Originally posted by CreationBear
Just to be clear about "highlight expansion," then: for a low contrast scene, expose normally and develop N+1?
Not quite. Since you are over developing the film to move your high values up more, you need to slightly underexpose so your low values also don't move up too much. Highlights develop faster and move further than the shadows.
An easier way to expand your tonal scale when your scene is flat is to follow Ansel Adams suggestion in his book,
The Negative, by Intensification. That is, soak the negative(s) in a solution of selenium toner diluted 1:2 with Kodak's Hypo Clearing agent for 5 minutes. You can do this anytime after the film has been developed. So you can decide later what frames you want to do this to.
Highlight compression and expansion can be done without a densitometer by trial and error. And highlight compression is easier to practice without a densitometer than expansion, I feel. To do it right you'd first would conduct a speed test of the film by measuring the density of Zone I. And once you have that you need to find a development time that places Zone VIII at a specific density that's different for a condenser vs a diffusion enlarger. That's a lot of work and you need equipment. So I wouldn't worry about highlight expansion just yet. In the image editor you usually can improve a low contrast scenes much easier than you could with wet printing.
For high contrast scenes and highlight compression where you want more DR than normal development, try starting off by over exposing one stop (shoot say 100 film at EI 50) and cut your normal development time down by 20% or so as a starting point. Look at the shadow detail on a light table or something and decide if you got them or not. If the shadows are too thin then you'd want to add more time and of course if the film looked over exposed keep reducing the development time. Do this until you are happy with the shadows. A one-degree spot meter and the zone system of metering helps you with this a lot! When you place a shadow area say 3 stops below the middle gray exposure with a one-degree, it is something you can visually see in the print or scan if it matched how deep of a shadow you expected once you got a feel for this sort of stuff.
Now not all developers are good at the more extreme highlight compression. Just like some are not good at highlight expansion or pushing film. You just have to experiment.
Good luck.