well, my PROBLEM that gets me so hopping fired up from a mathematical point of view? now tat i calmed back down and literally chewed up several generic tylenol, and drank a pot of coffee, dropping numerous throat lozenges into the coffee to open up sinuses that are kicking my @$$ soundly… and VYING with the rotten TOOTH infecting off and on downinto i suspect perhaps past the gum and into my very JAW… i honestly dont know if my sinuses kicked the toothinfection off this time, or, of the tooth infection kicked up into my sinuses? all i know is i have chills and fevers, i am hot and cold all at once, i am shivering and sweating… i have no longer “just” yellow and grees goo coming out of mu sinuses and nose and up from my lungs and throat? the goo now has scabe and blood in it as well… i mean really when you are coughing up blood, that just CANT be good. but, the radiating pain is coming from the whole head, not just my jaw and tooth, and not just from my sinuses and head… they have all joined forces to whoop my butt. LMAO.
ahem
MY position, is that the F-number means something. that the RATIO of lens diameter to focal length? does something. that it does something useful.
it means something to an “old hand”, its EASILY demonstrable. NEWBS can understand it all easily. an equation is an equation. not only THAT, its accepted in camera lenses, its accepted by photographers SWITCHING lenses, that might vary in diameter and might vary in focal length, inorder to set shutters and irises properly.
not only that, its perfectly accepted in the world of projectors, which use the same f number, the same way. and the SAME camera lenbses can be used as projector lenses if you really want, and the same projector lenses can be used as imaging lenses, again if you want to.
to the WHOLE camera world? F number MEANS something… and it means “brightness”
thats not really “my” position, thats pretty much the whole world of cameras and projectors and stage lighters, everyone.
===
now, what my “problem” is? is that each and every time i so much as MENTION the concept of an F number as a useful handy guide?
as soon as its in the fladhlight world? i hear the following…
“no no no, you dont know what you are doing. focal length is useless. focallength only affects BEAM SHAPE… only the diameter of the lens matters.”
and? they state it AUTHORITATIVELY. as if F-number as a measure of a lenses ability to transmit light is somehow some wacky flat earth theory.
then they start in with surface luminosity, and they start “estimating” lumens and kilocandela and luxes and all this stuff, and they start shining their ligts into these cool little meters and everything… and they somehow claim to “prove”, that the ENTIRE camera, projector, and telescope WORLD does not understand the “concept” that is so superior.
==
i get tired of this “beamshape” stuff too.
thats WHY camera people HAVE the F-number, it relates the dance between focal length and lens diameter, each of which contribute as per their ratio, to the final product.
and that waiven collar? i dont undersdtand what that has to do with the lens… if your putting “something” over and around the emitter that makes it brighter or whatever? fine…
but, staying on point?
1) my position was that lens diameter, focal length… which is the f-number… “mean something”. that it is a useful mathematical unit to assign relative ability of a lens to transmit light.
2) “they” position… and i mean EVERY SINGLE TIME i ever mention the f number, on this and 2 other sites? it gets stated WITH AUTHORITY that focal length is “meaningless”, that only DIAMETER means “anything”.
==
now, someone up there started himming and hawing around and i did notice the words “focal length” creep into the explanation THEY offered. THAT would indicate they were claiming that “option 1” was right.
===
but, newbs walk away from all the megalux candelabra estimated meter illuminance “thing” with one thing and one thing only…
“oh! sedstar doesnt know what he is saying… i just need the widest lens i can find, nothing else matters. thats easy. nothign else matters. everyone says so.”
and it AINT.
why does the entire camera world, the entire projector world, the entire telescope world… suddenly become invalid, when its a flashlight?
why all of a sudden does “diameter” claiming to be everything, somehow magically spring into life. why all of a sudden does anyone get to claim that F-number means nothing and is somehow invalid?
i listed the 2 options… i am #1. easy is #2. EVERYone always “corrects” me on my “supposed childish stupidity” when i dare mention the f number as if its some archaic concept that has no application.
the “interim” explanations up there? they are CONTAINING the word”focal length”…
heck, while were AT IT ? i think it was enderman? said the best observable lens he ever saw? to date? was a plano convex 100mm fast tech lens. how can THAT be? because according to “coghlan’s laws… of absolute throw”? (movie: “cocktail” joke, lol)
—- aspherical are ALWAYS better than ANYthing else. never any deviation.
—- only lens diameter does A-n-y—h-i-n-g, focal length is irrelevant, it only affects beamshape.
===
and newbs walk away thinking they can ignore focal length and that f-numbers mean “nothing” and that any aspheric, as long as it has a bigger diameter? will A-l-w-a-y-s win the day.
then what do we all do in REAL LIFE? we all do the same thing, and we all know it…
we pick the biggest diameter lens we can comfortably fit into our existing light, or feel comfortable fabricating, because i admit, theres no replacement for displacement… its true. but THEN we “trial” different focal length lenses, and with the “lovely asphericals” which cant be FL measured (i can, mathematically too) we pick different lenses, with different FLs… and we see which one “does better” and we can “see further” with…
but… you have your diameter, you ave your focal length which to ME clearly does “something”… and that “dance” is simply the F NUMBER…
and everyone waltzes in and smugly corrects me that “only diameter increases throw”… which is crap.