what is a "tint shift"?

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wle
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what is a "tint shift"?

is there a definition of ‘tint shift’?

does it mean anything besides ‘an odd color in the beam’?

(odd meaning i guess, purple, green or pink)

maybe it means “it was kind of white in the middle but the edges or some other spot had this weird color’‘?

or does it mean “it was one color while on low, but as the brightness [or heat, or whatever (?)] changed, the color did too’‘?

i mean, to me, ‘shift’ usually means something dynamically changes with external conditions, not just ‘it was a strange color’….

does it apply to blue or yellow colors (which one would expect since the actual LED is blue and the phosphor is supposed to be yellow)?

?
wle

Edited by: wle on 09/12/2017 - 08:12
WalkIntoTheLight
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Yes, I think you get the idea. I usually think of tint shift in two different ways:

1. How the color changes in a beam profile, as you move from the center out to the edge. For example, many Cree LEDs will give a beam pattern that has a warm yellow hot-spot, a green corona, and a cool purple spill. Okay, that’s an extreme example, but some are like that. The tint shift can often be made worse by anti-reflection coatings on the lens.

2. How a LED’s tint changes as more current is applied to the LED. i.e., the tint (and CRI) can be slightly different on max brightness, as opposed to a (constant-current) low brightness. Some people complain about this, and it is measurable with equipment, but I’ve never personally been able to see the difference even when I use a camera to expose beam profiles to the same perceived brightness.

wle
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how does anti reflective glass change the tint?

it can be slightly purplish in color, the glass itself, but it should not affect the light pattern unevenly or differently at different light levels…

?
wle

WalkIntoTheLight
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wle wrote:
how does anti reflective glass change the tint?

it can be slightly purplish in color, the glass itself, but it should not affect the light pattern unevenly or differently at different light levels…

?
wle

The coating sometimes has a color of its own, so the light going through it gets changed. Angles can make it worse, so the shift across the beam might be different. It depends on the quality of the coating. I think a good anti-reflection coating doesn’t cause any tint shift.

Lexel
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Cheap AR coating does not be as good through the whole spectrum as expensive broadband coating for laser optics

A purple reflecting coating means it transmits more green than red and blue, so the whole beam gets more greenish

If the color of the AR coating matches the light souce it doen not shift the tint

somnambulism
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Here’s a post by ToyKeeper where she goes into quite a bit of detail on tint shift.

From that post, here’s a side-by-side picture of one light with an AR coated glass and one without:

eebowler
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Tint shift use to have the second meaning walkintothelight posted above only, but recently, because of the popularity of asphericals and more recently, third generation Cree LEDs, the meaning has to be amended. lol

In my experience, the anti-reflective coatings (i’m referring to the pink-ish coatings,) on windows, hardly affects the tint of the beam however, many claim that makes the light a little cooler. (There are greenish and blueish coatings too that may add a little unfavourable tint.)

My gratitude to those who are willing and able to help others (in whatever way you can)! Being human is more than just existing for yourself. Smile