With your 5D3 raw files, what's your lightroom develop workflow?

Started Apr 19, 2014 | Discussions thread
MiraShootsNikon Contributing Member • Posts: 976
Sharpening Radius: in and out of depth

Hi, Jonathan,

I think I may have misled you, a bit, into a belief that there is an ideal Sharpening Radius slider position that can be "calculated" rather than simply discerned to taste.

Let me answer your questions in-line, below.

Jonathan Brady wrote:

MiraShootsNikon wrote:

The Photo Ninja wrote:

Do you use the camera calibration tab? First, second, last? Which setting do you use?

What other tweaks do you use on the majority of images?

My basic routine: Spot / Retouch --> Exposure --> Contrast and Tone --> Color --> Sharpen / Detail.

[12.1] Detail --> Sharpening, Amount: pull positive just to "cut" through any AA filter haze, not to actually add acuity.

[12.2] Detail --> Sharpening, Radius: pull to match your lens's smallest projected airy disk over your sensor's pixel grid. I.e., if your lens projected pin-point sharpness that corresponds to one-and-a-half of your sensor's pixels, your radius is 1.5. Back when I was shooting a Nikon D2Hs with massive pixels, I almost always set this below 1. Now, with the 5D3's much smaller pixels, I'm usually around 1 - 1.3.

Thank you for sharing all of the details! For someone like me who just purchased LR, it was great to see this and (try to - lol) understand the rationale behind it. Some follow up if I may...

  1. I googled Airy Disc and saw that it was named after the guy who described it, not actual Air which was surprisingly helpful. I also saw it was LOADED with math. Then I googled Airy Disc Calculator and found this: http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm This showed me that for a 50D, the pixel 4.7 µm, for a 60D it's 4.3 µm so I figure for my 70D it's probably about 4 µm. I also noticed that the Airy Diameter doesn't change at a given lens aperture regardless of the system used, only it's projection onto the pixel grid does (and how much area of a pixel is covered). Now that this is out of the way (and assuming my understanding is correct)...

Your understanding is close, but it will lead you to some confusion in practice.

It's my fault: I shouldn't have used the term Airy Disk--I should have used "Circle of Confusion."

The problem is that the concept of the Airy Disk is an ideal--it's the pattern of a perfectly focused point of light from an ideal lens. And as an ideal concept, you can calculate its size. But in practice, the *best* focused point of light from any given lens at any given aperture only approaches an Airy Disk, because none of our lenses are perfect. They suffer various optical distortions; there are uncorrected spherical and chromic aberrations; aperture blades don't form a perfectly circular opening, etc. Among other things, these issues prevent a mathematically *perfect* focus.

So really, what your lens projects on to your sensor are "circles of confusion" (essentially, bokeh blur) of various sizes, and the best focused point is essentially the smallest "circle of confusion" in your photograph, shot at your chosen aperture, focused at your chosen distance.

What we're really after, then, is finding a sharpening routine that considers how that smallest possible "circle of confusion" relates to the pixel size of your sensor's grid.

Why? Well, because of what Lightroom's Sharpening routine does. It's basically an unsharp mask, which means that it enhances contrasts and contours by overlaying a strategically blurred version of the same material. It's a sophisticated take on an old trick: you make something look sharp by smearing whatever's right next door. When you move the "Radius" slider, you are literally changing the pixel size of the overlay's "smear." That's just a really, really simplified explanation of it without getting into how the mask samples or overlays and the exact formula of its "smear," but you get the gist.

  1. Are you saying that whatever the Airy Diameter/Pixel Diameter is, that's what you set your radius at? In other words, if Airy Diameter is 8 and Pixel Diameter is 4, then you set the radius to 2? If not, can you correct me?

Yes, if you replace "Airy Diameter" with "Circle of Confusion" diameter. You got it!

However, the smallest "Circle of Confusion" you'll see from a given lens shot at a given aperture focused at a given distance is going to be pointlessly difficult to calculate, given the many factors that contribute to producing it for that specific shot.

Rather than attempting a mathematical approach, you'll probably want to simply "eyeball" the setting, but "eyeballing" it with a conceptual knowledge of what you're actually doing certainly helps to get the look you like best.

  1. What are the benefits/drawbacks to going higher or lower than this number?

Remember, the "Radius" slider alters the size of the unsharp mask's "smear." The size of the "smear" essentially determines the size of what we perceive as "sharp" when seen next to the smear.

So if I set my "Radius" slider to "3," what I am really saying is that I want any contrasts 3 pixels in size to appear sharper. If I set my "Radius" slider to "1," I'm saying that I want any contrasts 1 pixel in size to appear sharper. If I set my "Radius" slider below "1," then I'm saying that I want detail that's apparently smaller than one pixel in size to appear sharper.

In practice, what this means is that as you move the radius slider back and forth, your photograph will literally appear to move in-and-out of focus in a very, very fine way. If you managed to capture detail 1 pixel in size but "smear" three pixels, then that one-pixel detail will look defocused and blurred.  Likewise, if the smallest detail you captured was around 2 pixels in size and you chose a radius of ".5", then the sharpening routine will not appear to have much, if any, effect.

Thanks so much for any info you're willing to provide! And again, thanks for the detailed explanation!

You're welcome.

When I pre-sharpen with Lightroom, I find a few things helpful:

(1) I use the Detail pane's 1:1 view loupe and move around to important areas of the photograph as I'm working it, but I view photograph itself in 1:2 or 1:4. Why? Well, because it's often the case that your "ideal" sharpening at 1:1 is just too much when you're looking at the photo reasonably sized. Since you aren't presenting or publishing the photograph at 1:1, it's more important to get the look you want at 1:2 or 1:4.

(2) I often crank the Amount slider way higher than I really want it so that I can see the sharpening routine's effect very clearly when setting the Radius.  So, generally, I'll push the Amount to 75 or 80, pick my Radius, then back the Amount into place (usually somewhere around 30 - 40).

(3) Deconvolution sharpening--the Detail slider--is *really* subtle. You could just leave it at the default and be happy.

(4) Sometimes it can be difficult to "see the forest for the trees" with RAW pre-sharpening--you can get too tied up in pixel-peeping and not really take in the effect of what's happening, overall. I work with a personal sanity check: if I'm pushing the Amount slider past 45, or if I'm using a Radius past 1.6, then something is probably wrong and the picture isn't worth it--maybe it's out of focus, etc.

(5) Don't forget about output sharpening. Lots of photographers just always use Lightroom's pre-sharpening defaults because they know that output sharpening will have a much greater effect on the overall final appearance of their work. Output sharpening is also the reason you don't want to be pushing your RAW pre-sharpening levels very high.

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