Don't like the WHITE on your L?

kjuh · Feb 27, 2008

jpr2 said:
and yet many pro-whities are ready to discuss phoney reasons until
they are
blue in faces... just to wave somewhat puny "victory flags"

Ad hominem strategy (attacking the person instead of the argument) is the first mistake typically committed by those running out of arguments.

jpr2 said:
that neither myself personally, nor \i believe most of a real
pro-choice users do
care WHO is right, but rather about WHAT might be an actual truth

Yeah right. Funny that you mention this. Sorry if I have hurt your self esteem. Anyway, there's a few factual statements waiting for your comment or falsification, if you care to do use some other method than personal attack in your way to discuss what the "actual truth" is.

Daniella68313 · Feb 27, 2008

I thiink he missed all this and a lot more!

)

kjuh said:
kjuh said:

I looked up "hype" in the dictionary, and this was the definition. )

Click to expand...

... and don't tell me you never wondered as a little kid why bonnets
of black cars were so much hotter that white ones in sunshine.

...or that you didn't notice that black paper catches fire fastest
when you were playing with a magnifying glass.

... or that you never learned at school what "colour" means when
talking about radiation and reflection?

Secondary or primary reason, white is an engineering solution and the
benefit can be felt by hand.

--

http://www.pbase.com/zylen

'Never argue with an idiot, they drag you down to their level and beat you with experience'

Daniella68313 · Feb 27, 2008

Knackerman said:
Knackerman said:

Knackerman said:

and of course ONLY canonites are smart enough to realize this?

Click to expand...

Maybe the others don't want their lenses mixed with Canons plus that
they think the effect is not important enough to change the
appearance of their lenses.

Click to expand...

Actually, the Nkon 70-200 f2.8 VR can be had in light grey.

and I recently saw one of our friends who had a weather sealing problem with his Nikkor 500mm F4..and if he was to go under the sun, and it was a cold winter day, he would get condensation inside his lens, right in the center.

if he was to move in the shade, the condensation would evaporate. Again going under the sun would bring that back.

why? simply because even though it was very cold outside, you could see the effect of black under the sun.

My 80-200 F2.8 L is black, and it does become very hot during hot summer days. My 400mm F5.6 L stay cool to the touch in the same situation.

Knackerman said:
I don't know Nikon well enough to tell whether you can get other
lenses in light grey.

....and I don't know enough about optics and lens physics to give a
good reason why other manufacturers does not provide white lenses and
what they are made of.

I know though, that Canon uses somewhat "exotic glass" in it's L's,
the focus plane is critical in the long lenses, so any effort to make
the lens more "environment resistant" is welcome by me.

Regards
K

--
http://znapper.ath.cx/

--

http://www.pbase.com/zylen

'Never argue with an idiot, they drag you down to their level and beat you with experience'

Deezy · Feb 27, 2008

it's as simple as that.

Take a look at the pro photogs on the sidelines of the superbowl or any other major event in the world. Ever wonder what kind of cameras they use? Oh yeah all those white ones that are really easy to spot ......are CANON!!!! Canon must make good cameras.

It's not to sell SLR's or DSLR's or white lenses...it's to sell the brand. millions of P&S every day.

bronxbombers · Feb 27, 2008

simple solutions brought to you by the bronxbomber.

bronxbombers · Feb 27, 2008

shooting a game in hot sun, the white lenses were certainly more pleasant to hold, I can say that.

granted lots of it probably is just hype, but the white does help, evne if perhaps not critical.

bronxbombers · Feb 27, 2008

kjuh said:
kjuh said:

as a scientist you of course know, that almost always half-truths
are making much more chaos, than just plain old falsehoods - at least
so it seems from your's tangential arguments;

Click to expand...

Just as I expected. You don't comment in any way your falsified
arguments but stop making any factual statements and just resort to
name calling... gee.

So, do you continue to claim that black and white cars, otherwise
identical will reach same temperature subjected to same sunlight, or
did you understand the thing I tried to explain? Yes or No thank you.

