Highlight Clipping

Using a contrasting scene with many highlights and shadows, I was to take a series of five photographs to study how aperture and shutter speed affect the highlight clipping that I would experience in the final image. Starting at f/10 where I could first see the clipping occurring in my camera’s preview window, I then took another at f/11 (which would give me slightly more clipping) and then opened up my aperture to take a sequence opening up the aperture one stop at f/9, f/8 and f/7.1. This gave me my five shots to work with.

I opened the images up in my image editor, viewed them without any adjustments and turned on the highlight clipping warning to see where the clipping was occurring. The first thing I noticed was that the results were not as pronounced as in my camera preview. The main reason for this is that the camera gives a JPG preview (i.e. it is compressed) and I was viewing the RAW images (with all the information available). With the images open I was to look for the following artifacts within the clipped areas of the images:-

  • Completely lost areas of information
  • A visible break in the form of an edge between nearly-white and totally white
  • A colour cast along a fringe bordering the clipped white highlight
  • The colour saturation
ISO 200 f/11 1/125
ISO 200 f/11 1/125

In the image above I can see clipping in the clouds and on the tower top at the right. I blew up the image to 100% to get a close look at the clipping and to see if I could discern the artifacts as listed. I should mention that actually I was trying to get the ski-ramp to be over exposed and clipped but the camera was coping with that range quite well as it was close to my area of my exposure meter.

f/11 Highlight warning off
f/11 Highlight warning off

With the highlight warning switched off I can study the area of highlight;

  • Areas of lost information appear right at the centre of the clipped area (the horizontal bar at the top of the tower) and produce a white bar across the tower.
  • There isn’t a clear break in an edge between white and off-white as the structure goes in to shadow very quickly and this produces the definite break with the highlight.
  • In the original RAW image I can see some fringing (greenish in colour) along the borders. I don’t think this is very easy to detect in the JPG above.
  • The colour saturation as a whole for the image is fairly good as the highlight clipping is minimal which still gives a good colour saturation overall. If I had underexposed to stop the clipping then I may have found the colours starting to be muted.

Now I took the image and used ‘recovery‘ within my RAW converter software. This is a tool which will reduce the clipping in each colour channel of the image (RG and B) rather than just reduce the brightness and highlights as a whole. This has the advantage of only needing to rectify the clipped channels thereby leaving the unclipped colour channels to display their original colour.

I found the overall effect of using recovery, depending on the amount of clipping I had, ends up deadening the colours. This is due to the fact I have clipping in each colour channel and so it has to reduce each channel rather than just one or two. The final result of using the recovery tool on my image wasn’t too pronounced as there wasn’t too much clipping to begin with but I can detect slightly less contrast in this image below (again, quite difficult to pick up on the web-based image but there is slightly more detail on the balcony that was clipped).

f/11 with 'recovery' tool applied
f/11 with ‘recovery’ tool applied

Personally, I would prefer a small amount of clipping which doesn’t affect the overall ‘look’ of the photo too much rather than a ‘technically’ produced image that has had the highlights taken down but also the contrast that goes with it. My favourite (technical) image from the series still has some slight clipping on the tower but it is a tiny percentage of the overall image, so really does it no harm.

ISO200 f/9 1/320
ISO200 f/9 1/320

The hardest thing about this exercise was the inconsistency in weather and sunlight. To get consistency in these images took some some time and indeed I had to re-shoot once as the lighting varied so much and gave wildly different clipping on the same f-stop.

The conclusions I reach are;

a) I have no control over my lighting in this type of environment and will either need to shoot as-is if it is time critical or have some patience if I want to get an absolutely perfect image.

b) The smallest change in lighting (colour temperature, direction of light etc) makes a massive difference to the end result.

c) That although it would be desirable to have no clipping, sometimes in order to get the best overall result it may be unavoidable.

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