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Sony 75-300mm coverage with Sony A100
The Sony 75-300mm lens is designed to compliment the standard 18-70mm kit lens, and indeed they're often sold as a twin bundle with the A100. Since the 5mm difference where one stops and the other starts is essentially insignificant, the pair offer a wide range of 18-300mm, or an equivalent of 27-450mm, delivering wide angle to long telephoto capabilities.
To illustrate this coverage in practice we took a series of images on a tripod from exactly the same position with each lens at its shortest and longest focal lengths. Below is the coverage offered by the standard 18-70mm kit lens, which can capture wide landscapes while zooming-in beyond the 55mm maximum of most kit lenses to deliver good short telephoto capabilities.
Sony Alpha DSLR-A100 with DT 18-70mm
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18-70mm at 18mm, f8 (27mm equivalent)
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18-70mm at 70mm, f8 (105mm equivalent) |
Below are examples of the 75-300mm lens at its shortest and longest focal lengths taken from the same spot just moments later. It essentially takes over where the standard kit lens stops, taking you from short to long telephoto. The result at the 300mm focal length, equivalent to 450mm, as seen below on the right, is so tight it looks like many of the 100% crops from our standard outdoor test compositions. It's important to remember though this is the actual coverage of the entire 10 Megapixel frame, and a 100% crop would pretty much isolate only a couple of buildings.
Sony Alpha DSLR-A100 with 75-300mm
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75-300mm at 75mm, f8 (113mm equivalent)
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75-300mm at 300mm, f8 (450mm equivalent) |
Sony 75-300mm with Super SteadyShot
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The Sony Alpha A100 features Super SteadyShot which means any lens you attach enjoys anti-shake capabilities. This is one of the big selling points of the A100 and having seen it perform well with the 18-70mm kit lens we were keen to see how effective it would be with the longer 75-300mm. Since the 75-300mm has an effective range of 113-450mm, traditional SLR technique would recommend using a shutter speed of 1/450 or higher to avoid camera-shake when fully zoomed-in. This figure of course varies with every person and on the conditions of the day, but for the example below we found we could safely handhold the 75-300mm when fully zoomed-in at a shutter speed of 1/300 and enjoy a sharp result without stabilisation. The big question is how Super SteadyShot would handle slower exposures.
Sony Alpha DSLR-A100 with 75-300mm
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Super SteadyShot Off. Exposure 1/200 sec
75-300mm at 300mm, f10 (450mm equivalent)
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Super SteadyShot On. Exposure 1/200 sec.
75-300mm at 300mm, f10 (450mm equivalent) |
Above are two examples of a small building taken with and without Super SteadyShot.
We used a focal length of 300mm (equivalent to 450mm) from quite a distance and a shutter speed of
1/200 of a second. We've cropped 282x121 pixel sections from the original 3872x2592
images and reproduced them here at 100%. Under the day's conditions at this particular focal length we found shutter speeds below 1/300 without Super SteadyShot resulted in camera-shake - this is clear from the crop on the left, which at 1/200 is a little shaky. Switching on Super SteadyShot though eliminated any camera shake at this exposure as seen in the crop on the right.
While results will of course vary with different people and conditions, we found only a modest further reduction in shutter speed saw the camera shake return. Since we could safely handhold this particular composition without stabilisation or shake at 1/300, then the A100's claimed three and a half stops of compensation should allow the same result at 1/30 or even slightly slower. We found shake returning at exposures of 1/100 and below though, which in this particular instance equates to about 1.5 stops of compensation. We should also mention the view when fully zoomed-in was quite shaky and much harder to accurately compose than lenses with built-in stabilisation. This is one major downside of in-camera stabilisation, as you can't see the effect through the viewfinder.
Since in-camera stabilisation can also only physically shift the sensor by the same amount regardless of the lens you attach, it also becomes less effective as the focal length increases. This has always been Canon and Nikon's argument for in-lens stabilisation which can be tailored to the focal length in question. The results above certainly show the A100's anti-shake system offering lesser compensation at longer focal lengths than it does for shorter ones, but again this is a single example from one person on one particular day. It is however a subject we're examining closely and look forward to retesting the Sony A100 with other long lenses in the future to see whether its anti-shake effectiveness can maintain the 3.5 stops of compensation available at shorter focal lengths.
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