Do you think the same apply to other objects, like lenses? Like black
and white lens, otherwise identical.

kjuh said:

anyway - this is an puzzle which should not pose any problems to you
to solve with a rocket speed hopefully:

just take an aluminum cylinder 86mm in diameter, and 35cm long;

with it's walls uniformly 3mm this;

and with both ends just closed by two circles of the same material,

and the same wall thickness - so there is a give quantity of air trapped
within;

now, place it into a thermostat, set to an uniform 40 deg. Celsius;

considering that air was trapped at 20 deg. Celsius;

take a coefficient of linear expansion of aluminum and air in the

range
from 20 to 40 deg. Celsius;

and calculate by which percentages (you can also give it in absolute
numbers) [a] diameter of cylinder will increase, and what will be
it expanded length at 40 deg. Celsius.

being a Rocket Scientist you've no doubt realized by now, that a
cylinder
is a simplified model of a lens, and also the changing of units from SI
to any other system of your's choice will not pose unsurmountable
obstacle;

Click to expand...

Woohaa.

Your "model" totally fails to simulate real life lens barrel warming
because it does not contain radiation (sunlight) and does not include
the cover color, so I see no point of doing your excercise. It is not
particularly interesting puzzle in itself anyway.

What's your point? To prove that aluminium barrel expands when heated?

I tend to believe that you still don't understand the difference
between a white and a black barrel warmed up in an oven (as I take
"in a thermostat" meaning in your example) and warmed up by sunlight.

not to mention his oven is rather constrained environment.

in the real world, people don't shoot in little boxes and the reflected light has plenty of places to radiate away to that won't cause much counter heating.

jpr2 · Feb 27, 2008

bronxbombers said:
oven is rather constrained environment.
in the real world, people don't shoot in little boxes and the
reflected light has plenty of places to radiate away to that won't
cause much counter heating.

exactly, very well put, but then... how would it support the pro-white
arguments?

and to comment a bit on a hidden agenda (with simple traps) of that
mental experiment...

well, first of all hardly an oven - when a sole purpose was to rise
temp. from a mere 20 to still very modest 40 degs. Celsius;

however, the sole purpose of that rocket science exercise was to
allow for any doubting Tom do their own calculations, and to find
out how very little thermal expansion will be observed even for
such a simple (and simplified on purpose) lens model:

a single casing of 35 cm aluminum tube - the real lens casings are

segmented of course, so in true situations any observed thermal
expansion would be significantly less than calculated);

as the stress caused distortion of any tube depends on the ratio

between a tube length, and it's girth/diameter (easy to observe on
any building site, where tubes of different diameters are being rised by
cranes by their ends - thin ones bend quite significantly, but a broad
ones stay rigid), making lenses from short and broad tube fragments
reduces stress-distortion quite significantly - and it makes no difference
whether the stress is caused by external force, or by heating one side
of such a tube;

the real casings are nowadays not being produced from aluminum, but

rather from complex smelts of magnesium, titanium, aluminum, and
several other components, and actually these are not smelts in a simple
sense, but rather a so called powder-smelts, to make them both lighter,
but also much more resistant to any thermal expansion;

in short - should any rocked scientist be bothered to do the actual, very
simple, calculations on such a model (of course, being rocket scientists they
might prefer to run a CAD/CAM models of real lenses, but the results
will be of the same effect), they will find easily that there is no distortion
of any practical significance

)

however, such exercises would destroy many beautiful (if rather empty)
arguments, so... why to bother, right??? :LOL

jpr2

wilfredmrand · Feb 27, 2008

rsn48 said:
But the new owners would have none of this, they had the best cars -
in their mind - and the best car should have the "best" (premium)
gas; after all, everyone knows the "best" always costs more. So
eventually the folks at the Cadillac division caught on and designed
motors for Cadillacs that required premium gas.

Cadillacs, and other vehicles that have high compression engines, use a high octane fuel to prevent pre-ignition (knocking). Fuel doesn't go bang so much as whoosh, so to compensate, the spark is fired before the compression stroke finishes. The problem with engines that have turbos, superchargers, overbored cylinders, and multiport intake is that the additional compression will pre-ignite the fuel before the spark - thus trying to push the piston backward (you hear the collision as a ping or a knock). Higher octane fuels are formulated for less initial volatility so they don't pre-ignite, and for a little longer whoosh so that the compression stroke finishes its compression stroke without added stress on the bottom bearings.

