His last post on Photobucket seems to be end of Jan 2012
selling some lens hoods?

When you sand off the black paint on these for the extra contact
make sure you have sanded enough for the maximum available aperture
on the lens to be transmitted through all 3 tubes. Very often only
the aperture setting is going through.
You only sand the one spot... just make sure that you do a good job.

Strangely I've got a set of Triplus tubes marked Pz AF with 8
contacts on the body side?

Despite saying AF they aren't AF, but are the Rolls Royce
of extension tubes.... really well made

When you sand off the black paint on these for the extra contact make sure you have sanded enough for the maximum available aperture on the lens to be transmitted through all 3 tubes. Very often only the aperture setting is going through. You only sand the one spot... just make sure that you do a good job.

There's quite a bit of PF on the background on No: 2

Reminds me of the time I dropped my camera in
the Elephant House at Chester Zoo

To work quickly without lubrication there has to be quite a
bit of looseness/tolerance, plus when you get any item where
adding a bit to one side makes the other side look worse,
such as trying to centre a stone cap on a brick gatepost,
things look worse than they are. With a 8/9 sided iris
possibly 3 sides effect the appearance at once. Each
blade has two pins very close together one acts as a pivot
and the other slides in a slot on a metal plate so any
additional movement is magnified. Also these blades aren't
at 90deg to each other they are chords of a circle and
the slightest movement of one cause a big difference to
the adjacent blades.

I've just looked at two of my 55mm f/1.4 ( non-Pentax )lenses
and they both have the problem. One actually goes almost
triangular, but they are both razor sharp and open close
very fast so I'll just ignore it.


,

You need to get rid of Bullguard then Vic that link was
just a bog standard PDF file Try right click and
save.... to just get the file.

The actual website although in French looks interesting

http://usinette.org

Very little running in the background just usinette.org
and the site that hosts the pictures.... no spy sites

Also shown here:

http://www.dpreview.com/news/2001/2/16/pma04#siliconfilm

--

Sorry it is 8 on the 77mm.

I personally wouldn't bother about it as long as it's not
caused by a sticking iris. I've got some lenses like that
and they work perfectly. I might take one apart to see
what the problem is.... possibly change the blades around.

There's nothing wrong with the backgrounds

I'm amazed at the lack of knowledge about
industrial fashion photography in this thread

You don't throw backgrounds OOF that's the whole idea

Just type "industrial fashion photography" into Guggle
and select "images for industrial fashion photography"

It's been that way since at least the 70's

One has 9 blades the other has 7

Exposure is usually out at f/16 anyway even with a perfect iris.
You shouldn't need f/16 with a 31mm?