Darktable: Equalizer module

darktable is an open source photography workflow application and RAW developer. In this video I run through how to use the powerful Equalizer module. Thanks to Tobias and Johannes for fact checking this video.

Matt's blog post on making your photos pop with the equalizer: http://www.knowingme.org/make-your-photo-pop-local-contrast-with-darktables-equalizer/
Jo's blog post on the research behind the equalizer: http://www.darktable.org/2011/11/darktable-and-research/
My video on noise reduction in darktable: http://www.youtube.com/watch?v=4nBzAeM0tpI

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Closed Caption:

either one tonight I'm gonna do a video
on some things up in preparing for
quite a while actually trying to get my
own brain around
dats the equaliser to induct able this
is quite advanced module
there's a lot you can do with it speak
on a need to know what you doing any
need to know what each the splines
does so I'm just gonna run through the
way
that I worked at keep in mind that I
haven't worked on any at the code our
table
I'm just a photographer he likes to use
it but what I've tried to do
is break it down in such a way that some
normal
user can understand things that's doing
and just have a more intuitive
understanding of the way that works
their natural resources
on the equalizer %uh the first of course
as usual is the user manual its under
the correction group in here
and it's cool don't have a quick read
through this it's pretty high level
am but it gives you good year the
effects that are possible
with it I'm you go through some these
affects in this period
I've also got here a couple other
resources that i felt quite useful this
a blog post here on shopping and local
contrast
open link down in the be a description
and finally the last place about points
you if you're
interested in the technical side of
things is
this blog post by your house what Joe
and this goes through the moment medical
side
and in fact even links to the
scientific papers that the equalizer is
based on okay so it's getting to it
that's what I've done isn't loaded up an
image induct table
not loaded up an equivalent image and
can't hear and going to compare
so the features that the equaliser here
with a similar features
the wavelet decompose which is i plug
into the game that's uses a similar
image person perch the first things
first let's talk a little bit about the
user interface
of the equaliser it three times here to
limit the crime and the sharpness
alumina tab Andy Kravetz had both
content to splines
and the shop instead contains one now
the liver is
essentially brightness at the beach and
the Kramers the color
image so like a saturation if you will
the top one that gives you the ability
to change the smoothest
to the contrast Eunice the various
elements and we're going from the core
system in some left
to the finest donors on the right what
wavelets allow you to do is break image
down into the size of the various
elements
and that'll become clearer as we run
through this little more
the top one allows you to enhance
contrast love various different parts
your image
and you can see that if you want to
reset and individuals
line then you can do that by just
clicking on it on the way we can make
changes to various different parts of
the image
and just reset one and if you want to
reset the entire
module then you can do that with the
recent but missed as normal
the bottom one allows you to use or to
remove elements
what that's generally used for is noise
reduction you can see my email server at
these words change from
noisy to smooch and still from coarse to
fine
not just as an aside the reason why the
equalizer is called the equalizer is
because
it's very similar to the graphic
equalizer that you would get
in all year persisting where that you've
got the highest frequency
you know the high sounds the lowest
frequency the base
lowest sounds on on the left hand side
now the chroma is equivalent so we we
can increase the
saturation owes things using the the the
crooner
and we can also I removed the chroma
noise using the bottoms
line here a lotus as well as it's worth
pointing out at this point that you
don't actually grab these handles at the
bottom to pull up the bottom spline
actually grab slightly above it and just
drag up not pulls up
if you're if you click at the bottom
you'll actually be moving these
triangles which moves the handles the
spline
and you know moving handles the spline
is
is useful for doing shop affects that
you
if you want that kinda thing ok
let's reset back now again oh come back
to the shop miss
in a moment because shot this is
actually to do we is the
fix that you've applied to the image not
to do with the overall shops at the
image in fact
if you move this blind not you won't see
a need to change the image
at all unless you've applied some other
spline in one of the other
Thames I'm just going to quickly go
through some
the presets and this is something I
recommend you do yourself
because it got done enhance course great
shopping and in raising
book remedy know is only you can see did
you notice which the creditor
here we've got some teen wasn't
happening only inner in the smallest
element to the image which makes sense
because thats
sorting noise is they were quite
dangerous at all which does both
the lunar here just a bit and the
creamer
and that makes sense because crime in
