly represents a greater than 12 bit dynamic range or merely a marketing, "keeping up with the Jones'". We can estimate the full-well-capacity at about 55k electrons, similar to the Canon 1DII. The minimum sampling rate at 9fps is 9MHz per ADC. To exceed 12 bit dynamic range (DR), we require a read noise of better than 13.4e which is plausible, though whether this can be achieved at 9MHz is to be seen. The switchable 12/14 bit resolution may indicate that Nikon engineers do not consider the system having greater than 12 bit DR.

The D300 sensor is the most relevant to Sony's plans as on the surface, it looks like the IMX021 (left) recently announced by Sony. The D300 sensor is a Sony-made 12MP APS-C sized CMOS sensor with 5.49 micron square pixels and 14 bit readout at at least 8fps. The IMX021 only specifies 12bit output but at 10fps. It is unknown whether the D300 sensor employs parallel column ADC.

For such a smaller pixel (half the area and presumably FWC), the read noise would have to be half that of the D3 sensor to achieve the same DR. Hence, it is unlikely that the DR exceeds 12 bits, making the 14 bit ADCs superfluous, unless parallel column ADC and multi-sampling have been employed to significantly improve read-noise. A rough estimate gives a 36 multi-sampling with an ADC frequency of 1MHz at 10 fps leading to a reduction in read noise of 6.

It is this latter scenario which is promising for a future Sony DSLR. Though Nikon have a habit of ordering bespoke sensors from Sony (e.g. sensors for the D70s, D2x), the IMX021 seems to be a wholly Sony in-house development, hence the ability to use the parallel column ADC architecture for low noise, high DR imaging may not be proprietary to Nikon.

We will hopefully be able to infer more when Pentax makes its announcements soon, otherwise we will have to wait till Sony make their rumoured announcements early September.

PS A useful introduction to noise sources in CCD imaging is here. Much of the material on signal analysis applies equally well to CMOS sensors.

Sunday, 8 July 2007

Sony DSLR Speculations

Update (20/8/2007): Sony have released the details of the IMX021 12.47MP CMOS sensor which will presumably be in the new Sony DSLR. The main features include parallel ADC and 10fps.

My regular camera is a Konica Minolta Dynax 7D, I've had it for 2 1/2 years so far and it's given me stellar service. I was able to use the lenses I bought for the Dynax 7 (and AF 9000) to which I've added one reduced circle lens, the Tamron 17-50mm/2.8 XR di II. For (Konica) Minolta's first DSLR (ignoring the RD-175 and RD-3000, and even the video back for the 9000) of the modern era, it was a great camera, first with in-body anti-shake, more knobs and dials you could poke a stick at, and a nice hefty feel to the body.

However, times have moved on and it's time to upgrade. I think that 6MP is more than enough for 99% of the shots I take, but it's that 1% where higher resolution could come in handy that moves me to want 10MP or more. The AF was a step backwards compared with the Dynax 7, and digital flash has always had the problem of Off-The-Film (OTF) metering incompatibility leading to worse flash performance than in the film days.

So, with Sony having taken over the camera division of Konica Minolta and released the Alpha-100 DSLR last year, many Minolta AF mount (alpha mount) shooters are eagerly awaiting Sony's next move. From all indications, the next camera to be released will be the one on the right, referred to by Sony as an Advanced Amateur Model (hereby to be referred to as the AAM). No details have been released, nothing about the size of the sensor, the resolution, or any other features apart from the inclusion of Super Steady Shot (SSS). So I will dare to make some predictions, and wishes, about what this camera will bring. This is based on the technology developments which have occurred since the 7D was released in 1994 and what should be fitting for the spiritual successor of the 7/700/7000 in the Minolta line.

The heart of a camera is the sensor, whether it be film, a CCD or CMOS. Sony have jumped on the CMOS bandwagon, trying it out on the large sensor R1 previously and stating that it would be transferring its development and production efforts in this direction. CCD technology does have a few theoretical advantages over CMOS in the areas of fill factor, full-well capacity and fixed pattern noise but Canon has shown that practically, CMOS implementations can match or exceed CCD performance in the consumer space. However, some advantages of CMOS are too great to ignore hence Sony's interest in transitioning from CCD. CMOS sensors allow greater integration of image processing functionality into the sensor itself, and it is this functionality which Sony may well want to use to bring DSLRs into the mainstream.

Whenever I hand my 7D to someone else to use, I invariably get asked how do the turn the back screen on in order to frame the shot. I have to explain that they have to look into the viewfinder which leads to much confusion. Integration of Live-View into a large sensor is much more easily achieved in a CMOS chip. Instead of having to clock all the charges out of a CCD in order to rapidly display only a subset, in a CMOS sensor, region of interest (ROI) addressing is easily achieved by random access to each pixel.

Sony recently announced the IMX017CQE 1/1.8" 6MP sensor. What was interesting about this chip is the implementation on a consumer-type device of parallel or column analogue to digital conversion (ADC). Each column of the device has a dedicated readout circuit, hence the charge in each pixel can be measured much more rapidly than in conventional devices. This technology is not new, but so far has been confined to research or low volume high-end devices. It would not be inconceivable that Sony will implement parallel ADC on the new CMOS sensor for the AAM. This is assuming that the technology can overcome some potential hurdles: Cost, more circuitry means larger silicon, lower yield; fixed pattern noise, calibration of each ADC will be essential especially with changes in temperature. With so many ADCs, each one needs to only read out pixels less quickly, hence read-out noise can be much lower. This is due to lower intrinsic noise at lower frequency of operation and also from multi-sampling, where the number of electrons in each pixel is samples many times and averaged, leading to a reduction in the random noise by a factor of the square root of the number of samples. It should be quite possible to reduce the equivalent read-out noise to single electron figures by this method and still retain high frame rates. This would result in very high signal to noise and good low light performance. Video also becomes a viable option for DSLRs, though whether it would be a useful feature is to be seen.

