easyB? i am not being rude, nor do i think i am “right”…. hey, lets have fun dinner conversation. dinner tonight? coffee, cigarettes, a big bag of lemon cough drops and as many acetaminophen wont make my liver quit overnight, lmao. sick as a dog, keep me honest…
i still have “nightmares” and PTSD from way back when, i followed a gigantic, epic, turd of a thread really… on CPF years ago. it was supposed to be “the math of optics”, but… other than dr. hoozits (whose an optical engineer) chiming in and correcting everyone, before he gave up…
good lord, i read every post, every many long page, dutifully. Took hours, got me exactly nowere… it was a train wreck, someone needed to “clean it up and sticky it”. they never did. would be a small feat in itself. everyone is talking “beamshape” and “throw”, and these are “qualifications” not QUANTIFICATIONS. the engineer in me gets “queasy”.
my thing is… okay, i didnt do anything monumental or anything, i just introduced the easy “camera math” for f-number… but i know its valid quantification.
you state that beam intensity is proportional to the diameter of the lens. and i BELIEVE you… theres no replacement for displacement. but… lets assume i believe that “only larger lens diameter increases… ‘absolute throw’ ” (absolute throw is a term i need defined, it sounds like “beamshape” and other unquantifiable terms i hear a lot)
but, going with the given plot line… cool…. i can now ignore F number, it doesnt matter. I wonder why camera people worry about it so much, since they are focusing an image (light) onto film or sensor, and need a reliable quantification from lens to lens to determine the brightness of the image to accurately set shutter and stuff. F number is INDEPENDENT of changing lens diameters and focal lengths. you KNOW the brightness of the image.
before you say “oh, we’re doing the reverse… its different, were projecting light, not collecting it…”?
projector lenses have the same F numbers on them. you can take a “projector lens”, look at the f number, focus it up onto a sensor or film… and it works the same.
could you define this “absolute throw” term?
could you explain exactly how focal length does not “do anything”?
my crystal ball says, you will say something like “only lens diameter increases throw, focal length only affects beam shape”
on that definition? a 200mm flat piece of glass, should provide “higher absolute throw” than any lens on this OP he is entertaining, he should just go with that. whats the definition of “absolute throw”, and why dont the people that use camera lenses and projector lenses know anything about this much easier to use formula, where focal length can be effectively ignored, and only diameter does anything for focused brightness?
i cant understand the “why”, but some how, some way? camera and projector lens people only use increased diameter as the only factor when the focal length is the same… as soon as you change both? you have no working quantification other than F number. camera people never use the term “absolute anything” nor do the projector lens peole say anything about “beamshape”. they both use the F number.
if you want to get into the “dance” of comparing the smaller or larger focal lengths and diameters, and the relative brightness of the larger or smaller projected emitter image? thats already done thru numerical aperture equations which arent much harder than the other stuff. no complicated fourier transforms or ray tracing software.
what is the definition of “absolute throw”? whats the equation?
a happy meter reading is one thing, but in practical terms? i was focusing up IR emitters at long distance, to be picked up by IR sensors for my night vision projects. my eye cant be fooled by apparent brightness, since the same sensor and the same camera lens is picking up the image… its equal and fair.
the furthest imaging (at one time i had the “record” for distance on my night vision site, i might not still have it, i dont know) always happened with the lowest f number… but, the dance was, i had to get the focal length high enough the “spot” was small and intense enough to be visible to the sensor.
it was a dance of “hand tuning” of the 3 and 4 lens systems, but… in the END, i measured the f number of the overall lens?? sure enough, the “winners” were always the ones with the lower f numbers.