Colour Cast and White Balance

Natural Outdoor Lighting

To familiarise myself with the white balance setting on my camera I am going to shoot three outdoor scenes with different lighting conditions (Cloud, Sun and Shade). For each condition I will take four shots using a different White Balance setting each time (Auto, Daylight, Cloud and Shade).

First of all I chose a scene with some Red Dear being the main subject. This scene is in the cloudy condition.

Cloudy

Using the cloudy white balance setting, the colour of the dear appears perfect but I feel that the white clouds between the trees appear slightly pink or red.

Auto

The Auto balance setting has removed the pinky/red haze from the background but it seems to have dulled the tones of the dear's fur.

Daylight

Daylight has had a very similar effect, it has dulled the fur and also given the background a very blue haze.

Shade

Finally, the shade balance has kept the dear a nice colour but the background is now far too pinky/red.

From all the settings above, the Cloudy setting has definitely given the best result but I would prefer there to be less of a pinky haze in the background. I would be inclined to edit this shot using Photoshop to see if I could put it's colour somewhere between that of cloudy and auto.

Sunlight

Daylight

Auto

In the Auto shot, the colour of the lighthouse has turned slightly orange and could be mistaken for a shot taken as the sun is rising or setting. The sea is also very dark in this version.

Cloudy

Similar to the daylight shot, however it appears to lack as much depth and could do with more contrast.

Shade

The shade shot seems to have made the sea appear black. There is also still a slight yellow/orange tone to the white paint of the lighthouse.

The daylight white balance setting has definitely produced the best results in this sunny scene.

Shade

Shade

The shade setting has made a very good attempt at balancing this shot, it may be slightly too orangey though.

Auto

The auto setting clearly didn't know what to do here, this version is far too blue.

Daylight

This setting isn't actually that bad however it's sightly too blue which is most noticeable when looking at the highlighted areas on the red leaves. Saying that, I feel this shot is acceptable.

Cloudy

Cloudy has done a very good job at balancing the colour here, it's very similar to the shade shot, but still appears too blue.

After reviewing all of the shots from the shadey condition, the shade balance has definitely done the best job at balancing the images colour. I still feel that it's slightly orange but when viewed side by side with another it's obviously the more accurate representation of the scene.

In the three conditions above, the best results have been produced when shooting with the white balance setting that corresponds to the condition. If a specific effect/colour cast is desired, then choosing an opposing setting can give very nice results. Also, if shooting in RAW format, it is possible to change the White Balance setting after the time of shooting using RAW processing software such as Adobe Camera RAW. This is extremely useful for those times when you just forget to change your camera's white balance. With Adobe Camera RAW it is not only possible to alter an images white balance setting, there is a temperature slider that can be used to customise the white balance to give a very specific colour tone.

Mixed Lighting (Indoor and Outdoor)

Next I will look at white balance settings for a mixed lighting condition. I shall shoot one photo from inside the house looking out and one from outside looking in, experimenting with the Sunlight, Tungsten and auto balance settings as I go.

Auto

Using the Auto White balance setting, my camera has performed quite well in calculating the tone for the inside of the house, however overall the image appears to have a blue haze with the outside area in particular being very blue.

 

Daylight

Using the Daylight setting, the outside area now has the correct colour tone but the inside area appears quite orange due to the tungsten lamps.

 

Tungsten

Finally, using the Tungsten setting has turned the outside area extremely blue but has done a nice job with correcting the tones for the inside area. A lot of light from outside was spilling in through the patio doors (seen in the shot) and widows (to the right of the shot) and therefore even the tungsten light areas have a slight blueish haze when using this white balance setting.

Out of the three images above, I feel that the Daylight balanced image is the most accurate and aesthetic representation of the scene because the outside area has the most accurate colour tones; with it being the main focal point of the shot this is more important than the inside area having the correct colour tones.

Dynamic Range

The Dynamic range of an image is the range of tones between the brightest highlight and the darkest shadow. It is sometimes referred to as the contrast range but dynamic range is a more accurate and appropriate description. The dynamic range of a scene is the number of stops between the brightest highlight and the darkest shadow and therefore the dynamic range of a camera is the number of stops it can capture in a single frame. If a camera’s range is lower than that of the scene, detail is lost in clipped shadows and highlights, however if it is greater than the scene, no detail is lost and the image produced won’t contain any clipped highlights or shadows if exposed correctly.

