[LRflex] Re: Introduction
- From: David Young <dsy@xxxxxxxxxxxxxxx>
- To: leicareflex@xxxxxxxxxxxxx
- Date: Mon, 23 Nov 2009 23:51:38 -0800
Dave Simms wrote:
Hi, fellow Leicaphiles;
My name's Dave. I'm a retired physics teacher who has used Leicas
since 1967 when I bought my first Leica, a 3F with the 50mm Elmar
f3.5, from a place in New York for $38.
I have a confession to make though. After the EMP wipes out all
things digital, I'll still be able to take pictures. Mind you, there
won't be much of a wolrd left to take pictures of and there probably
won't be a lot of people left to appreciate my work but, you can't
ask for everything, can you ?
I've already acquired some important tidbits of digital knowledge
from David and I'm looking forward to learning a bit more. For
example, I know what 4/3s is in math but, I havent the foggiest idea
of what it means when applied to photography.
all the best to my Leica friends. I'm looking forward to learning and sharing.
Dave
Good Evening, David, and welcome to the zoo!
Not sure what, if anything, will be working after the EMP, but that's
something I hope I'll never find out.
For you, and for Charlie, 4/3rds is certainly "in the math", but it's
not quite as simple as being half a 35mm frame, re-formatted.
When television was first invented, all cathode-ray tubes were round.
It mattered not, whether it was an "Image Orthicon", "Vidicon",
"Plumbicon" or whatever other type of tube was needed to originate or
reproduce the image. But while the tubes were round, the image their
inventors/users wanted was rectangular.
A 1"(diameter) Vidicon tube had, because of it's internal workings a
useable working area of roughly 2/3rds of the face of the tube. And,
the most convenient way to carve a rectangle with both pleasing
dimensions and the most useable area, out of the round surface was to
give it the proportions of 4:3 (width to height).
Because the tubes were round, only one measurement was needed to
describe their size. Thus TV's, even today, are called 19", 21", 27"
30" etc. This is the diagonal measurement of the screen and is
equal to the diameter of a "round tube" which would have been needed
to get a rectangle of that size. Got that?
While few among us will remember round b&w tubes, some of us will
remember the large round tubes of mid-1950's American colour TV's ...
and the very large cabinets needed to mask of the glass not used for
the image. By 1959, most colour sets used rectangular tubes, as had
b&w sets, since the early 1950's.
Although tubes are long gone, the makers of CCD and CMOS sensors
still use the sizing standards developed in the 1940's and 50's for
describing their sensors.
Thus, a 4/3rds sensor, is a sensor with a 4:3 aspect ratio, that is
roughly 2/3rds the surface area of a 1 & 1/3rd inch (hence: four
thirds inch) diameter Vidicon tube ... which also happens to be about
50% of the area of a standard 35mm frame ... which is, in turn,
double the size of a standard, 35mm movie frame!
Because TV's were (until recently) all made in this 4:3 aspect ratio,
so were most computer monitors. Thus, this aspect ratio was kept, by
many camera makers, so that their images would fill most monitors and
TV's without wasted space. No matter how small the sensors, the image
ratio of most P&S cameras (which means most digital cameras) is 4:3.
And now you know why!
For more on this, see: http://homepages.tig.com.au/~parsog/photo/sensors1.html
Ask the time ... and find out how the watch works!
BTW: I first met Dave yesterday, whilst flogging a few of my wildlife
photos, in his home town of Clearwater, BC.... about a 2 hour drive
from Logan Lake. He's a nice guy, running with several M's and an R6.
So, once again, Dave, on behalf of Xavier and all of us here, welcome
to the zoo!
David (Zoo-keeper) Young.
---
David Young
Logan Lake, Canada.
Wildlife Photos: www.furnfeather.net
Personal Website: www.main.furnfeather.net
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