Mladen Sever; 9th September 2008

 

Sony a900 – introduction to Sony’s alpha flagship DSLR

Exactly a year after the a700 announcement, the wait is finally over and with that we can finally talk about what the a900 brings to the table.

 

There has been a lot of speculation fed with nonsense rumours or “leaks” -- some have even raised their expectation too much and others are expecting to see a cheap and incompetent photographic tool. I hope Dyxum forum readers have developed realistic expectations, since we have tried to hint over the past few months what should be realistic to expect. Now, we are finally in position to start discussing a900 based on facts and not rumours, leaks or unconfirmed leaks.

 

 

 

a700 on steroids?

 

The Sony a700 DSLR set the path for future Sony DSLR developments. From camera design control layout, menu system  to image processing and options provided it was a clear “break out” from quite a few Minolta-like solutions. With the quantity of dials and knobs reduced (and supposedly compensated by excellent quick-nav functions) Sony has made the camera “cleaner” and probably cheaper to produce. Everyone familiar with the a700 will find themselves at home with the a900.

 

With the a900 on the market, I think we have reached the point where any comparison with Minolta approach to camera bodies should be stopped (except for those few of us that will always rant about missing Minolta features :)) since it is now quite evident that Sony has set their own style and philosophy about what camera body should like. The control layout is intentionally kept very similar to the a700 and keeping this kind of consistency is certainly something to salute and proves that Sony didn’t find it necessary to change camera body design significantly.

 

The menu system is unchanged with only some new options added, changed or removed as a result of natural development progress.

 

I really like to describe the a900 as the a700’s big brother and I hope that once you know more about it you will agree with me that this is the best short description for it. A natural evolution rather than a revolution, and hence the a700 on steroids title.

 

So .. let’s start mentioning the most important things that separate the a700 and a900  in this very brief report, since a more in-depth “first impression” article will follow together with my usual rants ;)).

 

 

Meet the a900 ;)

 

Surprisingly Sony has decided to make the grip a bit shallower than the one found on a700 but has recessed the camera body to facilitate the handling.

Many have agreed that the mode dial on the a700 was a big step backward compared to KM 7D. Unfortunately things haven’t changed a lot on the a900 but at least the old memory recall settings are back and scene modes are gone :)

I would like to start with something that still places Sony DSLR apart; a milestone in body stabilisation. Despite what many have speculated or stated is impossible; the a900 comes with a stabilised FF sensor. No crop factor is needed; the whole frame is captured while minimizing the impact of camera shake.

 

Compared to the a700, the whole mechanism is larger and heavier (about 1.5x), more powerful and faster (to be able to stabilise larger area). Stabilisation effect is stated to compensate for about 2.5-4 steps which should be about the same as with the a700 and better than the a100/a200/a3xx and Sony has achieved this with improved drive power, speed, circuits and control. Brand new actuators are used to support larger SSS mechanism.

 

The a900 build quality seems to be excellent. Again, you can imagine a700 and then add some more.
Sony loves light cameras! They did it with the a700 and they did it again with the a900. In an effort to make the a900 as light as possible while increasing build strength Sony has redesigned camera chassis and improved the quality of materials used. Unlike the a700, magnesium alloy is used for top front and back covers. In reducing structural weight compared to the a700, some new materials are used (engineered plastic containing carbon fiber) to keep the strength. The strength and durability of the a900 body is stated to be about the same as with the a700.

 

The “usual” rubber sealing, cushion and gaskets are used to protect the camera from dust and moisture but the camera is not described as water or splash-proof (it is very alike a700 in this respect) .

 

We finally get a top LCD display, while quite smaller (21 mm x 23 mm) than on other brand cameras it is still a lot better than the one on a700 which is of course missing :).  This size allows only a limited amount of data to be displayed at once, but despite this Sony has decided to even further  sacrifice the amount of data displayed for a larger display view. Kudos to Sony for this decision; some other cameras have a larger top display but they are still so small that they are  difficult to read in many situations. Data displayed can be changed when the appropriate setting controls are used.

