human eyes vs. film

[Guest Ultra Definition]

Do you guys know is that if everyone had corrected vision (wore glasses), the lighting levels could be cut in half. We would save a lot of energy. Also the eye focuses better in higher temperature light. That's the reason why in Europe ambulances use blue flashing lights.

[John Pytlak RIP]

A few years ago I presented a paper to the SMPTE Fall Film Conference that demonstrated the importance of maintaining the proper screen luminance for projection (Standard SMPTE 196M specifies an aim of 16 footlamberts).

 

The presentation clearly showed the loss of apparent sharpness when screen luminance was too low, due to the loss of visual acuity at lower light levels. Dim projection also degraded tone scale and color saturation of the projected image.

 

Sadly, many "first run" theatres are underlit (Lucasfilm THX Theatre Alignment Program surveys show an average of only about 10 footlamberts), and some theatres much lower. :( Standard SMPTE 196M allows a range of 12 to 22 footlamberts for theatres, with no part of the screen being below 10 footlamberts.

[Alvin Pingol]

>>>Do you need glasses?

 

Yes, I wear glasses. Contacts, actually, but I wear my glasses when I'm just hanging around the house.

 

>>>Are you sure that wasn't just a point-source lens flare issue?

 

Positive. I know exactly what something looks like if it's out of focus (i.e. without my glasses), or if it's a "lens flare issue" (when my contacts get cloudy). The latter creates a sort of "smudged" light with a halo, whereas I can't really explain the quality of actual blurred vision. It's not that nice, pleasing, "feathered" out of focus you get from a camera lens, but rather a weird, "broken-up-and-scattered" type distortion.

[Dominic Case]

a weird, "broken-up-and-scattered" type distortion.

 

Now that's different. I've noticed that too - from distant, dim,LEDs, in the dark.

 

I've wondered if it's to do with the fact that most red lights are broad spectrum (just with peaks in the red), whereas LED's are totally monochromatic. Therefore there is nothing at all for the green and blue cones in the eye, leading the brain to interpret what it sees as a speckly source. In the case of a broad spectrum red, there is a trace of signal for the other cones, and the brain is smart enough to interpret that differently.

 

When there is more ambient light, there is maybe enough flare in the eye to fill the gaps anyway.

 

Just a theory, anyway.

[Mitch Gross]

I have particularly poor vision without lens correction. When I look at any point source of light without my glasses I see it as a ball of Swiss cheese or a pile of balls mushed together. I never knew what caused this pattern until a friend took a macro photograph of my eye (like that shot in 2001) and I recognized the pattern. I'm looking at a slightly out of focus version of the patterning in my eyeball. Makes sense to me now.

[John Pytlak RIP]

For those wearing contact lenses, and needed good vision in subdued light (including watching movies and looking in the viewfinder), ask your eye doctor about choosing higher quality lenses that have better optical quality and a larger "sweet" spot, giving better quality when the eye's iris is wide open. B)

 

Mass-produced "disposables" just don't have the optical quality of more expensive lenses.

 

Do keep them clean, protein-free, and disinfected between wearings.

[Mitch Gross]

Couldn't agree more. I had an optician try to convince me to get disposables instead of the hard gas-permeables that I wear, and when I argued the issue she pulled up some optical reports off the manufacturer's website. Since she couldn't figure them out and I could (!!), I showed her how inferior the disposables were. Of course she makes more money by selling a lot of disposables...

[Guest Ultra Definition]

I got involved once in a doccumentary project from which funding was pulled at the last minute.

 

You can get some free reports by Dr. Berman from Lawrence Berkley Laboratory. If nothing else, you'll see why the yellow and the pinkish sodium street lights are worthless and you'll see one more reason why we are so dependant on our Arab "friends".

 

If we would increase color temperature of general lighting and all people got their vision corrected, a lot of lighting energy could be saved. A lot less lamps and lighting fixtures would be produced, a lot less barrels of oil would be imported.

[Dominic Case]

you'll see why the yellow and the pinkish sodium street lights are worthless

 

It's certainly harder to resolve sharp images in those wavelengths (and sodium light, being very monochromatic, completely fails to illuminate some things).

