Olympus-OM
[Top] [All Lists]

[OM] Re: Dumb digital question...

Subject: [OM] Re: Dumb digital question...
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Sun, 01 Aug 2004 21:55:10 -0700

R.Jackson wrote:

>Thank you. Makes a lot more sense now. ;-)
>
>I'm still not sure how you'd calculate the exposure duration. I'm sure 
>there's some kind of formula that explains it. 
>
I believe the sensors have to be read and emptied/cleared at a rate 
defined by the pixel spacing in the direction of travel of the linear 
sensor array and the speed at which it moves. This is the way flatbed 
and film scanners work. A sensor array 1 pixel wide and the length of 
the maximum subject width moves mechanically across the subject. In a 
flatbed, the sensor moves, in film scanners, is is usually the film that 
moves past the sensor. A scanning film back works like a flatbed 
scanner, with the sensor aray moving across the focal plane.

>Still, if it takes that long for the sensor to traverse the image it's 
>probably still a fairly long exposure unless the sensor is seeing a *very* 
>small slice of the image at a time. Interesting technology. Seems to yield 
>amazing images.
>
It is seeing one pixel width at once, I expect, so it is indeed a "very" 
small slice. I can envision multiple pixel width sensors, but don't know 
if they exist. Certainly the processor power needed to operate them 
would be considerable. With a scan time (not exposure time) of a minute, 
it is almost certainly a single pixel width array.

>If that's what Gursky is using I was amazed at some of the images he 
>was showing at MOMA. Some of them were 15-20 feet wide and had so much 
>detail that I'd find myself with my face a couple of inches from the 
>image looking at what it said on someone's T-shirt in a crowd or what 
>kind of cigarettes someone was smoking. He had one that covered an 
>entire soccer field and you could examine each player in the kind of 
>detail that you usually only see in a closeup. That kind of work is 
>fascinating to me. It's the ability to really reach out and document a 
>moment in time with such fine detail that it transports the viewer in a 
>way.
>
Do you remember old photos of racing cars where the cars seemed to be leaning 
forward? It gave a really exciting image, like they were straining forward to 
go faster. That distortion was a result of the vertical focal plane shutters on 
Speed Graphics and similar cameras. Those 4x5 cameras had big, heavy shutter 
curtains that traveled rather slowly. Fine with a static or slow moving 
subject. With fast moving subjects, the image on the film plane moves fast 
enough during the slit travel time to significantly distort its shape. It's not 
blurred, as each individual part is exposed for a very short time, but their 
spatial relationships are changed in the image. Flip the camera over, and the 
cars would look like they are trying to hold back. If the images you are 
talking about are taken in this way, with total scan times of 60 seconds, the 
location of the people at one end will be different than where they were when 
the people at the other end were recorded. If you look carefully a
 t the soccer pic, the players' positions, where they are looking, etc. would 
be 'out of sync', since a lot can happen in a minute. You are looking a a 1 
minute time slice of the game spread across the image.

Moose



==============================================
List usage info:     http://www.zuikoholic.com
List nannies:        olympusadmin@xxxxxxxxxx
==============================================

<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz