Colour Grading Photos: Simulating Time of Day
Continuing my series on Colour Grading Photos, this week we are looking at how we can use the techniques we have learnt so far to change the time of day. In this series we are taking inspiration from the techniques used by colourists in film/TV to use colour to effect mood, time of day or create a stylised shot. Please note: we are not aiming for perfect colour reproduction, we are in the realms of creative photography and so there is no right or wrong here it is purely down to what you want to achieve as an artist.
As many of you will know weather and the time of day has a significant effect on our digital cameras white balance. If you look at the graph below you will see how. We measure the colour temperature of light using the Kelvin scale and as you can see illustrated the colour temperature of the mid day sun (~ 5000k) is considerably colder than sunrise (~ 2500k). So when suggesting the time of day we need to take this into account and change colour accordingly.
For the sake of illustration, we are going to use this picture I took of my good friend Dan when we visited the old disused gunpowder factory at Kennel Vale. The picture below is straight out of camera, with only minor white balance adjustment. One thing to point out here is you should address any white balance issues before you apply any of the adjustments.
Golden hour (or Magic Hour as referred to in cinematography) is used to refer to the first and last hours of light each day. During this time the colour temperature is a lot warmer and the sun gives off a golden light (note: Golden hour also gives you longer shadows but we are concerned with colour here, but keep this in mind in you are simulating this time of day). As we have seen in previous exercises we can use either Curves Adjustments or the Color Balance tool to push our overall colour around and simulate Golden Hour. For sake of simplicity, I am going to use the Color Balance tool here as it is easier for those unfamiliar with Curves.
The method I like to use, to achieve a Golden Hour look, is to push yellow into the highlights. Add a new Color Balance Adjustment Layer by selecting Layer > New Adjustment Layer > Color Balance... By default the Color Balance tool will be set to affect the mid tones, as we want to target the highlights we need to change tone to highlights then adjust the blue-yellow slider moving the slider towards yellow until you have a nice warm glow in your highlights. We can have warmth in the skin tones as this is the whole point of Magic Hour, but if you are introducing too much warmth (which are generally in the midtones) we can either add a mask to this layer and mask the tones out slightly or use the same adjustment layer and switch the Tool to the midtones. Then slide the same yellow-blue slider back into the blue to pull back some of the added colour. Note: your changes to the highlights are not lost when you switch the tool back to midtones.
When simulating midday we need to consider the weather and where the image was shot. If it is cloudy or was taken in the shade then our light needs to be cooler than if shot in direct sun, which would need our whites to be balanced correctly. Also when cloudy the light is diffused and so we have less saturation. In our example below, I am happy with the colour of the original and so we just need to increase the contrast slightly by increasing the exposure in the Highlights. We can do this easily with a Curves tool (okay I said I was avoiding curves but here we are going to simply adjust the luminance which is easier than adjusting colour) and dragging up the luminance (RGB) curve as shown below. I have also reduced the input range slightly to darken my shadows.
We can achieve an evening look again with the Color Balance tool, we need to use the yellow-blue slider again but this time we want to drag the slider towards the blue. You may find this starts to introduce red into the image in which case you can compensate slightly using the cyan-red slider, and slide towards cyan to remove the redness. Once again we can reduce the effect on any skin in the midtones slightly (remember we expect to have a blue cast on the skin as the main light source in coming from the sky which is blue) by switching the Color Balance tool to the midtones and adding yellow with the blue-yellow slider. We also need to reduce the overall exposure of the image, we can do this with a exposure adjustment or use curves, as I have done below, pulling down the midtones.
Day for Night
Producing a day for night grade can be quite tricky, but using the skills we have discussed here we can achieve a fairly convincing day for night look. Starting with the evening adjustments above, we can basically push these further to get a darker and bluer look. Firstly with the Color Balance tool, you can almost push the blue-yellow slider right into the blue. You may find this introduces magenta into the skin tones, again compensate slightly in the midtones using the blue-yellow slider towards the yellow. You can also pull some of the magenta out using the magenta-green slider and sliding into the green to suit.
Next we need to pull the exposure down further, return your input and output values to 0 and then pull the midtones down to get a much lower key shot.
Finally we need to reduce the saturation. Add a saturation adjustment layer and pull down the saturation until you get the desired effect.
So as you can see we can get some pretty convincing looks that can suggest a different time of day than from when they are shot, or you can use these techniques to emphasise the time of day of your shot.
Next week we will start to look at how we can achieve some stylised looks using these techniques.