Taking a few days out of taking photos due to being back at work, the weather not playing ball and the light fading fast! Decided to work a little on this learning blog. I am adding pages and gadgets and enjoying discovering others also studying with the OCA. I have found a few blogs covering the same modules so it is reassuring to see I am on the same lines as them <phew>. Flickr has an OCA group which I have joined and in a few weeks time am attending a London get together which I am really looking forward to.
My flashgun has been found YAY! Surprisingly enough it was in the cupboard in my bedroom where I keep photo albums, negatives, a few books and other photographic related stuff that isn't used much. Safe place to keep it but am so used to finding my stuff (whatever it is) under piles of paper on my PC desk was shocked not to find it there when I looked ;o)
Wednesday, 3 November 2010
Monday, 1 November 2010
Exercise 10: Colour cast and white balance Part 1 Review.
Sunny Day
The first set of photographs I took were on a sunny day at approximately 2pm, the four different white balance results are shown below :-
The next set were taken on a cloudy day at approximately 3.30pm.
I think that the variations were more noticable under the cloudy conditions. The AWB rendered the image quite well but the image seemed a little flat, while the daylight setting once more gave the image a cold blue cast. The Shade setting made the brickwork much warmer but gave the overall shot an orange/yellow hue, the Cloudy WB seems to have been the best option but is not that disimilar to the AWB.
Open Shade
This set of images were taken in open shade on a sunny day at about 2pm
I felt that the variations were more striking with these shots. The AWB has left the image dark and with a blue cast as has the daylight setting. Once again the Shade setting has given a very warm orange cast with the cloudy also not giving a very true result, erring on the yellow/orange side. The daylight setting seems to have the closest colour representation if I was pushed to choose.
This was an interesting experiment to undertake. A lot of the time when shooting outside I rely quite heavily on the AWB setting due to the changing nature of the weather and therefore the light. From these results I conclude that the AWB setting on my camera performs quite well on most occasions, with the Shade setting giving a very unsatisfactory result even in the shade. This will help with my decision making when shooting outside as far as white balance settings are concerned. I have as yet to experiment with the custom function but I can't see me always carrying a white card about or not always having the time to use it in certain circumstances ;o)
The first set of photographs I took were on a sunny day at approximately 2pm, the four different white balance results are shown below :-
 | ||
| File temperature read 5650
|
 |
| File temperature read 6750 |
 |
| File temperature read 5850 |
Out of interest I noted down the colour temperature readings on the RAW files and noted that the AWB value was very similar to the Cloudy.
I was surprised that although I can see there is a variation in the colour cast it was not more pronounced. The AWB I feel has represented the truer colours, the daylight setting has added a touch of blue which although makes the sky a lovely shade gives the grass an odd hue. The Shade WB setting is the least satisfactory giving the image a very orange appearance with the Cloudy setting not too bad a result but still a little on the yellow side.
Cloudy Day
The next set were taken on a cloudy day at approximately 3.30pm.
 |
| File temperature read 5550 |
 |
| File temperature read 5150 |
 |
| File temperature read 6750 |
 |
| File temperature read 6750 |
Once again I noted the colour temperatures and the AWB @ 5550 was closest to the Cloudy WB setting @ 5850.
Open Shade
This set of images were taken in open shade on a sunny day at about 2pm
 |
| File temperature read 4500 |
 |
| File temperature read 5150 |
 |
| File temperature read 6750 |
 |
| File temperature read 5850 |
Noting the file temperatures in RAW once more it was interesting to see just how far out the AWB reading was from the other settings on this occasion.
This was an interesting experiment to undertake. A lot of the time when shooting outside I rely quite heavily on the AWB setting due to the changing nature of the weather and therefore the light. From these results I conclude that the AWB setting on my camera performs quite well on most occasions, with the Shade setting giving a very unsatisfactory result even in the shade. This will help with my decision making when shooting outside as far as white balance settings are concerned. I have as yet to experiment with the custom function but I can't see me always carrying a white card about or not always having the time to use it in certain circumstances ;o)
Exercise 10: Colour cast and white balance
The first part of this exercise is to familiarise myself with the exact procedure for altering the white balance in my camera.
On the 400D there is a specific button that allows you to access the cameras white balance settings. There are eight altogether, auto, daylight (approx 5200K), shade, (approx 7000k), cloudy (spprox 6000K), tungsten light, (approx 3200K), white fluorescent light (approx 4000K), flash and custom.
The following settings are recommended :-
If you have a mixed light situation or less-than-perfect light you can set a custom white balance. In doing so you are telling the camera what should appear white in the specific light you are shooting in. As long as you remain shooting in those lighting conditions the custom white balance should render the whites accurately. This saves time that would otherwise be spent correcting colour cast post production.
