The Evolution of Renaissance Armor
No matter what era it's from, armor serves the same function - to protect the body from injury, usually in combat. However, technological advances during the Renaissance changed what armor looked like and how it worked.
Plate armor, which had protected mounted fighters from damage in battle, was heavy and ineffective against cannons and other primitive firearms. That means that the armor of the Renaissance evolved slowly away from the full body shell that had been popular in the High Middle Ages, and toward a lighter type that protected the body without being a liability.
That doesn't mean that the fifteenth and sixteenth centuries dispensed entirely with breastplates and greaves, however. These forms of armor lived on as part of ever more stylized tournament suits, used by nobles in mock battles, and as part of the lighter armor worn by officers and nobility on the battlefield. Examples include the elaborately decorated armor of Henry VIII, which is engraved and gilded, and a number of other ceremonial suits, which you can see in many museums.
One common myth you'll encounter about late medieval and Renaissance armor is that it was very heavy. While any metal armor will be somewhat heavy, the stories of knights who were unable to get to their feet if they fell are a later period exaggeration. Existing armor from the fifteenth century weighs around thirty to forty pounds, and that weight is spread out over the whole body. Some camping backpacks are heavier! Even thicker armor from the sixteenth century weighs no more than fifty to sixty pounds per suit - a far cry from the hundreds of pounds that some people claim.
Most soldiers through the sixteenth century wore what was called a half-harness, if they wore any armor at all. This Renaissance armor was composed of a helmet, breastplate, and gauntlets. Some sets of armor for officers armored the front of the thighs as well, but not the back. This is because most of the danger was from the front.
One element that you'll see in many modern reproductions of Renaissance armor is mail, or chain-mail. This type of armor is more common in medieval pieces, and is usually only an accent on Renaissance suits. However, it's much easier to produce in the modern era than hammered plates, and is thus very common.
When buying Renaissance armor for reenactment or theatrical use, you should ask yourself what you need your armor to do. Armor that's purchased primarily to be decorative will need to be much less durable than armor meant to be used in live combat! You should also familiarize yourself with the standards of your local group if you're planning to use armor for fighting.
They will have their own specific rules meant to keep you safe, and sometimes to maintain a certain level of historical accuracy. Remember - just because a seller says something is authentic or up to standards doesn't mean it is. Since the rules of many groups change regularly, sellers and craftspeople may be mistaken. It's best to do your own research before you buy. That will allow you to get the right set of armor for your purposes.