Take a look at this frame:
Click for 720p version.
Now compare it to this version:
Click for 720p version.
The top image is soft, and the second one is so sharp it almost
seems dirty. Something isn't right here. Recently I've been noticing
the extreme degree to which most video content has been over-sharpened.
I had posted some frame grabs from a recent project on a message board.
One of the comments I got was that the grabs had way too much
sharpening applied. The ironic thing was, I hadn't sharpened the images
at all. I took another look at the images, and sure enough. There were
sharpening artifacts and ringing all over the place:
Click for larger. Over-sharpening is most evident in the
texture on the cheeks, the left eye, and ringing around the right side
of the face and shoulder. Note: if you can't initially see the
artifacting, A/B it with a copy that has a .5 pixel Gaussian blur
applied.
It was the result of in-camera detail settings. The more I looked at
it, the more obvious it became, and I wondered how I hadn't seen this
before. Then I started closely examining the video content I was
consuming. What do you know... almost all of it exhibited the same
problems. I was so used to seeing these problems on commercial content,
that my eyes had gotten used to it.
Check it out:
The Hire - Hostage. Notice the ringing under the chin. Click for larger size.
The Hire - Hostage. Contrast enhanced edges. Click for larger.
24 Season 1. Ringing in high contrast areas. Click for larger.
The Italian Job. Ringing everywhere. Click for larger.
Why are these artifacts undesirable? They trick the eye in to
believing that the picture is sharper than it actually is. Isn't this a
good thing? Perhaps for distribution. For some, the examples from
commercial content posted above may have an acceptable amount of
sharpening. However, there are a number of reasons why this extreme
degree of sharpening should be avoided, especially in camera.
- Maintain maximum image flexibility for post - Sharpening
should be done as one of the final steps in the post production
process. Sure you can sharpen your image in camera, but once it's
sharpened, you're stuck with any added artifacts. Say for example
you're onlining your latest project, and realize that a shot is
slightly out of focus. This can be fixed to a certain degree with
sharpening. However, if you had detail levels turned up in camera, you
end up sharpening existing sharpening artifacts, making them stand out
even further. Better to do all sharpening post where you have more
control, and can "undo" your sharpening by simply turning off an
adjustment layer (or similar, depending on the onlining application of
choice).
-
In camera sharpening is generally inferior to what can be achieved later in the computer (unsharp mask, anyone?).
-
More control over sharpening in the computer.
-
Different deliverables require different amounts of sharpening. A
theatrical release will require a different amount of sharpening than a
DVD, which in turn, will require a different amount of sharpening than
a web version of your film.
- Film doesn't do it - With most digital video cameras, we spend a
huge amount of time and effort to get our images to "look like film."
With film, what comes in though the lens is what ends up on the film.
There's no fancy DSP to get in the way. Any sharpening that is done to
film originated images is done in the DI. We should be doing the same
with our digital cameras. Capture as pure an image as possible off of
the chip. Do the processing in the computer, with a higher degree of
control, and the ability to undo changes.
That's all well and good, but how do we control it? What settings do
we use? The following analysis deals with Panasonic's HVX-200, but the
principles apply to just about any camera.
The HVX-200 has several controls which deal with the detail and
sharpening of the image. These settings can be found in the menu, under
"Scene File Settings." The settings that we are concerned with are
"Detail," "V Detail," and "Detail Coring."
Detail
This setting functions by actually drawing new elements in to your
image wherever it detects an edge. For a good example of what this
setting could do in an extreme case, take a look at the image from The Italian Job
above. This setting is our biggest enemy. It has a value range of -7 to
7. It would seem that a setting of 0 would be the baseline. Any
positive numbers would be adding sharpening, and a negative setting
would add some sort of blur. Not so. By the time you get up to 0, a
significant amount of sharpening is already being added to your image,
adding an obscene amount of ringing. Positive values can look
absolutely awful:
Detail: +7, V-Detail: -7,Detail Coring: -2. Note how even
the image noise is being sharpened and standing out more. Click for
1080p version.
This image was shot with a Detail setting of -1. V Detail was set to -7, and Detail coring to -2:
3:1 crop. Click for larger.
There is even significant artifacting with detail levels set to -3:
Crop. FX element from The Inheritance. Click for larger.
It seems that the only way to get rid of the ringing is to set
Detail to -7. Even then, in high contrast areas, there are subtle areas
that still seem to exhibit small amounts of ringing. You really have to
stress the image to see it, though.
We can try moving the Detail level up to -6, but even here, we can easily see ringing beginning.
3:1 crop. Click for larger. Levels and Hue/Sat. Unprocessed image here.
Ringing evident where the leaves overlap the highlights on the car window. Click for 1080p.
Set your detail level to -7, and keep it there!
V Detail
V Detail is a lot more subtle than its evil cousin. This setting operates much differently on the image.
"Whereas DETAIL LEVEL works with edge enhancement,
artificially drawing outlines around objects to accentuate their edges,
V DETAIL LEVEL works with the existing image, accentuating vertical
contrast between horizontal elements." -The DVX Book, p.51
This type of sharpening is especially evident in the second image from The Hire - Hostage above.
This setting also has a value range from -7 to +7. Again, the -7 value has no identifiable effect on the image:
Click for 1080p.
As the value of the setting increases, naturally so does the effect
it has on the image, namely the contrast of what the camera perceives
to be "edges." By the time the value for this setting reaches 7, it
becomes much easier to see what effect it is having on the image.
You'll also notice artifacts really starting to show up, especially
banding and the like, on smaller textures that the camera perceives as
being edges.
4:1 crop. Levels applied to increase contrast. Click for larger.
In the two images below, you can really see the effects of the V
Detail setting. Both were shot with Detail: +3, V Detail: 0, Detail
Coring: +2
Click for 1080p.
Click for 1080p.
With this setting, you're probably safe to come up a few notches
above -7 without having a noticeably deleterious effect on the image,
but I'd recommend playing it safe, and dealing with it in post.
Detail Coring
This setting acts on the noise in the image, applying a slight blur to
what the camera thinks are noisy areas. One interesting thing to note
is that on the HVX, this setting doesn't have the full -7 to 7 range of
the previous two. It only goes down to -2. Given our settings above,
this setting will have a very minimal effect on the image (see page 52
of the DVX book for an explanation of this). At higher levels, this
setting can start to blur finely detailed areas of the image (hair, for
example). Here we see it having a posterizing effect:
2:1 crop. Click for larger. Detail Coring: -2
2:1 crop. Click for larger. Detail Coring: +7
Use with extreme caution. It may not have much of a noticeable
effect, but can really come back to bite you when you start pushing the
image in post. Instead of trying to smooth the noise in camera, look
into something like DE:Noise, an excellent noise reduction plugin that can achieve the same thing in the more flexible post-production environment.
Having read the above, you should now have a pretty good idea of how
to get an optimally detailed (or un-detailed) image out of your camera.
We still need to look into post production and see what to do with our
new, sharpening free footage. There is more to come:
Part II: Balancing the Equation
