On 24 February 2010 03:14, AlunFoto <alunf...@gmail.com> wrote:
> 2010/2/24 Miserere <miser...@gmail.com>:
>> Jostein,
>>
>> Does the rear element of that 35mm f/3.5 have "digital" coating?
>
> You mean fingerprints? :-)
>
> Seriously though, I have no idea. Please tell me what this thing is
> you're asking about, and why it is the single factor discerning
> digital from non-digital lenses?
>
> I made the observation that on the *istD the resolution and colour
> accuracy of this lens is comparable to the 31 ltd. Basically, that's
> enough for me to gauge its suitability for digital. But it wouldn't
> surprise me at all if Pentax draw some new lenses out of the hat in
> addition to the announced 55mm.
>
> Jostein
C'mon Jostein, you know what I'm talking about :-) On lenses
intended for digital sensors the rear element (at least) is coated to
minimise reflections coming off the sensor that could bounce back from
the rear element to the sensor, causing a ghost image. This coating
should be the easiest to observe tell-tale sign of a made-for-digital
lens.
On top of that, made-for-digital lenses attempt to shine light out of
their rear element as perpendicularly as possible to the sensor,
although this is not something that's easy to test at home.
Granted, the larger registration distance of the 645D might alleviate
the problem of sensor reflection (and maybe Kodak has produced a
sensor that reflects less light), but the 2nd problem is still there,
and is even worse with the 645D. With a little trigonometry you can
show that rays reaching the edge of the 645D's 48mm wide chip (with
reg. distance = 70.87mm) have a smaller incidence angle than those
incident on an APS-C chip in a K-mount camera. Then again, maybe Kodak
will use what they learnt when designing the Leica M9 chip
(progressive offsetting of the chip's microlenses with distance from
center of the chip) and apply it to lessen or neutralise this problem.
In any case, you're ready to write Pentax a cheque for a 645D, right?
--M.
--
http://EnticingTheLight.com
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