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DPChallenge Forums >> General Discussion >> unimportant questions, but curious
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06/20/2006 01:41:50 AM · #1
have you got any unimportant questions, but curious to know the answer? Just ask it here :) I'll start off with one of my own.

if my lens isn't super sharp, but I have a 5MP sensor which photosites are spread over a full frame sensor, would that give me tact-sharp results? say, as compared to a super sharp lens but used on a 18MP sensor which has a 1.6 crop factor?


Message edited by author 2006-06-22 04:50:55.
06/20/2006 01:43:52 AM · #2
what does crop factor have to do with sharpness?

Really, I don't know so I'm asking.
06/20/2006 01:46:10 AM · #3
Originally posted by crayon:


if my lens isn't super sharp, but I have a 5MP sensor which photosites are spread over a full frame sensor, would that give me tact-sharp results? say, as compared to a super sharp lens but used on a 18MP sensor which has a 1.6 crop factor?


nope. A cropped sensor wuld tend to fall more into the lens' sweet spot. Lenses tend to be sharper at the center than on the edges.

Also with more megapixels you could sharpen and down-size to the 5mp file size and get a sharper image.

Message edited by author 2006-06-20 01:48:18.
06/20/2006 01:46:34 AM · #4
Originally posted by Megatherian:

what does crop factor have to do with sharpness?

not directly - but seriously, I was referring to sensor size when I mentioned "1.6 crop factor" - basically pointing towards a sensor that is about 23.7 x 15.7 mm
06/20/2006 01:49:33 AM · #5
Originally posted by fotomann_forever:

nope. A cropped sensor wuld tend to fall more into the lens' sweet spot. Also with more megapixels you could sharpen and down-size to the 5mp file size and get a sharper image.

hmm you are right - I totally forgot to put the lens' sweet spot into consideration. Thanks for pointing that out, Leroy :) Now, on the more pixel for sharpening part - does that mean that more pixel on the same sensor size would produce a sharper image (assuming same lens used)?
06/20/2006 01:54:25 AM · #6
Originally posted by crayon:

Now, on the more pixel for sharpening part - does that mean that more pixel on the same sensor size would produce a sharper image (assuming same lens used)?


At low ISO and good light, yes it should.

But, where a smaller sensor would fail to be sharp is under high ISO, low light conditions. Noise would begin to be a major factor.
06/20/2006 01:55:27 AM · #7
hmmm - fotomann is smarter than the average cheese!
06/20/2006 02:01:42 AM · #8
Do elephants really never forget?

Isn't it possible to travel back in time if you travel west in a fast jet?
06/20/2006 02:05:11 AM · #9
Originally posted by justin_hewlett:

Do elephants really never forget?

AN ELEPHANT NEVER FORGETS - "First attested in the United States in 'Blue Ridge' (1937) by W. Martyn. The proverb is probably of Greek origin. The Greeks sometimes say, 'The camel never forgets an injury,' according to Burton Stevenson. 'To have a memory like an elephant' is used as a figure of speech." From "Random House Dictionary of Popular Proverbs and Sayings" (1996) by Gregory Y. Titelman (Random House, New York, 1996).

A second reference adds to this and has an earlier citation date: "Said of someone with a prodigious memory, usually for slights and wrongs. It was not the memory of the elephant but that of the camel that was renowned amongst the Greeks long ago. A Greek proverb ran 'Camels never forget an injury.' Proverbial reference to the elephant's memory is relatively recent. In 'Reginald: Reginald on Besetting Sins' (1910), the camel is usurped by the elephant: 'Women and elephants never forget an injury.' The author, Saki, was no stranger to elephants having been born in Burma and lived there, and would have appreciated the intelligence of the animal. The working elephant memorises a large number of commands given by the mahout and recognizes many other animals and people, thus remembering both kindnesses and injuries. Since its life-span is 50 or 60 years these memories are long-lived. Usage: Usually said of a person who does not forget injuries, but an 'elephantine memory' could just be a good one." From the "Dictionary of Proverbs and their Origins" by Linda and Roger Flavell (First published in the UK by Kyle Cathie Ltd, Barnes and Noble Inc, 1997, New York).

Originally posted by justin_hewlett:

Isn't it possible to travel back in time if you travel west in a fast jet?

I'm interested to know this one too
06/20/2006 02:11:03 AM · #10
I don't know about the past, but I'm currently traveling into the future... one second at a time.
06/20/2006 02:14:14 AM · #11
Originally posted by crayon:


Originally posted by justin_hewlett:

Isn't it possible to travel back in time if you travel west in a fast jet?

I'm interested to know this one too


Some theorists have argued that the matter of the universe only exists in the present moment. Thus, if one were to travel back from the 'present' to an earlier time, none of the material universe would be found there, because it will have remained in the present: the traveller alone is the only part of the universe to have gone back to the earlier time. In terms of a 4-dimensional spacetime, the traveller (or, more generally the atomic particles that comprise the traveller) would have travelled 'back' to an area of spacetime corresponding to an earlier value of 't'; but none of the other particles that form the universe will have done so, so the traveller finds precisely nothing when arriving back at the earlier time. This viewpoint eliminates all of the supposed paradoxes about time travel.
06/20/2006 02:15:34 AM · #12
Originally posted by Megatherian:

I don't know about the past, but I'm currently traveling into the future... one second at a time.

