The following is a direct copy and has been Pasted in for future reference from the Art of Photography coursework PDF Doc. (pasted in Maroon)
1 – 3 photographs – prints needed to note results
For this exercise, find a similar subject to the previous exercise. One that will show the results very clearly is a row of things seen from an angle: railings, parked cars, terraced houses, for example. Stand at an angle to this row and, if you have a tripod, set the camera on it so that each photograph will be framed identically. Focus on an obvious point somewhere near the middle, and make a note in your field notebook of this focus point. Take the first picture with the lens at its widest aperture. Take the second with the lens stopped down to the mid-point of its scale of numbers. Take the third with the lens at its smallest aperture. You will, naturally, need to adjust the shutter speed so that the exposure stays the same, or have the camera set so that it automatically adjusts the shutter speed for a constant exposure (see its instruction manual). Remember that there is a reciprocal relationship between shutter speed and aperture. Just as shutter speeds are graduated in steps that double or halve the time (and so the exposure), the main steps in the aperture control are separated by the same amount. Each stop down from the widest aperture halves the area of the circular opening. This means that, in practice, one stop down to a slower speed accompanied by one stop down to a smaller aperture makes no change to the exposure. Have a print made from each of the photographs; number them and compare them. There should be an obvious difference between at least the first and the third. With a pencil or marker, draw on each print what you see as the limits of sharpness. This will give you a more precise picture of the depth of field at different apertures. You can see that each pencil band is arranged around the point on which you focused. Keep these and other prints in, or with, your learning log for future reference.
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Equipment
Nikon D4
85 f1.4 lens
Tripod
Method
Again, like in exercise 2 in order to really compare each image I used a tripod, this way each composition can be identically compared and again I wanted to have something in the scene to allow the eye to follow the ‘in focus depth of field’ or otherwise known as the focal plane hence the idea of a garden fence, I wanted to use the good old railway track example here but I don’t live anywhere near an old disused track. The garden fence offers distance which in turn when taking pictures using apertures is the ideal way to give example of the visual changes involved.
Please see pictures and captions below.
Note – all pictures have been compressed hence there will be a quality reduction when enlarging.
Picture taken with 85mm fixed lens and an aperture setting of f1.4. You can see the centre of the image “in focus” and as the eye moves towards the outer edges of the frame the image gradually looses focus.
This picture was taken with an 85mm lens and an aperture setting of f5.6. In this picture the focus is still central but the out of focus effect is more gradual as the eye moves from the centre to the edges of the frame.
The final picture again taken with the 85mm prime lens and an aperture setting of f16. In This picture again the focus is still central but the out of focus effect is very slight, which is more noticeable at the lead in part of the image (right-hand side).
What have I learnt from this exercise
From this exercise I have learnt that even with the aperture at it smallest (supposedly infinity) a lens can not be trusted to provide infinite focus throughout the entire frame, although this image is demanding extreme focus especially being so close at the right-hand side. Focal stability obviously improves as the subject angle becomes less extreme.
stingray493 