 

 

 

The long-awaited FF sensor

 

The size difference between full frame sensor and APS-C one. Full frame sensor provides aprox. 2.35x larger surface

The most obvious difference is the sensor size. With the 35.9x24.0mm in size this “Exmor” CMOS sensor brings about 2.35x larger sensor area. Unlike some other “similar” cameras on the market (Nikon d700 being the most recent one) Sony has decided to use larger sensor surface to provide greater resolution which brings us to 24.6MP effective resolution (no other current 35mm DSLR offers that kind of pixel count !) The sensor is not unknown since the basic design has been announced and offered to the market this year. It provides Sony's column-parallel A/D conversion and “dual noise reduction” (as found on the a700 sensor), 12-bit AD converter, scan readout mode at 6.3fps (5fps implemented on a900) and window read out capability. Sensor dimension and pixel count bring us to pixel pitch size of 5.94µm. Here are short comparison tables.

 

	Sony a900	Sony a700	Canon 5D	Canon 1Ds III	Nikon d700
Size (mm)	35.9x24.0	23.5x15.6	36.0x24.0	36.0x24.0	36.0x23.9
Total pixels (MP)	24.61	13.05	13.3	21.9	12.9
Effective pixels (MP)	25.72	12.24	12.7	21.1	12.1
pixel pitch size (µm)	5.94	5.4	8.2	7.2	8.45
AD conversion (bit)	12	12	12	14	14

 

Technology used in a newly designed “Bionz” is improved compared to the a700 with the most significant change done to processing speed which is doubled to be able to process 24.6MP of data at 5fps.

 

 

As expected, Sony doesn't guarantee proper exposure metering when using DT lenses due to reduced circle coverage which can influence camera metering system.

Related to the sensor size is another new feature; APS-C crop mode. The camera menu provides the option to turn APS-C crop mode on and off. If a DT lens is used however, the camera will automatically switch to crop mode. Aside the already seen 16:9 markings (16:9 mode can’t be used with DT lenses), the viewfinder on a900 brings small marking for APS-C sized frame which helps framing. There are 3 different sizes one can choose when in crop mode; 3984x2656 (large), 2896x1928 (medium) and 1984x1320 (small).

 

 

Intelligent Preview

 

Our recent poll has indicated that most poll participants do not consider Live View an indispensable feature for a900. I’m pretty much sure that if and when Sony decide to implement a LV on higher priced cameras the implementation will be far more useful than on some current FF cameras. While a900 doesn’t provide live view it brings a so-called Intelligent Preview feature. The option is enabled in the custom camera setting. What it actually does is take an image (not stored on the card but rather in the camera memory) and displaying it on the camera LCD screen. In this “preview mode” we can change (and simulate) following settings:

• Exposure (aperture and shutter speed in M mode if not using BULB option or exposure compensation in PAS modes)
• DRO
• White balance

This option may be useful in certain situations but has some limits. First, the aperture is kept open (so will not replace the standard DOF preview as a small typo in our forum has suggested :)), focus should be achieved before the “preview”, any scene change will not affect the reading (since we are previewing an already captured frame stored in the camera buffer), preview enlargement isn’t possible (to increase speed), exposure simulation when using flash is disabled. 

 

 

Revised AF system

 

One of the biggest nightmares for many DSLR users is the AF inaccuracy and tendency to back or front focus so no wonder that AF tuning feature is getting almost a mainstream feature on modern DSLRs. The a900 is the first a-mount camera with AF Micro Adjustment feature (hopefully, this will be implemented on all future Sony DSLR). The principle is very similar to what Canon, Nikon, Pentax or Olympus have already offered, and since we will cover this topic in detail in the future just a few words at the moment.

Each lens we use has a certain ID number stored in the internal ROM. In a perfect world all lenses should have unique ID numbers (as in case with Sony lenses) but that isn’t the case for some Minolta and most third party lenses and that’s why registering a lens may be problematic in some cases.

The a900 allows up to 30 lenses to be registered and -20/+20 adjustment steps are provided.. While there shouldn’t be any problem with any Sony lens, the situation with Minolta lenses will depend on other factors and we will certainly need more user feedback to draw some conclusions. In short, as long the focal range and the aperture for Minolta lenses the camera should be able to “recognise”  and register a lens. Same goes for Sigma, Tamron, Tokina or any other a-mount lenses

 

 

Personally, I’m very, very happy to see Minolta tradition of excellent viewfinders continued on the a900. Again, unlike some have speculated, the a900 offers approximately 100% viewfinder coverage with still excellent 0.74x magnification.

 

	Sony a900	Canon 1Ds III	Canon 5D	Nikon d3	Nikon d700	Dynax 9
Aprox. coverage (%)	100	100	96	100	95	100
Magnification (x)	0.74	0.76	0.71	0.70	0.72	0.73

 

 

The viewfinder is not only large; significant efforts (highly refractive condenser lenses and multiple antireflective coatings layer coatings) were made to make it clear, precise and bright. The a900 viewfinder should be about the brighter VF currently on the market.

