The Masked Engineer: Mario Orazio
Widescreen Lenses? Flying Pigs, Too
You might not have noticed that lenses are round. Also, P. T.
Barnum is alive and well and living in a lens factory. Okay, so
he really ain't. But when he said, "There's a sucker born every
minute," he didn't know the half of it –or should I say the
9/16 of it? Geez!
Step into a video facility anywhere in the world with a piece
of paper that has "16:9" written on it, and you'll be greeted as
a member of the club. Love it or hate it, everyone in the TV technology
biz thinks he or she understands what 16:9 is. Hah!
Calculators down. What's wider, 16:9 or 37:20? This ain't some
academic exercise. 16:9 is the globally accepted shape for widescreen
TV, aka "Television of the Future." As for 37:20, that's
the shape of most Hollywood movies.
"But, Mario, we've never even heard of 37:20!"
Of course, you ain't. What cinematographer would ever call an
aspect ratio 37:20? Okay, calculators up. Ayup, 37:20 is 1.85:1.
Our beloved 16:9 is 1.7777...:1. Call it 1.78:1 for short. And
why don't we just call it 1.78:1? That's because playing with a
number like 16:9 makes it sound like we have a clue, and we ain't
got one.
For instance, why 16:9? Yeah, I've heard the stories. If the set
is 16:9, you can fit one big 4:3 image on it with three little ones
down the side. So what? If the screen is 2:1, you can fit one big
4:3 image on it with two little ones on the side. If it's 5:3, you
can stick one big 4:3 image on it with four little ones down the
side.
DO YOU BELIEVE IN MAGIC?
Then there's the idea that this is a magical ratio for electronic
cinematography, the lowest spatial loss if you consider every aspect
ratio between 4:3 and 2.35:1. Never mind that the result is 1.77:1,
not 1.78:1. Who said those are the limits?
The latest American Cinematographer Manual says that anamorphic
movies are 2.4:1, not 2.35. And isn't the idea to get rid of 4:3
someday? If you do the minimum spatial loss thing between 1.85:1
and 2.4:1, you end up with something a lot wider than 16:9.
Anyhow, it's here, and we're stuck with it. But that doesn't mean
we need to go out of our gourds about it.
Here's a wee silly example. Marshall Electronics makes LCD video
monitors. They even won a Mario Award (whatever that is) last year
for one model.
Well, now, it seems they've got a widescreen model with some pushbuttons
underneath it. One says "BARS;" another says "4:3/16:9." Suppose
you see something 4:3 on the monitor, and you push the "4:3/16:9"
button. Shazzang! The picture gets stretched out to fill the full
screen.
So far, so good. If the stuff you're looking at was shot 16:9,
it's got the right shape. If the stuff you're looking at was shot
4:3, it's got the wrong shape. So you push the "4:3/16:9" button
again, and nothing happens.
Following proper engineering procedures, you start pushing every
other button you can find. When you hit the one marked "BARS," instead
of colorful stripes appearing, the picture changes back to 4:3,
with black bars on either side of it.
Hey – no harm done, and maybe Marshall just wants to keep
you on your toes. As I said, it was a wee, silly example. The lenses
ain't.
Repeat after me:
There is no such thing as a 16:9 lens. There is no such thing
as a 16:9 lens. There is no such thing as a 16:9 lens.
"But Mario, …" No. There is no such thing as a 16:9 lens.
And there is, likewise, no such thing as a 4:3 lens.
ROUND, I SAY!
Kindly re-read the first sentence of this lunar cycle's rant.
Lenses are round. The images that come out of them are, likewise,
round. Those round images have a diameter, not a rectangular shape.
Now, let me be the first to admit that the diameter doesn't bear
much relation to what we call it. Ever heard of a 2/3-inch camera?
Of course, you have! Ever found anything in it that's 2/3 of an
inch, aka 17 mm? Of course, you ain't! You ain't since the era of
imaging tubes anyhow.
A 2/3-inch tube had an outside diameter of 2/3-inch. The image
on it had an 11-mm diagonal. A 2/3-inch imaging chip has an 11-mm
image diagonal likewise. Ergo, a lens designed for a 2/3-inch camera
makes an image with an 11-mm diameter.
Kindly note that not once in the last paragraph did I mention
4:3 or 16:9 or 1.85:1 or any other aspect ratio. Circles ain't got
aspect ratios. Period.
