Additionally, maybe you guys can share your workflow when editing your photos for:
1. showing or proofing online
I put photos on Flickr, 500px, and several other web pages, including my own pages. Generally I shoot with some model of Canon which creates raw files. The files are opened with Adobe Camera Raw and after initial adjustments it gets passed to Photoshop CS5. Default settings usually result in colour mode and profile being set and embedded. On another forum, we were doing blind critiques for which we emailed our files to a contact person who posted them for us. For those files, I used “Save For Web”, which strips EXIF data. The rest of the time, I just use “Save As” and keep the data attached.
2. sending to printing lab (which I think involves converting to CMYK, if I understood what I read correctly)
You need to have a chat with your lab to see what they need. If memory serves, CMYK is used by offset printing presses which are 4 colour presses. Once in a while someone I deal with will want a TIFF but the vast majority just want a JPEG with enough pixels.
3. choosing between saving the final work as JPG vs TIFF (or do I even consider PDF)
Some final work is saved as PSD which is the Photoshop format. If it is going on the web, it will be JPG, GIF or PNG. If it is going to someone who needs a 16 bit file and can’t use a PSD, then they will probably get a TIFF. Some final work is just saved as the original CR2 file with the XMP file that ACR creates to hold the edit instructions, and the print. Having my own printer, I can print without saving at all if I desire, though I usually build a set of layers so I save that as a PSD in case I have to print a second copy.
When a program like Photoshop opens a file, the data available is plugged into variables stored in memory which the program will use for display and printing. You don’t have to save data unless you want to keep any changes you have made. If you want to save it for later use, you might as well save the data using the native file format of the program you are using. The native format will be best able to maintain the maximum amount of data. Most of the rest of the formats are compromises because they are generic.
Some things are required, like most web pages only accept a few basic file types for images, others are up to the photographer’s whim. Asking for work flow from a number of people will probably result in that same number of different answers.