ahmadzargon. Creating a good photo means talking about exposure. I have been talking about triangle of exposure: ISO, Shutter Speed, and Aperture. Every point of those build their unique character to your photo. In this article, I will try explain aperture and depth of field existence in addition.
Aperture introduction
The first thing is aperture. Aperture is a hole within lens that determine the amount of light that travels to your camera sensor. This hole has a function just like a gate. Imaging a pipe with a lot number of water flowing within the pipe, the amount of light traveling the gate base on aperture hole size. In consequence, the coming light determine how long sensor will render your photo.
In Digital LSR camera, aperture value regulate in electric instrument. Its measures in one stop series and the values should be f/1, 1.4, 2.0, 2.8, 4, 5.6, 8, 16, and so on. The lower f/stop gives more exposure and represent with small number. A good lens determine by their largest aperture value, better known as wide open. Standard lens such as 18-55 mm for Nikon, Sony and canon have f/3.5 at 18 mm and f/5.6 at 55 mm. Leica 50 mm Noctilux-M manual focus lens is the biggest aperture value that I ever known. It is f/0.95 and it aperture value larger then its focal length.
Depth of Field or DOF
Depth of Field simply means the range of sharp area in front of your camera when you take a photo with your amazing lens. Range of DOF becomes longer as far as the closest focus sharp point. Here the length of sharp are in front of focus point in 50 mm focal length lens.
Table of sharp image, unit in meter
Aperture Value
|
f/4
|
||||||||
Object range
|
0.50
|
0.70
|
1.00
|
1.50
|
2.00
|
3.00
|
5.00
|
10.00
|
∞
|
Closest Point
|
0.49
|
0.68
|
0.97
|
1.45
|
1.90
|
2.80
|
4.00
|
8.00
|
10.00
|
Farest poin
|
0.51
|
0.72
|
1.05
|
1.60
|
2.10
|
3.80
|
7.00
|
15.00
|
∞
|
Depth of Field
|
0.02
|
0.04
|
0.08
|
0.15
|
0.30
|
1.00
|
3.00
|
7.00
|
∞
|
Aperture Value
|
f/8
|
||||||||
Object range
|
0.50
|
0.70
|
1.00
|
1.50
|
2.00
|
3.00
|
5.00
|
10.00
|
∞
|
Closest Point
|
0.48
|
0.68
|
0.82
|
1.35
|
1.75
|
2.50
|
3.20
|
5.00
|
8.00
|
Farest poin
|
0.52
|
0.78
|
1.06
|
1.75
|
2.50
|
4.20
|
9.80
|
∞
|
∞
|
Depth of Field
|
0.04
|
0.10
|
0.18
|
0.40
|
0.75
|
1.70
|
6.60
|
∞
|
∞
|
Aperture Value
|
f/16
|
||||||||
Object range
|
0.50
|
0.70
|
1.00
|
1.50
|
2.00
|
3.00
|
5.00
|
10.00
|
∞
|
Closest Point
|
0.47
|
0.54
|
0.86
|
1.20
|
1.48
|
1.90
|
2.70
|
3.20
|
5.00
|
Farest poin
|
0.55
|
0.80
|
1.30
|
2.10
|
3.50
|
8.00
|
∞
|
∞
|
∞
|
Depth of Field
|
0.08
|
0.26
|
0.44
|
0.90
|
2.02
|
6.10
|
∞
|
∞
|
∞
|
(Range values are approximation value)
In other consequence of aperture value, wide-open aperture produces sharper image than small-open but has a shorter DOF. Base on the table dates, wide-open aperture is good setting for modeling and close up photograph and landscape photography is good to use small-open aperture. The last tips from me is wide-open aperture is best way to take image of galaxy.
Lens with different focal length has a different DOF point. DOF area shorter as high as lens focal length. This characteristics is basic point for grouping the lens become fish eyes lens less then 16 mm, Super-wide lens 16 mm - 35 mm, Wide lens 35 mm -50 mm, Portrait lens 50 mm – 80 mm, telescope lens 135 mm – 200 mm and super-telescope lens more the 200 mm. Enlargement factor is not only depend on focal length of lens but also size of sensor.