 

However, the longer wavelengths have one adantage in the dark - they don't stimulate the rhodopsin in the eye so much (that's the chemical that causes adaptation to brighter lights). Brief exposure to white light or blue light destroys your "night vision" for up to 15 minutes: after exposure to red or yellow light you can still see in the dark.

[Mitch Gross]

$1 to Dominic for pulling the word "rhodopsin" out of his hat!!

[Guest Ultra Definition]

The yellow light is low pressure sodium and is monochromatic. The pinkish high pressure sodium has some spectrum.

 

If you are defficient in vitamin A, it takes you many times longer to adapt to dark than if you are not. If it takes you long time, eat a lot of carrots.

 

It is the higher color temperature spectrum that regulates the pupil opening. So if you add more bluish light, the pupil closes more and your vision becomes sharper, but not noticably darker because there is mechanism that compensates for the less light exposure.

[Alvin Pingol]

Couldn't agree more. I had an optician try to convince me to get disposables instead of the hard gas-permeables that I wear, and when I argued the issue she pulled up some optical reports off the manufacturer's website. Since she couldn't figure them out and I could (!!), I showed her how inferior the disposables were. Of course she makes more money by selling a lot of disposables...

 

I wear disposable Accuvue2 (sic) contacts that I must replace once every two weeks.

 

I have to put lens drops in my eyes almost every half-hour if I want to maintain the sharpest possible vision I can (either that, or blink A LOT).

 

And I know it's the lenses and not my prescription, because I got my eyes checked again as I felt my contacts weren't powerful enough. The results came back that the correction should be bringing my eyes to 15/20 vision, but also that my prescription didn't change!

 

I guess those weird rubber-ish contacts simply can't reproduce the quality of those massive glass lens adjuster things in the optometrist's office...

[Mitch Gross]

Alvin, you should really try the hard gas-permeable lenses instead. They are much sharper and last forever. I don't need drops all day but will sometimes take them out and clean them if I'm working on a 20+ hour music video. I've had my current set for at least 15 years and every time I get my eyes checked I have the lenses inspected but there's been no need to replace them. I actually have a spare set that I wear every once in awhile just so I think to clean them every now and then.

 

Hard lenses are not as much of a pain as people seem to think. I'm "blessed" with extra-large pupils so I have to wear 13mm lenses instead of the standard adult 11mm lenses. Putting them in and taking them out each day really isn't much of an issue at all. If I've had a really long day with a short turnaround, I might need to slug back some Coca-Cola to help open the eyelids a bit, but the lenses pop right in no problem. From my brief experience with soft lenses, the incredibly unnerving act of peeling the lenses off my eye at the end of a long day was far worse.

[GeorgeSelinsky]

Brief exposure to white light or blue light destroys your "night vision" for up to 15 minutes: after exposure to red or yellow light you can still see in the dark.

Interesting point. When I was in Russian scout camp we'd have these high tech dudes who'd want to sneak up on the camp (it was a game - you had to steal the flag in the middle of the night), and they'd use red filters on their mag flashlights. We'd be up for night duty (a task we never enjoyed - try being woken up at 2 am and told to patrol the woods for an hour and a half) and when you saw a red flashlight it somehow psychologically made you less alert that a person was creeping up. The reduced intensity was a part of it (I mean, a 25 filter cuts at least 2 stops out), but the redness made it harder to detect them.

 

Suckers stole our flag quite a few times that way, and to get it back you had to do some silly stunts of their invention in front of all the girls the next morning. Silly.

 

- G.

[Phil Rhodes]

Hi,

 

I have very slight astigmatism in my left eye; other than putting an irritating misshapen flare around point sources, it isn't much of an annoyance, so I don't correct it. Must admit that the last check up I had, it was nice to see it corrected briefly via the optometrist's test apparatus...

