For most of my photos, I want to make sure that white is white and black is black and I normally adjust this via the tone curve panel in Lightroom. This is an aesthetic and purely personal choice - you might instead prefer to "lift the blacks" to get a "vintage"/washed out look.

So how do I do this? Well, depending on how contrasty the photo is to begin with - with possibly some global contrast added - there might be more or less to do in this step. After making any basic exposure adjustments via the Exposure slider, I have a look at the Tone Curve (RGB channel) that I inverted in a previous step to make the negative into a positive. The greyish so called histogram behind the tone curve shows where on the scale from white to black via grey there is information/pixels in the photo, and how much/how many of each particular lightness/darkness. This might be a bad explanation, so please bear with me and do a search for tone curve/histogram on the Internet if you are not familiar with it. :)

Anyhow, I want to slide the leftmost point of the curve along the "roof" of the square containing the curve and histogram until it just meets the leftmost part of the histogram. This tells Lightroom that the lightest pixels of the picture should be white. Then I do the corresponding action with the rightmost point of the curve - grab it and slide it along the "floor" until it meets the rightmost part of the histogram, telling Lightroom that the darkest pixels should be pure black. It can be a great help when doing these adjustments to click the little upwardpointing arrows on either side of the Histogram in topmost left-hand panel in Lightroom, if they are not already enabled. If you do this, anything that is pure white in the picture will be colored red and everything that is pure black will be colored blue. This is useful for knowing when you have moved the left and right curve points too far into the histogram so that you are clipping the highlights or shadows too much....unless you actually want to lose some of the grayscale in favor of a more graphical approach - that's up to you. If you are not used to make this kind of adjustments, feel free to play around with it a bit to see what the effects are for different actions.

The same kind of effect can be accomplished by using the Blacks and Whites sliders in the Basic panel further up, but keep in mind that black is white and the other way around, since we inverted the photo earlier on. :) Same with Shadows and Highlights sliders - if you want to decrease the highlights as seen in the inverted photo, you need to pull Shadows to the right. The logic of which Lightroom controls change to their opposite when inverting the curve (not all of them do) can be sometimes confusing but if you want to dig into that in detail, there is more info elsewhere on the web if you search for it.

My goal is to get as much as possible of the black frame to be completely black i.e. colored blue by the "shadowclip notification functionality", or at least the outer parts of it since I want a seamless transition into the pure black artificial frame that I will add on later. If I can't succeed with that without clipping too much shadows in the actual motif, I work mainly with two options using Lightroom's adjustment brush: 1. Make the actual picture or selected parts of it lighter by locally decreasing exposure there (remember the inversion...) which allows me to drag the global black point further, or 2. Darken the outer parts of the frame by increasing the exposure there. Weird thing is that as opposed to e.g. Exposure, the Blacks and Whites does NOT seem to swap function with each other in the adjustment brush tool when you have inverted the photo. You'll just have to try it out, I guess. But If you are not into this "adding a frame in connection to the original one" stuff that I'm doing for these half-frame diptychs, you can just keep an eye on the highlights and shadows in the actual picture and disregard what happens to the frame (if you haven't already cropped it away completely).

At this stage, I might also fine-tune the highlights and shadows of the motif (often seemingly blown-out skies are not as empty as they seem), and sometimes I also decide to adjust the overall exposure up or down in case I can't get the highlights and shadows to my liking without clipping too much of them for my taste.

In this example, you'll see that there is very little room to adjust the white point and black point as the contrast is already high. And as you can see in the screenshot, I have not managed to make the frame black enough, although this is as far as I can go considering the shadows in the motif. So the next step here would be local exposure adjustments to be able to make at least the outer parts of the frame pure black. I would also most likely want to balance overall exposure better between the right and left picture (also using the adjustment brush) since I think the right one is a bit too dark in comparison.

If I haven't already done that earlier on in the process, I will likely now also remove dust and/or any especially annoying irregularities in the film emulsion. Regarding dust, drying marks and other stuff that I consider are from the development and handling of the exposed film, I remove as much as possible. When it comes to flaws in the emulsion I mostly consider these to be a feature rather than a problem, unless they really draw the eye in a bad way i.e. disturb the reading of the picture in which case I'll remove them.

Tree Cholla, Cylindropuntia imbricata, backlit in Oak Grove Campground in Lincoln National Forest, New Mexico, USA