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Decent exposure
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I wrote previously[1] about shooting film in
manual mode without a lightmeter. I really
enjoyed the process, want to do more of it
and really get good at estimating exposure
with nothing other than my eye and brain.
For the last roll I put through my Spotmatic,
for each shot I set the camera to my best
guess and then check with the meter before
taking the shot. I definitely got better
toward the end of the roll. At some point I
told myself that I should stop checking and
go with my instincts, but I was very rarely
able to overcome the temptation. I think I'm
going to take the battery out for the next
roll so I have no choiced but to trust my
gut, like when shooting my FED.
Part of getting better throughout this last
Spotmatic roll was just experience, but a big
part was lots of reading and study. This
post is my effort to share some of what I
learned but also systematise some of the
things I think I've figured out for myself,
just to help clarify my own understanding.
I'm going to propose an alternative set of
rules of thumbs to the traditionally Sunny
16. I want to emphasise that I haven't
actually tested these rules yet. I'm going
to with my next few rolls. For now they're
just ideas. They are nothing radical, they
are 90% the result of applying standard
exposure arithmetic to the traditional
recommendations to come up with a system that
makes more sense for me, based on my style of
photography.
The classic rule-of-thumb for manual shooting
is the so-called "Sunny 16 rule"[2], which
tells you that on a sunny day you can get a
correct exposure by setting your aperture to
f/16 and your shutter speed to the value that
is closest to the reciprocal of your film
speed, e.g. 1/125 for ISO 100, 1/500 for ISO
400, whatever. Of course you don't have to
actually shoot at that setting, but it's a
starting point for adjustments, e.g. instead
of f/16 at 1/500 you could shoot f/22 at
1/250 or f/11 at 1/1000.
All well and good, but what do you do in the
not uncommon situation when it's not actually
sunny? Obviously if it's less than sunny
you'll need to expose for longer, and/or open
the aperture wider, but by how much? After
shooting semi-automatic modes on cameras with
built-in meters for years, I have very little
intuition about judging how many stops darker
than "sunny" a given situation is.
With a little searching I came across an
expanded version of the rule, which offered
recommended apertures for various other
weather conditions. They are:
Light Aperture
----- --------
Sunny f/16
Slight overcast f/11
Overcast f/8
Heavy overcast f/5.6
Sunset f/4
To some extent, this doesn't help too much.
It just replaces the problem of guessing "is
this light two or three stops weaker than
sunny?" with the problem of guessing "is this
weather *heavy* overcast or just ordinary
overcast?". It's not totally useless,
though, it's informative just to know that
there are about four stops of exposure
between the brightest and dimmest levels of
sunlight. More detailed guides to using this
rule (which, by the way, are rarer than you
might hope - the vast majority of online
articles about the Sunny 16 rule are written
for people, and maybe even by people, who
don't even understand the basic idea of the
exposure triangle!) have made this a bit
easier to judge by describing typical
shadows. When it's "heavily" overcast, no
shadows are visible, when it's "normally",
shadows are faintly visible, when it's
"slightly" overcast shadows are clearly
visible but have soft edges and when it's
"sunny" shadows have clear, solid edges. I
like this advice, it removes some guess work.
One thing I don't so much like about this
extended Sunny 16 rule is that it's stated
in what we might think of as "shutter
priority" format: as the lighting conditions
change, you keep your shutter speed fixed at
1/ISO and change your aperture to let in
more/less light.
I understand *why* the rule is formulated
this way: it's easy to state one rule which
applies for all film speeds when you link
film speed to shutter speed, because film
speed and shutter speed both vary linearly
with amount of exposure, whereas aperture
f-stops have that pesky sqrt(2) factor in
there. So, the rule more or less has to be
stated this way for the sake of generality.
Fair enough.
But as an actual table of settings to study,
memorise and use in the field when shooting,
this makes very little sense for most people,
or at least for me. Shutter priority is for
sports photographers! If you are
photographing mostly stationary things, then
shutter speed makes very little difference
to how the resulting photo will look - any
two speeds fast enough to avoid camera shake
are identical. In contrast, aperture can
have a dramatic effect on the result. It
determines depth of field, and also
influences image quality; Most lenses give
their best results around f/8 or f/5.6, and
suffer increasingly worse problems
(diffraction, soft edges, vignetting,
chromatic aberations) as you push them to
either extreme.
I think it makes much more practical sense to
try to memorise an "aperture priority" table
of rule-of-thumb expoures. Yes, a table like
this is ISO-specific, but plenty of people
only shoot one film stock anyway, and I get
the impression that few routinely shoot more
than two speeds. Let's convert the extended
Sunny 16 table above into a table for
shooting ISO 400 film, which I would say is
the mostly likely candidate for a general
purpose film speed, and at f/8, which is
again a typical "general purpose" aperture
("f/8 and be there", as they say) at which
most lenses will perform well, DoF is wide
enough that you have some margin of error for
focussing, etc.:
Light Shutter @ ISO 400 f/8
----- ---------------------
Sunny 1/2000
Slight overcast 1/1000
Overcast 1/500
Heavy overcast 1/250
Sunset 1/125
Well, that's not ideal, is it? Shooting on a
sunny day requires a shutter speed of 1/2000.
Most classic film cameras from the 60s or 70s,
or at least the Japanese SLRs that I'm most
drawn to, have maximum shutter speeds of
1/1000, or sometimes even 1/500. According
to this table, they're unusable at f/8 until
the clouds roll in.
For this reason, ISO 400 film is actually a
touch fast, IMHO, to really be considered a
good general purpose film. ISO 200 honestly
seems better, and while ISO 200 film exists,
there is a much wider range of stock at ISO
400 and ISO 100 (or roughly 100 anyway, for
whatever reason manfacturers seem to like
producing just slightly faster films, e.g.
Ilford FP4 is rated at ISO 125 and Kodak make
Portra in ISO 160), and those speeds have
much better availability both online and
offline than ISO 200.
So, what do we do? Well, personally, almost
all my cameras can do 1/1000 and I'd be
reluctant to acquire any more which can't.
So, one option for me is to deliberately
overexpose every shot by one stop, yielding
this table:
Light Shutter @ ISO 400 f/8
----- ---------------------
Sunny 1/1000 +1
Slight overcast 1/500 +1
Overcast 1/250 +1
Heavy overcast 1/125 +1
Sunset 1/60 +1
Now, this is a very practical table! Every
shutter speed which is fast enough to be shot
handheld with a 50mm lens with no risk of
blurring is used, and it lets me shoot in any
daylight condition outdoors at a very nice
aperture of f/8. Of course, sometimes I
might want to use something other than f/8,
but in those cases I will usually only want
to move one or two stops away from this
table, whereas the traditional extended Sunny
16 table is likely to have the reference
point for a given lighting condition much
further away from what I want. But, this
nice table has come at the cost of +1
overexposure across the board. How do I feel
about that?
Well, not fantastic to be honest, but I don't
doubt that it will yield workable results.
Modern film stocks have quite wide exposure
latitutde and tolerate overexposure better
than underexposure. In fact, quite a lot of
people online think that a lot of films look