Do you think time is actually like a tape recorder?
Imagine that we, at what we call "current" or "present" is actually like the head of a VCR, and our future and past are all part of a fixed/pre-destined VHS tape... hmm...
06/20/2006 02:17:08 AM · #13
Originally posted by fotomann_forever:

Some theorists have argued that the matter of the universe only exists in the present moment. Thus, if one were to travel back from the 'present' to an earlier time, none of the material universe would be found there, because it will have remained in the present: the traveller alone is the only part of the universe to have gone back to the earlier time. In terms of a 4-dimensional spacetime, the traveller (or, more generally the atomic particles that comprise the traveller) would have travelled 'back' to an area of spacetime corresponding to an earlier value of 't'; but none of the other particles that form the universe will have done so, so the traveller finds precisely nothing when arriving back at the earlier time. This viewpoint eliminates all of the supposed paradoxes about time travel.

Hey this is highly interesting. I have not read about this intepretation before. Interesting, and logical.
06/20/2006 02:23:29 AM · #14
Originally posted by crayon:

Originally posted by Megatherian:

I don't know about the past, but I'm currently traveling into the future... one second at a time.

Do you think time is actually like a tape recorder?
Imagine that we, at what we call "current" or "present" is actually like the head of a VCR, and our future and past are all part of a fixed/pre-destined VHS tape... hmm...


Oh no, I am definately moving into the future, unfortunately everythings coming with me though.

Think about this, what if time moved at different speeds but since we all move at the same time with it we would have no idea because there is nothing to compare it to.

4th dimension 4th shmension. I still want to see proof of the first 2 dimensions. Nice theories but where's the proof? Everything I or anyone I've ever heard of has only come across that which lies in 3 dimesions. Seems to me we have to prove the first 2 before we could hope to prove the 4th.

Message edited by author 2006-06-20 02:24:30.
06/20/2006 02:24:50 AM · #15
I live in the 8th dimension - one far superior to your 4th. Where I go, no man can follow....unless of course he is really cute. :p
06/20/2006 02:31:36 AM · #16
Originally posted by fotomann_forever:

Originally posted by crayon:

Now, on the more pixel for sharpening part - does that mean that more pixel on the same sensor size would produce a sharper image (assuming same lens used)?


At low ISO and good light, yes it should.

But, where a smaller sensor would fail to be sharp is under high ISO, low light conditions. Noise would begin to be a major factor.


I was under the impression that the more pixels you shove onto a certain sized sensor, the more noise you get, no matter what the situation because they "interfere" with each other when they are too close together
06/20/2006 02:32:30 AM · #17
Originally posted by Megatherian:

Think about this, what if time moved at different speeds but since we all move at the same time with it we would have no idea because there is nothing to compare it to.

That would be exampled to the way those old vinyl records spin - the inner circle has a lower velocity than the outer circles, but they reach the same location at the same time.
06/20/2006 02:39:07 AM · #18
why are manhole covers round?
06/20/2006 02:41:38 AM · #19
Originally posted by stare_at_the_sun:

why are manhole covers round?

this one is simple - so the cover wont fall into the hole, no matter the position :)
06/20/2006 04:45:20 AM · #20
why do people always say there is no such thing as a stupid question?

I beg to differ, I really think that there is

*lol, not saying there are any here... yet* hahahahaa
06/20/2006 05:45:34 AM · #21
Originally posted by fotomann_forever:

Originally posted by crayon:


Originally posted by justin_hewlett:

Isn't it possible to travel back in time if you travel west in a fast jet?

I'm interested to know this one too



Based on the theory of relativity, the speed of objects relative to each other results in time moving at different speeds, but does not allow time to reverse. Time slows down if you are moving very fast relative to the speed of time on a stationary object.

This has been demonstrated in the fast jet proposition made by fotoman forever. In the Hafele and Keating experiment four atomic clocks was were placed on commercial jet liners travelling regularly on long haul flights east and west. They were expected to lose a small amount of time heading east and gain a large amount of time heading west (due to the revolution of the planet) compared to a stationary clock on the planet surface.

The experimental results were close to the predictions for time lost and gained, and well within the calculated margin of error.

So every time you take an international east/west flight, time will pass differently for you than for people on the ground. A return flight will leave you slightly younger than the people you left behind. In that sense, you have been a time traveller.

I am not sure that this is a prescription for long life, however, as we are talking nanoseconds for current flight speeds and distances, and the increased radiation at high altitude is likely to get you first!
06/20/2006 05:49:07 AM · #22
Originally posted by legalbeagle:

Based on the theory of relativity, the speed of objects relative to each other results in time moving at different speeds, but does not allow time to reverse. Time slows down if you are moving very fast relative to the speed of time on a stationary object.

I think I've read somewhere that stated - the faster you are moving, the slower time becomes (for you). But I'm pretty sure the velocity must be massive to make any difference!
06/20/2006 09:22:44 AM · #23
Originally posted by crayon:

I think I've read somewhere that stated - the faster you are moving, the slower time becomes (for you). But I'm pretty sure the velocity must be massive to make any difference!


Time slowing down for you will have the effect of making it appear to you that time elsewhere is travelling faster: you will not notice any slowdown yourself (eg your hand will not move slowly in front of your eyes) because you will be travelling at the same speed as the rest of your body. You would notice that time on objects that you are speeding past (if you could see them) would be moving faster for them than for you. However, this would all be confused by the fact that relative distance and mass also change with relative speed.

Any velocity makes a difference, but only very high velocity would make a noticeable difference.
06/20/2006 09:30:48 AM · #24
Would Adam and Eve have had belly-buttons?
06/20/2006 09:28:42 PM · #25
Originally posted by legalbeagle:

Any velocity makes a difference, but only very high velocity would make a noticeable difference.

So theoritically, if we could someday travel much faster than the speed of light, "time travel" (to the past, anyway) would be possible?
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