This database was started in early spring of 2007 with a very simple idea in mind. At that time I was about to buy some additional lenses for my Canon EOS, but as a student I also was extremely low on budget. I recognized bigger sets containing my targeted lenses selling on Ebay for very low prices. So I bought some of these sets and sold what I didn't need. By the summer of 2008 I had collected a good load of equipment for a bargain. But all this buying and selling also had some side effects. Besides getting kind of addicted to learn something new about that lens I did not yet had held in my own hands I for example realized all these weird variations of Sigma lenses, of which nobody could tell for sure whether they would work with newer camera bodies or not, how old all these lenses are at all (not only the Sigmas), what the small differences in their specs and behavior are (just try to find something about the Tokina 17mm F3.5 AT-X non-Pro) and so on, so on, so on.
 
At that time a few good resources existed: besides the Canon Camera Museum and other manufacturers' product listings and discontinued product archives there was Patrick Murphy's lens list (that was taken off the web a few weeks after I started), an outdated lens list focusing on Pentax by Martin Trautmann and PeNum.de, just to name a few. They were all very good, but not complete, nor mainly focused on Canon EOS. To retrieve information about discontinued stuff I digged through The Internet Archive most intensively. Finally the database collected here is, to my thinking, the most comprehensive one dealing with Canon EOS at the moment. And since I also like playing around with web servers and web publishing I decided to keep all this information available online. So far about the story.
 
Let's have a comment on quality. I try to stay on a rather scientific level, but I can't manage to note, where every information was acquired. You can find very different specs even within the same manufacturer's local website at times (just try to figure out, which Tokina lenses other than AT-X 242 AF indeed are parfocal, whether the Kodak DCS 1c has ISO 80 (according to Kodak) or ISO 50-100 (according to Canon), or compare the tech specs given by Kodak for their DCS 520 and by Canon for the identical D2000 (AF operation, sensor size ...), so don't take all this too seriously (mainly size and weight, as well as production years may vary).
 
I prefer first hand information from the manufacturers. Many specs also were/are acquired from Ebay auctions by analyzing product pictures, collecting serial numbers (vintage Vivitar and russian lenses) or simply contacting the seller. Sometimes even the information acquired from sellers proofs to be wrong by their own product pictures. If I witness inconsistencies, data will usually be deleted or suspended into my so called process logs until further approval. So most widely you can take these lists as serious as any other wiki.
 
So what is the vision? Besides keeping it up to date there is the idea of adding highly detailed pictures of each lens to the site. And here is one way, HOW YOU CAN ADD to the content. Support this project by sending in good pictures definitely identifying the lens, it's design and it's features. If you want to participate, also by adding to the specs, be highly welcome to contact me. Also financial support will be of help. Read more about why and how to support the Canon EOS Technoclopedia on the supporters page.
 
Using the database: Basically it's all about getting an idea of what kind of equipment is available to use on your Canon EOS or your Canon EF mount lenses, about digging up tech specs and comparison. The major part of the project consists of huge tables. To compare stuff you can mark each row by checking the checkbox in the first column of every table's row to highlight the same for not losing the line while scrolling. The highlighting is not bound to cookies, so you will either lose your selection when leaving for another menu point or you need to work with multiple tabs or windows to compare specs within different lists. For the EF mount lens lists I also added printable detail pages (see the symbols in the columns after the model name), that will stay open, giving you the oportunity to see all specs on one single view without scrolling and to compare them by switching windows. Some of them are also linked to each other if they are related to each other (being rebadges for example).
 
There also is the Change Log: News & Additions available, which can be a good way for you to stay up to date with list additions and new products on the market, as long as you are not required to know things "before they happen" (and just to tell it, minor corrections and addition of single specs to existing entries are not logged anywhere).