Camera Dynamic Range

To roughly test the dynamic range of my camera I will shoot a scene containing both bright highlights and dark shadows and calculate the range between them in f stops. To do this, first I needed to wait for a sunny day and find an appropriate scene. Luckily I didn’t have to wait long, I decided to use the bright white door of our garage as the main highlight of my shot. A shaded area under a bush in the background provided an adequate area dark shadow.

I set my camera at ISO 100 to minimise the possibility of noise and chose an aperture of f/8 to keep the entire scene in focus. I also used the evaluative metering mode so that the my camera would tell me when the scene was correctly exposed. Before taking the shot, I made sure that there was as little highlight clipping on the door as possible. I couldn’t under expose too much as I would’ve lost a lot of detail in the dark areas.

1/160 sec

The shutter speeds written on the image indicate what it would’ve taken to correctly expose these individual areas. In order to find these shutter speeds I changed my camera’s metering mode to “spot” and zoomed into each area using my 200mm telephoto lens. I also took photographs of each image as I recorded the shutter speeds, these can be seen in the gallery below. I didn’t use a tripod so in the shots of the darker areas with slowest shutter speeds, there’s a quite a lot of camera shake blur.

Spot Metered Shots VIEW SLIDE SHOW DOWNLOAD ALL

Using Photoshop’s pixel value sampler I can see that the majority of the door’s tonal values are between 240 and 247; this is obviously right at the brightest end of the scale which runs from 0 (black) to 255 (white), any brighter and the area would have been highlight clipped. To find the darkest area that still contains detail I moved to the shadows at 100% magnification and increased the exposure by 2 stops so that the detail was visible. The image below shows the shaded area under the bushes clearly has a lot of noise now that I have increased the exposure.

The darkest pixels I can find that contain actually detail and aren’t “just noise” have values between 15 and 30 with the red channel having the highest and blue the lowest values in each area I test. The values drop to between 5 and 18 when I undo the extra exposure, telling me that the detail I see is in fact detail because if the values were now below 0 then what I saw a moment ago will have just been noise as detail can not just appear out of pure black. It is blatantly apparent that photographs contain much more noise in dark areas and therefore to retain as much detail as possible it is best to over expose these areas and then darken later using image manipulation software such as photoshop. However, overexposing an image with very bright areas will result in highlight clipping and so should be avoided. Slightly underexposing a shot of a bright scene and then increasing it’s exposure later is also something to think about. If a scene has a higher dynamic range than that of the camera, a tripod can be used to capture multiple versions of the shot, each at a different exposure and these can be merged together during post processing to create an image of maximum detail with a higher dynamic range than previously possible by a single shot alone.

Dynamic Range in stops

I have also calculated the dynamic range of my shot in stops. If the darkest area (containing visible detail) needed to be shot at 1/10 sec and the brightest at 1/1600 in order to correctly expose them and my camera was able to capture these areas in a single shot (without shadow or highlight clipping) it means that my camera’s dynamic range is at least 7 stops, if not 8. This seems to approximately comply with the findings of other people for my model of camera (Canon EOS 500D) but I have read claims of a range up to 11 stops.

Scene Dynamic Range

In this section of the post I shall explore study a variety of different scene to find their Dynamic Ranges in stops using the same technique as above.

High Dynamic Range

ISO 200  f/5.6  1/100s

Bright Area (Top of Hedge) – ISO 200  f/5.6  1/2000s

Dark Area (Shaded area of tree in foreground) – ISO 200  f/5.6  1/8s

Range in stops – 8 stops

 

Average Dynamic Range

ISO 200  f/9  1/640s

Bright Area (Flower) – ISO 200  f/9  1/1250s

Dark Area (Moss in background) – ISO 200  f/9  1/13s

Range in stops – Approximately 6 and a half stops

 

Low Dynamic Range

ISO 200  f/9  1/320s

Bright Area (Bottom Right Slab) – ISO 200  f/9  1/400s

Dark Area (Crack in middle between slabs) – ISO 200  f/9  1/30s

Range in stops – Approximately 4 stops

At a glance this scene appears quite flat thus one would assume it has a low dynamic range, however I would consider a range of 4 stops to be quite average and when viewing the histogram the values are spread quite far across the tonal scale therefore giving it an average range.