An 11-mm diagonal fits perfectly into an 11-mm diameter. Again,
there ain't a single aspect ratio in that sentence. A rectangle
of any aspect ratio can have an 11-mm diagonal. A 4:3 rectangle
with an 11-mm diagonal has the dimensions 6.6 mm x 8.8 mm. A 16:9
rectangle with an 11-mm diagonal has the dimensions 5.4 mm x 9.6
mm.
Once again, allow me to be the very first to acknowledge that
5.4 ain't 6.6 and 9.6 ain't 8.8. But 11 is 11, and that's all the
lens cares about.
A 2/3-inch-camera lens works on a 2/3-inch camera. An 11-mm image
diameter lens works on an 11-mm image diagonal camera. Have I made
myself clear enough? Let me be a little dainty about it:
THERE IS NO SUCH THING AS A 16:9 LENS! THERE IS NO SUCH THING
AS A 4:3 LENS!
IN A PERFECT LENS
What there is is extra glass that certain lens manufacturers,
which I shall refer to by fictitious names such as Canon and Fujinon,
stick on the backs of their lenses. The fictitious Canon calls its
extra piece of glass a 4:3/16:9 "crossover;" The fictitious Fujinon
calls it a "ratio converter."
If you had a perfect lens, would you want an extra piece of glass
on the end of it? Me neither. Extra glass means extra distortion.
Extra glass means extra cost. Extra glass means extra nuisance.
"What do you mean by 'nuisance,' Mario?"
Oh, back-focus issues, flare, and my all-time favorite, vignetting
(or seeing the lens barrel in the image). If you stick one of these
supposedly switchable 4:3/16:9 lenses on a plain old ordinary 4:3
camera, and the lens is in the 4:3 position, you get the lousy pix.
To eliminate them, you need to switch the lens to the 16:9 position.
I am not making this up.
"But, Mario, how can this be?"
It can be on account of us being superstitious idiots. Ever walk
into a tall building and discover there's no 13th floor? What did
they do, leave an empty space? Do they think the folks on the 14th
floor will never figure out that they're the floor over 12?
Likewise (before reading this rant, of course), when folks decided
to switch from 4:3 cameras to 16:9 cameras, they figured they'd
need everything new. Well, there are 16:9 monitors. There ain't
any 16:9 cables, connectors, amplifiers, recorders, or distribution
amps. And there ain't any 16:9 lenses.
But a lens won't deliver the same picture in 16:9 that it does
in 4:3. Well, duh! 8.8 ain't 9.6; the picture will be wider in 16:9.
6.6 ain't 5.4; the picture will be shorter in 16:9. If you're used
to getting a certain width at 9 mm with your 4:3 camera, then with
most broadcast 16:9 cameras (don't try this with BTS/Philips/Thomson/RCA),
you'll get a wider shot.
Got that? Good. Because those "crossover" or "ratio converter"
pieces of glass don't do diddley-squat to affect that difference.
What they do do is play with the difference between the 4:3 of
a 4:3 camera (6.6 x 8.8 mm in a 2/3-inch model) and the 4:3 of a
switchable 16:9 camera (5.4 x 7.2 mm). That ain't an 11-mm diagonal
anymore. Ergo, you're only going to get about 4/5 as wide as you
would have on a real 4:3 camera. But you're also going to get about
5/4 tighter. If your lens went from 8 mm to 80 mm, it'll have the
same kinds of shots as one that went from 10 mm to 100 mm.
Most of the time, so what? And, if you need a really wide shot,
rent a really wide lens for the occasion. All a "crossover" or "ratio
converter" is is a roughly 0.8x wide-angle adapter. Buy yourself
a 0.7x that fits on the front of a lens, and you can go wider still
and not worry about back-focus. And not worry about obsolescence.
"But, Mario, what do you mean by 'obsolescence'?"
I mean that, once you start shooting 16:9 all the time, that rear
0.8x element is useless. Remember that vignetting and seeing the
lens barrel that you get when you run one of these lenses in 4:3
mode on a fixed 4:3 camera? Well, that's because the 4:3 camera
has an 11-mm image diagonal, and after crossover ratio conversion
these babies have only 4/5 as much image diameter.
Guess what: Your switchable 16:9 camera has the same 11-mm image
diagonal in 16:9 mode (again, not counting BTS/Philips/Thomson/RCA).
Ergo, once you give up on 4:3 shooting, you can never use that crossover
ratio converter again.
Got that?
This way to the egress.
Mario Orazio is the pseudonym of a well-known television engineer
who wishes to remain anonymous. Send your questions or comments
to him c/o TV Technology. Or drop him a note on e-mail Mario_Orazio@imaspub.com .
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