Testing White Balance

I tested the white balance on the camera, indoors on a window sill, so that I still had the natural light shining in. I used a white mug and put it in a location with a white background, I did this because the contrast will be seen better with white objects and surroundings rather than with a blue cup on a darker background. 

The outdoor conditions at the time of shooting were: -

I have taken still images, with different K values to show the white balance and adjusted the I.S.O to compliment the image (for the majority of the images the I.S.O is the same and only two differ). 

From this you can see that the lower the K value (like 2500K) the deeper the blue tint to the image and the higher the K value (like 14000K) the deeper the red/orange tint to image. At 4500K the image looked the same as it did through my eyes. 

White Balance

White Balance
What is White Balance?

The white balance can have a real impact upon the shots you take. The reason to adjust white balance is to get the colours in the shot as natural as possible. without adjusting the white balance shots can come out with an orange, blue, yellow etc tinge to them. this is because images with different sources of light have a different colour of temperature to them.




White Balance is measured by the Kelvin Scale. This is a scale that measures the temperature of light and provides a numerical value for each colour. Shorter wavelengths have a lower temperature and longer wavelengths have a higher temperature.

Tungsten lighting, sometimes referred to as 'hot lights' because they emit heat, are skewed to the lower end of the light spectrum, hence the look warmer or more reddish/yellow without proper filtering. one major problem to tungsten is that they are not reliable over a period of time as their colour will change as they age (variations in voltage will also change the colour output).

Florescent lighting is skewed towards the blue end of the spectrum, so again without proper filtering, you end up will a cool or blue/green colour cast to images or footage. however they are not as hot as tungsten lights, so are safer to work with.

Tungsten                                     Florescent

Aperture and Depth of Field

Aperture and Depth of Field

Depth of field from Simmone Dudley on Vimeo.

Larger aperture openings, like f/4, will tend to have shallow depth of field and a smaller aperture opening, like f/16, will tend to have everything in focus. Depth of field is doubled by closing down the lens two stops.


jack shallow depth from Simmone Dudley on Vimeo.

The size of the stop is one factor that affects depth of field. Smaller apertures (larger f numbers) produce a large depth of field, allowing objects at a wide range of distances to all be in focus at the same time.

jack deep focus from Simmone Dudley on Vimeo.

Decreasing the aperture opening increases the depth of field, which describes the extent to which subject matter lying closer than or farther from the actual plane of focus appears to be in focus. In general, the bigger the aperture (smaller f numbers), the shallower the depth of field. 

Beyond the depth of field

In the depth of field

In front of the depth of field 

                       

Aperture

Aperture

Aperture is how wide the lens iris opens. The wider it opens the more light gets in. It’s the same as the human eye, the less light the more the iris needs to be open, to allow more light in, and the more light, the smaller the iris, as less light is needed.

The lens controls the amount of light they let pass through to the film of video receptor. Bigger apertures and smaller numbers, like f/4, and smaller apertures have bigger numbers like f/16. These numbers are called the f/stop and this is the mathematical relationship of the overall size of the lens to the size of the aperture.

The f/stop (or stop) is a unit of light measurement. An increase in the amount of light by one stop means there is twice as much light. Subsequently a decrease of one stop means there is half as much light. Every time the aperture is increased by one whole stop, the quantity of light reaching the film is doubled. The f/stop is the ratio of the focal length of the lens to the diameter of the entire pupil. Thus, each stop is greater than the previous by the square root of 2, which in turn corresponds to a factor of 2 change in light intensity.  

f/stop = focal length/ diameter of lens opening

OR

f= F/D

F/stop numbers are fractions, with the relationship f = F/D. so for example f/16 really means ¹/₁₆; the diameter is ¹/₁₆ focal length. And f/8 is ¹/₈ , which is a larger fraction than ¹/₁₆, so the size of the iris is wider for f/8 than it is for f/16. Think of it as the larger the f/stop number the smaller the iris opening, and the smaller the f/stop number the wider the opening. 

ISO

I.S.O

           

I.S.O is the indication of how sensitive a film is to light. The lower the ISO number (100, 200, 400, 800), the lower the sensitivity of the film and the finer the grain in the shot, whereas a higher ISO gives more noise or grain. Higher ISO settings are used in darker shots/locations to give a faster shutter speed.

High ISO


cut1 from Simmone Dudley on Vimeo.

Low ISO


Low ISO from Simmone Dudley on Vimeo.

Because one-third stop is the minimum exposure difference detectable by the unaided eye, film sensitivity is rated in no finer increments than this. This makes the relationship between intervals easier to see. For example ISO 200 is 1 stop faster than ISO 100, and ISO 320 is 1 stop faster than ISO 160. It makes it easier for odd intervals as well, like ISO 80 and ISO 32 (1^1/3 stops).