 

Average Dynamic Range (2)

ISO 200  f/9  1/80s

A lot of the sky has been clipped in this shot but there are parts where it’s blue colour is still slightly visible.

Bright Area (Sky in background) – ISO 200  f/9  1/2000s

Dark Area (Leaves at top of image) – ISO 200  f/9  1/60s

Range in stops – Approximately 5 stops

 

Low Dynamic Range (2)

ISO 200  f/8  1/1000s

Bright Area (Whitest Cloud) – ISO 200  f/8  1/2000s

Dark Area (Grey Cloud) – ISO 200  f/8  1/500s

Range in stops – 2 stops

RAW

I’m going to shoot three images in RAW and JPEG format to try and discover the differences between the two and the advantages of shooting in RAW. I shoot in RAW already and know a bit about the format. One advantage that immediately comes to mind is that with RAW you can alter settings such as White Balance after a photograph has been taken (using a computer). Another is that RAW files have a higher bit-depth and in theory should be able to capture a slightly higher range of brightness.

Artificial Light (Ring Flash)

JPEG (Camera Processed + Slight Post Processing)White Balance set to Flash

RAW (Processed entirely on computer)

There doesn’t appear to be that great a difference between these two images however it took me much longer to process the JPEG file exactly how I wanted it to look than it did the RAW. With the RAW I simply applied the flash colour balance and boosted the blacks, contrast and clarity to make the detail stand out. The JPEG was more complicated. I increased the contrast and darkened the shadows using Photoshop’s levels tool but this in turn darkened the entire image so I had to also increase the exposure by 1 stop and the saturation as some colour had been lost. The effects I have ended up with are very similar but I prefer the RAW image as it appears stronger and the white area in the background is actually white and not a strange tone like in other image.

Daylight

JPEG (Camera Processed + Slight Post Processing)White Balance set to Daylight

RAW (Processed entirely on computer)

This shot in particular appears deeper in the RAW version. The sky is practically identical in both versions but the main difference is in the grassy area in the foreground. In the RAW version the grass is much lighter but still has a lot of contrast. For both images I selected the grassy area and made adjustments to it. In the JPEG version I had to increase the grass’ exposure yet it is still darker than that of the RAW.

 

High Dynamic Range

JPEG (Camera Processed + Slight Post Processing)White Balance set to Cloudy

RAW (Processed entirely on computer)

I like both of these images, however in the JPEG version the highlight clipped areas look much more harsh. The RAW version is very smooth and it seems that the camera has coped better capturing the highlights in this format. The colour tones are slightly different and I had to reduce the saturation of the JPEG image as it was very bright yellow. I haven’t altered the colours of the RAW version I just darkened the blacks to boost the contrast.

In conclusion the difference between shooting in RAW and JPEG isn’t that drastic. Some problems can occur when applying strong post-processing to JPEG files and if you forget to set your camera to the correct white balance at time of shooting. The main advantage of RAW is definitely the ability to alter the white balance using a computer. RAW files almost certainly capture a higher range of brightness which can be seen in my high dynamic range examples. As for post-processing, extremely similar effects and results can be created by editing either format however RAW is much easier and quicker to edit as the tools are both simple and powerful. Also with RAW, once a setting has been altered, the information is stored in a separate file and so can be altered again without damaging the quality of the image. The more a JPEG image is manipulated, the lower its quality becomes.

My Tolerance for Noise

To test the effects of noise on photographs I am going to take a shot of a single scene at each ISO setting my camera is capable of. Noise is more abundant at high ISOs and so I am expecting to see more and more as I progress from ISO 100 to ISO 3200. I will place my camera on a tripod so the scene is identical for each image, keep the aperture fixed so that the depth of field is constant and won’t use any shutter speeds longer than 1/2 sec as this could introduce another kind of noise.

All of the shots were taken at f/5.6 and lit by daylight coming through a window.

Original Shots

ISO 100 + 200

  

ISO 400 + 800

  

ISO 1600 + 3200

 

Crops

The red boxes on the first image show where I have taken my crops from.

