Previous tutorial articles have looked at how to create light drawings / light trails and illumination light painting. This article looks at how I post process my light painting photos.
Optimal Camera Exposure
The most important step before you post process your photo is getting the exposure right in the first place. Shoot in RAW. Whilst in-camera JPEG processing engines have improved considerably during the last decade, you will get much more control of the your final photo if you shoot in RAW. Spending many years shooting JPEGs is one of my biggest regrets in my photography journey. There are still a handful of light painters who push a "straight out of camera" JPEG agenda. This is quite uniformed as ALL photos are post-processed. JPEGs are post processed according to manufacturer's JPEG engine algorithms, RAWs are post processed by the artist. The same goes for local adjustments. Local adjustments can be made with film in a darkroom, so there is absolutely no reason why you can't use local adjustments in digital post processing.
Make sure you focus correctly, as you cannot correct a blurry photo in post processing. For most use cases, use as bright a flashlight/torch and tool combination(s) as you can get away with so that you can use as low an ISO as possible. If you need to use an ISO above base ISO, take advantage of your camera's second noise floor if available (for example on the Sony A6400 it is ISO400). Try and use an aperture that will result in a sharp photo, this will depend upon the lens, but f/5.6 to f/11 is usually optimal. Thankfully most new lenses (including kit lens) are sharp enough throughout the whole aperture range. Much to the annoyance of other light painters, I always have Long Exposure Noise Reduction turned on. This increases the amount of time you have to wait for the photo to appear on the back of the camera, but gets rid of hot pixels most of the time, even during >30C Australian nights. I set White Balance to Auto, as Temperature/Tint can be adjusted in post processing. Use available in-camera tools to make sure the horizon is straight. If you intend on posting a portrait orientated photo to Instagram, compose the photo taking into the account the annoying Instagram 4:5 aspect ratio limit.
Most importantly, don't overexpose any element in your light painting (unless your are purposefully intending on doing that). Most cameras can show overexposed (clipped highlights) areas of the photo on the back of the camera. Pay attention to parts of light painting tools that are closer to the light source (e.g. the light source end of a lightsaber), as these are often overexposed. Additionally, zoom into the photo and check for any obviously overexposed areas. Checking the histogram may help, but light paintings tend to defy the usual rules of using histograms. Review the exposure, and if over or underexposed, adjust your camera exposure (Aperture or ISO) and/or light source brightness as required.
RAW Processing
This section describes how I usually post process light painting photos in Adobe Lightroom Classic. There is no right or wrong way to post process photos, this is just how I currently do it. Techniques may vary depending on the camera used and post processing software, so this advice cannot always be taken verbatim.
After importing the photos, I place them in Collections organised by Month and Year to keep things tidy. I will then review the photos in Library, and give 1 star rating to photos that will proceed to post processing. I then filter by 1 star ratings, and move into the Develop module.
Approximately 95% of my light painting photos are processed in a similar way, with some exceptions, usually light painting portraits. To make it easy for myself, I saved my usual settings (below) as a Lightroom preset, and apply that preset when I start post processing each photo. Update June 2024 - I have created a Lightroom preset pack which contains the below settings. The list below lists the presets and how I may modify them:
Treatment: Colour; Profile: Adobe Colour
Temp/Tint: As Shot. The white balance will be adjusted as desired, though my camera usually gets it right. Photos using lights with RGB colour mixing usually require an increase in Temperature, as RGB LEDs mixed results in very cool white.
Exposure:0. This will be increased as desired (typically between 0 and +3)
Highlights: -70
Shadows: +70
Whites/Blacks: 0. I rarely need to touch this my current Canon R8, and previous Sony A6400. With my older Nikon D3300, I often had to make small adjustments by holding Alt+adjust slider with mouse until Black or White clipping was just starting to appear. If the average of these ended up being +/- O, then I would advise further adjusting Exposure, and then re-adjust Whites/Blacks.
Texture: +35. I prefer to use Texture to add local contrast instead of Clarity and Dehaze. I may occasionally add +10 Clarity for my Urbex photos. For noisy photos I will decrease Texture to +15 or even 0, as adding local contrast introduces more noise.
Vibrance: +10.
Saturation: +10 (+25 for RGB lights).
Tone Curve: Point Curve - Medium or Strong Contrast. I rarely use Linear.
Sharpening: I use the default of Amount:40; Radius: 1.0; Detail: 25; Masking: 0. I rarely change these.