Substituting the name 'Premium' or 'Super' as a marketing gimmick is a marketing ploy to the gullible for sure. It isn't better gas. It doesn't cost more to make. It won't improve your mileage. It won't make your engine run cleaner. And some of us who drive cars with high compression engines wince when we pay 25 cents more per gallon than you do.

--
Wilfred M Rand
http://www.pbase.com/wilfredmrand/

Token · Feb 27, 2008

Sorry, have been on travel and just got back to this thread.

jpr2 said:
Token said:

Fluorite lens elements have a greater expansion coefficient than many
other lens elements. This means they physically change more with
temperature than other lens elements as they heat and cool.

Click to expand...

but certainly fluorite elements would not expand more than the metal
ones, and also more slowly - thus, any expansion of fluorite aill be
lagging behind it's metalic mount;

I was not thinking of damage or movement, but rather that fluorite would be more susceptible to actual prescription changes in the optics faster than more traditional optical glass lenses. Very much simplified, since the material expands in correlation with its thickness (mass), the thick portions expand more than the thin portions, causing a change in the curve of the surface. A factor against the use of fluorite, to be sure, but the advantages of FL outweigh the problems of dealing with it, as indicated by the use of FL in so many high end optical ventures.

jpr2 said:
and anyway the real danger is not as much associated with heat, but
rather with extreme colds and increased brittleness of fluorite at such
temperatures:

Possibly the real danger is not heat, but rather cold as you have said. However, heat is quoted more as the problem, and the associated expansion and potential to expand and crack the element in the mount. But then again, that is not an argument I really buy in favor of light colored lens barrels. Possible? Probably, but really unlikely unless the mount has been designed without thought to expansion, something I have never seen from any real design house.

jpr2 said:
jpr2 said:

Like I said, this question comes up often. Here is an experiment I
did a few years back:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=12671815

Click to expand...

your's past experiences are even more interesting. However, in
connection
with your's thermal images, there are some questions about cooling
rates of
white surfaces of 70-200/4L as compared to the vivitar's 600mm - perhaps
that mirror lens was covered with black paints of entirely different
heat
dissipating properties (that is both as to it's reaction to heat and
esp. as to
it's cooling rates), that is much more in line with behavior of
plastic parts
of 70-200 which both heated most and cooled the slowest - in short a
"plastic paint" with very poor and not optimized thermal properties?

Possibly what you have said is correct. As I have actually handled the lenses in question I do not think so, but really don't know. But if that IS true then what happens to all of those folks arguing that "black radiates heat faster than white, and so cools quicker"? Well, of course, the answer is never that simple.

Transmisivity and reflectivity, particularly in the IR instead of visible light, can be a hard thing to equate to the color we see.

jpr2 said:
another interesting bunch of facts concerns 70-200's rubber bands, which
have stayed at much lower temperature (that is if these thermal photos
were calibrated to measure everything "equally": plastic, rubber, and
paint
covered metals - but I'm sure they were), compared to both canon's and
vivitar's metal elements - and as these were measured, and not felt by
hand, it can not be said those were subjective observations

If you look closely at the images what you will see is the black rubber parts of the sunlight exposed Canon lens were always warmer than the light colored metal parts of the same lens. Remember that white is hot in those images. Both the clear plastic range ring / scale and the flat black after-market filter ring were the only things warmer than the black rubber grips (also the rear lens cap, but that would not be on the lens in use). And the actual temps of the rubber rings on both the lenses at the first "warm" shot is pretty close, but the Canon rubber seemed to cool quicker, I personally attribute that to the lower temps of the material behind the rubber, wicking away the heat, but can not be sure.

Because of how we (our eyes and minds) perceive images we should never trust "how it looks" for these kinds of things, actual measurements are the way to go.

The black colored, light metal, ring at the front of the Vivitar cooled very quick once out of the sun, but it also had no mass behind it, and no optics behind it. From the time the first "warm" image was taken until the last, that was the only metal part of the Vivitar lens that was measurably cooler than the warmest (but not coolest) spot on the Canon L.

