I just heard that John Mark Karr will not be charged in the Ramsey case. I could
smell this coming for several days, and I even sensed a few in the press trying
to hedge their position. Jack Cafferty said the press was ‘played like a tin
drum’ on this case. I say they did it to themselves, once again.
I'm sure [that right] after Alexander Graham Bell said ‘Watson come in here. I need you,’
he said ‘What are you wearing?’
A funny and poignant observation by Jon Stewart about how changing technology alters the norms of decency.
Early in my exploration of photography, I learned about the relationship between
aperture (ƒ-stop) and depth of field — the phenomenon that describes
how much of the image taken in by the lens is drawn in sharp detail. I've recently
discovered, though, that there are interesting nuances to this distinction.
[With a shallow
depth of field, only a narrow plane of view is sharp, while things in front
of or behind that plane are rendered out of focus or ‘soft.’ In
a photo with a deep depth of field, virtually everything in the scene can be
sharply in focus. Apertures like ƒ/2.8 give a shallow depth of field — isolating
the face of one person in the foreground from a crowd standing behind, for
example; while apertures like ƒ/16 or higher offer a high depth of field,
and might well record everything in a landscape sharply.]
The first nuance is bokeh, which describes how the lens handles the part of
the image that is outside the depth of field. There is such a thing as bad
bokeh, and good bokeh has to be designed into a lens. Bad bokeh puts hard edges around out-of-focus elements. Ken Rockwell has a
How can you gauge the bokeh in your lens? Ken says:
Find a point of light in the distance. You can do this easily at night by
finding a distant point streetlight, or you can do it indoors by taking the
reflector off of a Mag-Light flashlight and just setting it up on the other
side of the room.
Now look at the ground glass as you focus. If you see perfect round disks
your lens has neutral bokeh, if you see soft-edged shapes you have good bokeh,
and if you see doughnuts you have bad bokeh.
I began to find out about this issue when I was researching the new Zeiss
lenses for Nikon mount. A cryptic message on a discussion board said ‘the
bokeh will suck.’ As I looked further into it, I found out that while
the legendary Zeiss name connotes the pinnacle of German optics and a history
that dates back to 1846, many Zeiss lenses
are manufactured under license in Asia, and many of the Zeiss design patents
have expired, so lots of companies can make more or less the same lenses
(Think off-brand low-cost lenses that boast incredible performance).
Of course, the quality of the glass and the components used can vary greatly.
More interesting, the Zeiss lenses for Nikon mount are being brought to market
first and foremost because Kyocera has killed the Contax camera line — once
an important outlet for Zeiss photographic lenses. Zeiss has responded by marketing
some of their best-known lenses in Nikon F-mount format, and by increasing
their partnership activity with companies like Sony, who market the Alpha
The Zeiss ZF lenses are manual focus lenses, and offer what is essentially
only a physical compatibility with my Nikon body. The prospect is not exciting.
What is exciting is that the Nikkor 85mm
ƒ/1.8 is a really nice, light, fast lens,
perhaps the perfect portrait lens for me, and it's not so expensive. [I think
it's the next lens to get.] The 85mm ƒ/1.4 is
an even more impressive lens, but it weighs about a pound, it costs more than
triple the price, and its performance characteristics are only marginally better.
Yeah, when I get a really nice windfall, I might think about it again, but
maybe not — there's always more kit to get when you're doing photography.
Now for the second nuance. In 1932, 11 West Coast photographers (Ansel Adams,
Imogen Cunningham and the Westons among them) dubbed themselves Group
ƒ/64. The name comes from
the smallest available aperture for a large-format view camera at the time.
It was an aperture that provided infinite depth of field, making it very useful
for landscape photography.
35mm camera lenses can't stop down to ƒ/64m but
they often go down to ƒ/22, and for some time I've heard that the smaller the
aperture, the greater the depth of field. Why do we care? With a great enough
depth of field, focusing becomes a non-issue, which is a boon to street photographers,
and even event photographers who need to shoot fast.
When I was shooting with my D100 last summer, I started to notice that some
of my landscape shots seemed to be coming out soft, even though I was intentionally
pushing the aperture to ƒ/22. I thought it was some weird focusing
problem, but it
turns out that I had bumped into an optical limitation of the system. The small
aperture causes a diffraction effect, which substantially degrades sharpness.
You might want to think twice about using ƒ/22, especially if you're shooting
What causes the problem? An incompatibility between the size of the photosites
on the camera's sensor and the size of the circles of confusion produced
by the lens when it's stopped down to such a small aperture. Depending on your
camera, this effect could kick in at apertures as moderate as ƒ/5 or so. Most
mid-range and high-end digital cameras won't show the effect until you pass
ƒ/11- ƒ/16. Here's a link, if you want more
detail on this.
There's actually another reason to think twice about stopping down [setting
a high ƒ-stop #] (or opening up [setting a low ƒ-stop#]) too much: many lenses,
and especially zoom lenses, only exhibit optimal sharpness through several
stops in the middle of their range of apertures. You'll lose sharpness in your
image if the lens is wide open, or if it's closed down too much.
For me, that means I don't plan to stop down beyond ƒ/11-16, and I might think
twice about using ƒ/3.5-4.5. ƒ/8-9 is starting to sound like a real good range
to aim for.