ways you can't push a bit more
then you can alluded to is because your
eyes are more sensitive to noise
up covered that in a previous on a dean
waiting period
I was raised for one's here then we have
balloon which you can see is dragged
lawyer here so if you if you want to do
that
effect and really really pushy can and
then we have Clark clarity which is
obviously be loved by the like retired
people
and then then is so it's a subtle and
this is the less subtle version the
other thing is we've got the mix
if you like the effect you want to turn
it down slightly could do that just by
by doing the mix and then you can also
push it even more if you want
and go see at the noble blending coach
but we have in every module
wanna do is reset back to normal and
what I've done here is up
loaded up the same image in the game
this is just a Jay pig
vision on persist this profile
I'm going to do a way that decompose
okay so we now have divided the image
into
5 wavelet scales term Witcher
who this guy is even slightly concede
that very very fine details on the
on the B and as I show you progressively
coarser
weightless Kelsey concede progressively
coarser items
notice here most important thing to
notice is that this is the course items
the others that the his a completely
missing the finest scale
and the largescale become essentially
independent from each other and this is
the key to this technique because it
allows you to modify
different sized items within the image
independently of one another but you
can't do
on the full image if you think about the
wavelet scales we have here
from the finest to the coarsest these
correspond essentially to these
this klein's here on from the finest to
the coarsest but the other thing to keep
in mind is that
induct a balloon and the kreimer split
apart we have
the brightness information from the
color information separate
whereas in the game there combined with
each other
few more if I can see this green here he
modified this
you might find both the criminal it but
they're close enough
to be illustrated in this case what I
want to do
is I want to applying effects would be
seen on the
on the B plan affect to say the smallest
items in the image you can see that I've
now shoppers just the smallest things
and uplift the large things alone no up
what does that mean
in the give here well let's apply an
unsharp mask
to just this way the scale to me like
this could be a
me see if I can find the be here so
let's
checks are shop and thats let's make the
radius be a so-so a bit more obvious
maybe not too big
something like that make the effects
nice invisible
do okay so let's earners put all that
this stuff back together
this is the original image let me hide
the original image you can see that shot
dead
so now if I get back into doc table we
can see that we
essentially have the same effect one
thing you'll notice is that
the color information has not been
enhanced
see how these has announced lightly gray
compared to these these add more
yellowish
the other thing you'll notice is thats
the noise in the dock table version has
not been affected whereas the Norris is
being made more splotchy in the
compression
the other thing I'd like to point out at
this point so we can we can bridge the
Kramer
to make it look more like the the be in
the game would now enhance
the color on essentially the saturation
at the final ans
know if I do this even more you'll see
that that's
what the effect it's having saturation
those items
and you can see I'm using the mouse
wheel to change the size at this
this circle here and that affects how
much
you know if I have it right at the top
did that fix every handle
if I have it small lot then it just 6
the handle in a motor when the armed
I would like to return to point out that
you can do in
doctor body contouring the gimpy despite
least unaware how to do it
his check out the edge fix remember that
are saying that the
shot missed had is relevant only to the
edge affects
all the wavelet fix that the because it
has put in
if you look here we've got to be what's
called an inverted gradient we have the
doc blocks
area here then we have a lineup
area and then we have a doctor area
again so it's almost like the opposite
of Halo in fact
and we actually can she get in the way
that the wavelets behaved by using the
shop miss here
look how the would now made this look
much more natural
by toning down the effect now if I pull
this write-up you'll notice
that I have an investor gradient it's
much stronger so
doctor will has a decent approximation
at that with the default
spline but the nice thing is that we can
modified if we know that we want to
to fix those edge affects so you might
be wondering at this point
a so if you've got the inverted
gradients
or the risk radiance what's the opposite
effect you might see future if you end
up dragging this client to cut down
this image isn't a good example so to
switch over to this imagery
just as a example something that will
exhibit this problem
and let's say I want to increase the
contrast
both this part d-mich by dragging this
up
they can already see that there's been a
bit in in 30 gradient career-best
gradient here
so if I go into the shot missed had
drags down you can see that I can reduce
that if I J 25 you already see
that we're getting halos around the edge
so this is the opposite effect that you
can get when
when the shot missed one is dragged too
