Imaging at the Quantum Limit

Update 6th August 2009: Typos and clarification of assumed pixel size.

Just like 0-60mph times, the ability to take pictures of black cats down coal mines seems to be an overblown metric of the worth of a camera. For some photographers, this may be an essential quality of a camera but for the majority of situations, the image quality of any current DSLR at ISO800 or below is perfectly acceptable for most purposes. For printing at 100mmx150mm, even ISO3200 is typically unobjectionable. But once we have tasted the forbidden fruit, the desire and expectation for ever better performance is stoked. Hence one might ask what are the fundamental limits to low light imaging.

There are of course practical issues, namely to do with geometry and mass. I assume that we cannot build arbitrarily large lenses. An f/1.4 lens about the limit for fast affordable mainstream lenses (notwithstanding f/1.2, f/1 or even f/0.7 lenses). There is not much scope in any case to extend the light gathering properties of a lens; even if it were possible to fully enclose your subject within your imaging device you would only have a fixed amount of light to collect. Large lenses also weigh more, require greater precision in manufacture, and consequently cost significantly more than slower lenses.

Hence, the sensor is the place where significant gains can be made in allowing low-light photography. Fundamentally, the sensor samples the electromagnetic (EM) field at a spatio-temporal location. The objective is to be able to retrodict the value of the EM field from the output of the sensor. At very low-light levels, quantum features of the EM field emerge. We can describe it as being made up of quanta, or discrete packets of energy called photons. In fact, photography has always used this feature of light for its functioning. Film consists of tiny silver halide crystals which can absorb photons of certain frequencies. The absorption of a photos triggers the nucleation of a silver metal grain, which is then accelerated in the development process. In a digital camera, a photon is absorbed by a silicon diode, each photon interacts with the semiconductor and the energy is transformed into liberating an electron. This electron is collected in the pixel, the more photons absorbed the more charge which builds up. At the end of the exposure, this charge is measured and its magnitude correlated to the amount of light which was present at that pixel. Ideally, each photon arriving at the pixel would be absorbed producing one electron, and then each electron would be counted exactly.

Hence, the main bottlenecks to greater low-light sensitivity are quantum efficiency (the probability that a photon incident on the sensor ends up producing a photo-electron which is then stored in the photodiode), and read noise (the error in counting the number of collected photoelectrons). In principle, the quantum efficiency can be made close to 100% and the read noise can be made insignificant, i.e. we can count individual electrons with negligible error. Assuming this is the case, why can't we achieve arbitrarily "high ISO"? The problem lies with the quantum nature of the electromagnetic field. A conventional sensors tries to estimate the number of photons in the field, and a single measurement will give an integer number, i.e. 0, 1, 2,.... Even if the true average value of the field is, say 15.6 photons, a single measurement will give an answer of 16 or 15 most of the time, 17 and 14 less often, but in general the outcome will be random. Thus, from the actual measured result, we will have only an approximate estimation of the true value of the average photon number.

Noise in this case is given by the randomness in the estimation of the true photon number at each point of the picture. The signal to noise ratio determines the overall picture quality and this quantity varies as the square root of the average photon number. One can simulate various amounts of noise corresponding to the average photon number received at the sensor (corresponding to ISO) and determine an acceptable amount of noise for various pictorial uses. We show various cases below (click the thumbnails to view the full sized version).

"Noiseless"

Max photon level 2550.

Max photon level 255.

Max photon level 153.

Max photon level 26.

In all the above, the only noise comes from the quantum nature of the light. Looking at the full versions of the images, the 255 photon version would give a reasonable print, and the 153 photon version would be acceptable in a pinch. For extreme cases, even the last case would be recognisable.

Assuming a 6 micron pixel, the 255 photon maximum per pixel picture represents an ISO of approximately 75,000. Consequently an ISO128,000 for the 153 photon maximum per pixel and the last example shows an ISO of 750,000.

We have not considered other types of measurement, such as homodyne measurement. We could think of doing a measurement whose outcomes correspond not to photon number but to "coherent" states but whether this would provide higher sensitivity is not clear.

Pining for the A700 Successor

There has been much anticipation of upcoming Sony Alpha cameras, especially after the debut of the refreshed 2xx/3xx series led many to fear the dumbing down of the the higher end models. A recent leak of the A500/550/850 model names on the US Sonystyle support site has stirred speculation about what these models represent, and what features they will introduce or omit. A recurring theme in many of the online discussions is the fate of the A700 and its lineage. Many are anxious that the current "7-series" of camera will the be the last of its breed, either dumbed-down in the form of the A500 or priced out of the reach of its traditional market by a premium A850 model.

