Exercise: Focus at different apertures

The brief: to find a similar subject to the previous exercise (I have used the same subject) and stand at an angle to this row and using a tripod take three photos. Frame each photo identically. Focus on an obvious point near the middle and note this in the field book. Take the first photo with the lens at the widest aperture, the second with the lens stopped down to its mid-range and the third with the lens at the smallest aperture. Adjust shutter speed accordingly.

I actually performed this exercise with all f stops, beginning at f1.8 and increasing by 1 stop until I reached f16. My focus point was on the centre bowl on the blue strip on the 2 o’clock position above the fish’s eye. For my learning log I am only including those images taken at the widest and narrowest aperture and the mid-range. Every click on the dial indicates 1/3 of a stop: 3 clicks on the dial give one a full stop increase or decrease in aperture or shutter speed.

Ex 03 F1.8 aperture - centre focus

f1.8, 1/160, 50mm, ISO 200

Ex 03 F5 aperture - middle focus

f5, 1/20, 50mm, ISO 200

Ex 03 f16 aperture - middle focus

f16, 1/2, 50mm, ISO 200

The wider the aperture value, eg f1.8, the less time is needed (shutter speed) to make the image. The smaller the aperture value, eg f16, the more time is needed. Because both aperture settings and shutter speeds settings function in the same way in terms of halving or doubling the amount of light hitting the sensor, this means that there are many combinations of aperture and shutter speed settings that will result in the same exposure.

I was then asked to print the photos, number them and draw on each print what I see as the limits of sharpness. I have only reference the aperture setting and not included all the other camera settings on these photos as they are the same as above.

No. 1

Ex 03 f1.8 - area of sharpness

f1.8 – area of sharpness

At f.18 the area of sharpness is along the same focal plane as the focus point. It is very narrow and includes only the middle bowl.

No. 2

Ex 03 f5 - area of sharpness

f5 – area of sharpness

The area of sharpness doubles at F5, including two bowls, but the foreground is still soft and out of focus as is the last bowl.

No. 3

Ex 03 f16 - area of sharpness

f16 – area of sharpness

At f16 the area of sharpness is again doubled (4 bowls) and extends all the way to the last bowl. I have not included the front bowl in the area of sharpness, as upon magnification, one can see there is a slight soft focus on that bowl. However, it is not easily discernible to the naked eye.

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