In addition, I have done other test, but do not have images to share related to those. At work we have a few (ok, actually quite a few) long focal length visible light lenses. We have done some measurements to affirm if we need to specify light colors on the outside of the lens when we request a quote for new lenses. Keep in mind we are in the desert. In the reflective optics lenses (almost universally some variation of the Cassigrain design) we have embedded thermal sensors. We have taken measurements of the internal temperatures of those lenses. Pretty much universally the lighter the color of the skin the cooler the core temp off the lens has been at the hottest time of the day. I am not talking a degree or two here, but often 10's of degrees F. However, even if it was only a degree or two it would still say the same thing, in general lighter colored external surfaces result in cooler core temperatures in a lens.

T!
--

Token · Feb 28, 2008

Token said:
mind we are in the desert. In the reflective optics lenses (almost
universally some variation of the Cassigrain design) we have embedded

I suppose I should not attempt to write such responses while setting beside a fire in a hotel lounge after several Scotch's. Such conditions tend to bring my latent inability to spell to the surface, and also leads to incomplete thoughts.

Cassigrain=Cassegrain and / or Maksutov

And:

Almost universally some variation of Cassegrain and / or Maksutov design when the native focal length is over 400mm.

T!
--

jpr2 · Feb 28, 2008

...and never mind few spelling slips, but I do hope that at least
some your's observations of 2005 and IR experiments are still
valid? It would be a pity if you're going to retract them all

do you happen to know WHAT might be a longest piece of
continuous metal casing now in existence on any of canon's
whities? (preferably the ones hosting a FL element too ?) - perhaps
not counting the new 800mm IS, as this one will not be available
to perform any experiments with for quite a time yet;

btw. I was going to ask you this before - what do you folks
observe/shoot at using these long astroscopes in a broad
daylight, and having them mounted facing the Sun the same
side for hours?

have another one when relaxing next time,
jpr2

Member said:
Token said:

mind we are in the desert. In the reflective optics lenses (almost
universally some variation of the Cassigrain design) we have embedded

Click to expand...

I suppose I should not attempt to write such responses while setting
beside a fire in a hotel lounge after several Scotch's. Such
conditions tend to bring my latent inability to spell to the surface,
and also leads to incomplete thoughts.

Cassigrain=Cassegrain and / or Maksutov

And:
Almost universally some variation of Cassegrain and / or Maksutov
design when the native focal length is over 400mm.

kjuh · Feb 28, 2008

jpr2 said:
jpr2 said:

oven is rather constrained environment.
in the real world, people don't shoot in little boxes and the
reflected light has plenty of places to radiate away to that won't
cause much counter heating.

Click to expand...

exactly, very well put, but then... how would it support the pro-white
arguments?

Let me explain this to you in very simple terms:

You put 20C black and 20C white lens to an oven heated to 40C. They both end up 40C warm.

Now expose 20C black and 20C white lens to SUNLIGHT in 20C ambient temperature, and they will not end up equally warm, but the temperature of the black one will rise faster and SIGNIFICANTLY higher than the white one.

Got it? Both results are general practical knowlege.

Furher help: Oven contained 40C air that CONDUCTS heat to both lenses the same way and light doesn't play any significant part inside an oven.

(Yes there's IR radiation I know that complicates things, that might make a small difference between black and white object behaviour)

jpr2 said:
in short - should any rocked scientist be bothered to do the actual,
very
simple, calculations on such a model (of course, being rocket
scientists they
might prefer to run a CAD/CAM models of real lenses, but the results
will be of the same effect), they will find easily that there is no
distortion
of any practical significance )

The expansion is very small, but aren't tolerances in lenses rather small? Anyway heat related stress (supposedly) in extreme circumstances was enough to cause a part come loose inside my 100-400, and I guess it was not that hot that something melted... More details in this post:
http://forums.dpreview.com/forums/read.asp?forum=1029&message=26932492

jpr2 said:
however, such exercises would destroy many beautiful (if rather empty)
arguments, so... why to bother, right??? :LOL

Uneven expansion is only one of the undesirable effects of lens heating. I don't claim to be an expert in Canon lens design to say how important that consideration is compared to others.

All I can confidently say is that every undesirable effect there is, it is greatly magnified by black colour compared to white if all the other parameters are the same.

photonius · Feb 28, 2008

Deezy said:
it's as simple as that.

