IR filters

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I have been giver three filters that will not fit my lenses so I cannot experiment with them. The have values of 760,850 and 950. As they are very dark and I cannot see through them I wonder how the can be used. Any ideas of the use and results?
 
I'm assuming they're dark as they only let IR light through (or mostly).

The 760 is the weakest I think and can be used handheld, however the others would need a tripod similar to an ND filter when taking a long exposure.

Are they miles out or could you get a cheap step up or step down ring to use with them? Only other thing is to consider which lens you'll use them with as some are more suited than others.
 
Almost certainly, there are IR pass filters blocking shorter wavelength light at 760nm, 850nm and 950nm respectively.

Most camera sensors have some form of IR block filter on them, which often only attenuates the light (but usually blocks more as the wavelength increases). Therefore they will take IR only images, the 760nm filter letting through all light with a wavelength of 760nm, etc

Because of the IR block filter on the camera sensor, using these filters will require longer expsoure times, and unless on a very bright day, you may not be able to shoot handheld with them. It is very likely that the 950nm filter may require fairly extreme exposure times, as the camera sensor IR block filter is likely to be working better by the time it gets to this wavelength.

The results will produce a red/magenta image, which is easy to convert into monochrome, though some people change colour channels and generate a faux colour image.

There are some good tutorial articles on the kolari website including these examples of different filters http://kolarivision.com/articles/choosing-a-filter/


BTW I'd reckon that the 950nm filter will be all but useless unless used on a full spectrum sensor.

Hope that helps
 
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Thanks to all for your help and the link. I also have a D70 that has been converted to IR that I have had a play with so I will stick with that. The link was informative thanks again. I think the filters will be going.
 
charlychuckchuck said:
I have been giver three filters that will not fit my lenses so I cannot experiment with them. The have values of 760,850 and 950. As they are very dark and I cannot see through them I wonder how the can be used. Any ideas of the use and results?
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The human eye can see at the extreme end out to 760nm. Experiment you could do is to turn on a burner on the stove, gas or electric, let it get hot, darken the lights in the room, then hold the 760 filter up to your eye looking towards the burner. You might be able to catch some glow. I have a 720 filter so much easier to see thru it visually, and the EVF on the camera has no problems showing a bright scene with it.
 
Nothing to do with the filters but, out of interest, women's eyes are tuned more into the IR end of the spectrum than men's. This is why most ghost sightings are by women. What they are usually seeing is the heat trace from where someone has walked.
 
Quote from the article "Of course, that is only anecdotal evidence, but it perhaps tells us a little about the way that apparently identical shades could appear strikingly different to a tetrachromat."

Just because someone claims something doesn't make it true. For example, plenty of con artists claim to talk to the dead, it doesn't mean they can.
 
Ploddles said:
Quote from the article "Of course, that is only anecdotal evidence, but it perhaps tells us a little about the way that apparently identical shades could appear strikingly different to a tetrachromat."

Just because someone claims something doesn't make it true. For example, plenty of con artists claim to talk to the dead, it doesn't mean they can.
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The joy of selective quotation. Here's the bit that preceded it.

But what do those colours actually look like? Unfortunately, Jordan’s much-prized subject has not been available for media interviews. But once the abilities of the woman “with super-human vision” became known, many more potential tetrachromats have come forward who might be able to give us an insight.
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The story is about a research at the Institute of Neuroscience of Newcastle University where they appear to have found an individual with demonstrable tetrachromacy, which is not anecdotal evidence.

Proving that these people actually see the world differently has involved a two-decade journey, however. Although the relevant combination of genes does not seem to be especially rare – perhaps 12% of women might have four distinct cones – many of the people that Jordan tested just didn’t seem to show any differences in their perception. But by 2010, she had found a subject who perfectly acted the part of a tetrachromat. Jordan’s “acid test” involved coloured discs showing different mixtures of pigment, such as a green made of yellow and blue. The mixtures were too subtle for most people to notice: almost all people would see the same shade of olive green, but each combination should give out a subtly different spectrum of light that would be perceptible to someone with a fourth cone. Sure enough, Jordan’s subject was able to differentiate between the different mixtures each time. “When you ask them to discriminate between the two mixtures, a tetrachromat can do it very quickly. They don’t hesitate,” says Jordan.
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The 'anecdotal evicence' you highlighted is from one one of those potential tetrachromats who came forward, not the single research subject (of 24 subjects in the study) for whom it has been demonstrated.

You can read the published paper here if you like

http://jov.arvojournals.org/article.aspx?articleid=2191517#88229775
 
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