Noise Reduction (Luminance): Luminance: 30; Detail: 50; Contrast: 0. I will increase Luminance as required, but don't like to go over 70 in extreme situations. I only tend to use the AI denoise for very low light portraits, and rarely for light painting. The AI denoise requires newer discrete graphics cards (GPUs) for best performance.
Noise Reduction (Color): Color: 25; Detail: 50; Smoothness: 50. I only need to increase Color setting on the very rare occasion that there are hot pixels, which tends to only occur on very hot summer nights in Australia.
Lens Corrections: Set to apply default lens profile lens correction.
Additional global settings that I occasionally apply (<20% of photos) include:
Crop/Straighten - I will crop and straighten as required. For portrait orientated Instagram photos you need to crop to the rather restrictive 4:5.
HSL - sometimes I may adjust Hue, Saturation, and Luminance if one colour is "not quite right".
Transform - it is very rare that i need to use this for light painting photos, though I use it often for Cityscapes.
Effects - I may occasionally add a post-crop vignette up to -20, though my ultra-wide lens adds a vignette by default anyway!
Calibration - this can sometimes be more useful than HSL or Temperature/Tint to make global hue adjustments. Useful for getting a nice Cyan.
Local adjustments that I occasionally apply (<20% of photos) include:
Adjustment Brush/Graduated Filter/Radial Filter - I try to use local adjustments sparingly. I may use these to adjust settings in parts of the image if there is a deficiency that affects the overall balance of the photo (such as removing some lens flare with locally applied Dehaze).
Spot Removal - whilst I prefer not to add or remove pixels, sometimes it is useful to remove unavoidable blemishes such as light painter's feet in light painting portraits, unsightly paint splodges on tunnel floors, obscene graffiti in tunnels, and other things you just don't want in the photo. Update June 2024 - the new generative AI spot removal tool is Lightroom is a big improvement!
Below are some exceptions to my usual post processing settings. The first is a light painting portrait using black fiber optics and an RGB light. Here I wanted a black background, so I left shadows at 0. I also wanted to the light trails and model to have optimal brightness in the photo, so the exposure was increased, but highlights decreased. Indoor light blading against a black background often works well with similar post processing.
The second example is a slow shutter speed / low light portrait. Whilst I used manual mode with set aperture and shutter speed, the ISO was automatic (essentially ISO priority), and the camera nailed the exposure. For this photo I only had to make a very slight adjustment to exposure, and all the other sliders were at 0. I avoid raising the shadows in high ISO portraits as it just adds more noise to the photo, requiring heavy use of noise reduction to resolve.
Organising and Exporting
When I am happy with a post processed photo, I usually increase the photos rating to 2 stars, and if further image selection is required (such as after portrait sessions) I may use more star ratings to narrow down the field. I'll export the photo separately for each purpose, and I don't apply any further processing such as sharpening. I usually export with sRGB colour space, JPEG at 92 quality. Image sizes exported are Instagram and Facebook at 1,080px on horizontal edge, Reddit at 1,200px on horizontal edge, and for this Website at 2,560px on longest edge. Ignore DPI/PPI unless you are printing, as DPI is irrelevant for web use.
Composites and AI Generative Fill
Composite or layered images are where two or more photos are blended into the final image. This may be performed as an in-camera double exposure, or in post processing applications such as Photoshop. Some members of the light painting community can be rather "anti-composite post processing", but don't let that stop you being creative. Many light painters who perform commercial work use Photoshop in their post processing steps. If you can realistically create a light painting in one image (don't forget about lens capping technique) then absolutely do that. If it is not realistic (e.g. like a double exposure from 2 different locations on separate nights), then do it in-camera or in post processing. There is still considerable skill required in aligning in-camera double exposures and Photoshop technique! It can also be fun to add digital manipulation to light paintings in applications such as Photoshop (in particular adding blur layers) or Mirrorlab (which can do far more than just mirror images).
In the last few years generative AI has become more popular. It can be used to change a background, or fill out a "too cropped" composition. It isn't my cup of tea, but I've seen some interesting creations by other artists. If you do use composite images or AI generative fill then I would highly recommend being honest in the image description on social media, and mention how the image was created.
Conclusion
There is no right or wrong way to post process light painting photos, but getting the exposure right in the first place will help considerably. Make use of RAW processing to add that extra polish to your photo, and don't be afraid to use Photoshop or AI if you want to add some creativity.
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