How and Why to use 32 bit in 3D Renders – 32 bit workflow Photoshop tutorial

How and Why to use 32 bit in 3D Renders – 32 bit workflow Photoshop tutorial

August 20, 2019 5 By Peter Engel


hi my name is Joonas and next I’m going to
show you how to use 32-bit float workflow for your cgi images first I’ll
explain it in theory with some diagrams and then I’ll show it show an example
how to do it in practice so okay let’s go to the computer now I’ll try to
explain this rather simple thing in a simple way so let’s imagine that you
have a CGI scene with a very bright Sun and some some very bright light source
and some areas that are really really dark so your scene has a very wide
dynamic range and let’s say that this high histogram is representing that dear
the whole dynamic range of your scene and when you normally render out an
image JPEG or gif 8 or 16 bit image you basically have to choose which part of
your scene is exposed correctly and you kind of have to leave out something so
part of the image is going to be overexposed and part of the image is
going to be underexposed or like totally black so totally white or total black
because these areas that fall below zero or are above 100 those are going to be
clipped and the information is gone it’s just total white no details and this is
the year this is something that is common to 8-bit images and 16-bit images
so 58 jpg PNG and all those images but if you use 32-bit float images and then
you have the option to still bring back information that is fallen above 100 or
fallen below zero so basically you don’t see it when you when you look at image
the white parts over over exposed parts they look overexposed but the
information is there so basically it means kind of like I’m trying to explain
by using this transform function so I can kind of ugly lift stuff from
total black and I can recover highlights by compressing them inside the zero and
100 pounds and just to be clear when we do this this basically decreases
contrast but it increases dynamic range when we’re compressing the image it so
when we compress the dynamic range to fit into this zero and hundred space we
lower contrast so I’m going to explain by these two images and let’s pop up the
histogram just a second let’s put it to lumiose city okay it’s the intagram here
is a very low contrast image and as you can see the histogram is like compressed
it’s only in the middle but if I show you the high contrast version you can
see the histogram is spreaded to left and right so you’re going to hear you
can see that a contrast and dynamic range are kind of like well opposite
opposite things well kind of the same thing but on the opposite side anyway so
this is the theorem that if a scram and when you take a picture you lose
everything that falls below zero or is above 100 if you use 8 or 16 bit images
but if you use the dual bit load then you can recover stuff because the
information is still there so that’s the theory anyway
mmm so in practice here we have this is a 32 bit float image and as we can see
here we have some issues like the neighboring Wharf should not be white
and there’s another issue that sometimes you have when you render out 32-bit
float images is that the colors close to zero that are close to black kind of
start to go invert inverted so I’ll fix that
and let’s fix this window as well so let’s start with the window so in the
fix the window will use the levels adjustment layer most of the adjustment
layers are not accessible in 32-bit float but the levels is so let’s use
that and here and we’re going to use this down up
a slider below the main one that we normally use this but the this time
we’re gonna use this and this basically decreases contrast and by decreasing
contrast it will increase dynamic range so let’s see we slide it back we start
to get detail like the bricks individual bricks of the walls start to be visible
so now we have the highlights recovered next let’s kind of fix the color issues
here so I don’t really know how what causes this but I know that this weird
coloring is because the hues are inverted and we can do it by clicking
this slider and bring it up in this case about 30 the word 24 maybe so now it’s
very very very low contrast image but again low contrast in is high means high
dynamic range and the colors are kind of straited out straight and well
straightened out so it goes up what they supposed to be they are not inverters so
now this is basically the 32 bit float part and now we just go mode 16-bit
image mode 16-bit and yes we want to merge the whole thing I’ll choose
exposure and gamma because this keeps the the image visually identical and
okay and then I’ll bring back and now you can see we have these adjustment
layers back back on track so we’re going to use them as well as we want so I’ll
choose the exposure now though I’m in the curves and I’ll just bring it back
blacks down and then I’ll make nice kind of like gamma adjustments all in like
this something like this and now we basically have well image that we have
we have controlled we have what’s the word we have been mastering the dynamic
range of the images correctly and next I’m going to show you how to do after
this like look after this global assessment I’m going to show you how to
do local adjustments I’ll now show you two techniques the first one is
example the first one I’ll I’ll give a nice pop to the floor so I’ll make
another curves adjustment layer then I’ll be tough I will be watching just
the floor and I’ll add a bit of contrast to the floor so it looks good
it’d be too much well I guess it could be nice that’s just it a bit more let’s
say that’s that’s good and into an – to effect this only to the floor
I’ll make the mask inverted and then I’ll take the brush tool make the brush
big and nice and add the flow about 20 somewhere there and then I start I will
add white and I start painting in the mask so painting white to the mass so it
will wherever it’s the wherever the mask is white there it will say it will be
applied the layer will be applied and welds black the delay will not be
applied so that’s about it so now again we now going to see that the floor got a
quite nice remake and now I will show you another one
so this was this kind of like brute force technique just by well adding
white paint in white but next let me do a bit more advanced and this time I want
to bring more kind of like want to bring more clarity I would say that they’re
highlights the window part I’ll create another contrast slider again and then
I’ll just bring down the exposure like this and then I’ll add em now I’m
looking only at the window because we can unmask it quickly and then I’ll add
this bit of vibrance and bit of saturation and if we put this into a
group you can see that they well the outside looks bit better now so to to
apply this layer only to the window I’ll use something called a luminance
mask so I’m going to create a mask based on the luminance values of the image and
that is done easily with this free plugin from Jimmy McIntyre and with this
blocking I can just create a price mask and now it created these extra channels
where I can choose what I want to like what part what part of the luminance I
want to emphasize and let’s say this looks well let’s use this this this
looks quite nice on them so our ass again and here I can chain of blue black
parts are not affected and the white parts are affected and everything in
between depending on the shade of the gray will
will be gradually more and more affected so let’s create a Content a second here
yep let’s create a mask to this group let’s invert it so basically making it
invisible then choosing this pride mask one pressing command and then pressing
click on this now we have this and we have to click this RGB layer by the RGB
channel back to have the correct colors and now I’ll start painting in just the
part that I want to affect so let’s make a big nice brush a maybe not that big
and I’ll just paint in with the whole flow is good
well paint in what I where I wanted to effect I’m just painting like this okay now I’ll command D to deselect the
marching ants and here you can see that I kind of give a slide well I brought
the down the highlight part set a bit and if we want to add the mask as you
can see here this is a mask and all the dark parts are not affected only the
white parts but I still want to kind of refine it and I’ll just add a bit of
black to this edges let’s have the glow bit lower there and I’ll just add a bit
of map black to restrict the effect of the layer just do the parts that I
wanted to effect so let’s see maybe not something like this okay let’s see not good yeah okay so he were here we
had the two techniques of just brute force painting the masking or then using
this free blocking from Jim Jimmy McIntyre to create this luminance mask
and then do a bit more defined work okay so here it is thank you and go ahead and
practice bye