Take a look at the pro photogs on the sidelines of the superbowl or
any other major event in the world. Ever wonder what kind of cameras
they use? Oh yeah all those white ones that are really easy to spot
......are CANON!!!! Canon must make good cameras.

It's not to sell SLR's or DSLR's or white lenses...it's to sell the
brand. millions of P&S every day.

Too bad it's not exclusive, since Sony lenses are white too.

photonius · Feb 28, 2008

jpr2 said:
the real casings are nowadays not being produced from aluminum, but

rather from complex smelts of magnesium, titanium, aluminum, and
several other components, and actually these are not smelts in a simple
sense, but rather a so called powder-smelts, to make them both lighter,
but also much more resistant to any thermal expansion;

in short - should any rocked scientist be bothered to do the actual,
very
simple, calculations on such a model (of course, being rocket
scientists they
might prefer to run a CAD/CAM models of real lenses, but the results
will be of the same effect), they will find easily that there is no
distortion
of any practical significance )

Well, hmm, if lenses have no thermal expansion at all, why do many lenses from several manufacturors have a "range marking" for infinity, rather than a single point, even on wide angle lenses?? (e.g. sigma 17-70, or canon 10-22?, Canon 24-105L, Canon 16-35L...) The reason given is to accommodate different thermal conditions.
So, explain that then.... Is that also just a marketing gimmick?

jpr2 · Feb 28, 2008

photonius said:
Well, hmm, if lenses have no thermal expansion at all, why do many
lenses from several manufacturors have a "range marking" for
infinity, rather than a single point, even on wide angle lenses??
(e.g. sigma 17-70, or canon 10-22?, Canon 24-105L, Canon 16-35L...)
The reason given is to accommodate different thermal conditions.
So, explain that then.... Is that also just a marketing gimmick?

while i'm not sure as to what might be your's meaning? it can hardly
be associated with any thermal expansion of even longest of lenses
barrel, as any such expansion in length is negligible,

jpr2

Frank Oddsocks · Feb 28, 2008

Token said:
I was not thinking of damage or movement, but rather that fluorite
would be more susceptible to actual prescription changes in the
optics faster than more traditional optical glass lenses. Very much
simplified, since the material expands in correlation with its
thickness (mass), the thick portions expand more than the thin
portions, causing a change in the curve of the surface.

Assuming its coefficient of expansion is the same in all directions of the crystal (and if not, one suspects neither would its refractive index be), the whole element will get bigger. For a spherical element this will make no difference in the lens formula, because it will expand around the optical centre of the lens and the light cone is centred around that too.

You are doubly wrong, because crystals don't bend but shear under stress. Especially calcium fluorite, which is notoriously brittle.

kjuh · Feb 28, 2008

jpr2 said:
while i'm not sure as to what might be your's meaning? it can hardly
be associated with any thermal expansion of even longest of lenses
barrel, as any such expansion in length is negligible,

Negligible to you they may be to you but not to others.

Here's a Minolta patent related to thermal compensation for focusing:
http://www.freepatentsonline.com/5679946.html

Here's a same problem with telescopes.
http://www.astropix.com/HTML/I_ASTROP/FOCUS/SCOPES.HTM

It says there: "Focus will also change as the temperature changes due to the mechanical contraction of metal (usually aluminum) in the telescope tube."

Of course you can label them too as "marketing gimmicks" or "phoney reasonings".

Disclaimer: I don't actually know anything about the above patent. I have no deeper knowlege of astrophotography and it's operating conditions related to photography of terrestrial objects. My practical experience just says that the same laws apply, that reflective devices, be that lens or mirror that move and change size and shape = BAD for pixel peeping.

Rather than just repeating over and over again that it's negligible, negligible, negligible, negligible, negligible and negligible, you should determine how much thermal expansion would be bad in telephoto and why and prove it's not exceeded in practise.

We who don't claim to know better than Canon think just that it should be avoided, and anything that helps prevent it is a move in the right direction.

mmullen · Feb 28, 2008

kjuh said:
Rather than just repeating over and over again that it's negligible,
negligible, negligible, negligible, negligible and negligible, you
should determine how much thermal expansion would be bad in telephoto
and why and prove it's not exceeded in practise.

