Assignment 2: Digital image qualities

The following set of images have been taken to illustrate various lighting conditions, including:

• A high-dynamic range (high contrast) scene
• A low-dynamic range (low contrast) scene
• Mixed lighting conditions e.g.
• daylight and incandescent
• fluorescent and incandescent
• Low-light conditions which require a high ISO setting

The technical challenges I found with taking high contrast images are trying to balance the different intensities of light, particularly when there is a strong light source,.  This was evident when I shot Carnbooth Hotel, as it was a sunny day.

In camera I attempted to overcome this by:

• Keeping the sun and its effects out of frame, cropping into the subject
• Keeping the sun at an angle between 90° to directly behind

One could also

• Consider using a filter, either a circular polarising filter (saturates the sky) or graduated filter

Post camera one could:

• Take several images at differing exposures and use a HDR technique
• Alter the levels within the photograph in a software package, such as Photoshop and using
• layers,
• masks and
• blending modes

merge them together to create a final image.

I took the following images to illustrate high contrast.

I took the following images to illustrate Low Contrast:

The image below was taken when the sun was low in the sky, overcast leaving little light to expose the image.  This however was a set of circumstances resulting in a nice end product.

The image was taken at Av f/11, Tv 1/400s, ISO 100 using a 2 x extender on a 70 / 200 f2.8L @ 180mm.

The challenge faced in taking this image were overcome using a tripod.  Although not really pertinent to this image the low contrast or flatness usually can be overcome by introducing light.  If I had taken this image when the sun was out and in the correct position of in other circumstances, using a flash then these measures tend to make the image less flat and with more contrast.

I took the next images within the hall to my house using incandescent light within and the ambient light outside.  One can see that the areas of exposure are correct in different areas of the image namely, correct outside in the first and inside in the second.

Two exposures were used and the third image a photo merge of both together, booth were taken at Av f/9, ISO 100, 16 / 35mm @ 16mm, with the shutter speed of 1/25sand 1/3s respectively.

The next image were taken within a First 35 sailing yacht, in low light conditions.

The image was taken at Av f/11, Ts 1/60s at ISO 800 with a Canon 16 / 35mm F2.8 lens at 35mm.

The ISO was increased to 800 which allowed the image to be taken at a shutter speed of 1/60s which can be achieved without the need for a tripod.

The last image was taken using mixed lighting conditions, e.g. daylight and incandescent.  It is a view onto my back garden from the sitting room.

It took until late in the day before the ambient light, outside, was at a similar level to the incandescent light from within.  Normally, to create this shot, I would have exposed the image to the outside (ambient) light and would have lit the interior using a flash and altered the power of the flash until I had balanced both light sources.

I took the image approximately at 8.30pm using the followng settings:

• Av - f/5
• Tv - 0.80s
• ISO - 100
• 16 / 35mm f2.8 lens @ 16mm

Exercise 10: Colour cast and white balance

Temperature

I processed the images, for this exercise, by changing the temperature in Adobe bridge, rather than altering the camera settings on each of the images when taken

The first set of images were taken on a sunny day at Carnbooth House Hotel, Carmunnock, Glasgow.
Thanks go to the staff for allowing me access to the grounds and permission to take these photographs..

The images were taken at Av F8, Ts 1/125s at ISO 100 with a Canon 24 / 70mm F2.8 lens at 24mm.

The temperature of the light within the image, "as shot" was 4650K. 

The temperature settings were changed to:

• Auto - 4600K - this created little change from the image as shot.
• Daylight - 5500K - this created a red cast and a very small amount of highlight clipping,
• Cloudy - 6500K - this created slightly less of a red cast but an increase of highlight clipping and
• Tungsten - 2800K - this created a blue cast and a large amount of highlight clipping.

The second set of images were taken on a cloudy day at Ardrossan Marina, with the round the world yacht Drum, of Simon La Bon's fame, in the foreground.

The images were taken at Av F11, Ts 1/60s at ISO 100 with a Canon 70 / 200mm F2.8 lens at 70mm.

The temperature of the light within the image, "as shot" was 5350K.   In this image the sky was over exposed with a large amount of highlight clipping.

The temperature settings were changed to:

• Auto - 6200K - there is a slight increase in highlight clipping and red cast from the "as shot" setting,
• Daylight - 5500K - the areas of highlight clipping appear to be similar but the image appears slightly less of a red cast, 
• Cloudy - 6500K - there is an increase in highlight clipping and the colours return to the same saturation as in the "auto" image.and
• Tungsten - 2800K - this created a blue cast and a large amount of highlight clipping.

The third set of images were taken on a sunny day in the shade in my back garden.