Another interpretation looks back to the significance of the 7-series camera in the alpha mount. Starting from the Minolta 7000 (first AF SLR system), 7000i (creative expansion cards), the 7xi (power zoom), the 700si (multi-predictive focus), 7 (rear LCD, control setup), 7D (Sensor Anti-Shake), A700 (Quick-Navi), each new 7-series camera has set the tone for that generation of cameras. What can we infer from this? The current fad in DSLRs is live view and video, two features which it was widely believed Sony would implement quickly. That it has decided to go a different route to the mainstream indicates that it sees that the traditional approached suffer drawbacks in their implementation and utility. It may be that Sony is waiting until its development of these features is polished enough before it will introduce main sensor live view and video into its line of DSLRs with the true successor of the A700. A guess would put this around the time of PMA 2010.

Where does this leave the A500/550/850? The Alpha line-up would benefit from a camera appealing to those upgrading from the A2xx/3xx series, yet who feel that the A700 is too long in the tooth. Hence the need for the A5xx cameras. The A850 is quite a mystery, though it is certainly possible that Sony will try to open up the "affordable full format" market by introducing a camera with a 36mm x 24mm sensor in a body intermediate in build to the A700 and A900. This could mean a viewfinder with specifications akin to the film 7, rather than the 9 series, and a body derived from the A700. The 8000i and 800si point towards a camera which serves as a refinement of the features of the 7-series camera but with an injection of the build of the 9-series camera.

Despite the economic downturn, Sony seems to be committed to the Alpha line and is playing for the long turn. This means capturing new DSLR users (through the A2xx/3xx cameras), keeping them with the A5xx/7xx cameras, and having halo products in the form of the A8xx/9xx cameras. With a solid line-up of cameras and a growing lens catalogue, Sony is looking to establish itself as a credible alternative to the big two. Hopefully its resistance to jump on the main-sensor live view/video bandwagon will mark it as a serious player interested in providing photographic tools, not gadgets.

Update 1/8/2009: Before I had a chance to post the above, the A850 manual has been leaked. Basically, the A850 is the A900 but with a 98% viewfinder and 3fps instead of 5fps. Indications are that it has the same body and sensor otherwise.

Some have said that this would kill A900 sales, and that a lower pixel-count, low-light sensor packing body would have been better. I see the possibility that Sony will introduce an upgraded version of the A900, but also the curious lack of an A800. In analogy with the A300/350 duo, it would make sense for Sony to release an A800 which was based on the chassis of the A900/850 but with a 16MP sensor, possibly with a higher frame-rate. The next generation 7-series may still herald a truly mainstream 36mm x 24mm full format sensor camera.

Second Thoughts on the A900

The Alpha A900 was released two weeks ago and turned out much as expected. The build is a step up from the A700, the viewfinder is superb at 100% and x74 magnification, and the effective incorporation of SteadyShot with the 36mm x 24mm sensor has silenced the naysayers. Due to unrepresentative JPEG output, the true image quality of the 24.6MP sensor has been overlooked unfortunately. The forte of the A900 is high resolution at low ISO, something which seems to be forgotten by the (partisan) critics. Suitable development of the RAW files have shown that image quality is comparable with the A700 at the per-pixel level, unsurprising given the similar pixel pitch and presumably similar pixel architecture and readout. Downsizing to a half or a quarter image size seems to be give acceptable results up to ISO3200. There is not doubt it will be an effective photographic tool for its intended use.

However, for my own personal use I shall wait. It is not that the A900 is not good enough, it is that the A700 (which I have) satisfies my needs so well. For single shot performance, 12MP is sufficient for most of my needs. For ultra-high resolution panoramics, stitching several 12MP shots serves me well, though having twice the resolution would halve the number of required shots. I can only hope that Sony will offer a new model which complements the A900, one which would be optimised for lower light. The different features I would ask for are:

• ~16MP 36mm x 24mm sensor and column-ADC with slow-scan low-noise readout
  
• In-built flash for wireless flash control
  
• Auto-exposure metering with non-AF lenses
  
• Extended exposure bracketing (7 exposures at 1EV steps)
  

I do not need live-view or video recording but their inclusion would be an added bonus as long as it did not compromise photography. The A900 viewfinder and 5fps would be welcome though. The greatest barrier for me to upgrade to the A900 is the compulsion to get the ZA 16-35mm and ZA 24-70mm lenses to make the most of the high resolution sensor. There only so many organs I can sell :-).

