I received a few questions regarding some of the suggestions I made in the Portra film Presets for Aperture usage document. Specifically my comments about the Aperture black point adjustment in the exposure block. Thought I would go into a bit more detail here and just show a couple examples of how I use it to fine tune images.
In fact I went on to say for 90+% of images my adjustments and fine tuning are limited to a fairly simple preset, WB, and the exposure adjustment block. This is absolutely the case and in fact within the Aperture 3 exposure adjustment block I would have to say that 100% of my images have a black point adjustment and maybe 30% have an exposure adjustment, down around 10% have a recovery adjustment. Almost all of my images have a WB adjustment - mostly because I don't like Nikon's take on Daylight or the skews that they choose for Auto WB. I have tried to use the WB fine tuning for my Nikon's but even the smallest increment of fine-tuning is too much.
Moving on to black point. The image at the top doesn't have any really deep shadows at all. Even on an image like this that is pretty much all mid-tones a tiny tiny black point change has some fairly substantial effect. My Nikon D600 defaults to a black point of 5. Other cameras will be different, I think my Fuji defaults to 3. Generally speaking I think most cameras default to something too high for images of people and it tends to introduce overall contrast and color saturation that I don't necessarily want. Landscape or scenic shooters will probably feel differently. The point isn't what particular recipe I prefer it's more that even a minor adjustment here at this point in the image processing is pretty substantial.
In the screenshot above the image on the left has the black point set to a value of 2. Three points less than the D600 defaults to. The image on the right goes the other direction by the same amount, it's set to 8. Even on an image like this with a very tame histogram that is all in the middle you can see the effects of that tiny 3 point change in either direction. For images that have more extreme histograms the effect is far more significant. Here's the histogram for the image on the left.
And for the image on the right…
You can see the way saturation is affected. It's subtle but that's the name of the game when post processing. Much more subtle than even the finest increment of the saturation control. It also manipulates contrast quite a bit. Overall contrast but more so in the shadows and lower mid-tones. That's obvious from the difference you can see in the histograms. What's way more important than the statistics of the histogram is how it actually looks. Take a look where granddaughter #1's nose meets her check on the left side of the face and the shadow side of her foot. The image on the left has a much softer feel in the shadows than the image on the right. I happen to prefer that softness in the shadows over the hardness observed in the image on the right, at least for people images.
On my D600 I tend to hover some where in between 0 and 2 for black point. Sometimes even less it goes all the way to -5. That' doesn't mean I don't like my contrast - I really like it. This image happens to have a fairly aggressive curve increasing contrast. The curve happens to put that contrast where I want it, which for people is not in the shadows, it's in the mid-tones.
Experiment based on your particular taste and subject matter but do bear one thing in mind. By taking black point out, making it less it really starts to unblock lower values in your image by a significant degree giving you much much more flexibility to add contrast more precisely where you want it via curves. Try it. I personally do not like the default contrast curves of any RAW processor. The black point control and especially in the direction of less gives you a bunch more flexibility to use some of the other tools to achieve the look you want.
Moving back to the Portra Presets for Aperture, The curves built into the presets assume a lower black point than the default. Typically 1 or 2 for my D600 and 1 for my Fuji cameras for my taste. Unfortunately I cannot build that in to the presets as it presents other issues. Specifically if I target the exposure adjustment block in the presets every time a different base preset was chosen it would reset/undo any changes made to the exposure controls. I thought this was actually far worse than allowing people to adjust it themselves for that particular image. It's a valuable fine tuning control, only slightly less valuable than the most important one - the exposure slider.
Ps. The preset used on the random example image happen to be from my upcoming Fuji film emulation pack for Aperture 3. Hopefully it will be out soon.