Well put. It's easy to say something doesn't matter but science requires measurements and tests to make final conclusions. The Minolta patent you linked to is amazing in that it shows Minolta has spent a vast amount of time and money studying the effects of temperature and temperature change on lens performance and found it significant enough to file a patent for a method to use multiple internal temperature sensors to compensate for optical properties that change with temperature. I found this part especially interesting:

"The change in temperature inside lens barrel TB (FIG. 4) caused by direct sunlight is explained below with reference to FIG. 7. Temperature sensors SE are placed around second lens element G2 (FIG. 4) inside lens barrel TB (four points: top, bottom, left and right). The change in temperature when direct sunlight is received from the upper left of lens barrel TB in the longest focal length condition was measured, the result of which is shown in FIG. 7.

From the measurement result shown in FIG. 7, it was learned that there is an approximately 10° C. maximum temperature differential between the side on which the sun shines (the upper left side of lens barrel TB) and the opposite side (the lower right side of lens barrel TB) and that the degree of compensation for the fluctuation of the lens back varies significantly depending on which point is used for the measurement.

In order to deal with this difference in temperature, the constructions described below may be used. In the first construction, temperature sensors SE are placed inside lens barrel TB such that the temperature is measured at four points, i.e., top, bottom, left and right, and the compensation for the fluctuation of the lens back is performed using the average of the measurement results for the four temperature sensors SE."

Note that the temperature sensors are not being used to collect study data, they are proposed to be installed inside production lenses to help compensate for the changing focus when the temperature of the lens changes. Also note that this patent does not solve the larger problem of thermal currents inside the optical tube. As I mentioned in a previous post, a cold lens placed on a tripod in the sun will cause warm convection currents to form in the cold air inside the lens and warm air has a different index of refraction than cold air. Thus, the image quality will be negatively impacted, much in the same way that warm air rising off a parking lot will create a visual shimmer effect.

Canon, to my knowledge, has not gone to such lengths, you might say their strategy of painting the most affected lenses (telephotos) white and calling it good is a practical way of minimizing the negative effects of what is obviously a very complex problem.

--
Mike Mullen

photonius · Feb 28, 2008

jpr2 said:
photonius said:

Well, hmm, if lenses have no thermal expansion at all, why do many
lenses from several manufacturors have a "range marking" for
infinity, rather than a single point, even on wide angle lenses??
(e.g. sigma 17-70, or canon 10-22?, Canon 24-105L, Canon 16-35L...)
The reason given is to accommodate different thermal conditions.
So, explain that then.... Is that also just a marketing gimmick?

Click to expand...

while i'm not sure as to what might be your's meaning? it can hardly
be associated with any thermal expansion of even longest of lenses
barrel, as any such expansion in length is negligible,

jpr2

What do I mean: oo this type of marking. You can also say you can focus past infinity.
And here from the Canon manual:

"To compensate for shifting of the infinite focus arising from changes in temperature, the distance scale can be rotated slightly past the normal infinity focus mark."
It doesn't say what is affected, but clearly temperature is important...

As mentioned by others, temperature affects many things:

the metal expands/contracts causing lenses to shift against each other.

While the overall expansion of the whole lens may be very tiny,tiny shifts of the complicated lens designs might have bad effects, perhaps not necessarily on focus, but might affect other optical properties, since lens combinations are used to correct for CA aberrations etc.

Refractive index of the glass material changes with temperature, and the refractive index changes not in a linear relationship with the expansion/contraction of the lens glass material.
Air turbulence inside the lens is a real problem, especially with long focal lengths.
Different temperature air has different refractive index.

Satire on -

After all, based on the simplistic comments that temperature is not important, a single lens element should do fine, right?

, who needs expensive, complicated lenses?

If the wavelength difference between blue and red (just a couple of 100nm, negligible, right? ;-) ) is sufficient to cause CA problems, perhaps small changes can cause large effects?

Or if a spherical lens element causes soft focus due to spherical aberration, which can be corrected for example, by shaving of tiny, micrometer amounts (negligible, right ?;-) ) from a lens to make it aspherical, then surely these tiny corrections might be important?

So, small changes induced by temperature, perhaps they can impact the lens performance ? Right?

Don't like the WHITE on your L?

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