A900 Quick Comments

Image courtesy of Xitek

The leaks have begun just under a week before the official announcements on the 9th/10 September next week. A leaked ad from National Geographic and a Danish photography magazine have confirmed the name as Alpha 900. Other salient details include:

• 24.6MP CMOS EXMOR sensor (as announced earlier in the year)
  
• Dual BIONZ processor
  
• Intelligent Preview
  
• 100% Viewfinder 0.74x
  
• 3 inch, VGA Hybrid LCD (Same as the A700 presumably)
  
• 9-point Centre Dual-Cross AF (with f2.8 sensor and 10-point wide-area assist)
  
• 5 fps
  
• SteadyShot Inside

It's pretty much what was expected. I may make a few speculations and comments as on some of the details.

As the previously announced 24.6MP 36mm x 24mm sensor was specified with a 6.3fps (12 bit) maximum frame rate, the 5 fps seems reasonable. I hope, though don't expect, that a low-noise, "slow-scan" mode could be employed which lowered the frame-rate but reduced read-noise by operating the ADCs closer to their optimal corner frequency. Unless the dynamic range of the sensor can exceed 12 bits, I do not see a compelling reason to use more than a 12 bit RAW bit depth.

The data throughput of the A900 is twice that of the A700, ganging up two BIONZ processors is a simple way of handling this. It will be interesting what processing Sony decides to implement, especially after the "cooked RAW" issue.

Intelligent Preview could indicate an off-the-main-sensor live view, with Live View being reserved for the fast-AF style of live view as in the A350 and A300. Intelligent Preview could possibly be a way of differentiating (delineating) this type of pre-capture composing. It is presumably not suitable for quickly moving subjects and more suitable for posed, macro and landscape style photography.

The viewfinder coverage and magnification is quite good. In comparison, the Dynax 9 film camera had a 100% 0.73x viewfinder.

The rear LCD seems to share the same specifications as the one in the A700. I suspect that it may be hinged similarly to the A300/350 as a photo of a prototype spotted in Canada could have shown such a feature (unfortunately the photo was not clear enough to positively identify this).

The AF set-up is not entirely clear but it could be interpreted as meaning having 9 dual-cross sensors, of which the central one is f/2.8, and a further 10 (line) sensors to assist wide-field AF tracking. I speculate that the 9 dual cross (x and + type) sensors cover the central rectangle of the frame corresponding to an APS-C sensor. A further 10 sensors would lie outside this region to help with peripheral subjects. Having the 9 most sensitive AF sensors in covering the central region would be ideal for use with a 10/12MP "crop-mode", either with use with DT lenses or in order to boost frame-rates (though I doubt the latter as this would mainly be constrained by the mirror/shutter assembly, though some sort of electronic shuttering in Intelligent Preview mode could be possible). It is ambiguous at this stage whether the f/2.8 sensitivity is only for the single centre dual-cross sensor or extends to all 9 dual-cross central sensors. Edit 1: Possibly, in keeping with how the A700 AF system is described, only the centre AF sensor is dual cross, the other 8 main AF sensors could be line or single cross sensors. The 10 additional wide-field sensors may not be user selectable. Edit 2: Dual-cross probably doesn't mean + and x, but two crosses side by side as on the A700.

"SteadyShot Inside", as opposed to SuperSteadyShot, is an intriguing change of terminology. I suspect that it is merely a marketing rebranding of SuperSteadyShot to eliminate the "Super" as it may not fit in with the image of cameras at the high end of the market. Time will tell whether the effectiveness of the image stabilisation on the A900 is comparable to the systems employed on the APS-C sensor cameras.

Of course, we have no reliable indication as to the pricing position of the camera, especially in comparison to the Nikon D700. It is expected that Sony will announce several new lenses to complement the existing range, especially the ZA 24-70mm/2.8 SSM. A ZA 16-35mm/2.8 SSM is strongly rumoured to be among these. A replacement for the 70-200mm/2.8 G SSM is an outside possibility. Telephoto lenses may also be announced, especially as the 300mm/2.8 G SSM is the longest (non-mirror) prime lens in the Sony line-up.

It will be interesting how the A900 will be received, not by the minority of online forum posters, but by the general photographic community. The A900 could serve as a "halo" product, much as the existence of the ~US$8000 Canon 1DsIII has for Canon. Its importance could extend to much beyond its immediate sales but as a symbol of Sony's commitment to the Alpha system. I will eagerly awaiting the first user reports in the hands of real photographers. For most, the A900 is not appropriate for their style of shooting but for those who can make the most of the resolution (with nice glass), it looks at this point to be a very promising tool.

