Exercise 2 – Focus at Different Apertures

TAoP-Excercise-02-3-NI8_0493I carried out exercise 2 at work, a chef was producing a few hundred petit fours and as I had lights rigged to take some food shots I borrowed a tray for the exercise.

The tray of chocolates was ideal as any variation in sharpness would be easy to spot.

 

I set the tray up under one fixed light (from left/rear ) and a soft box with a hot shoe and my flashgun (right/rear).

Image 1 - focus on central petit four taken at f/3 1/125 ISO 100

Image 1 – focus on central petit four taken at f/3 1/125 ISO 100

I have focussed on the petit four in the centre (on yellow line, third in from either side). The yellow line shows the subjects in focus . There are varying degrees of blur further away and nearer to the camera. The further and nearest petit fours are very blurred.

Image 2  - focus on central petit four taken at f/8 1/100 ISO 450

Image 2 – focus on central petit four taken at f/8 1/100 ISO 450

In the second image I chose f/8 as the mid point. Focus is on the same petit four and I have drawn two yellow lines to show the approximate area in focus. There is less blur at the extremes.

Image 3  - focus on central petit four taken at f/36 1/100 ISO 6400

Image 3 – focus on central petit four taken at f/36 1/100 ISO 6400

The third image has the aperture stopped down to minimum at f/36, I have focussed on the same central petit four. The whole tray is in focus.

As these images were captured under lights indoors and I did not want to set up a tripod in the kitchen I ensured that my shutter speed did not fall below 1/100 which I generally use as my minimum shutter speed to avoid camera shake. (Vibration control on lenses was invented just in time for me as it has become harder to avoid camera shake as I get older). When I am shooting in the kitchen I usually set the ISO to automatic as my “client” is more tolerant of a bit of grain than of not getting the shot. The consequence of shutting down to f/36 and holding the shutter speed at 1/100 is a jump in the ISO to 6400.

I have been reading Bryan Perterson’s 3rd Edition of Understanding Exposure. I have found Peterson to be very good at explaining how to use depth of field and shutter speed for creative effect. I understood the reciprocal relationship between aperture and shutter speed but had not realised that ISO also changed in direct proportion to changes of the other two until I read “Understanding Exposure”. On reflection it is fairly obvious that it would act in this way but I had never thought of it in such terms. I have found his “Photographic Triangle” to be a helpful way to think of the relationship between these three controllable settings.

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