Why is red light used in the dark
Red lights are used in black and white darkrooms when making prints.
It is not safe for most widely used fillms, either color film or panchromatic.
Panchromatic means it is sensitive to all colors of light.
,However with B&W films the negatives are only black or shade of gray transparent.
,TO make prints the negative is exposed through with white light to cast an image onto photographically sensitive paper.
Since the negative has no coloration no color information is lost with colorization of the exposing light.
,And photographic paper, unlike the film is not panchromatic - it is insensitive to red light for the most part,or at least much, much less sensitive.
,Thus in most B&W printing darkrooms, a dim red light is used so you can do most setup without having to feel your way aroundu2026 setting the timer, setting the enlarger, handling negatives and paper, performing dodging and burning, manipulating the prints in the developer solutions.
,Blank paper is kept in safes that cut out even the red light, but a few minutes exposure was no harm.
THe enlarger exposures were usually a handful of seconds for easy printing control.
Do photographers still use dark rooms
Why is red light, so dark
This question is a double false statement.
And should be reported.
But let me be as short and consistent with my rebuttals:,Why did Scythians appear European with blue/green eyes, red or light hair, but modern Iranians are so dark?,I would love to hear more about your recent encounter with a Scythian from 4000 years ago.
,Maybe you should give out some free flashlights with a headband to these u201cso darku201d Iranians so that people driving cars at night can see them on the streets.
,Can it be that modern Iranian are mixed with Arabs and Mongols?,Or can it be that Mongols and Arabs are mixed with ancient Iranians/Scythians?,Newsflash: Iranians were and are not related to neither Arabs nor Mongols.
Facts dont give two Cr*ps about your opinion:A huge genetic study actually confirmed that Iranians have had the same DNA for at least 10.
ly/irangen0This refutes this u201cArab/Mongol theory of yours as Iranians rarely and barely have non-Caucasoid Haplogroups in their DNA.
Using red light in photographic darkroom brainly
The term u201ccolouru201d is used to refer to several different things in common usage.
We may say that an object has colour, and that we see colour, but those are two different meanings.
When we want to be precise, we may talk about the spectrum of illuminating light (not its colour), the spectral reflectance of a reflective object like your skirt (not its colour), and use colour only for the perception that happens in your eye and brain.
But informally we use colour to refer to all of those things.
,Again in general use, with (approximately) white light illuminating our environment, your skirt reflects more blue light than it does other colours of the spectrum.
You will say that the skirt itself is blue, because you see it as blue, and there is no conflict between the two meanings.
It isnu2019t even necessary for you to tell me which of the two meanings you intended to use, because the result is the same.
,But in darkness, or when the illuminating light is highly coloured, the two meanings give different observations.
The skirt retains its blue colour in any case, but the colour that you see changes.
If you were in a photographic darkroom where the only light is deep red, your blue skirt would either look grey or black (but you could still see where it is).
In a completely dark room, everything looks black, and you canu2019t even see where the edges of objects are.
,So I would say that your skirt remains blue (but you may not be able to tell that in some lighting conditions), but your skirt can look blue or grey or other colours, depending on the interaction between the illuminating light and the objectu2019s reflectance.
Can any red light be used in a darkroom
As User says in his answer, Black and White paper is not very sensitive to red light, so that is what is used.
Iu2019ve also seen u201csafe lightsu201d that were more of an amber/yellow color.
The main requirement is that the wave length of the light be such that the photographic paper doesnu2019t u201cseeu201d it and become exposed.
Any color will work as long as the paper youu2019re using is not sensitive to it.
,Film is very sensitive to light and ALL colors of light should be avoided.
,[Edited to clarify that itu2019s the photographic paper Iu2019m writing about]
Can film be exposed to red light
Five guys actually volunteered to stand at ground zero of a nuclear blast just to see what would happen.
,No, they were not crazy.
Nor were they being punished.
It just shows how stupid some people can be (Iu2019m joking guys, donu2019t take out your pitchforks).
,,During the Cold War when the US and Russia were both trying to set the world record for spending the most amount of money on nuclear weapons, the general public was getting a little bit worried about these weapons of mass destruction.
,Despite US claims that nothing bad would happen if a nuclear bomb detonated above civilians, nobody was buying it.
,So what did the US do?,They decided to prove it.
,On July 19, 1957, five exceptionally brave Air Force officers and one cameraman (probably reevaluating his life at that point) stood about 65 miles northeast of Las Vegas.
,Sure enough, two F-89 jets flew above their heads and shot out a nuclear missile.
Thankfully for the group, the missile did not malfunction and promptly detonated directly above their heads.
,According to Major Body as it happened,,u201cWe felt a heat pulse.
A very bright light.
A fireball it is red.
The sky looks black about it.
It is boiling above us.
It is rapidly losing its coloru2026u201d,Then the blast could be heard and he continued to say,,u201cThere is the ground wave! It is over folks, It happened! The mounds are vibrating.
It is tremendous! Directly above our heads! It is a huge fireball.
u2026 Wasnu2019t that a perfect, perfect shot.
u201d,Now, at this point you might be wondering about all of that radiation from that blast that was hovering over their heads.
