gdanmitchell
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bibek wrote:
Scott,
Though I have not seen this with the R5 CR3 files, I have seen this with my CR2 files from the 7D MKII and 5DMkIV as well as an 1DXMkII. I traced mine down to sharpening in Lightroom, specifically pronounced in the shadow. I have since started using "masking" to isolate the sharpening to the areas I want to.
A couple of things.
First, it helps a great deal when posters embed jpg samples of their issues directly in the post on FM. In general, I'm unenthusiastic about going to some website and downloading files from sources I do not know onto my computer. You can all perhaps imagine why! In addition, a problem can usually be illustrated with a crop from a larger image instead of a listing of files. I went to the download page and couldn't tell what I was looking for in the list of files there — and surely it should not be necessary to download the entire anonymous list to see the problem and offer some help.
Second, YES to using the masking slider with sharpening. That should be pretty much standard procedure for sharpening. The only cases in which you would not bother raising the masking fader at least a bit would be in images that are completely filled with extremely high detailed subjects, with no areas of continuous tones or gentle gradients.
I do this in ACR, though the same controls exist in Lightroom. (You can also access them in Photoshop via the raw editing "filter.) In the "details" (unfortunate name!) panel where the sharpening settings are found hold down the option key (on Mac, or equivalent on Windows) as you change the masking slider's setting. You'll see a black and white image in which the areas affected by sharpening will be white and those not affected will be black. The ideal is to NOT sharpen any larger areas that have no particular details — things like blue sky or (nearly) black backgrounds, etc. This CONSTRAINS the sharpening to the areas where you need it, keeping it away from those where the only effect would be to sharpen noise — which is virtually always not what you want to do!
In addition, consider raising the "details" slider. This applies more sharpening to high frequency areas (e.g. things like edges) and, from what I can tell, may increase noise along those edges a bit. But that noise is generally not visible when constrained to those areas... unless you turn details way too high and look very closely. A setting like 25-50 often works well for Canon files. (Using a very large radius setting in conjunction with a high details setting may create some problems — see "halo of noise" below.)
Finally, it is important to understand how the sharpening settings interact with one another. For example, the radius setting controls how "wide" that sharpened areas are. (Also note that sharpening doesn't exactly "sharpen." It increases contrast along edges, though it is a bit more complicated than that...) If radius is too large, you'll get the infamous "halo" effect. That's not the issue here, but with radius too high your details setting may cause a "halo of noise" around high contrast edges.
A decent general strategy is to use a fairly high amount setting (I often start with 40 with my Canon files), a very small radius (I usually start with something in the .3 to .5 range), some "details" (I usually use 25-50, but may have to vary this), and whatever masking level keeps sharpening away from areas where sharpening does no good and may do harm.
As to the ACR issue with lens profile corrections, this ties with something I've occasionally noted while using the masking slider with the option (on Mac) key pressed. There can be a slight patterning (it looks like an interference pattern) to the noise that you'll see as you move the masking slider. I assume this is due to interpolation of adjacent pixel data as spherical and similar distortion is corrected by Adobe. I've never seen it in the actual final image though — which isn't to say that it might not show up in some situations.
Using lens profiles is not a bad thing, and in most cases it is a distinctly good thing. (Though you may wish to add back in some vignetting manually.) But in cases where it doesn't improve the image in any visible way and especially in rare edge-case images where it could cause some harm, be ready to disable it.)
If you are pushing ISO to extreme levels AND looking very closely at dark areas AND the dark areas are of one tone or smooth gradients AND you have sharpening turned up pretty high AND you did not raise the masking slider...
... that might be the perfect storm that could make these edge cases visible.
Finally, while I know that some of you understand all of the sharpening controls really well, others may not. And some may be daunted by all of those different controls for sharpening and noise and details and masking and so on. I recall when I was.
A useful approach is to play with sharpening a bit. To understand what sharpening does to edges, create some test subject images, such as high contrast checkerboard patterns, then run those adjustments (amount, radius, details, masking, etc.) up and down and watch what actually happened at edges. You might try other versions of this where you add some noise to your checkerboard pattern and/or use gray instead of black and white objects... and see how you can use the controls to minimize the noise in areas while sharpening the boundaries.
By playing around with this you can learn a whole lot about sharpening very quickly! :-)
Dan
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