I have one of these - they are good fun.
1. Who nose? With 8mm in colour you get chroma effects on the rim in
sky areas so perhaps it was to mask that problem. It certainly cuts
off a lot. Nowadays, Photoshop does it better.
2. The lens 'breaks' into two parts (press the 'lock-Unlock' button
and twist) and the filters screw on to the back of the front set. The
'normal ' filter should always be in place if you are not using any
others. There is no 'drop-in' filter at all anywhere. If you want a
set, I have a spare set of Sigma 22.5mm filters - yellow, orange, red
and ND2 - yours for the postage.
3. The only reason I can think that it would not work with a 4T is
metering - many 8mm lenses really screw-up fancy averaged metering
systems because of all the black area around the edge. You get
serious overexposure or the system has a hissy fit. You really need
spot metering for a circular fish or a hand-held but often that
doesn't work properly either - no idea why. You aren't normally in a
rush or snapshotting with a fish so take a reading with the widest
lens you've got, note the numbers and then switch to the fish. Or
meter with a second camera or hand-held, whatever you have. Oh and
bracket.
Andrew Fildes
afildes@xxxxxxxxxxxxx
On 18/05/2007, at 11:46 AM, Jay Drew wrote:
> In a moment of madness I acquired a Sigma 8mm F4 fisheye
> filtermatic lens.
> Naturally it does not have a manual. So for those that have had
> one in the past
> I have a few questions:
>
> 1. The lens cap is in two pieces. One piece reduces the circular
> image to a
> smaller circle. I've got a 16mm Sigma that has the same type of
> cap. For the
> 16mm I understand that this split cap's purpose was to create a
> circular image
> (pseudo fisheye) of the rectilinear image of the 16mm lens. What
> purpose does
> this provide on the 8mm which is already circular? Is it to
> provide circular
> cropping to reduce problems at the edges?
>
> 2. No additional filters were provided. There is a filter labeled
> "normal" that
> is in place. My understanding is that the other filters are 22.5
> mm drop-in.
> Eyeballing the "normal" filter I see female threads. So do the
> "drop in"
> filters drop in or do the screw onto the back of the "normal"
> filter or do they
> replace it. I had read that if the clear filter was not in place
> the lens would
> not reach infinity focus correctly. Are the only filters that fit
> the Sigma for
> the 8mm and 16mm? I've seen a spot were there were drop in filters
> for a Sigma
> 600mm labeled as 22.5, just wondering if they would work.
>
> Finally, searching through the archives I found a post stating that
> the lens did
> not work with a 4T. After eyeballing the mount to see if it would
> shave off the
> reset button I put this on my OM4 and shot one frame without a
> mirror hang
> (which is what I feared was the incompatibility). I'll steel my
> nerves and put
> this on my 4T and try that. Anyone know why it shouldn't work with
> a 4T? The
> meter does couple and that coupled with the spot metering would be
> the ticket
> for getting correct exposure as opposed to requiring the use of an
> external
> meter.
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