Sony Alpha DSLR-A900 review

[godwell]

Features
At the heart of the a900 is Sony’s Exmor sensor, scant details of which were made public at the start of the year. It’s a full-frame CMOS chip, with a total count of 25.7MP and an effective output of 24.6MP, and it contains over 6,000 parallel analogue to digital (A/D) converters. This, Sony claims, allows data to be converted quickly to resist noise and other interference, with noise reduction applied on-chip both before and after the signal has been converted. The sensor has been designed to match the capabilities of Sony’s Alpha range of lenses, in particular its G series and those manufacturers under the Carl Zeiss brand.

Images from the camera measure 6048 x 4032 pixels at their maximum resolution, with an average JPEG weighing in at just under 70MB when opened. In addition to the three levels of JPEG compression, the camera supports Raw and compressed Raw (cRaw) formats; this latter setting reduces files by around a third in size, with a supposedly negligible effect on image quality. So much so, in fact, that Sony’s intention is to make it the primary Raw recording option in its future models.

[rongarrett]

Anyone here got this camera yet? Nikons crazy pricing of the D3x has made me much more interested in the A900. Sony has seemingly priced the A900 for a very attractive pricepoint.


As I see it I can buy a A900, a Zeiss 24 - 70 F/2.8 and a 70 - 200 F/2.8 lens, and have lots of change left over. Those already owning these lens stand to really get the seemingly deal of a lifetime.

I once bought a Canon 400mm F/2.8 IS lens and a 40D for 1K less than I would have spent for a Nikon 400mm F/2.8 VR lens alone. Is Nilon pricing themselves out of most of our budgets?

Back to the A900, I would very much like to hear first hand experiences from anyone that has aquired this camera. Are there any reviews up yet for actual use?

[Anbesol]

60 megabyte JPEGS?!?! Whew!!!

[SmartWombat]

Well 20 megapixel times 3 bytes each (8 bits for each colour) is 60meg.
Anyone who can do simple maths can work that out.
The files on disk are not 60 meg.

RAW files are usually compressed, Canon's are very similar to TIF format - so much so that my ThumbsPlus raises a TIF format error occasionally when reading .CR2 files. The importance is that the files are lossLESS compressed. A JPG file uses a lossy compression, so each time you save a jpeg it gets worse and worse.

A/D on chip is normal, and you're likely to do it either on the long edge 6048 pixels/converters or the short edge 4032 of them.
The real problem is in shunting the pixel data across the 4032 rows without losing quality, or in low light causing streaky noisy lines in the shadows.
That's why it has on-chip noise reduction.

[Anbesol]

Tell me then, why doesn't a 12 megapixel camera produce JPEGs as large as 36MB? Your "basic math" would tell me my a700 should produce 36MB images, but not even my raws consume that much space. Instead, they are typically between 6.5 and 11 MB on the lowest compression setting. Have you ever seen a JPEG size larger in MB than in Megapixels? I haven't. Then, of course theres the fact that JPEG is a 'compressed' file format, and can vary depending on the captured data.

I guess I'm just too brainless to understand your basic math, so self-titled smart guy, please explain this to me...

Godwell - what do you mean just under 70MB when opened? Certainly the jpegs couldn't be that big, and whats the point of stating a pre-compression file size?

[Anbesol]

Wait, does this mean that the a900 produces lossless, uncompressed JPEGs?? Why not just TIF or Raw then?

[SmartWombat]

why doesn't a 12 megapixel camera produce JPEGs as large as 36MB
what do you mean just under 70MB when opened

To make it more impressive the figure Sony are quoting is when expanded in memory.

whats the point of stating a pre-compression file size

It's marketing designed to impress the buyer with big numbers.

Have you ever seen a JPEG size larger in MB than in Megapixels?

Yes! For example, I have a JPEG that is 640x427 and on disk is 67.67K - but ThumbsPlus says the file is 800.63KB ... that's the size in memory.

my a700 should produce 36MB images, but not even my raws consume that much space

They shouldn't take that much space, because they are compressed.
I don't understand why Sony is making such a big thing about it, because other manufacturers already compress their raw files. Apart from the first reason, marketing.

does this mean that the a900 produces lossless, uncompressed JPEGs?

