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Author Topic: Do you wish your 70-200L were black?  (Read 12611 times)

jthomson

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Re: Do you wish your 70-200L were black?
« Reply #15 on: May 22, 2013, 05:50:50 PM »
The relationship between colour and temperature of bodies receiving radiation is not as straightforward as 99% of postings on the net say. Although black absorbs heat better than white, it correspondingly radiates heat better. The inescapable consequence is that black and white bodies reach the same temperature when they are in sunlight but black gets there faster.  Conversely, the black body will cool down faster when taken out of sunlight.  So, the Nikon lens heats up faster than the Canon L, but both eventually reach the same temperature and the Nikon cools down faster.

While not as straight forward as some postings would indicate, the basic fact that a typical flat black object will reach a higher temperature  in the sun that a typical white painted object is correct.  The black traps more of the suns energy, the white reflects it.  That is why things like propane tanks are painted white.  You can verify this yourself on a sunny day.  Put one hand on some ashphalt surface and the other  on same grass alongside it.  The asphalt will be much hotter than the grass, guaranteed.

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Re: Do you wish your 70-200L were black?
« Reply #15 on: May 22, 2013, 05:50:50 PM »

crasher8

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Re: Do you wish your 70-200L were black?
« Reply #16 on: May 22, 2013, 06:38:39 PM »
comparing a plant with a rock?

Harv

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Re: Do you wish your 70-200L were black?
« Reply #17 on: May 22, 2013, 06:44:57 PM »
 ;)

LensCoat to the rescue.....

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Pi

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Re: Do you wish your 70-200L were black?
« Reply #18 on: May 22, 2013, 06:48:36 PM »
comparing a plant with a rock?

How about comparing rock to rock? Black sand is hotter than white one.

neuroanatomist

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Re: Do you wish your 70-200L were black?
« Reply #19 on: May 22, 2013, 06:59:40 PM »
The relationship between colour and temperature of bodies receiving radiation is not as straightforward as 99% of postings on the net say. Although black absorbs heat better than white, it correspondingly radiates heat better. The inescapable consequence is that black and white bodies reach the same temperature when they are in sunlight but black gets there faster.  Conversely, the black body will cool down faster when taken out of sunlight.  So, the Nikon lens heats up faster than the Canon L, but both eventually reach the same temperature and the Nikon cools down faster.

I think chemistry ≠ physics.  ;)

While you're correct that the black object will both absorb and radiate heat faster, you are incorrect that they will reach the same equilibrium temperature under constant illumination by sunlight.  You're not considering reflection, and the 'white' paint will reflect more of the incoming solar radiation than the black paint, meaning the equilibrium temperature (combination of the effects of absorption/radiation and reflection) will be higher for the black lens.

Try a simple empirical test - go to a decent-sized parking lot on a sunny day, find a black car and a white car parked next to each other that have been there for a while, and put one hand on the hood (or perhaps bonnet in your case?) of each.  Your statements suggest that they will be the same temperature, but you'll find that's not the case.  Don't leave your hand on the black one too long...
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vscd

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Re: Do you wish your 70-200L were black?
« Reply #20 on: May 22, 2013, 07:08:02 PM »
If you shoot football for hours, you may get heatingproblems in the full sun. Maybe. I think normal usage of lenses won't cause you troubles with black lenses. I like the smaller attention with a black lense, even if it's more prone to heating.

I guess Nikon has a lot of professional lenses, too, without painting them white. So... if I'd had the choice I would always buy black ones. Maybe we can meet us at 18% grey. So we can even adjust the whitebalance at any time on it?  ;D ;D ;D
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Renegade Runner

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Re: Do you wish your 70-200L were black?
« Reply #21 on: May 22, 2013, 07:12:09 PM »
Sure you get looks holding a white telephoto lens but think of the alternative.  If you were holding a large black lens such as the sigma 800mm, would it not look like some type of weapon from a distance?

And of course if you use it like the guy below then people are sure to run.  :o

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Re: Do you wish your 70-200L were black?
« Reply #21 on: May 22, 2013, 07:12:09 PM »

raptor3x

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Re: Do you wish your 70-200L were black?
« Reply #22 on: May 22, 2013, 07:39:32 PM »
The relationship between colour and temperature of bodies receiving radiation is not as straightforward as 99% of postings on the net say. Although black absorbs heat better than white, it correspondingly radiates heat better. The inescapable consequence is that black and white bodies reach the same temperature when they are in sunlight but black gets there faster.  Conversely, the black body will cool down faster when taken out of sunlight.  So, the Nikon lens heats up faster than the Canon L, but both eventually reach the same temperature and the Nikon cools down faster.


