Saturday, 13 August 2011

Part 4 Light–Project:The Intensity of Light

Measuring Exposure 2: The second part of this exercise was to make five or six photographs of any subject using a range of exposures at ½ stop increments one stop above and below the metered average; five exposures in all. I chose to take these while out walking on the South Downs, looking for landscapes where there were different colours dominant in the scene. The first thing to point out is that I had inadvertently left the ISO setting on 3200 after experiments the previous evening. However, for the purpose of this exercise, noise is not a problem and it meant that I could enjoy the luxury of fast shutter speeds. I have also used a fixed focal length lens (35mm) for this exercise.
I have presented the five images as a contact sheet with metadata incorporated and the image which I consider most acceptable is enlarged below it with a histogram.
1. Buriton Pond
This sheet shows one of the shortcomings of attempting manual exposure measurements using  the matrix system. You will see that the exposure values for 7193 and 7194 are identical even though I had set the exposure indicator bar in the view finder from +1 to +½ by scrolling the f stop wheel, indicating that the scene’s brightness had changed due to cloud movement. This happened on  several occasions during the day.
7196 seems to give the best average exposure with some clipping of the highlights as shown by the histogram. This is as I would have expected for this type of scene with an extended tonal range. None of the others were acceptable, either with a completely burnt out sky or blocked up shadows.

2. Harebell
Although made in shady conditions, the fast changing light has meant that I have ended up with two  identical exposures at the  –½ and –1 f stop settings. As can be seen from the histogram below 7209 has an even spread of tones with no clipping at either side. Also, the slight under exposure has saturated the colour of the flower, whereas the over exposed examples have washed out the delicate colour. With a suitable crop (see below) 7209 makes the most suitable image.


3. Ditcham Park
I did manage to get the full range from f8 to f16 on this series. I was aiming to show the effect of exposure on a cloudy sky. 7236 and 7237 gave the most detail in the sky and the deepest blues. All of the tones were within the histogram range in both images. A shift in the clouds has put more sunlight in the mid ground 7237 so this would be my choice despite the lack of contrast in the foreground. Although 7235 gave acceptable results, the sky is washed out and the overexposed images loose all or most of the detail.

4. Bridlepath
7224 is a very acceptable version of the image and shows all of the tones within the range of the histogram. However, any of the exposures could be used  depending on the mood you were hoping to evoke with the picture This is because of the range of tones is very narrow . A darker tone would perhaps be more menacing, a lighter one less so.

5. Hundred Acres
7256 is the best exposed of this group. Half  a stop either side of this is a bit light and dark respectively while 7258 and 7259 are distinctly muddy. The selected image is shown below with its histogram.

What did I learn from this exercise? First of all I learned the importance of checking all of the camera settings before starting an exercise!
From the first part of the exercise I was able to make both high and low key images. Care is needed in choosing exactly how much of the image detail you sacrifice to achieve the high and low key effects as shown with my candle images. I think I need to practice a little more with these.
I learned how reliable and effective the Matrix metering system on my camera is for landscape photography  in particular, although I know to be wary of over exposing bright skies and to be on the lookout for extremes of tonal range which may leave areas of the image over or under exposed. I could use a graduated neutral density filter to cope with these extremes.
I made one or two more landscape images but they were of similar subjects and would only have repeated what I’ve already done.

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