No.

[SmartWombat]

so self-titled smart guy

Self-titled Wombat guy ... who drives a Smart car - hence smartwombat

Unfortunately WOMBAT can mean Waste Of Money Brains And Talent - as in a project not worth doing

[Anbesol]

Thanks for clarifying it was a bit confusing when I first heard that the images were 60MB, I thought you were being rude when you made the 'basic math' comment. I would be surprised if even the raws were up there around 60-70, I would expect that they would be between 40-50mb...

Anyway, a silly thing for sony to do mentioning 60 mb jpegs, I don't know anyone who'd want to be dealing with 60mb jpegs, tifs or raws yes, but jpegs - no.

[rongarrett]

What I want to see is someones impression that owns and uses the A900 and the A700.

[SmartWombat]

I don't know anyone who'd want to be dealing with 60mb jpegs

On disk? True.
The whole point of jpeg files is to compress the image down to a far smaller size to reduce disk space, transmit it faster across the www, but still be visually close to the original.

A jpeg image when uncompressed just has to have 3x as many bytes as there are pixels.

Or perhaps 4x, as I discovered opening up one sent form a Mac recently.

Normally a jpeg file from a camera has 1 byte of red, one of green and one of blue for reach pixel.
I was caught out by a CMYK print-ready jpeg file, that has 4 bytes per pixel Cyan, Magenta, Yellow, Black - and my jpeg viewer showed it as blue instead of orange.


There is an almost unused extension to the jpeg standard that allows 12 bits instead of 8, mainly used for medical imaging in 12-bit greyscale.
There's another even less used extension that allows lossless jpeg compression with between 2 and 16 bits/sample.

RAW format has to get all the pixels of the image, plus the EXIF information about the image parameters, into a file format that is as small as possible without losing ANY information in the process. Not just that, but the camera uses more than 8 bits (1 byte) per colour, maybe 12 bits or 14 bits.

[Abel1337]

Thanks for the info, very useful

[NoKnees]

"with an average JPEG weighing in at just under 70MB when opened"

Key point, "when opened". Actually means the data size when uncompressed in Photoshop or similar tool. Disk footprint is closer to 20mb... For some reason I remember seeing this number first mentioned in a 3rd party review, not by Sony themselves... But maybe they read a Sony press release that I missed.

It does seem strange someone would use this number, but when trying to express the amount of detail captured, I can see the desire to show a raw, uncompressed value.

Anyway, check out the forums at either DPReview or Dyxum if you want some first hand user comments. There are a good number of upgraders, and first time a900 studio photogs that have shared their thoughts and photos... Another resource is PhotoclubAlpha...

Basically, ISO performance is similar to a700 with v4.0 firmware upgrade, but a little better with the a900 on a per pixel basis. When put in print, the a900 shows clearly less noise per the same print size, thanks to its increased resolution. In many cases, similar to D3/D700 up to 3200. After that, it drops off pretty quick though...

Focus speed is about the same, with an impression of slightly higher focus accuracy compared to a700, although this was already very good with the a700... Controls are all basically the same, felt the same in the shop when I played with one a few times...

Wouldn't mind owning one, but can't justify it for my use yet...

[rongarrett]

There is a full review on the A900 now on dpreview.

[Canuck935]

There is a full review on the A900 now on dpreview.

There is one at cameralabs too. I prefer cameralabs reviews over dpreview because they are a lot more UN-biased IMO. Dpreview has a tendancy to even contradict themselves sometimes.

Of course, I prefer photographyreview over all others.

[pisco]

As Canuck said, I used to read dpreview until I realized that they are used to other brands that they like better.
Check David Kilpatric's webpage http://www.photoclubalpha.com/ also.

[NoKnees]

Yep, lot of other reviews out there. Read many, compare, then try to get your hands on the camera and test things yourself.

From what I've seen, good photographers are getting good to great results. That works for me!

Still not purchasing it myself, unless I win the lottery, but... ;)