hi i'm robin whalley welcome to lenscraft today we're covering the new divide blend mode that was
introduced in affinity photo 1.9 to explain the divide mode we'll use it to correct the colors
in this image which i shot in manchester one evening in case you think that the people are
standing too close to each other i did shoot this back in 2008 as you can see the image is
suffering from an orange color cast caused by the street lighting what i want is to show you how to
correct this using the divide blending mode but without causing problems in the scene i'll start
by adding a new fill layer to the image which is filled with white you might find that yours is a
different colour depending on your active colour when you create the layer the reason i want to
start with white is that it makes the fill layer invisible when i set the blend mode to divide
to be sure you have a white layer go to your swatches studio panel and choose the grey
swatches from the drop down you can then click on the white swatch which fills the layer with white
now i want to show you something that will help you understand the divide blend mode
watch what happens to the image brightness if i click one of the light gray swatches and use
that to fill the layer the image becomes lighter then if i pick a gray swatch that's around the
midtone gray the image becomes even brighter the way the divide blend mode works is that values
of the colour channels are divided by the value of the fill color on the layer when the layer
was at white it had a value of 1. if we divide any number by 1 it stays the same which is why a white
layer doesn't have any effect on the image but when we use a mid-tone gray it has a value of 50
or 0.5 if you divide a number by 0.5 you double it which creates the brighter image we can even
take this to an extreme by filling our layer with black which has a value of zero when we do this we
turn our image white because a number divided by zero becomes infinity now for those of you who are
big into maths ignore zero divided by zero for the purposes of the divide blend mode you still
get white now don't worry about the mathematics because you don't need to understand it to use
this technique what you do need to understand is that if you use the divide blend mode with a dark
color you will lighten the image and the darker the colour you use the lighter the image becomes
but when we use a light colour with the divide blend mode we don't lighten the image as much
and white has no effect now let's see how we can use this to fix the orange color cast in the image
the reason we see the color cast in the first place is because we don't have the correct balance
between red green and blue if we take the example of this greystone work and sample its colour we'll
find more red than green or blue that's what's creating the colour cast what the divide blend
mode gives us is an easy way to bring the three colour channels back into balance
the way to do this is to sample the colour from an area that should be neutral i can easily do this
using the colour picker tool in the tools palette when i click on the stonework it samples that
colour and applies it to the fill layer but look what happens because the stonework is quite dark
it makes the image too bright instead what i need to do is pick a light area that still has
a colour cast like the stonework near to the light now here's something to watch out for if
you click on the image to sample a color once the fill layer is visible you won't sample the color
correctly instead you'll sample the corrected color and this cancels out the effect of the layer
what you need to do is disable the layer before taking the sample then when you turn the layer
on again you'll see the correction now there's a second way to sample the colour in the image
that's potentially more helpful to us if i click and drag on the sample tool in the
swatches panel as i move over the image i see a magnified area this can help me see the pixel
area that i'm sampling better still i also see a readout showing the values of the red green and
blue channels for that point this tells me which of the channels is out of balance at that point
if i move over an area that should be a neutral color the three color channels should have roughly
the same value but if one of them is a higher value than the others it creates a color cast
then when i release the mouse button i take a color sample at that point this then appears in
the swatches panel if i'm happy with the sample i can apply it to the fill layer by clicking on it
this neutralizes the color cast but it's still affecting the brightness of the image a little
bit too much if you look at the area around the light you can see that it's becoming blown out
i don't mind this happening a little bit but the effect is just too strong at the moment
i think we can probably do better using a trick i'll show you now
so far we've taken a colour sample that corrects the colour cast although it may not be perfect
but if we use the controls in the colour studio panel we can tweak our results let's start by
checking if we can improve the color correction to do this we can use the rgb view in the color panel
be sure the fill layer is selected in the layers panel before doing this this will then show the
red green and blue channel values for the color that's filling the layer we can then use the
sliders in the color studio panel to adjust the fill color but before making a change i'm going
to first take a snapshot in the snapshots panel so we can compare our results later
now if i increase the red slider in the color panel it adds green to the image
and if i reduce it it adds red you can see what each of the color controls will do by looking at
the opposite side of the slider often you don't need to make any fine adjustments to the colour
balance at all but sometimes you have these complex lighting situations or it may not be
possible to take a sample at the area you want that's when you can use this technique in this
image i probably want to have a yellow color cast still on the ground because of the street light
but at the same time i want to have a cooler blue tint to the stonework higher up in the building
now we have the colours correctly balanced we need to do something to prevent the light areas
becoming blown out once we have the correct colour in our fill layer to neutralize the
colour cast the colour itself is too dark we can fix this by making it lighter using the hsl
adjustments in the color studio panel when i move the lightness slider to the right it creates
a lighter version of the same color now when i turn off the layer you can see that it's hardly
blowing out the light areas of the stonework this is much better but the color cast is back
because our fill colour isn't intense enough the way to fix this is to increase the saturation
let's take another snapshot now and call this refined correction
if i turn off the fill layer you can see the original image which is quite different from the
correction now let's compare this to the initial correction we made by returning to that snapshot
that made a reasonable job of correcting the colour but it's caused the image to
become too bright when we return to our refined correction it's clearly better
so that's how you can use the divide blend mode for colour correction
sampling the colour is important but you need to understand how the different components of colour
affect the result this allows you to use the rgb and hsl sliders to refine your results and
give you total control i hope that you found today's video helpful if you have
please let me know in the youtube comments and please share this with other affinity
photo users i'm robin whalley you've been watching lenscraft i'll see you soon for another video