To set the custom white balance on the 400D :-
I need to find the four following outdoor lighting situations. Sunlight, Cloudy,Open shade on a sunny day, Auto. For each scene I have to choose a scene or object to photograph and shoot four versions using the four different white balance options.I then need to compare the results.
For the second part of this project I need to find and shoot a mixed-lighting scene. Suggestion made is to shoot a mixed indoor/outdoor shot at dusk. Shoot three versions using the following white-balance settings
On the 400D there is a specific button that allows you to access the cameras white balance settings. There are eight altogether, auto, daylight (approx 5200K), shade, (approx 7000k), cloudy (spprox 6000K), tungsten light, (approx 3200K), white fluorescent light (approx 4000K), flash and custom.
The following settings are recommended :-
- Sunrise, although you can use AWB it is recommended that if possible use the custom white balance.
- Midday, the Daylight setting is a reliable choice.
- Sunset, the Cloudy white balance setting is a good choice.
- Diffused light, on cloudy or foggy days, awnings etc again Cloudy is a good choice.
- Flash, using the on camrea flash for use indoors or outdoors as a fill-in use the Flash option.
- Tungsten light, this is the light most commonly found in household lights and lamps it produces a yellow/orange cast. Setting the cameras tungsten wb setting retains a hint or the warm colour of the tungsten light while rendering the colours accurately.
- Fluorescent, commonly found in offices and public places this light ranges from a yellow to a blue-gree hue in these instances use the Fluorescent WB setting.
- Other light, other types of lighting include mercury-vapor and sodium vapor found in public arenas and auditoriums, it is recommnded that in these situations you set a custom white balance.
If you have a mixed light situation or less-than-perfect light you can set a custom white balance. In doing so you are telling the camera what should appear white in the specific light you are shooting in. As long as you remain shooting in those lighting conditions the custom white balance should render the whites accurately. This saves time that would otherwise be spent correcting colour cast post production.
To set the custom white balance on the 400D :-
- Position the camera so that a sheet of white paper fills the centre of the view finder, ensuring that it is correctly exposed.
- Press the menu button.
- On the Shooting 2 tab, press the down cross key and select Custom WB
- Press the Set button. Make sure the image displayed is that of the white sheet of paper.
- Press the Set button again, The camera then imports the white-balance data from the selected image.
- Lightly press the Shutter button to dismiss the menu, and then press the WB cross key. The White Balance screen will appear.
- Select Custom White Balance.
- Lightly press the Shutter button to return to shooting.
I need to find the four following outdoor lighting situations. Sunlight, Cloudy,Open shade on a sunny day, Auto. For each scene I have to choose a scene or object to photograph and shoot four versions using the four different white balance options.I then need to compare the results.
For the second part of this project I need to find and shoot a mixed-lighting scene. Suggestion made is to shoot a mixed indoor/outdoor shot at dusk. Shoot three versions using the following white-balance settings
- Sunlight
- Tungsten
- Auto
*refer to Lowrie C K (2007 p26/27 and p86-89) Digital Rebel XTi/400D Digital field Guide
White Balance and Colour
To appreciate the importance of setting the correct white balance on your camera you first of all need to understand fully that light can have different colours, usually refered to as "colour temperature". Photographically colour temperature is measured in degrees Kelvin. I scouted about on the net but an awful lot of the sites give such highly technical explanations you'd need to be a scientist to fully grasp their meanings!
Our eyes adjust no matter what the lighting conditions are, sunlight, shade, tungsten or flurescent, however a camera sees what is literally there and records all the differences in colour. This is why it is important to set the camera to an appropriate colour balance.
Noon sunlight is generally 5500 Kelvin, late afternoon is around 4000 and possibly at around 3000k at sunset. Sunlight gives a red cast whilst in the shade you will get a blue cast. Tungsten is notorious for giving a very yellow/orange result while flurescent can be blue/green. These websites explain some areas of white balance and the settings that can be found in camera to deal with different lighting conditions.
http://www.digitalpicturezone.com/digital-cameras/importance-of-white-balance-and-its-settings-in-the-cameras/
http://www.cambridgeincolour.com/tutorials/white-balance.htm
http://journal.phottix.com/photography-tips/importance-white-balance/
Our eyes adjust no matter what the lighting conditions are, sunlight, shade, tungsten or flurescent, however a camera sees what is literally there and records all the differences in colour. This is why it is important to set the camera to an appropriate colour balance.
