A quick intro: small caps are the uppercase (capital) letters that have similar or the same height as the lowercase letters. They are used in headings and body text to emphasize abbreviations, acronyms or definitions.
There are actually two types of small caps: the real (you see in books) and the fake ones (you are likely working with). The real small caps are designed by type designers to match the stroke thickness of other characters. The fake ones are generated automatically by scaling down the capital letters. As the result, fake small caps don’t have the same stroke thickness.
This scaling trick creates an inconsistent text color: the uppercase letters appear bolder and darker in comparison with the fake small caps. In example below the first headline has thicker capital W, T and M, while the second headline looks consistent.
In a paragraph fake small caps appear like visual gaps, since they are much lighter than the surrounding text.
Now the bad news. In MS Office you always get the fake small caps even if the font contains the real small caps. That's the way MS Office works with small caps: it will always scale down capital letters. Sometimes you can find a font that has small caps as a separate file (usually such fonts have an SC abbreviation in their name). In this case you can work with small caps as with any other font.
Unfortunately, neither Mac OS nor Windows has system fonts with a separate small caps file. This means you will never work with real small caps in MS Office if you only use the preinstalled fonts. Never ever in your life you will create those beautiful small caps. The easiest solution to this problem is to abandon small caps altogether (in most cases you don’t really need them). There are many other ways to highlight text without sacrificing good typography. But if small caps are absolutely required for your project, I recommend to check out a free font Alegreya (both serif and sans serif versions). This font has small caps as a separate file, so it can be used in Microsoft Office.
If you work with Adobe software, the situation is a little bit better. You can use real small caps that come with certain fonts. Although be careful: if the chosen font doesn’t have real small caps in the main file, you will get the fake ones generated the same way as in MS Office. It is safe to use the following fonts in Adobe software, since they have the real small caps:
Two free fonts to consider:
If you have MS Office installed, keep an eye on Calibri and Palatino Linotype. Even though MS Office itself doesn’t allow to use the real small caps, you can access them through Adobe software.
My general advice: never use fake small caps. If you are not sure which small caps you get in a particular font, just don’t use them.