FEE and ERR99 – what are these, what do they mean, and why do I see them being talked about online all the time? Good questions, and if I had a few pages to cover all the instances, we could get into a great deal of detail… and quite probably help solve a lot of sleeping issues at the same time. So let’s try to keep it basic, shall we?

Both error codes will be visible in the top LCD screen on the camera

FEE is an error that is specific to Nikon. The camera not being able to read the minimum aperture on a lens causes this error. There are two common reasons that the lens will cause this error, and one common reason that the camera will cause this issue. On the lens, the two reasons are: 1) the aperture ring is not set all the way to the minimum aperture (the number on the aperture dial that is red or orange), or 2) the tab on the end of the aperture ring that holds down the f-min block switch lever is broken. The first problem is quite easy to fix – turn the aperture ring until it is set to the minimum aperture, and problem solved. The second means that the aperture ring has to be replaced, and the lens must be sent to a repair shop. On the body, the main reason is that the f-min block switch lever is broken. The f-min block switch is the switch that tells the camera that the lens is set to its minimum aperture, and this switch is triggered by a tiny lever on the front of some models of Nikon cameras. This lever usually is broken when someone who is not familiar with the camera system attempts to put the lens on incorrectly, although it can come from impact damage as well. 
ERR99 is exclusively a Canon code, and this is the cameras way of telling you “Something is wrong with me and I have no idea how to interpret the information I’ve been given!” If you were to Google ‘ERR99’, you would quickly find yourself overwhelmed by the amount of information you can find (good, bad, horrible, and just plain wrong), so hopefully we can help separate the truth from speculation. True, it is a generic code for “I’m broken”, but what we’ve seen here in the repair department is that there are two main issues that cause this error: 1) your shutter has blown out (or locked up, or is in some other way not functioning correctly) and will need to be replaced. Or 2) your lens has a damaged or broken aperture control unit. What this means to you as a photographer, is that you should do a little troubleshooting on your end before sending the equipment in to a repair shop (like KEH!). Once you get the ERR99, either when you are shooting or right when you turn on your camera, turn the camera off, change to a different lens, and turn the camera back on. If you still get the ERR99 either immediately, or when you press the shutter release, then the problem is in the camera. If the error does not occur, then most likely the problem is in the lens. Just to be sure, put the lens on another body and see if you get the error again.
Hopefully this has helped somewhat in your search for answers to strange error codes that seem to arrive from nowhere. There are, of course, many other reasons that both of these error codes will appear, but we felt that the most common issues are the ones that should be addressed. When in doubt, always send your equipment in to a reputable repair shop (*cough* KEH *cough*), for a technician to diagnose properly.

- Sean McCreery