The images were taken at Av f/5, Ts 1/160s at ISO 100 with a Canon 16 / 35mm F2.8 lens at 16mm.

The temperature of the light within the image, "as shot" was 5050K.   The sky had highlight clipping.

The temperature settings were changed to:

• Auto - 6950K - there was less highlight clipping in the sky area and colour more saturated,
• Daylight - 5050K - the areas of highlight clipping appear to be similar but the image "as shot",
• Cloudy - 6500K - there is an decrease in highlight clipping and the colours seemed a but more saturated
• Tungsten - 2800K - this created a blue cast and a large amount of highlight clipping.

Exercise 9: Scene dynamic range

Following on from determining the dynamic range of our camera we were asked to quantify the f stop readings and therefore the range of a number of additional images.

I did this by using the following method:

1. Set the camera to Av mode, using evaluating metering and took the initial image. 
2. Noted the shutter speed setting,
3. Reset the camera settings to manual setting and dialed in the Shutter speed as noted in step 2,
4. Change camera settings to spot metering,
5. Change to my longest lens (200mm)
6. Zoom into areas and take individual f stop readings throughout the image.

For the first image of Carnbooth Hotel in Carmunnock, whom I want to thank for allowing me to take some photographs, I used the following initial settings:

• Camera: Canon 5D MkII
• Lens: Canon 24/70mm f2.8L @ 24mm
• Mode: Aperture priority - f8 @ 1/200s
• ISO:  100

I recorded the individual f stop settings as show in the representation below.

For the second image of our house in East Kilbride, I used the following initial settings:

• Camera: Canon 5D MkII
• Lens: Canon 24/70mm f2.8L @ 24mm
• Mode: Aperture priority - f7.1 @ 1/40s
• ISO: 100

I recorded the individual f stop settings as show in the representation below.

For the last image of the garden I used the following initial settings:

• Camera: Canon 5D MkII
• Lens: Canon 100mm macro f2.8L
• Mode: Aperture priority - f8 @ 1/50s
• ISO: 100

 I recorded the individual f stop settings as show in the representation below.

Camera Dynamic Range - REVISITED

I struggled during the first shot at Exercise 8, understanding the concept, but I hope that I have found the Dynamic Range of my camera as demonstrated in the following images.

As always it was difficult finding a sunny day, particularly one where time allowed concentrate on the subject but I took an series of images of my garage which I hope fulfilled the criteria.

The right garage door gave me the area where I could set the highlights, with adequate shadows within the garage to look for noise.  I decided to put a grey card in the shot which would allow me to ensure accurate colour correction.

The garage door ans initial shot was taken at the following settings:

• Av - f/22
• Tv - 0.6s
• ISO - 100
• Lens - Canon 24 / 70 @ 32mm

After taking the image, with the camera on manual, I changed the exposure metering to spot and took additional readings at different parts of the photograph as show below.

This done, I opened the image in Photoshop and, after zooming in on selected areas, found the exposure level with noise started at f/5.6.

I have marked the areas within the image where noise was evident.

I therefore think that the Dynamic Range of my camera, Canon 5D MkII, is the difference between f/5.6 and f/22 giving a value of 5 stops.

Dynamic Range

Dynamic Range

This project is designed to establish the dynamic range of your camera in f stops.

I initially followed the subsequent procedure which was best carried out during a sunny day.  This proved extremely difficult as the sun has been scarce this year so far.

I selected my mother's house front door, which faces the morning sun and, I thought, was in enough shadow to find the lower end of the range by displaying noise. (image 1)

I placed my white / grey card next to the front door (image 2) and, putting my camera on a manual setting, set up to show highlight clipping in the white /grey card at an aperture setting of f2.8 at a shutter speed of 1/1000 (image 3). 

I there after took a series of other images, all with a shutter speed of 1/1000 at f4 then f5.6.

On both these images I increased the brightness, in Photoshop, allowing me to see whether or not noise had been introduced in the shadows (image 5).

I felt that this occurred at f5.6.

This gave the image and camera a Dynamic Range between f2.8 and f5.6 or 3 stops.

Image 1





Image 2



Image 3

Image 4

Image 5

Project 2: Digital image qualities

Exercise 5: Sensor linear capture

The original image is taken in Italy with our friends' son Lucas coming down the slide.

The curve described in the course notes is applied givind a representation of what an image that has not had a gamma correction curve applied.  This image, as seen below, is darker.  The applied curve is shown at the side.

A curve was thereafter applied to bring the altered image, without the gamma correction curve, back to its original state. 

Looking at the image which has been converted back, as near as possible, to the origina, is more noisy.



Project 2: Digital image qualities

Exercise 8: Camera dynamic range