low or
you might be an effect its present and
you could correct it by dragging
the shot this plan upwards in order to
to correct that their
a case let's return to our original
image
and let's talk a little bit about the
other function that the equaliser
provides and that's noise reduction
has a min a little bit on this area here
and then go into settling Metab and
bring up this bottoms Klein we can see
immediately
I'm not sure that you'll see it on
YouTube because at the including
the the noise is produced by drying up
just describe hand
potholes the is bottoms line and in fact
it's worth
large community checking out the Dino
easing preset if you wanna see
how this works you can always see that's
drawn up more the right hand side than
it is
at the left and that's because no is is
inherently just small
I tend to like using the Dino is subtle
but it's up to you what what profile you
use
one might just do is switch over to this
image here which
I've included because it's such high
Norway's just show you the power
what's what's possible let me just reset
this back
if you look at this noise in the wall
and in the the girls face here
I'm gonna try to reduce this new ways
in such a way that I retain as much
detail as possible. I'm gonna stop with
the chroma
tad here and I'm just gonna drew bring
this up here and you can start to notice
that
the noise in this small area here
becomes more uniform
becomes more almost black and white if
you like you'll notice that I can drag
this up
really really high at this point I just
hit the wrong spline lemme
let me whose dis in size and drag this
right to the top
you notice that you don't really notice
that much difference you'll notice that
her face is gone kinda
gray and let me to let me drag this down
so that I don't include her face so much
this color in the background here is now
just been made more uniform
let's now switch to Lumut and the let's
play with these bottoms flying again
I'll just pull this up little and you
notice that the noise is already
significantly reduced
but you'll see that if I drag this up on
too far to the left
I'll start to lose these lines in the
bricks those a larger features that are
represented by
these areas here so if I'll just reset
that by double clicking on it and all
reduce the size of my circle by
mass killing up you know drag this out
now a little bit
just be a little bit careful about what
I'm doing here just
really attempt not to lose the Daytona
bricks but
but reduced noise as much as I can
now looks pretty good now Posey night
you'll notice that the new is almost
completely
removed from this image and whether a
you know that's enough acceptable loss
and a telephone is is really up to you
but this you know this is my attempt at
noise reduction and you can compare
the splines with say the teen was subtle
and where with those end up that's a
pretty good
pretty good approach of course at this
point you have to compare the deal
raising thats
that's available in here with the denies
in profiled and the jewel
dual instance approached you can do with
the denies profiled which is the same
take underneath the same wavelets
but it also offers a non-local means
mode and
he also knows something about your
particular camera sensor and a
particular I so so can often be a
shortcut to removing the noise
you can see more about that in my nose
reduction video actually so I'll
post a link to that blood but it's
another technique that's available to
you
and and it's always good to have as many
this is possible it's always good to
understand how they work
okay suit one last thing before I finish
up this video not
and thats these dark grey Dan's email
may not have noticed in the background
here
what they signify is the bans that we
divided the beach up into let me just
reload this an image that we started
with
you can see here that we have various
different way that scales and you recall
that these signified the different
detail levels
of of the image now
what the doc Ray Bans correspond to is
essentially the same
being how is used but it into the
various wavelet scales
and what this actually indicates is that
because there's no bands in this
righthand section in the image
that means that our on a current
actually see what we do in that section
the image so let me just reset is back
to normal
and just make some changes in the very
far right-hand side of this
me make this little bit be a you see
that
the actual apparent difference on the
images is nothing
and that's because I there's no way that
scale that we can see
at this zoom level that is that is being
affected by the changes that are making
outside these these areas here which
have bands
you'll notice that as I Z mean these
bans moved to the right
some zooming in now right down into the
him to be
and you see now as I drag these changes
up and down
the we can actually immediately see the
the difference in the contrast
anyway I hope you enjoyed this video I
hope it gives you a sense
of the possibilities in this very
powerful module with that the local
contrast enhancement at various
different detail levels
whether that be I reduction in noise
whether that be bloomin other artistic
affects you know soft focus type:
affects
that a possible and I would really
encourage you to go check out some the
resources that are linked to below
and as always have a look at the
doctored manual
and read more deeply see later