Three types of user interchangeable focusing screens are available; G, L and M type. For each focusing screen a proper option in the camera menu is provided to adjust camera metering. Special care is taken with the sealing between pentaprism, holder dioptre unit and SI screen to minimise dust injection even when changing focusing screen type. As goes with high end cameras, a mechanical eyepiece shutter is incorporated as well.

 

 

Aproximate viewfinder view

It’s hard to write about AF without going into more details than this short introduction can contain. Even so if we know that AF is an aspect that should be judged after a period of time, in various conditions and with various lenses. Still the way AF on a900 is provided should provide a solid knowledge about what to expect.

Unlike on the a700 (but similar to Minolta film cameras) the a900 comes with 9 AF sensors AND an additional 10 AF assist points, which is new for the Sony system. Just like on previous cameras only the center AF sensor is of crossed (double) type but to use its full sensitivity a f2.8 lens or faster is required. It’s a quite outdated design compared to most capable AF systems currently on the market but this is where additional assist points should help.

The AF chip integrated in the a900 is the same as found on the a700 but the rest of the AF system is specifically designed for the a900 and is supposed to provide the fastest, the most accurate and most reliable AF performance on a-mount to date. Reduced sensitive area of each AF sensor (by 10%) is probably the most significant improvement and is supposed to guarantee more precise AF and separation between the subject and surrounding area.

Newly added AF assist points are placed close to main AF sensors and while effective only in the wide area focusing mode should help AF tracking. Sony has rightly chosen not to mark AF assist points to make viewfinder view clear.

Worth noting is that when in wide area AF mode two or more AF sensors LED indicators may be illuminated if in focus.

 

 

Mirror mechanism changes

 

The larger sensor required significant changes in the mirror box and shutter mechanism and here we have further new things. Most obvious is the parallel link mirror drive mechanism; the mirror not only swings but the axis of the mirror mechanism is moving upward at the same time. This is resolving a potential danger with mirror slapping the rear lens element because of the larger mirror size.

 

A new coreless motor and moving magnet actuator are designed to speed up mirror movement and the addition of a magnet mirror stopper should help with reducing unwanted slap vibrations. All of the mentioned improvements have resulted in reliable 5 FPS shooting capabilities.

 

Mirror related is the new separate mirror lockup mode. On previous cameras MLU is implemented with a 2 sec timer. A900 brings a new drive mode for MLU feature. This MLU option can be used via PC remote ("remote camera control" software is bundled with the camera) or with a wired remote but will NOT once again work with the supplied wireless remote control.

 

 

Good news is that we finally get a 2EV stop option for exposure bracketing. The option for bracketing numbers of frames is unchanged (3 or 5) but only 3 frames can be used when 2EV step is selected :(

There are other minor menu changes and unfortunately I need to mention one of them. Unlike with the a700 (and previous Minolta cameras) but like the a3xx the “shutter release without lens attached” is gone from the menu. We can still use M42 lenses in manual mode but those who are like me will not like this decision especially because I see no point in reducing such options for a flagship model.

 

With the a900 we lose eye start AF (will not be missed ;) and unfortunately the grip sensor (which was not used at it should anyway). Of course we lost an onboard flash too (shame on you Sony for this) and I will comment further on this in the future.

 

As with previous Sony DSLR announcements I will be open to answering additional questions in our forum (if I can of course) and may possibly update this article with more details. We will try to keep tracks here on every significant a900 report and I’m sure there will be plenty of interest for this new great photographic tool.

 

And in the end .. just once again; the a900 is the only FF camera that provides in-body stabilisation. So, when looking and comparing this camera to other brands’ products, do not underestimate the importance to have all your a-mount lenses stabilised !

 

A first impression article will follow up. But since I can’t help myself with being subjective and express my personal honest opinions (and there are things that I do NOT like) I’ll wait a bit and let you enjoy the excitement about this great camera. At the time this will be published (official announcement) you will have the chance to read about a900 on different websites since Sony has provided significant amount of camera samples to various magazines and website editors. I rather leave the good news to them .. I’ll take ungrateful duty to be more critic (but constructive I hope) and I’m willing to be exposed for new personal attacks .. just as I’m used to :)

 

 

Happy shooting !

 

 

 

 

 

 

>>> Dyxum alpha 900 forum !! <<<