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In Reply to: I think you mean UV is not "visible" light. (nt) posted by Joe Murphy Jr on August 28, 2001 at 15:35:03:
Ultraviolet and infrared are sometimes incorrectly referred to as 'light'. The human eye 'sees' radiation between 400 and 700 nm. Wavelengths above or below this are not visible, and hence, not 'light', unless there is such a thing as 'invisible light'. For that matter, we can refer to X-rays and radio waves as light too.UV and infrared is correctly called 'radiation'.
Why all this fuss? I got nailed big-time on an exam freshman year about this, a lesson I'll never forget!
Regards,
Bill Zarycranski
Follow Ups:
Go back to school and get your point. Both UV and infrared ARE light, though for us humans they are not visible to us. Just because we can't see them doesn't mean they aren't light (they're just not "visible" light). Infra (below) red is just below our sight threshold and ultra (beyond) violet is just above our sight threshold. Many teachers, even when they know better, will follow what a textbook says just to get through the class. I've seen it in high school and college. Some even admit it! Maybe this is what your teacher was doing. Think about how we classify sound. Human hearing is nearly always listed as 20Hz-20kHz. Soundwaves below 20Hz are called infrasonic: those above 20kHz are called ultrasonic. If someone could hear a 23kHz tone, would we say they are hearing "inaudible" sound (to use your "invisible" suggestion)? Of course not. We'd say they were crazy (HA HA). Of course, physicists are strange sometimes. They are much like the French -- they try to be difficult to get on your nerves. All of this because I asked a question about filters. Please accept my sincere apologies. Now back to something to soothe and calm... the Audio Asylum. HAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA!!!!!!!!!!!
he was correct and this was one of the first courses at RIT in Photographic Science and Instrumentation. Yes, I have an undergrad degree in Photography.Joe, certainly this point won't help you take better pictures but the term light only refers to radiation we see. We don't see infrared radiation or ultraviolet, nor X-rays, microwaves, radio waves, et. al. Of course we sell untraviolet 'lights' and maybe even infrared 'lights', but any radiation emitted from these sources are not UV or IR. They are blue or red wavelengths which fall within the roughly 400 to 700 nm spectrum. Believe me, you cannot see UV or IR any better than you can see microwaves.
To get back to the original question, films are sensitive to UV and therefore unseen UV could have some impact on the film image. My experience over the past 35 years in photography suggests present films are much less impacted by this exposure than those years ago. I see no difference between identical color prints taken with or w/o a skylight filter. Ditto for 'haze' filters, which begin to filter into the far blue visible wavelengths. Maybe if you are an aviator and take alot of picures from the air where the effect of UV is greater or potentially more noticeable, then the haze filters may have some impact. However, this will be most important with color transparency films as printing effects can easily mask any differences.
So whether UV is or is not light, like they say at AA, try it in your own system. Your results may vary.
Good luck in your photography! A good hobby to have along with music and audio.
bz
nt
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