Moscow

I just came back from a trip to Moscow, it's an amazing place full of photographic opprtunities as well a rewarding cultural experience. Luckily I had a Russian-speaking Ukrainian friend along who managed to keep me out of trouble, even as I was wondering around disreputable areas clutching my tripod and looking very much the tourist.

Red Square and the Kremlin are definite must-see sites. Red Square at night is lit up beautifully. The city is a street photographer's dream, with many interesting characters. Ironically, photographic hysteria seems to be absent, I was not stopped once and questioned by police, something which is unfortunately becoming increasingly likely in the UK (a supposedly free and open society). Russia has as great a terrorist threat as the UK and has a totalitarian legacy to boot yet photography is tolerated to a much greater degree and photographers are not instantly branded as terrorists to be feared and hounded.

Moscow, and Russia in general, is not an easy place to visit compared to Western Europe but is well worth the effort. They have a long and proud history which is being restored since the fall of Communism and the place is full of an optimism for the future (despite their problems) balanced with their rich past.

Tips:

• Moscow is a dusty city. Bring a blower, lens cloth and brush to clean your equipment. Check your sensor for dust spots regularly.


• Go in a group. Like any large city, Moscow has its fair share of petty crime to contend with. When photographing, it is advisable to have a spotter alert to other people in your immediate vicinity and to keep an eye on your equipment at all times.


• Tourist areas are generally safe, however on the underground (Metro) and less tourist friendly areas, it is best to be discrete and keep equipment out of sight. It is a legal requirement for visitors to carry their passports at all time, photocopies are not acceptable. Hence, you need to securely carry your valuables.


• Be aware of photography restrictions. The Kremlin has strict security, no large bags are allowed within the walls (there is a bag check for you to deposit items). Lenses with a diameter of more than 70mm are not allowed, nor are tripods. In some churches, photography is prohibited. Otherwise, photography seems to be tolerated to a greater degree than in the UK. I was happily wandering all over Red Square with a tripod, A700 and panohead with not a glance from the numerous police patrolling the area.


• English is not commonly spoken. Having a Russian speaker is invaluable, though you may be able to get by with a phrase book and lots of hand gestures. Take the time to become familiar with the Cyrillic alphabet since most signs are written in the local script. An up-to-date guidebook is a must as Moscow is a rapidly changing city.

General Travel Tips:

• Have a photo-storage plan. Even on a comparatively short trip of one week, I kept over 1500 cRAW photos totalling nearly 20GB. Every night I would download photos to my laptop, and would burn a DVD every 4GB. I would not delete a memory card until I had a copy on the laptop and on DVD. I gave the DVDs to another person to carry them out of the country separately.


• Consider bringing along laptop to review your photos every day, as well as to check for dust spots and log into wireless internet to check email. The smaller the laptop, the better. I use a Fujitsu-Siemens P1510 tablet PC which weighs 1.1kg with the extended battery which lasts 5-6 hours and which is slightly bigger than an A5 piece of paper. An external DVD burner can be left at your accommodation.


• Bring along an electrical adapter, multi-plug adapter, and a sufficient number of power cords. Have at least one spare battery which is recharged at every available opportunity. Bring along lots of spare memory cards, consider getting large capacity cards which will minimise card changing. I have an emergency 4GB memory stick pro duo in my A700, as well as several 4GB Sandisk Extreme II/IV CF cards. I also have a few 1GB Lexar cards as backup. Faster cards allow faster review and deletion of missed shots.


• Insure your equipment. Have some peace of mind will allow you the freedom to take out your equipment and take photos. Make sure your policy covers your trip and read the fine print.


• Travel light. After a few hours, your shoulders and back will protest against any extraneous piece of equipment in your bag. Bring the minimum of lenses to cover the photography you want to do. I travel with three lenses, the Tamron 17-50mm/2.8 zoom as a general walk-about lens, the Minolta 100mm/2 for detail and portrait shots, and the Peleng 8mm fisheye lens for taking spherical panoramics. A tripod is a must, especially for night shots of landmarks, group shots and in low light. Be prepared to invest in a good tripod, the better ones are made of carbon fibre which is light and strong. Unless you are using long heavy lenses, a small 4 or 5-section leg tripod will be adequately stable, fit into your luggage more conveniently, but still provide reasonable height. Reverse the centre column for greater compactness. A Nodal Ninja 3 panohead completes my equipment list.

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 :-).

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.

Reflections

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.

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.

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.