Noon sunlight is generally 5500 Kelvin, late afternoon is around 4000 and possibly at around 3000k at sunset. Sunlight gives a red cast whilst in the shade you will get a blue cast. Tungsten is notorious for giving a very yellow/orange result while flurescent can be blue/green. These websites explain some areas of white balance and the settings that can be found in camera to deal with different lighting conditions.
http://www.digitalpicturezone.com/digital-cameras/importance-of-white-balance-and-its-settings-in-the-cameras/
http://www.cambridgeincolour.com/tutorials/white-balance.htm
http://journal.phottix.com/photography-tips/importance-white-balance/
Exercise 9: Scene Dynamic Range
The instructions for this task were to shoot five differently lit scenes, ensuring one had high dynamic range and another with low dynamic range, and within each find and measure the brightest and the darkest areas.
Hazy Cloud
This image has low dynamic range, the histogram values are clumped together in the middle of the graph. The shutter speeds ranged from 1/250 - 1/25. The dynamic range for this scene is 3.3 stops.
Open Shade
The lightest area metered at 1/60 the darkest at 1/13. The dynamic range for this scene is 2.3 stops.
Overcast Cloudy
The lightest area metered at 1/40 and the darkest 1/4. The dynamic range of this scene is 3.3 stops.
Sunlight
This image has a high dynamic range, the values on the histogram stretch from one end of the axis to the other. The brightest area metered at 1/1250 and the darkest at "0.4. The dynamic range for this scene is 8.3 stops which is not far from the results I found online for my camera.
Having shot five different scenes under different lighting conditions and calculating the dynamic range for each I have come to the conclusion that my camera has the dynamic range to cope with most conditions. Any clipping could be recovered in ACR and in the deep shadows when enlarged there was no discernable noise. Special attention should be taken mainly when the scene is of a very high dynamic range with a large amount of bright or reflective areas, very deep shadow or a higher ISO which will begin to introduce noise.
Hazy Cloud
Open Shade
The lightest area metered at 1/60 the darkest at 1/13. The dynamic range for this scene is 2.3 stops.
Overcast Cloudy
The lightest area metered at 1/40 and the darkest 1/4. The dynamic range of this scene is 3.3 stops.
Sunlight
The brightest area metered at 1/1000 and the darkest at 1/40. The dynamic range for this scene is 4.6 stops.
Indoor Mixed Light
Having shot five different scenes under different lighting conditions and calculating the dynamic range for each I have come to the conclusion that my camera has the dynamic range to cope with most conditions. Any clipping could be recovered in ACR and in the deep shadows when enlarged there was no discernable noise. Special attention should be taken mainly when the scene is of a very high dynamic range with a large amount of bright or reflective areas, very deep shadow or a higher ISO which will begin to introduce noise.
Exercise 8: Camera Dynamic Range.
I must admit when I looked at this section I did think oh dear.....I had heard of dynamic range, I knew what it meant, but knowing and applying are two different things. Trying to discover what the dynamic range of my camera didn't seem like a task I fancied doing.....I discovered that typing out exactly what I have to do has clarified the exercise for me.
To complete this exercise, to find the range between the darkest and brightest points I need to do the following :-
An example given is a brightly lit house, a piece of white card/paper, an open door with a dark surface visible inside. Ensure the ISO sensitivity is at its lowest, and noise reduction in-camera switched OFF. Set the exposure and shoot so there is just no highlight clipping on the card.
I then need to measure and make notes about the brightness of the card and two or three of the darkest shadow areas.
To measure these areas I have the options of either :-
For this exercise I decided to keep my aperture the same and note the shutter speeds, therefore I need to make sure I know what my increments are. Following the adoption of a standardized way of representing aperture so that each major step exactly doubled or halved the amount of light entering the camera (f/2.8, f/4, f/5.6, f/8, f/11, f/16, etc.), a standardized 2:1 scale was adopted for shutter speed so that opening one aperture stop and reducing the shutter speed by one step resulted in the identical exposure. The agreed standards for shutter speeds are:
1/1000 s
1/500 s
1/250 s
1/125 s
1/60 s
1/30 s
1/15 s
1/8 s
1/4 s
1/2 s
1 s
To get my readings I walked closer to the areas I wanted to meter. I'm uploading this image but to be honest I think I may need to shoot a different scene. The reason being my shadows were not that deep and the darkest areas (the windows) when I zoomed in on them did not display any noise, so although I can calculate a "range" I think it is not the full dynamic range of my camera.
Using the white sampler eyedropper in ACR and zooming to 100% the values on each channel for the white card read R 252, G 251, B 254.Using the exposure slider I regained details in the cream paintwork on the window frames and the doors/shutters, the bright reflecting window remained clipped.
The slowest shutter speed was 1/10 which was the dark inside (this is a 2/3 of a stop below 1/15) the fastest shutter speed was the white card with metered at 1/1250 (which is 1/3 of a stop over 1/1000) the dynamic range of this scene is therefore 7 stops. However as there is no noise in the darker areas I can only presume my camera has a larger dynamic range and I will have to experiment to find an alternative scene with darker shadows.