Surely they have been exposed to a decent amount of ionizing radiation, right?,Since the blast occurred pretty high up in the air (around 18,000 feet or 5.
5 km from above), no ground material was sucked up to create a giant mushroom cloud, and thus no giant radioactive cloud was present.
As for the material in the bomb itself and surrounding dust, those radioactive particles would have traveled quite a large distance before descending back down to Earth.
EDIT: As others have pointed out in the comments, you donu2019t need to worry about gamma rays because by the time it reaches them, the radiation is halved by 20 times.
Thanks Lyle McElhaney and Graham Ross Leonard Cowan .
,So it made sense that later on when the men were being examined, it turned out that they were exposed to negligible amounts of radiation from the bomb.
It was even less than the amount the pilot was exposed to.
,The irony here is that while this was entirely devoted to proving the safety of nuclear blasts high in the air, radioactive particles from such tests often ended up settling on nearby towns, leading to a number of health issues.
,While itu2019s not certain that its related to this particular blast, interestingly enough all 6 men (including the cameraman) eventually ended up with cancer later in their life.
,This is the propaganda film from the governmentu2019s archives:
Red light room for pictures
In the five boroughs of NYC, if youve received an unjust red light camera violation, your only recourse is to plead not guilty and have a hearing to contest the alleged violation.
,It should be noted that red light camera hearings in NYC are held at Parking Violations Bureau offices, not traffic court.
You go to traffic court for a red light ticket where you were stopped by a police officer and issued a ticket.
A red light camera violation notice is sent by mail to the registered owner of the vehicle.
,I was a parking violations judge (#2097) for eight years before I transferred to the Traffic Violations Bureau, and I was trained to handle red light camera hearings.
From my experience, unjust camera violations were violations that occurred because you were in a funeral procession, or a police officer was directing traffic at the location and waved you through -- incidents like that.
,Ill tell you about the best unjust violation I ever saw.
This guy came into my hearing room and handed me his notice of violation.
On NYCs notices for red light camera violations, you see three photos.
One shows the vehicle approaching the intersection (with data indicating how long the light was red when the picture was taken), one shows a close up of the rear license plate, and one shows the vehicle leaving the intersection.
,On this guys notice, the pictures showed his car being towed by a flatbed truck, so it was the tow truck driver that committed the violation! I looked at the pictures, then I looked up at the guy, who looked like he was ready to explode.
I smiled and said, You werent driving, were you? He threw his hands up and yelled out, NO! THE GUY TOWED MY CAR AND THEN HE WENT THROUGH THE LIGHT! I DIDNT DO THIS! YOU GOTTA HELP ME!,I calmed the guy down and told him the case was dismissed.
I explained to him that a technician reviews the photos taken by a red light camera before the notice of violation is printed up, and if the tech sees something unusual in the photos (like vehicles in a funeral procession, or this guys car being towed) he or she is supposed to dispose of them.
I guess that didnt happen.
Darkroom red light wavelength
,Of course, it is still controversial.
,Here are the two opposing arguments.
,The argument for Red LightThis is a very old hypothesis.
It is based on the idea that your rods are not very sensitive to red light and do not start to shut down when exposed to dim red light.
It is loosely supported by the usage of red lights in darkroom for print papers.
Of course, the eyes do not work the same way as photographic paper works, but is still seems like a good argument (to some people, myself not included).
,However, since your eyes are not very sensitive to red light, you need a fair amount of red light to see anything.
,Note: the published sensitivity curves of the cones is shown here:,The method used to establish these response curves does not explain how violet is perceived as not just blue but a combination of blue and red.
That is a discussion for a different question.
,It has been only recently that someone actually determined that to see well with red light, you need enough red light to start to turn off a lot of the rods.
,The argument for Green LightAs a result of the last point above, some people have been pushing the idea that it would be better to use green light at 510 nm.
The rods are very sensitive at this wavelength, and so the intensity of green light needed to see things is much reduced with respect to red light.
,Comments on the old MythI quote from Doug Kniffen:nIt is unfortunate that the red myth, perpetuated by half baked logic, misinterpreted facts, and unsupported assumptions, has been needlessly forced upon generations of unsuspecting stargazers.
Maybe the origin of the red light myth has roots in the early days of photography, when early emulsions were insensitive to red.
Much of the myth has certainly been supported by the existence of numerous studies showing red light, of a given intensity, has less effect on night vision than other colors.
While this is true, a light source that has the least effect on night vision is not the same thing as a light source that will allow visual perception at the lowest possible level of illumination.
Image credit: Doug Kniffen.
Let me explain this chart.
The horizontal axis is the wavelength.
The vertical axis is brightness.
,The thick dotted gray line is the level at which rods get saturated and quit working altogether.
The thin dotted black line indicates where the rods switch over to the cones.
The thick blue, dark green, and yellow-green lines show at what levels the cones start working.
The thick black line is the level below which you canu2019t see anything.
,Now letu2019s look at the red line.
It represents the minimum red LED level you need to see a star chart.
Notice that it is well above the line to switch the rods off.
,The green line is the minimum green LED you need to see a star chart.
Notice it is just about the level to switch from rods to cones, but it is well below the level at which the rods switch off.