Recently, Kodak announced a "new" Bayer pattern array which mixed clear or "white" pixels with green, red and blue pixels primarily to increase the sensitivity of a sensor. This was touted as a revolutionary development, but in fact is merely one permutation out of many possible Bayer patterns, many of which have been proposed and tried before. For maximum sensitivity, a monochrome sensor would be optimum, however there would be no chroma information recoverable. At the other extreme, the traditional Bayer RGBG pattern gives reasonably good chroma resolution. In between these two points, a continuum of possibilities balance sensitivity versus chroma resolution. One pattern implemented has been the use of complementary filters, Cyan (Green and Blue) Magenta (Red and Blue) Yellow (Green and Blue). An alternative would be to use White (R+G+B) Cyan and Yellow in a CWYW pattern. This would be equivalent to a RGB pattern in terms of chroma resolution, but would have an average photo-electron absorption of 5/6ths compared to 2/6=1/3 of an RGB array, or 2 1/2 times greater sensitivity. In terms of colour accuracy, the CWYW pattern may be more sensitive to noise so this would have to addressed in the de-mosaicing process.

Flash performance on DSLRs has been problematic. This stems from the fact that digital sensors have specular reflection characteristics. OTF metering relies on diffuse reflection from the surface of the film in order to calculate flash exposure. However, the light reflected from the surface of the sensor (of the order of a percent or less due to anti-reflective coatings on the IR filter/anti-aliasing stack) bounces like as from a mirror, which means that the usual flash metering sensors cannot intercept the rays. There are several ways this could be overcome in an all-electronic flash metering system embedded in the sensor. Most sensors incorporate overflow drains, pixels which exceed full well capacity dump their excess electrons into these drains and not into neighbouring pixels. By suitable high speed monitoring of these drains, overexposure could be detected and the flash output cut-off. The overflow regions could be segmented allowing a degree of selective exposure. More sophisticated would be a layered structure, the top surface pixels would be the conventional picture taking elements but below would be larger light sensitive regions which would capture a small fraction of the photons falling onto the sensor. These metering regions could also be used for on-chip continuous metering, useful for mirrorless operation.

With the use of Live-View, contrast AF becomes feasible. This could be used in conjunction with phase-difference AF as a Minolta patent shows. Phase-AF would provide coarse AF after which the mirror flips up and then contrast AF fine tunes the focus. I can imagine several permutations being available depending on the shooting situation. Sony may also implement an electronic shutter (like Kodak's CMOS Global Shutter). This would also mean far higher flash-sync speeds.

Another Minolta patent may show a future development, though it is not likely in the near future. This being the integration of in-lens image stabilisation with the current in-body SSS. This would combine the advantages of both systems, long lens performance of the in-lens system, and universal performance (especially wide aperture short focal lengths) of the in-body system.

The above are the more revolutionary aspects of the camera I envisage Sony releasing shortly. More mundane features I would like are: interchangeable viewfinders screens, type M/ML in particular; intervalometer; focus distance display; custom metering programs; a real mirror lock-up (MLU) as well as the 2s option; 1/2 pixel shift using SSS; Bluetooth GPS compatibility; good ergonomics.

My specifications/wishlist for the Sony AAM:

  • 24mm x 16 mm (approx.) 12MP CMOS Bayer Array (White,Cyan,White,Yellow this is pure speculation)

  • 5.5 micrometer pixel with 50,000 e- FWC

  • Parallel ADC readout, 10e- equivalent noise in normal mode, 5e- in "slowscan" mode

  • Pentaprism 95% coverage viewfinder, x0.85 magnification. Interchangeable screens including Type M/ML (for manual focussing/gridlines)

  • 9 AF sensors (distributed wider than on the 7D). Centre X and + type, outer + type

  • Imaging AE in pentaprism, colour sensitive

  • Live-View, real-time histogram and metering

  • 4 fps with conventional mirror flip up, 10fps with live-view

  • 30s to 1/8000th shutter (mechanical) or 1/16000 (electronic)

  • On chip flash metering system. Flash sync to 1/16000

  • Wireless flash control, compatible with 5600HS/3600HS

  • Red focus assist lamp

  • Super Steady Shot with improved low frequency drift

  • Focus distance display on rear LCD

  • Dual CF and SD card slots

  • Compressed RAW format/DNG

  • Bluetooth connectivity for GPS, file tagging, camera control

For David Kilpatrick's take on things, look here.

Wednesday, 14 February 2007

D-Wave to Wave Goodbye?

D-Wave just recently "demonstrated" their 16 qubit prototype at the Computer History Museum. It has understandably garnered quite a lot of press, particularly amongst the geekier elements of the World Wide Wibble. From what I've read, they are trying to build an adiabatic quantum computer from superconducting qubits (Josephson junctions). Other quantum information scientists have commented on the plausibility of the device actually working, some more optimistic than others. I would class the general plausibility as just above Steorn, but I will reserve final judgement for if or when they actually release technical details, like temperature, energy gaps, decoherence rates, speed of operation, charge fluctuator noise levels and algorithms run. If they do actually manage to build a 1024 qubit device which is controllable by 2008 (and I don't mean just a bunch of SQUIDs connected to each other), then I will be very, very, very surprised.

I hope that the whole media circus surrounding the company and its claims will not seriously damage quantum information and computation in general. Inevitably, when commercialism meets science, science usually takes a back seat to publicity and PR.