Archive (IA), and Google Books (GB), which all have been conveniently aggregated in the portal of the Post-reformation Digital Library (PRDL 2011) hosted by the H. Henry Meeter Center for Calvin Studies, or subscription-based, such as the Institute for Reformation Research at the Theological University of Apeldoorn (IRR), the Digital Library of Classic Protestant Texts (DLCPT), and Early English Books Online (EEBO). Although some students and scholars of Reformation studies, and Calvin studies in particular, are fairly at home in the digital world, others are bemused. Therefore a brief examination of a selected number of digital primary sources of Calvin, restricted to 16th hcentury editions - the Calvini Opera excepted, may suffice to acquaint one with the research opportunities and limitations both for open access and subscription based. 1. OPEN ACCESS: BNF, BSB, IA, E-RARA, AND GB.The Calvini Opera (Baum, Cunitz & Reuss 1861-1900) is available at Open Archive at the University of Geneva (Open Archive 2011) and partially at GB (Google Books 2011) Access to the former initiates the downloading of the requested work -a step not required by GB, and constrained by available bandwidth. The accessed document, viewed as scanned pages of the original letterpress edition, can be searched for specific key words, whereby GB presents all search results, highlighted in context by page number, which Open Archive offers one at a time. Although both venues offer download functionality (PDF format), the search function is lost with GB but remains functional in an Open Archive document. Furthermore, the entry of multiple words or phrase in the search field reveals that the search engine offers proximity in a sentence or paragraph. For example, the phrase "in summa" presents search results with the words "in" and "summa" sequential or separated by words, and sentences. In other words, the accuracy of the search results requires much discernment and interpretation of the user.The works of Calvin digitally present in Latin, French and English at the BNF, such as Interim adultero-germanum (Calvin 1549), Defensio orthodoxae fidei de sacra Trinitate (Calvin 1554), and Le Catechisme (Calvin 1552) and Sermons of upon the epistle to the Galathians (Calvin 1574) are only available in black / white image format, and search by words is not possible, though download in a PDF or JPEG format for research purposes is available to the user. Furthermore, Calvin's works published in the French language are listed in the BNF but originates from e-rara Calvin 1548) and the BSB (Calvin 1538).4 It presents the page image in color, and is non-searchable but downloadable, whereby the BSB contain works translated into German, and both contain various commentaries, sermons, treatises and other works. Finally, the IA offers assorted Calvin works not only in various online formats, such as viewer, PDF - color and black / white, e-pub., Kindle, Daisy, DjVu and full text, whereby the read-online and both PDF versions are searchable - a functionality that remains after the PDF downloading.These works then, available through open access, offer an entry globally to the rare editions of Calvin's work, which were previously only available locally. In