SX50: thoughts on digital zoom

Started Jun 17, 2013 | Discussions thread
gardenersassistant
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Re: SX50: thoughts on digital zoom
In reply to Don_Campbell, Jun 21, 2013

Don_Campbell wrote:

I wouldn't be surprised to find that it depended on the type of metering selected, but that would take more tests.

I used evaluative metering because I assumed that the effect would not apply for centre-weighted or spot metering. However ...

... I just did a test. I was wrong.

Here we have a pair of captures, on the left using 4x digital zoom, on the right using full optical zoom only. This pair of captures used centre-weighted metering. I did this several times and although the breeze was causing a lot of movement in the trees the results were consistent. Here too, there is a one stop difference. I was a bit surprised by this, but not totally dumbstruck - after all it is weighting the metering towards the centre, not basing the metering on the centre of the image.

I could not draw any conclusion about spot metering. With the breeze keeping the foliage in constant movement, the metering changed between readings. For 4x digital zoom it varied (over 20 or so measurements) from 1/160 to 1/500. For a similar number of measurements using only full optical zoom it varied from 1/60 to 1/320. This might look like an average one stop or so difference, but it is "the wrong way round" (the digital zoom measurements giving faster shutter speeds rather than, with the other two tests, and understandably so in the context, slower), so I suspect what I saw with spot metering was just a statistical fluctuation.

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