I'd like to lay out some definitions, terms and clarifications so that we are all on the same page.
There are different ways to talk about the phases of the roasting process. Though the terms I'm going to use have been the traditional ones, there are now more technically accurate terms. I'm going to break it down in the best way I know how.
The beginning of the roast, while the beans are still green, has been traditionally referred to as the Drying Phase. I have been told and have read that the beans aren't technically drying during this phase. This poses a problem for some roasters because the phases name is wrong. I don't personally know if that's true or not. However, I am going with tradition here and am going to call this phase of the roast the Drying Phase. It's what coffee folks have called it for a long time, and that's good enough reason for me.
The next phase is the Browning Phase. This phase starts when the beans begin to take on a yellow color, and goes until First Crack begins.When the beans start to turn yellow the Maillard Reaction has begun (Maillard is a French name so it's pronounced My-yar). Once the Maillard Reaction begins, it doesn't stop; it continues until the coffee has cooled.
The last phase is called the Development Phase. This phase starts when First Crack is observed and continues until the roast has been dropped - meaning the roaster door has been opened, dropping the coffee into the cooling tray, ending the roast.
So there are three phases of every roast - Drying, Browning, and Development.
For me, the Browning Phase has begun when the beans take on a yellow color. This may sound obvious, but before they turn yellow, they turn white. The reason why the Browning Phase begins when the beans yellow is because that is the technical start of the Maillard Reaction, not when they are white. The white color tells you that the Maillard Reaction is about to begin, but it hasn't begun yet. On our roaster yellowing happens right around 300F. This temperature, as well as all of our temperatures, will certainly be different from your roaster; that's just how it is.
The Development Phase has begun at First Crack. What that means to people is different. For me, I say First Crack has begun after I have heard about 5 cracks. There seems to always be a few small, pre-pops. I don't count those. I wait until I can hear the sound of the roaster's environment change and then hear a few cracks start simultaneously. First Crack happens on our roaster right around 390F.
Second Crack happens during the Development Phase. Though Second Crack doesn't denote a new phase, what's great about it is that it's an objective marker during the roasting process that can be used as a reference. Second Crack happens around 445F for us.
The last thing I think is worth addressing here is the labels assigned to different roasts - City, Full City, Vienna, French. There are more types of roasts than this, but these are the ones that the people I have worked for use the most. These terms are subjective. I think I'm going to use the temperature as much as I can, and try to avoid these labels, but I won't make any promises.
Here are a couple sketches that may help the visual learners.
The sketch above is a roast profile dissected by the definitions.
This sketch is a conversion table I use when I'm comparing two different roaster's temps. This helps me translate what is happening between roasters. I use the objective markers of First and Second Crack. I take the temp difference between the two cracks, divide by two and add that to the First Crack temp to get the middle temp (MJ's 417F). Then I take the difference between the middle temp and First Crack temp and divide by two. I add and subtract that from the middle temp to get the quarter temps (MJ's 403F and 431F).
The You in this example is based off of a Diedrich IR-3 that we also have at the shop. But if you want to compare your roasts to ours, all you have to do is insert your First and Second Crack temps and do some simple math. Then the numbers that I'm using from here forward will be much more applicable to what you are doing.