I expect ISO to be tested with grey card covering the whole image, a lens
with known accurate aperture and a controlled light source. Real scene
should be used to challenge the metering system not ISO system.
C.H.Ling
----- Original Message -----
From: "Andrew Fildes"
> Even so, I suspect that a lot of one colour in the image may cause
> variations. Grass is supposed to be 18% grey, like caucasian skin but
> an unusual image with a lot of red or a portrait of a very dark skin
> face might confuse the ISO response? I've got no idea - just
> speculating.
> But DxO claims to test in Studio/Portrait, Sports/Action and
> Landscape situations - while DPReview tend to nip out and photograph
> Tower Bridge! Which sounds more objective?
> Andrew Fildes
> afildes@xxxxxxxxxxxxx
>
>
>
> On 30/01/2009, at 2:46 PM, C.H.Ling wrote:
>
>> There should be a standard to measure the ISO for digital cameras,
>> I believe
>> it check the grey rendering. For example, the grey card should read
>> 128 (?)
>> if properly exposed. But they have to first make sure the accuracy
>> of the
>> grey card and their external meter. Either or both must be wrong if
>> DXO and
>> DPreview are different. For the maufacturer, they always not follow
>> the rule
>> for some marketing reasons, like a F2 lens could be F2.1, a 35-80mm
>> lens
>> just a 36-76mm...
--
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