 

Phil

[John Pytlak RIP]

When you look at a color photograph under illumination from a low pressure sodium vapor (589nm) "safelight" used by some labs for color print film darkrooms, it appears to be amost totally monochromatic. My SMPTE paper "Shedding New Light on Darkroom Illumination" talks about using red light (or higher levels of the amber "safelight") even outside the darkroom itself, to help keep workers' vision dark-adapted.

 

LEDs have become a very useful means of darkroom illumination, especially suited to "path lighting" and "task lighting", allowing a significant reduction in overall darkroom illumination and its potential to fog unprocessed film.

 

http://www.kodak.com/US/en/motion/support/...on/page01.blind

[Phil Rhodes]

Hi,

 

I got out of home processing when I got bored with pinhole cameras... but I'm sure I read somewhere about colour darkrooms being able to use an extremely dim green safelight. How on earth does that work?

 

Phil

[John Pytlak RIP]

Panchromatic camera films are very sensitive to ANY light. The eye is most detail-sensitive in the green portion of the spectrum. So green is usually chosen for maximum visual sensitivity, as long as it is only used for path lighting (dim green LEDs) or task lighting (e.g., lighting a gauge), and does NOT illuminate the unprocessed film.

 

Slower lab films like color print film, with a deep "notch" in the spectral sensitivity near 590nm, can tolerate some level of exposure to amber safelights like a Kodak Number 8 safelight filter, amber LEDs, or a low pressure sodium vapor source. It's all discussed in my SMPTE paper.

 

Kodak offers engineering consultancy services (including "Process Lighting" for darkrooms) in its Motion Picture Services:

 

http://www.kodak.com/US/en/motion/products...=0.1.4.28&lc=en

 

http://www.kodak.com/US/plugins/acrobat/en...esslighting.pdf

[Rob Belics]

I had lasik done and have floaters and need reading glasses and I'm such a mess.

[Alvin Pingol]

From my brief experience with soft lenses, the incredibly unnerving act of peeling the lenses off my eye at the end of a long day was far worse.

Is that so? How, then, exactly do you remove the gas-permeable lenses? With my soft ones, I simply "pinch" my pupil area and the lens sort of folds right out.

 

Also, how hard are these lenses? Can you feel them in your eye? Can they "shatter"?

 

Heh... sorry, don't answer. I'm gonna visit my optometrist. (Either that, or go back to my glasses ;) )

[Mitch Gross]

From my brief experience with soft lenses, the incredibly unnerving act of peeling the lenses off my eye at the end of a long day was far worse.

Is that so? How, then, exactly do you remove the gas-permeable lenses? With my soft ones, I simply "pinch" my pupil area and the lens sort of folds right out.

 

Also, how hard are these lenses? Can you feel them in your eye? Can they "shatter"?

I push outward against the side of my eye, stretching the skin and flattenning it against my eye. The lens just pops out without me coming in contact in any way. "Hard" lenses are basically a bendable plastic. Soft enough to squeeze about a bit, but I don't know if I could fold one in half without it breaking (never would want to try). When you first insert them you certainly can feel them, but the sensation goes away shortly afterwards. You actually feel them against your eyelids when you blink, but you get used to that as well. I don't think they would shatter unless you took a hammer to one.

[Alvin Pingol]

Thanks Mitch. Soft plastic sounds nice. Everytime I think of hard lenses, I always imagine sticking a piece of glass in my eye.

 

But after reading up on them a bit more, they certainly can't be much worse than soft lenses that require you to basically play with your eyeball until the lens sticks in place. :D

[Dominic Case]

they'd use red filters on their mag flashlights.

When I ran a scout troop (yes, that too!) flashlights were banned for that sort of activity (red or any other colour). They don't help you see all that much (and you see far less outside the area of the beam). Night adaptation works very well after about 15 minutes. Also, I used to say that the flashlight might not help you find the other guy, but it certainly helps him know where you are.

 

For a similar reason to that we use "path lighting" as described in John's paper, in our darkroom corridors in the lab. Point source LEDs at 580nm, hit the low-sensitivity spot in print film emulsion, and are very dim in terms of illumination, but very bright in terms of intensity. Easy to see the way when you enter the darkroom, and if you can't see part of the row of lights, you know there's someone in the way.