TrashTheLens: Hong Kong Night Cityscape (exposure blending: RawTherapee, GIMP)

Hello and welcome to the second TrashTheLens tutorial Have you ever wondered how to make a night cityscape which has details throughout even in the extreme highlights? Well, today I will show you how we do it! Here we have a series of images I took one cloudy night in Hong Kong

I was looking across Victoria Harbour towards Wan Chai The tall tower here is called the Central Plaza and this structure below it, which looks somewhat like a turtle is called the Hong Kong Convention and Exhibition Centre We'll be using this is our base image because it has the nicest overall exposure It looks like what you would expect to see with your eyes when you were looking at a brightly lit city like Hong Kong at night But this image has some problems because here the highlights are completely blown out

They lack detail and the screens on the buildings over here are just rectangles of white light but we can fix that In order to do so we'll be using the highlights from the other exposures As you can see here when the image is under-exposed the screens are nice, crisp and readable So we'll be using the highlights from this image in order to recover the highlights from this image

In order to do so, we need to have those images match in exposure, more or less This image was taken at 1 second, our base image was 16 seconds so we need to take this image and bump up the exposure compensation by 4 stops We do so by going into the exposure tab and putting the exposure compensation of 4 here Here we go

The images more or less match when it comes to exposure but the darker image is somewhat more magenta There's some color difference between them But we can fix that by going into the white balance section and bumping up the tint towards green Like so The difference might be slight, but as you can see, when I switch between those two images they are a better match

We'll use the profile of this image and we'll just copy it into the other, darker images We do so by pressing Ctrl+C selecting the other two images and and pressing Ctrl+V As you can see the darkest image, here has lots of problems because it has some banding here the noise is terrible, but still the screens are nice and readable so I think we will still be using this image but we'll be selecting only the screens OK, so since our images are more or less ready let's select them all and load them into GIMP we do so by pressing Ctrl+B to put them on the queue, where they are processed Here we go

So here'we have our images loaded into GIMP Let's start off by hiding all the layers but our base layer Now, what we wan't to do is to replace the highlights of this layer with the highlights we take from other layers The shorter exposures So, in essence, we need some means of selecting the highlights of this layer

In order to do so we can duplicate the layer, and convert it into black and white using Colors > Desaturate > Luminance Like this Now we have a grayscale copy of our main layer In order to make a selection out of it we go to Channels and duplicate any one of the channels Like so

Let's call it "L" for "Luminance" We select back the Red channel go back to our Layers and get rid of the layer we just created So now we can use the channel we created as a layer mask for one of the shorter exposure layers So we go to the shorter exposure layer Let's reveal it Add a layer mask

and select Channel > L Now if we zoom in you can see this layer affects only the highlights Let's zoom out and take a look Overall it looks quite good We've replaced the blown-out areas with some details taken from the other layer

This here looks quite good The screens are readable But there are still some problems Most notably, the screen here is orange but the halo around it is rather blueish-like And also the halo around this screen seems to have some weird coloration

But we can fix it quite easily We do so by modifying the layer mask, by applying a curve to this layer mask Colors > Curves and let's apply an S-curve a steep one As you can see the halo around here looks much better

But let's do something about the remaining problems Namely this weird coloration here some greenish stripes and also this pink-magenta thingamajig here We can do so by selecting the layer mask Selecting a paint brush Black color paint and just paint over Like so It may not be automatic but it's easy and quick to do

Here Now, technically, this is blown-out but I think when the area is so small it looks just better Let's take a look I think what we should try to do now is to replace this orange screen with a version we have in our darkest exposure For start, let's just revert this area here to our original image Instead of this orange thing we got from our darker exposure

We do so by switching to the layer mask selecting a paintbrush black color paint and just painting in Like so OK Now let's place our darkest image on top of it Make it visible

select it switch the opacity down to, say, 50% and let's try to manually align it Pressing "M" for "Move" and something like that

It doesn't have to be precise Yeah, I think that's about it OK Now, let's first disable this layer by creating an empty, black layer mask Like so

Now, remember the channel we had for selection of lights? We can use it as a selection OK See, now it selects only the brightest areas So now we can paint in the layer mask Like so

Now choosing a smaller brush we can revert what we've what we've overdone Like so Now, it's important not to have hard edges But still retain some detail Let's see what we can do here No, it looks worse

How about here? Nah, it also looks worse Here? Also looks worse This is the only screen we can salvage from this darkest exposure Ok, let's get rid of the selection by pressing Ctrl+Shift+A Now

The screen's not really perfect but it has some detail in it, so I think we can leave it as is So here we have it The highlights restored, the image looks good All we need to do now is crop it, straighten it, maybe add some color corrections and we're ready Thank you for watching! If you want to find out more about by photography and travels you can visit my blog at TrashTheLens

com And if you're a photographer yourself and you want to have your photos reviewed by a friendly but constructive community you can check out LearnShotscom