Take a Hasselblad camera out on an EVA of 4 hours, and this would suggest that, if it had the same reflectivity as the lunar surface, it's outer casing would heat up by 8 degrees. In fact, it was designed to be more reflective, and hence it would accept less heat than this.
Optical (visible light) reflectivity isn't the only important property. Its behavior at far infrared wavelengths is also important, as is its thermal mass.
Objects in thermal equilibrium with sunlight at our distance from the sun do not get anywhere near hot enough to emit significant visible light, or even near infrared light (the two bands where the sun radiates most of its power). Peak radiation occurs in the far infrared spectrum around 10 microns, where objects can "look" very different than in the visible. (Passive IR motion detectors also work in this region, detecting people by their own thermal emissions.)
A material that appears optically dark to our eyes might be highly reflective in the far IR, and vice versa.
A material that looks bright in the far IR will also be a poor radiator of heat at those same wavelengths, so a material that appears (relatively) dark to our eyes but bright in the far IR will get
very hot in sunlight. Examples include metallic gold. It appears yellow because it absorbs blue light, unlike most metals, but like most metals it appears reflective in the far IR, so it radiates poorly.
Conversely a material that looks reflective to us but dark in the far IR will remain quite cool even in direct sunlight; examples include "second surface mirrors" such as thin films of Teflon, Kapton or Mylar with aluminum on their rear surfaces. Kapton and Mylar are (mostly) transparent to visible and near IR radiation but opaque in the far IR, where they radiate well. They're commonly used on the surfaces of thermal radiators, like those inside the Shuttle payload bay doors.
What's crucial is the
balance between the visible and far IR properties. Polished aluminum metal (without a film coating) will still get very hot in the sun even though it reflects sunlight well because it's even
brighter in the far IR than in the visible. In other words, you can't tell how hot the material will get by just looking at it; you also need to know how it looks in the far IR.
This is fundamental to spacecraft thermal engineering. Because they can only exchange heat with the outside world by means of radiation, various optical coatings and blankets are used as needed to keep the equilibrium temperatures close to the design values.
The Apollo lunar surface cameras were treated with a paint that not only reflected sunlight but kept heat trapped inside. Combined with their relatively large thermal mass, this kept the internal temperatures relatively constant as they were carried around on the surface. But after being jettisoned on the lunar surface, and slowly accumulating a thin layer of dust from electrostatic effects, eventually they'd reach temperature extremes similar to the lunar surface itself during its monthly cycle.
