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Anti-Shake

The DiMAGE A1 has a unique feature among the higher end 'prosumer' digital cameras, it has an anti-shake mechanism designed to enable you to take hand held shots at slower shutter speeds. The system is enabled by pressing the Anti-Shake button on the rear of the camera (which glows green when on). The system will only activate during the 'half-press' where you prime AF on the target (it also engages when using magnification in manual focus mode). The Anti-shake symbol will then show on the LCD screen as either blue (Anti-shake is active), yellow (Anti-shake is active but shutter speed is too slow to be effective) or red (camera is overheating, system is disabled - I never saw this myself).


Standard Test Scene

In my experience of using the DiMAGE A1 with AS I can say that I did feel that it worked and does provide at least a stop (for some two stops) slower shutter speeds or more flexibilty and telephoto focal lengths. The DiMAGE A1 manual clearly states that 'the system may not work with moving subjects or when the camera is panned' so it seems it's not designed to be used in a sports environment.

Our test of AS was rather basic (but was really the best I could come up with). The camera was hand held in a room with moderate light and a series of shots were taken of the same subject at gradually slower shutter speeds both with AS disabled and enabled. The lens was set to an equivelant focal length of approximately 140 mm (obviously at wider angles there is less of a need for AS). The results are below.

Anti-Shake disabled Anti-Shake enabled
ISO 100, 1/30 sec, F3.2, 140 mm equiv. ISO 100, 1/30 sec, F3.2, 140 mm equiv., AS
ISO 100, 1/15 sec, F4.5, 140 mm equiv. ISO 100, 1/15 sec, F4.5, 140 mm equiv., AS
ISO 100, 1/10 sec, F6.3, 140 mm equiv. ISO 100, 1/10 sec, F6.3, 140 mm equiv., AS
ISO 100, 1/5 sec, F9, 140 mm equiv. ISO 100, 1/5 sec, F9, 140 mm equiv., AS

The Anti-Shake system appears to work well up to 1/15 sec (at ISO 100) and possibly slightly slower given a little longer to 'settle' or with a few shots of the same subject. Interestingly the 1/30 sec AS shot showed some blur, this I put down to the AS system 'drifting' and inducing blur which wasn't evident in the 'just hand held' shot.


Image Size / File Quality Options

The DiMAGE A1 provides a fairly good range of image size and quality options. Firstly you can choose from JPEG or TIFF at a variety of image sizes or RAW (considered to be a 'digital negative') which is a record of data directly from the image sensor (12 bits per pixel), RAW images can only be viewed or converted using DiMAGE Viewer. Available image sizes for JPEG or TIFF are 2560 x 1920, 2080 x 1560, 1600 x 1200 and 640 x 480. JPEG image format can be saved at one of three compression levels; Extra Fine, Fine and Standard.


Standard Test Scene

To give an impression of what some of the combinations of image size and quality produce the table below is a cross reference of some of them:

  • 2560 x 1920 RAW (to TIFF using DiMAGE Viewer 2.20)
  • 2560 x 1920 TIFF
  • 2560 x 1920 JPEG Extra Fine
  • 2560 x 1920 JPEG Fine
  • 2560 x 1920 JPEG Standard
  • 2080 x 1560 JPEG Fine
  • 1600 x 1200 JPEG Fine
  • 640 x 480 JPEG Fine

Crops below are of the same 240 x 100 area of each image nearest neighbour magnified 200%.


 
2560 x 1920
RAW
7,343 KB .MRW + 5 KB .THM (Not available for download), as 2,842 KB JPEG
TIFF
14,492 KB .TIF + 5 KB .THM (Not available for download)
JPEG
Extra
Fine

3,367 KB
JPEG
Fine

2,480 KB
JPEG
Std.

1,262 KB
   

 
2080 x 1560
JPEG
Fine

1,600 KB
   

 
1600 x 1200
JPEG
Fine

1,091 KB
   

 
640 x 480
JPEG
Fine

301 KB

The DiMAGE A1's "Extra Fine" setting delivers TIFF like images at a fraction of the size of a TIFF image, at this low compression setting there will be virtually no loss of image quality and no visible JPEG artifacts. Drop down to the Fine setting and you're going to get a much better storage ratio and still very few JPEG artifacts, indeed this to me seemed to be the best compromise between storage and JPEG quality.

Minolta chose to add a three megapixel-ish size to the DiMAGE A1, this being the 2080 x 1560 size, it's a little difficult to understand why they didn't settle on the fairly standard 2048 x 1536 size. The DiMAGE A1's downsampling interpolation algorithm appears to be fairly good, if not the best we've seen, 640 x 480 does appear slightly blocky (more like a bilinear rather than bicubic downsample).

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