What is the difference between EF and EF-S lenses and what is STM?

[RobertTheFat]

TCampbell wrote:

If you use the 60Da to take "normal" terrestrial photos, you'll notice everything looks quite "warm".  You can back this off via white balance (of course you'd do this for every shot you take).  As such, the 60Da isn't well-suited for normal terrestrial photography, but it's fantastic for astro-imaging.

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Wandering far OT (and admitting it), ...

I've always wondered why physicists and astronomers (and especially photographers) persist in referring to a red bias in an image as "warm". We all know that higher temperatures are correlated with bluer radiation and that, if anything, redder colors are generally associated with cooler objects. I suppose that the anomoly is entirely linguistic, deriving from the fact that fire is red and the sky and large bodies of water are blue. In truth, I have a great affection for linguistics, but I still confess to finding the usage a bit jarring. 

[TCampbell]

Yes - for stars, the bluer the light, the hotter the star and the redder the light the cooler the color.   For emission nebulae, the colors tell us which elements are present in the gases (and read like a "bar code").

And yet for photography, we still refer to red as being "warm" and blue as being "cold".

[RobertTheFat]

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@TCampbellwrote:

Yes - for stars, the bluer the light, the hotter the star and the redder the light the cooler the color.   For emission nebulae, the colors tell us which elements are present in the gases (and read like a "bar code").

And yet for photography, we still refer to red as being "warm" and blue as being "cold".

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But when we talk about color temperature, we get it right: bluer = a higher temperature.

[ScottyP]

Clearly you guys don't keep up with cartoons. If a character freezes, he turns blue, and indeed, ice is drawn as blue, ergo blue = cold. The entire Disney merchandising Goliath that is the Frozen movie observes this coloring convention for the youngsters. Elisa's ice dress is blue. Cartoon fires have a warm orange glow.

Seriously, though, no one on the street, not even most photographers or even scientists would look at a blue color palette at the paint counter and think "warm colors".

[TCampbell]

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@ScottyP wrote:

Seriously, though, no one on the street, not even most photographers or even scientists would look at a blue color palette at the paint counter and think "warm colors".

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Most people (photographers, etc.) do associate the yellow/orange/red with being "warmer" colors.  But in science... blue is technically warmer.  

See:  https://en.wikipedia.org/wiki/Black-body_radiation

Anything that isn't at absolute zero emits radiation in the form of heat.  This isn't just things in the visible spectrum... it goes much farther.  People are black-body radiation sources (we emit heat) ... which is why we show up so easily on thermal imaging cameras.  Although those wavelengths are down in the infrared spectrum and our eyes can't see in infrared.  

The warmer it is, the more energetic the photons are as they are emitted.  Eventually if they are warm enough... the light shows up in the visible spectrum (but on the 'red' side of the spectrum).  As the temperature gets hotter and hotter ... the curve starts to favor the 'blue' side of the spectrum (the hottest stars are blue).