Originally posted by Balez
reply to post by Balez
Something else i am curious about is this.....
Let's say we have a object (small object) close to the camera that is moving.
When we zoom in on that object, will it's actual speed look different from the unzoomed view?
If that is 'so' what would be the difference with a far away object that is moving and being zoomed in on?
If you noticed... I am not very good when it comes to cameras and their inner workings
Jim and all the other camera experts, please chime in on this
I'll be waiting
well, there are two different things
1) The speed of an object relative to a reference system. It is meassured on distance gone by the object divided by time lasted. Let's say it has 5
meters/second. This is a property of the object, doesn't depend on the observer's (camera) position.
2) the angular speed relative to the observer. It is the distance gone by the object as seen from the observer (which is itself at some distance away)
divided by time lasted. THIS IS THE SPEED WE, THE OBSERVERS, SEE OR RECORD. That's way a fly can appear to have a greater speed when flying 1 meter
in front of the observer, comparing with an airjet flying 10 km up...or the ISS going with 8km/sec somewhere at 300 km up and appearing to move SLOW.
One distance divided to other distance means it is AN ANGLE. So, this angular speed, can be measured as angle units/ time...let's say 8 degree /
minute as an example.
Now, this angular speed is the one we, the observers, are aware. Only this.
Answering to your question... this angular speed DOENSN'T DEPEND ON THE ZOOM CAPACITIES OF THE OBSERVER.
Therefore, let's say that, relative to the observer (shuttle's camera), the tether has an angular velocity of 5 degree/minute, for example purposes,
(and we know is at 100 miles distant) and one particle of debris has also 7 degree/minute (and it is only 10 meters away for example purposes).
Because their angular speed doesn't depend on the observer's seeing abilities, their angular speed is the same no matter the zoom.
The only difference, is that when unzoomed, the observer see a slow moving accros the field of view, and when zoomd, it will see a fast movement
accros the field. That's why, when you film a star/planet/moon unzoomed, you are aware to see a static scene, but when using a big zoom, a telescope
for example, without tracking capabilites, the sky objects go away fast in the FOV (due earth rotation), and you see this. You can also judge the
shaking of a camera holded on hands: bigger the zooms, easy to be aware of the shakings.
The zoom, is only a power of magnification of the angles (or angular velocities).
This are basics in my opinion!
And this confusion goes to much many people..for example those, when seeing a bug/bird streaking fast on a camera, without enough resolution to
understant what it is, they say "it is too fast to be a bird/bug, look how fast is going in the image... it must be supersonic or something".
Or here, with some debris only meters away from the camera, and having speed in the centimeter/meter/second (slow) relative to the shuttle, will make
David Sereda to promote in his documentary "look they must have tremenduos speeds".
[edit on 7/11/09 by depthoffield]