Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Mar 9, 2006, 10:20 AM   #31
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Don't confuse the diameter of the lens and the aperture iris with focal length. They are too different things.

JimC is offline   Reply With Quote
Old Mar 9, 2006, 10:23 AM   #32
Senior Member
 
tmoreau's Avatar
 
Join Date: Dec 2005
Posts: 477
Default

Theory is wonderful, but all the theory you can muster still wont move the earth. Schools and books rarely, if ever, teach the hard lessons of practical application.

Your also completely ignoring the physics of lens construction. Try taking a look at several types of lenses that are known to accomplish aproximatly the same thing. Or wrap yourself in a warm blanket of ignorance and forget about it, I wont judge you for that.

tmoreau is offline   Reply With Quote
Old Mar 9, 2006, 10:26 AM   #33
Member
 
Join Date: Jan 2006
Posts: 91
Default

JimC wrote:
Quote:
Don't confuse the diameter of the lens and the aperture iris with focal length. They are too different things.
Rising Above

Simply stated, the primary function of a telescope is to collect light. The larger the telescope, the more light it can collect. The more light collected, the fainter and more distant the objects that can be observed.


That was a quote taken from here:

http://www.astrophys-assist.com/educ...ble/hubble.htm
Mark47 is offline   Reply With Quote
Old Mar 9, 2006, 10:27 AM   #34
Senior Member
 
Tom LaPrise's Avatar
 
Join Date: Oct 2004
Posts: 324
Default

I'm not quoting anything from a book, and I DO understand what I'm posting about.
The only things I quoted were your own incorrect statements and an explanation of how light travels in space (along with an URL so you can check up). I am aware of the "wave" nature of light, but that doesn't change anything about how lenses and cameras work with light.
Mark47 wrote:
Quote:
Mark47, you're arguing with people who know a lot more about lasers, lenses, sensors, and film than you do, and with every post you make, you prove it.




Being able to quote something from a book doesnt mean you understand it, and I have seen nothing so far to prove otherwise, so stop being smarmy. Using a few technical terms doesnt equate to understanding either.

http://au.search.yahoo.com/search?p=...aves&meta=

Take your pick
Tom LaPrise is offline   Reply With Quote
Old Mar 9, 2006, 10:29 AM   #35
Junior Member
 
Join Date: Sep 2005
Posts: 23
Default

The truth about light is simply that we don't know if it acts as a wave or a particle. In fact, it acts as both, depending on the circumstances. It is easiest to treat light as a wave and assume that interference fringes are caused by electromagnetic interference (much like waves in the ocean building and canceling each other out), but experiments following Young's double slit experiment showed that if light is released one photon at a time, it still creates an interference pattern on the target after millions of photons have been allowed to hit the target. How can a single photon of light interfere with itself?!?! Furthermore,we cannot observe light's true nature directly because, in order to "see" a photon, we must reflect another photon from the subject in question. This process alters the course, and the nature of the photon we are trying to observe. In short, there arenothing but educated guesses out there, so none of us can pretend to know how light works.

I think this topic has run its course, so why don't we all calm down and enjoythe fact that it doesn't matter what our lenses do, it matters that we can make great pictures--like today's photo of the day.

-Blake
GWHayduke is offline   Reply With Quote
Old Mar 9, 2006, 10:29 AM   #36
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Larger does not need to mean greater focal length. You have to take the largest available aperture (which means the lens will need to be larger for any given focal length), as well as the medium (film or sensor) into consideration.

If you have a sensor with more density as far as photosites are concerned, it can resolve just as much detail as a larger sensor with the same number of photosites, provided the lens is not outresolving the sensor.

You can see the results of this in many real world examples and comparisons.

I can point you to resolution charts where a consumer model with a *much* shorter focal length lens is resolving more detail compared to a lower resolution DSLR, for example 6 Megapixels for the DSLR, compared to 8 Megapixels for the prosoumer model) for the same framing.

The apertures may be rated the same (because it's expressed as a ratio between the focal length of the lens, and the diameter of the aperture iris), with the shorter focal length lens gathering just as much light for the smaller sensor size as the longer focal length lens is for the larger sensor.

With film (for example, going from 35mm to 645 format), you usually see more difference, only because the film resolution is increasing with surface area. With sensors, that's not usually the case (yet, anyway).

JimC is offline   Reply With Quote
Old Mar 9, 2006, 10:30 AM   #37
Senior Member
 
Tom LaPrise's Avatar
 
Join Date: Oct 2004
Posts: 324
Default

Yes, and the quote refers to light-gathering, which is a function of aperture--not focal length. The HST's focal length is actually relatively short--especially compared to larger, ground-based telescopes.
Mark47 wrote:
Quote:
JimC wrote:
Quote:
Don't confuse the diameter of the lens and the aperture iris with focal length. They are too different things.

That was a quote taken from here:

http://www.astrophys-assist.com/educ...ble/hubble.htm
Tom LaPrise is offline   Reply With Quote
Old Mar 9, 2006, 10:32 AM   #38
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

And that should have read two versus too. I do that kind of thing often when responding quickly. You may see me use won't versus want, too versus two or to, etc.

One of these days I'll start using a grammer and spelling checker. :?
JimC is offline   Reply With Quote
Old Mar 9, 2006, 10:34 AM   #39
Member
 
Join Date: Jan 2006
Posts: 91
Default

Tom LaPrise wrote:
Quote:
I'm not quoting anything from a book, and I DO understand what I'm posting about.
The only things I quoted were your own incorrect statements and an explanation of how light travels in space (along with an URL so you can check up). I am aware of the "wave" nature of light, but that doesn't change anything about how lenses and cameras work with light.
Quote:

I said light travels in waves, you tried to say it didnt, you were wrong, so dont try to twist it around. I havent said anything that is oncorrect, you have just misinterpreted it.
Mark47 is offline   Reply With Quote
Old Mar 9, 2006, 10:36 AM   #40
Senior Member
 
Tom LaPrise's Avatar
 
Join Date: Oct 2004
Posts: 324
Default

You have said several things that are incorrect. They have been pointed out to you by several people.
Mark47 wrote:
Quote:
Tom LaPrise wrote:
Quote:
I'm not quoting anything from a book, and I DO understand what I'm posting about.
The only things I quoted were your own incorrect statements and an explanation of how light travels in space (along with an URL so you can check up). I am aware of the "wave" nature of light, but that doesn't change anything about how lenses and cameras work with light.
Quote:

I said light travels in waves, you tried to say it didnt, you were wrong, so dont try to twist it around. I havent said anything that is oncorrect, you have just misinterpreted it.
Tom LaPrise is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 10:36 AM.