The aperture of the camera in the scene. Choosing a low value will have a wide depth of field where everything is in focus. Choosing a high value will create a shallow depth of field (DOF) where objects in the foreground and background will be out of focus."
(source: http://render.otoy.com/manuals/Standalo ... age_id=407
)so the Question:
isn't the .25 in aperture the same as having f/4?
Update / Edit:
Its seems the source of the confusion is actually what we are talking about when we use the term "aperture". The whole area of the opening? The radius? or the Diameter?
How ever that may be in the F-stop formula the aperture diameter seems to be used.
Update / Edit 2:
In version 2.20 of OctaneRender Aperture is indicated as the radius of the opening trough which light falls.
The OctaneRender aperture value is measuered in cm.
When writing this post I used the formula posted on wikipedia that is based on the aperture diameter and uses the unit mm.
Aperture Diameter = 2 * Aperture RadiusExample: 50mm = 2 * 25mm
value in cm = 0.1 * value in mmExample: 1 cm = 0.1 * 10mm
- - -The short answer:
I could asume that you mean 25mm with .25.
Only if you are using a lens with a focal lenght of 100mm an F -stop value of f/4 equals an aperture diameter of 25mm.
- - -
If you really meant to use an aperture diameter of 0.25mm then only if you would be using a lens with a theoretical focal lenght of 1mm an F - stop value of f/4 would equal an aperture diameter of 0.25mm.
- - -
In any case
The F stop value is a ratio between the focal lenght of the lens and the diameter of the lens opening created by the lens blades.
- - -
- - -The longer answer:
First lets have a look at what an aperture is:
The aperture diameter is the diameter of the opening of the lens trough which light enters.
The aperture diameter is measured in the unit mm.
The larger the aperture the more light will enter trough the lens.
The F stop value is a ratio between the focal lenght of the lens and the diameter of the lens opening created by the lens blades.N = f / D
N = f stop value
f = focal lenght
D = diameter of the lens opening(effective aperture)
- - -In practise this means:
At F stop f/1.4 a lot of light will enter trough the very wide aperture.
You will have a narrow depth of field meaning the background is blurred.
The aperture value in OcaneRender is large.
- - -
At F stop f/22 only a small amount of light will enter trough the now very small opening of the lens.
You will have a wide depth of field meaning the background is sharp.
The aperture value in OctaneRender is small.
- - -
For more information about depth of field compare:http://en.wikipedia.org/wiki/Depth_of_field
- - -
- - -Some examples:Example 1:
You are using a lens with a focal lenght of 50mm. The aperture diameter is 25mm.
N = 50 / 25
N = 2
The F-stop value is f/2.
- - -
In order to answer your original question.
With an aperture diameter of 25mm.
4 = focal lenght / 25
focal lenght = 4*25 = 100
Only if you are using a lens with a focal lenght of 100mm an F -stop value of f/4 equals an aperture diameter of 25mm.Example 3:
Lets asume that you really entered an aperture diameter value of 0.25 mm in OctaneRender.
4 = focal lenght / 0.25
focal lenght = 4*0.25 = 1
Only if you would be using a lens with a focal lenght of 1mm an F - stop value of f/4 would equal an opening diameter of 0.25mm. While in theory it would be possible to have lenses with 1mm focal lenght in real life the smallest focal lenghts you will be using without any adapters are around 16mm to achieve some wide angle landscape photographs.
- - -
- - -
A more practical explanation can be found on:http://www.uscoles.com/fstop.htm
- - -In any case thank you A LOT for this script. I do not understand why this is called "old school" though.
I would call this "photography standard" camera values.
On current photocameras F-stop is the standard value used to indicate the effective opening of the lens created by the blade positions.
Focal lenght is the standard value indicated on any lens you purchase.
Examples: Wide lens 16mm, Portrait lens 85mm, Zoom lens 200mm.
You will in most cases not find any mention of aperture or field of view when working with photo cameras or lenses.
From my point of view aperture and field of view are "very old school".