Astrophotography challenges are often around the foreground compositional elements rather than just capturing the milky way. There have been many ways to deal with lighting the foreground – light painting, moon lighting and so on. Something that I will only briefly comment on is exposure blending and composites.
Quality of light – I’m really referring to aspects like the quantity, direction, size – soft/hard, tone and so on. It’s also very reasonable to have a silhouetted foreground interest.
Light painting often has problems with the very sensitive exposures which may over expose the foreground. I use a broad beam LED light and directly paint far objects (due to light drop off) and diffuse paint closer surfaces. Lighting tends to be very hard light when direct. Diffusing the light I tend to reflect off my cupped hand or have reflected off something else (handy having a friend here with a white shirt). I tried using an actual reflector to use to shine through or reflect off before, but this wasn’t as controllable as cupping off the hand for a brief moment, and also the wind tended to make it difficult. Issues that I feel are with light painting can be around colour balance (it’s white – and you may have to colour balance a different sky or ambient).
Light painting tones will depend on whatever form of light you’re using – such as a white or red LED. If you’re bouncing the light off a surface, then it will adopt some of the colour of that reflected surface. You can also consider using gels to change the colour.
I have found that a lower ISO (or aperture) setting worked well for a light paint – it wasn’t so harsh because it was easier to control. This was done on an ISO of 400 (Canon 550d F2.8 ISO 400 120s) on a barn door tracker. The light paint was for 15s and then the barn door tracker was then activated for another 1 minute 45 seconds.
This is my favourite form of lighting. It paints light over the whole landscape and can create shadows and depth. It’s also much harder to manage.
- Moon luminosity – a bright luminescent moon will cause the sky to go blue as it lights the atmosphere. It can also overexpose the landscape. My preferred moon luminosity is <20% – and closer to 10%.
- Moon elevation – a moon that is high in the sky is just like shooting in the middle of the day – the angle of light will create similar shadows as if you’d shot a normal landscape shot in the middle of the day. A rising or setting moon will be less luminescent and can create more depth to the image with shadows.
- Moon in relative position to the Milky Way core – if the moon is too close to the milky way core, it will overpower the detail.
- Clouds – if you’re shooting and the moon is behind clouds – then the luminosity will decrease and the light will diffuse. Otherwise it will be hard light.
- Rising/setting moon will often change the tone of the light as well – when the moon is getting close to rising/setting, it’s just like a sunrise/sunset and atmospheric refraction may cause it to go red.
- Considering moon lighting – you’re then looking at the the direction of light as well.
Moon lighting at about 40% luminosity and at about 45-60 degrees elevation and about 5 o’clock (ie behind to the right). The brightness of the moon causes the sky to adopt a bluish tone and the milky way becomes a little less distinct.
Moon lighting I recall to be about 7% rising from 4-5 o’clock (behind me) resulting in a front lit situation. I exposed longer in this instance to bring out more of the foreground due to the lower luminosity – however front lighting still results in a bit more of a flat lighting.
Moon lighting of about 13% – this was side lighting and created more depth in the image with the foreground casting shadows. Due to being a panorama – the moon is visible in the top right.
There was another direction of lighting off course – back lighting. This year there was only twice that it was available at the right luminosity and direction and unfortunately a cold front hit each time and I was unable to get the image. For the tests – I can see that it did create long shadows – which was exactly what I wanted – but was spoiled by the amount of clouds. This was shot at about 20% moon luminosity (brighter than what I would normally prefer) – noting that as the moon sets, it loses brightness.
If you expose enough – star lighting will still light the landscape. However since it’s coming from everywhere, tends to be very diffused and rather flat lighting. Probably a better way of lighting here is actually combining lighting elements. the ambient light would light the landscape and you could still use a hint of light paint to create more depth in the foreground elements.
Light pollution is a problem – but you can always use it as an opportunity to help create depth as well. Depending on your location, the combination of star light and light pollution can create slightly diffused directional lighting.
You can use flash to light the environment or be a component within the image. When using it to light the environment, you have the issues of light drop off with the inverse square law and possibly issues with size and direction of light. The advantage of using flash to light is that it’s able to be precisely controlled (power/direction) rather than relying on how quickly you flash a light over the scene with light painting.
In terms of flash lighting – I’m still ultimately exposing for the ambient and using the flash as supplemental light. So in this image – the darkened areas behind the Pinnacles is still visible by the exposure – but the flash will create more depth around the landscape. I used 1/128 for this image with a Gary Fong (GF) lightsphere – so that the flash would spread in a particular pattern around – rather than having a narrow direction. Since the flash was at it’s lowest power – the GF also causes some drop in light. If I needed to drop the light even further – I could have used gels or put something else in the GF to reduce the light (like paper on the flash etc). Also in this particular image, doing a panorama – after taking the image with myself, I placed the flash on a tripod to gain consistency of light with the rest of the panorama images.
EXPOSURE BLENDS and COMPOSITES
I’ve done both before, but don’t generally do them just due to personal preference.
Exposure blending is taking a separate exposure for the foreground interest with a combination of – lower ISO, narrower aperture, longer exposure. All of which is done differently to the sky exposures with the view to improve image quality. Using them for the sky would usually result in star trailing. I’ve seen quite a few on 500px as well that the exposures have been done at significantly different times so that the pre-dawn or post dusk light can be used to generate foreground interest with some texture in the foreground generated by the light (back/side/front).
Composites – generally you can use anything. since the milky way is disconnected to the other elements of the photograph.
While I don’t really do these – all that really matters is that you’re happy with the image.
This list is off course not meant to be exhaustive.