Having said that I don't think it is too far out as a review on a website found that the 400D produced a consistent dynamic range of 8.4 with ISO 100-800 and 7.8 at ISO1600.
http://www.dpreview.com/reviews/canoneos400d/page19.asp
Useful website :o)
Understanding Shutter Speed | Basic Photography | Digital Photography Magazine | Illustrated Photography
Understanding standard shutter speed stops and my camera's dynamic range should help me correctly expose images. Practise will hopefully make perfect and therefore enable me to reduce clipping and the need for too much adjustment in post production.
To complete this exercise, to find the range between the darkest and brightest points I need to do the following :-
- find a scene with a distinctly high dynamic range
- bright sunlight
- one brightly reflecting surface
- an area of deep shadow with a dark surface.
An example given is a brightly lit house, a piece of white card/paper, an open door with a dark surface visible inside. Ensure the ISO sensitivity is at its lowest, and noise reduction in-camera switched OFF. Set the exposure and shoot so there is just no highlight clipping on the card.
I then need to measure and make notes about the brightness of the card and two or three of the darkest shadow areas.
To measure these areas I have the options of either :-
- using spot metering
- zooming in to the maximum
- walking close to the area I want to measure so that they fill the frame.
For this exercise I decided to keep my aperture the same and note the shutter speeds, therefore I need to make sure I know what my increments are. Following the adoption of a standardized way of representing aperture so that each major step exactly doubled or halved the amount of light entering the camera (f/2.8, f/4, f/5.6, f/8, f/11, f/16, etc.), a standardized 2:1 scale was adopted for shutter speed so that opening one aperture stop and reducing the shutter speed by one step resulted in the identical exposure. The agreed standards for shutter speeds are:
1/1000 s
1/500 s
1/250 s
1/125 s
1/60 s
1/30 s
1/15 s
1/8 s
1/4 s
1/2 s
1 s
To get my readings I walked closer to the areas I wanted to meter. I'm uploading this image but to be honest I think I may need to shoot a different scene. The reason being my shadows were not that deep and the darkest areas (the windows) when I zoomed in on them did not display any noise, so although I can calculate a "range" I think it is not the full dynamic range of my camera.
 |
| Image with white card just showing clipping |
 |
| Shutter Speeds all metered at f5.6 |
 |
| Zoomed window showing no noise |
Using the white sampler eyedropper in ACR and zooming to 100% the values on each channel for the white card read R 252, G 251, B 254.Using the exposure slider I regained details in the cream paintwork on the window frames and the doors/shutters, the bright reflecting window remained clipped.
The slowest shutter speed was 1/10 which was the dark inside (this is a 2/3 of a stop below 1/15) the fastest shutter speed was the white card with metered at 1/1250 (which is 1/3 of a stop over 1/1000) the dynamic range of this scene is therefore 7 stops. However as there is no noise in the darker areas I can only presume my camera has a larger dynamic range and I will have to experiment to find an alternative scene with darker shadows.
Having said that I don't think it is too far out as a review on a website found that the 400D produced a consistent dynamic range of 8.4 with ISO 100-800 and 7.8 at ISO1600.
http://www.dpreview.com/reviews/canoneos400d/page19.asp
Useful website :o)
Understanding Shutter Speed | Basic Photography | Digital Photography Magazine | Illustrated Photography
Understanding standard shutter speed stops and my camera's dynamic range should help me correctly expose images. Practise will hopefully make perfect and therefore enable me to reduce clipping and the need for too much adjustment in post production.
Dynamic Range
Cameras can not always capture all the information in a scene, either losing detail in the highlights or in the shadows.The problems of highlight clipping and digital noise and problems only associated with digital photography rather than with film. They are the opposite ends of the tonal scale, 0 being black and 255 being white. These define what is known as the dynamic range of the camera.
The dynamic range of a scene in the number of stops between the brightest highlight and the darkest shadow. The dynamic range of a camera is the number of stops it can capture in one exposed frame. Knowing the dynamic range of your camera can help overcome a lot of exposure problems.
The link below went into greater detail and has helped me understand more what dynamic range means and what other problems can occur.
http://www.dpreview.com/learn/?/key=dynamic+range
The dynamic range of a scene in the number of stops between the brightest highlight and the darkest shadow. The dynamic range of a camera is the number of stops it can capture in one exposed frame. Knowing the dynamic range of your camera can help overcome a lot of exposure problems.
The link below went into greater detail and has helped me understand more what dynamic range means and what other problems can occur.
http://www.dpreview.com/learn/?/key=dynamic+range
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