>Matthias wrote:
>
>> friend and I compared the Tokina and the Zuiko 18mm. The Zuiko was
>> brilliant from 3,5. At 5,6 and smaller, there was no difference in
>> brilliance. But this specimen of the Zuiko showed a very slight second
>> spectrum picture, like the Zenitar 16mm fisheye does, whereas
>> the Tokina
>> seemed to have no visible second spectrum picture.
>>
>
>Not sure what you mean by "second spectrum picture", is this colour fringing
>on high contrast edges. Would it be possible to post an example somewhere ?
>
>I have not noticed any such artefacts with my 18mm.
>
>...Wayne
I am not sure about the right term in English. I mean that there seems to
be a picture for some colours of the visible spectrum with a different
focal length. It's difficult to post an example, you wouldn't see it at a
monitor. But I can try to explain the situation where it sometimes becomes
visible under great magnification. When you take a picture of a landscape
with a forrest in the background, and in this forrest some trees are
greater than the average trees, and these greater trees stand as a
silouette in front of a much brighter sky, then you can see sometimes such
tree "shadows" twice, if they are near the corner of the picture and small
enough not to overlay. The one shadow is dark and the second is much more
difficult to see, coloured and brighter. This is maybe because the lens has
a different focal length for the colours which produce the second picture.
But you have to use a relative great magnification (25X workshop microscope
for example or a projected slide, which you look at from a close distance)
to see it and I am not sure if it's present in any 18mm. I have seen this
also with the Zenitar fisheye. I think it's a kind of chromatic abberation.
Such effects should be absent in apochromatic lenses.
Matthias
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