Not true at all.  The equilibrium temperature will vary with the 1/4th power of the emmissivity.
« Last Edit: May 23, 2013, 12:14:52 AM by raptor3x »
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Re: Do you wish your 70-200L were black?
« Reply #23 on: May 22, 2013, 07:53:39 PM »
Sure you get looks holding a white telephoto lens but think of the alternative.  If you were holding a large black lens such as the sigma 800mm, would it not look like some type of weapon from a distance?

And of course if you use it like the guy below then people are sure to run.  :o




The word "shooting" takes all its sens here.  ;D

Pi

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Re: Do you wish your 70-200L were black?
« Reply #24 on: May 22, 2013, 07:54:19 PM »
Not true at all.  The equilibrium temperature will vary with the 1/4th power of the emmissivity.

You are ignoring the other ways heat dissipates. Also, once sunlight has heated the object, the radiated heat is at much lower frequencies and the emissivity is more or less the same then (this is somewhere on Wikipedia).

It is a fact that brighter surfaces reach lower eq. temp., not just because the day is too short for them to reach it.

yogi

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Re: Do you wish your 70-200L were black?
« Reply #25 on: May 22, 2013, 09:25:22 PM »
Could it have something to do with how quickly it heats up--that is the rate of expansion/contraction of the metal in the lens?

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Re: Do you wish your 70-200L were black?
« Reply #26 on: May 22, 2013, 09:30:51 PM »


I guess Nikon has a lot of professional lenses, too, without painting them white. So... if I'd had the choice I would always buy black ones. Maybe we can meet us at 18% grey. So we can even adjust the whitebalance at any time on it?  ;D ;D ;D
Nikon does not use Fluorite in their lenses.  That is why they are longer and often have more CA's than Canon lenses, and often do not focus as closely.  Fluorite allows better correction of CA's which allows a shorter lens.
 
Maybe black paint is more expensive??  That Nikon 800mm sells for $18,000 ;)
 

Swphoto

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Re: Do you wish your 70-200L were black?
« Reply #27 on: May 22, 2013, 09:59:11 PM »
Nikon does not use Fluorite in their lenses.  That is why they are longer and often have more CA's than Canon lenses, and often do not focus as closely.  Fluorite allows better correction of CA's which allows a shorter lens.
 
Maybe black paint is more expensive??  That Nikon 800mm sells for $18,000 ;)

The new Nikon 800mm does use fluorite: http://www.nikon.com/news/2013/0129_lens_06.htm

Edit: Despite the negative comments about it here: http://imaging.nikon.com/lineup/lens/glossary.htm#ed

"However, fluorite easily cracks and is sensitive to temperature changes that can adversely affect focusing by altering the lens' refractive index. So Nikon designers and engineers put their heads together and came up with ED glass, which offers all the benefits, yet none of the drawbacks of calcium fluorite-based glass"
« Last Edit: May 22, 2013, 10:07:06 PM by Swphoto »

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Re: Do you wish your 70-200L were black?
« Reply #27 on: May 22, 2013, 09:59:11 PM »

neuroanatomist

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Re: Do you wish your 70-200L were black?
« Reply #28 on: May 22, 2013, 10:01:17 PM »
Nikon does not use Fluorite in their lenses.  That is why they are longer and often have more CA's than Canon lenses, and often do not focus as closely.  Fluorite allows better correction of CA's which allows a shorter lens.
 
Maybe black paint is more expensive??  That Nikon 800mm sells for $18,000 ;)

Actually, Nikon's new 800/5.6 does use fluorite elements - two of them.  This, despite previous Nikon marketing blurbs that fluorite was used long ago, but they made ED glass so they could avoid using temperature-sensitive, fragile lens elements (e.g., this link).

I wonder how the fluorite will do in a black barrel?  If it has thermal issues, Nikon will be blasted. If not, it supports the idea that Canon's white paint is purely a marketing ploy (already supported by the white lenses with no fluorite, like the 300/4L IS).  Either way, I see egg on the face of one or maybe both...
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STEMI_RN

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Re: Do you wish your 70-200L were black?
« Reply #29 on: May 22, 2013, 10:16:29 PM »


Pentax made a white DSLR body.  The reasons they gave were for heat distribution according to DPS

http://digital-photography-school.com/pentax-k2000-k-m-white-dslr-review
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Re: Do you wish your 70-200L were black?
« Reply #29 on: May 22, 2013, 10:16:29 PM »