Sony Alpha DSLR-A100 sensors and files
The Alpha A100 is equipped with a Sony 10.2 Megapixel CCD sensor which
measures 23.6x15.8mm. The specification may be the same as the Nikon D200's
sensor, but Sony claims they are only from the same platform, and that the A100's
sensor was designed specifically for it.
Either way, the maximum 'L:10' image size of the A100 matches the Nikon
D200 with 3872x2592 pixels. This gives the A100 around 400 extra pixels horizontally
and 300 extra vertically over the 8 Megapixel Canon EOS-350D / Rebel XT.
In practice this allows the A100 to make 13x8.5in prints at 300 dpi, giving
it about an extra 1.5in diagonally over the Canon EOS-350D / Rebel XT. The difference
is greater over 6 Megapixel cameras, where the A100 enjoys a two to two and
a half inch diagonal advantage when printed at 300 dpi. This is quite a big
difference in practice.
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The A100 additionally offers two lower resolutions: 'M:5.6' with 2896x1936
pixels and 'S:2.5' with 1920x1280. Both these and the highest L:10 modes can
be recorded at two different JPEG compression levels: Fine and Standard. We
used the default L:10 Fine JPEG mode for most of our shots, with files typically
measuring between 2.5 and 4MB each. This is a relatively high compression ratio
compared with, say, the Nikon D200 which with the same resolution images delivered
JPEGs typically measuring between 4.5 and 5MB.
The A100 alternatively offers a RAW mode at the full resolution, accompanied
if desired by a JPEG, although only in the best quality L:10 Fine mode. The
A100's 'ARW' RAW files typically measured between 11 and 12MB each which is
a great improvement over the unnecessarily hefty 20.5MB RAW files of the Sony
Cybershot DSC-R1. Sony supplies the A100 with its Image Data Converter SR 1.1
for Windows and Macs to process RAW files. See our Sony A100 RAW versus JPEG results.
Sensitivity is offered from 100 to 1600 ISO in one-stop increments, with Auto
ISO working between 100 and 800. There's also Lo80 and Hi200 options which Sony
describes as being able to prevent over or underexposure with high-keyed or
low-keyed subjects. Noise reduction is optionally available for exposures longer
than one second, which appears to use dark-frame subtraction - ie the subsequent
processing time matches that of the original exposure. See our Results and Gallery pages to compare the A100's noise levels.
New to the Alpha A100 is Sony's BIONZ image processing engine, which like other
image processors performs colour, sharpness, white balance and noise reduction
manipulations (to name but four) on the raw data from the sensor. Sony's BIONZ
processor goes further though to additionally offer Dynamic Range optimisation
Colour and white Balance
Selecting DEC from the A100's function dial gives the choice of eight
colour modes: standard, vivid, portrait, landscape, sunset, night view, B&W
and Adobe RGB. This menu also allows you to adjust contrast, saturation and
sharpness from -2 to +2.
While the vivid mode delivers the kind of punchy images familiar to any Sony
compact owner, the A100's default standard mode is quite restrained and will
be preferred by more experienced photographers. As discussed earlier, all of
our Gallery and example shots were taken using this Standard colour mode with
contrast, saturation and sharpness set to their middle zero positions.
Selecting WB from the DSLR-A100's function dial brings up the four main White
Balance options of Auto, Preset, manual colour temperature, and Custom. Selecting
Preset offers the choice of daylight, shade, cloudy, tungsten, fluorescent and
flash, with each tweakable up or down by three steps; apart from fluorescent
which runs between +4 and -2. This degree of fine adjustment is welcome in a
camera of this price.
Switching to manual colour temperature allows you to select between 2500 and
9900K, while custom lets you choose your own white balance based on a reading
taken from the spot metering area.
Dynamic range optimiser
The Dynamic Range Optimiser, or D-Range Optimiser is a key feature of Sony's
BIONZ image processor. The D-R position on the function dial allows you to select
between Standard and Advanced modes, or switch it off altogether if desired;
the default is the Standard setting, and this is what we've used for our Gallery
and example shots.
The D-Range Optimiser automatically prevents loss of detail in dark shadow
or bright highlight areas in strongly backlit or high contrast scenes. It works
by automatically adjusting the gamma curve and colour balance settings.
Standard mode adjusts brightness and contrast settings across the whole image
and works in real-time. Advanced mode performs further analysis, adjusting tone
and colour for each area of the image separately; this process takes around
half a second, so is not appropriate for continuous shooting situations.
We tried the D-Range Optimiser under a variety of conditions, but found the
results were often subtle to say the least. In our example here, detail on the
snow of the background mountains frequently burns-out when the foreground is
correctly exposed - an ideal opportunity for a dynamic range optimiser. To see
how Sony's D-Range Optimiser coped we shot the same scene with the setting switched
off, then again with the Standard and Advanced modes - these are pictured from
left to right with histograms from Photoshop below each.
Sony A100 D-Range off
Sony A100 D-Range standard
Sony A100 D-Range + advanced
|18-70mm at 35mm f8, 1/125
||18-70mm at 35mm f8, 1/125
||18-70mm at 35mm f8, 1/125
Histogram D-range off
Histogram D-range standard
Histogram D-range advanced
It takes a high-end monitor to spot any difference between our three example
images, although shadow areas are clearer with D-Range activated; sadly it didn't
make much difference to the snowy highlights though, and we in fact prefer the
sky on the first image with D-Range off. We did however find that when shooting
directly into the Sun, D-Range allowed the rest of the image to be exposed correctly.
The effectiveness of the system depends greatly on the source material, and
you ultimately may enjoy greater mileage than we did. The system certainly sounds
good in theory anyway for challenging lighting conditions and we look forward
to testing it further in the future.
Like the Konica Minolta 5D before it, the Sony Alpha A100's continuous shooting
is rated at 3fps. Unlike it's predecessor which was limited to firing-off ten
frames before slowing to 2 fps though, the A100 claims to keep shooting JPEGs
until you run out of memory on the card. This is thanks to the combination of
the BIONZ processor and new DDR-SDRAM memory.
We put this to the test using a SanDisk Extreme III 1GB Compact Flash card.
Setting the A100 to Continuous and the shutter speed to 1/1000, we held the
shutter release down and the camera indeed kept firing away without ever slowing
down. We timed one 50-shot burst taking 18 seconds which corresponds to a shooting
rate of 2.8fps.
Switching to RAW mode though greatly reduces the buffer's capabilities. Sony
quotes six frames at 3fps although we managed nine before the rate slowed to
around 1 fps. Opting for RAW plus JPEG mode reduces it further to just three
frames at 3 fps after which it again slows to around 1 fps.
Other drive modes include exposure and white balance bracketing along with
the choice of two or ten seconds for the self-timer.
In terms of handling, the Alpha A100 started quickly and felt responsive in use.
Compared to rival digital SLRs, the mirror and shutter mechanism made quite
a distinctive 'slap' sound which sometimes gave the mistaken impression a slower
shutter speed had been selected, but it's nothing to be concerned about. The
overall handling experience was very good for a camera of its price, and the
addition of the eye-start gives it a slight edge over the competition.