The crops below were taken from the red boxed area on the left of the image above. From these crops it is visible that noise doesn’t really become noticeable until using an ISO above 400. At ISO 400 any noise at all could easily be mistaken for detail. I took these crops at 100% magnification as this is the point at which noise starts to become visible and where it is most accurately differentiated from detail.

ISO 100

ISO 200

ISO 400

ISO 800

ISO 1600

ISO 3200

The shot taken at ISO 3200 is very visibly noisy, however in certain situations this noise could make a desirable addition by giving the shot an attractive grainy effect.

Closer Crop

I have also taken crops at 400% magnification of shots from either end of the ISO range in order to display the drastic difference in quality. At this magnification at ISO 100 there is some slight pixilation but this is not noticeable when the shot is viewed as a whole because it simply looks like detail. At ISO 3200 there is clearly a lot of noise in this shadowed areas and it is very obvious that it is noise because the crop was taken from a smooth part of the photograph and therefor this area contains no detail.

ISO 100

ISO 3200

The noise isn’t a problem if the photographs are only going to be viewed at a small print size e.g. in an album. It is when large prints are required that noise becomes more of an issue.

Noise Reduction

I have added one final image to display one of the powerful tools of Adobe Camera RAW. This tool is the Noise Reduction tool and can be found in the ‘Detail’ tab. I opened the RAW version of my ISO 3200 shot into the processor and altered some of the noise reduction settings to see if I could obtain an acceptable image. I am very pleased with the results however as well as removing noise, the tool has smoothened out some of the intricate detail of the dry decoration. If high ISOs are a necessity but grainy noise is not desired, Adobe Camera RAW’s noise reduction tool is a valuable asset to any digital photographer.

 

ISO 3200 Crop with Noise Reduction Applied

For comparison, here are the ISO 100 and ISO 3200 crops.

ISO 100 + ISO 3200

 

Highlight Clipping

All of the shots below were taken at ISO 200 and at f/11. I altered the shutter speed each time to change the exposure. My camera was mounted on a tripod. My subject is a small ornament of a family of three carved from a piece of wood.

Shot 1 – Highlight Clipping Appears (One stop over exposed) - 1”6sec

Shot 2 – More Highlight Clipping (One stop brighter/Two stops over exposed) – 2sec

Shot 3 – Less Highlight Clipping (Almost non, correctly exposed, One stop darker than first shot) – 0”8sec

Shot 4 – No Highlight Clipping (Another stop darker/one stop under exposed) – 0”4sec

Shot 5 – Again no Highlight Clipping (yet another stop darker/two stops under exposed) – 1/5sec

To demonstrate just how severe the highlight clipping of the brightest shot is I have opened a RAW version in Adobe Camera RAW and taken a screenshot of the image with the clipping warnings switched on. From this image it’s clear that a good portion of the subject has lost all detail.

Highlight Clipping Close-Ups

I took these close-up crops from the back of the child’s head as this area has a very high concentration of clipping.

Shots 1 + 2

 

Shots 3 + 4

 

Shot 5

It is clear that from the shots above, highlight clipping is most abundant in the first two shots. These were the shots that were most brightly exposed. In the brightest shot (shot 2) there is barely any detail and more than half of the crop is pure white. As the exposure time is reduced, more and more detail begins to appear and in shot 2 there is a clear break between the detail of the subject and the lack of detail in the clipped areas. With the lack of detail, there also comes a lack of colour and therefore zero saturation in these areas.

Recovery

Even in shot 3, the correctly exposed shot, there are still areas of highlight clipping. The most aesthetically pleasing shot is shot 4 however it is slightly underexposed and so I will open the correctly exposed shot in Adobe Camera RAW and experiment with the Recovery settings. The Recovery control uses the information from all of the RGB channels to ‘re-build’ the clipped channel. The channels do not all clip at the same time and therefore some of the detail may still be available on another channel.

Original Shot 3 + Recovered Shot 3

Cropped Clips

Original Shot 3 Crop + Recovered Shot 3 Crop

 

Using the Recovery tool in Adobe Camera RAW I have managed to regain some detail in shot 3’s Highlight Clipped areas. The recovered image looks less saturated and much smoother. The highlights are also a lot less obvious and overall it contains much more detail. The recovered version is much more pleasing to the eye.