Monday Wk6 (Exposure Triangle)

This evening was devoted to bringing the three exposure modes together. We began by revisiting the Shutter then the Aperture and lastly the ISO. All three are connected; by adjusting one usually means another will need to be altered to correct for less or more light entering the camera and affecting the brightness of the image. The way these exposure modes work can be represented as a triangle showen in the illustration below, courtesy of the Digital Photography School.

The Shutter has been documented in a previous post which can be refered to for a quick re-cap.

The Aperture; a hole in the lens the diameter of which is controlled through f numbers or f stops.

The smaller the f number the larger the diameter, and vice versa.

First and foremost the Aperture controls the amount of light entering the camera; the larger the aperture the more light and vice versa.

The other use is its creative application. The key word is 'Focus', the larger the aperture the shorter the depth of focus otherwise known as Depth of Field (DoF), the smaller the aperture the longer the depth of field.

The largest aperture you can achieve is normally using e.g. f1.8, the smallest is achieved using e.g. f22, the standard scale goes something like this:

1.8, 2.8, 4, 5.6, 8, 11, 16, 22, each step is referred to a stop, changing the f5.6 to f8 would be one stop, f8 to f4 would be two stops. Each stop increases the light by double or decreases by half.



Image form dpreview

For more indepth information regarding the Aperture try dpreview

ISO is the term used to refer to the sensitivity of the sensor to light. In old school terms it was used to describe the emulsion of the film, the larger the grain structure the more receptive to light it was. The creative effect was a grainy image.
With digital the word grain has been swapped for 'Noise' and refers to the pixels that become apparent the higher the sensor is set.

In low light the ISO function permits more light in to the camera and if we refer to the Exposure triangle by making this adjustment will allow you to access faster shutter speeds or a smaller aperture.

A word of warning; 'Noise' is not as aesthetically pleasing as 'Grain', it often means red and green pixels randomly filling the shadow ares/s of your image.

Finally you can put all three together.

Exposure

Now you know the basics of using the different exposure modes you can work in 'M' mode - you are free!

First and foremost each exposure mode allows you to control the level of light entering the camera and therefore the brightness of your image. So in manual mode your first job is to get the correct level of light for the image you want to create.

Use the in built light meter.

On a Nikon D60 it looks like the image shown left, taken from dpreview. The graphic below the shutter speed and aperture has a zero at the centre and a '+' and '-' at either end, this is your meter reading.

The marks in between refer to stops as we discussed earlier.

The bold mark denotes a full stop and the smaller marks denote a third of a stop. The graphic shows 2 stops but if the plus or minus is flashing then you are more than 2 stops too dark or light, otherwise referred to under or over exposed. In most situations you will want to have just one vertical mark below the zero to get the best possible exposure, you will do this by adjusting the shutter speed, aperture and/or ISO, what you choose is explained next.

Priority Setting

You want to "Zero" your light reading, as I have referred to it. In some situations you may not have much choice other than to adjust all three modes in order to alter the light reading from too little light or too much light. But in most situations the adjustment you make is based on the creative effect you want to achieve.

The Shutter allows you to freeze movement or create motion blur. To achieve such an effect, in most cases, will involve letting less light in (e.g. 1/2000 to freeze movement) or letting lots of light in (e.g. 1" to create motion blur). Either of these setting will have a dramatic affect on the brightness of your image so you will need to compensate by adjusting the aperture and/or ISO.

More light into the camera may mean balancing the levels of light by stopping down the aperture.

For example - the following setting is 2 stops too dark - 1/1000 / f5.6 / 100

By adjusting the aperture setting from 5.6 to 2.8 will balance the brightness of your image and allow you to maintain a fast shutter speed.

The same is true of the aperture. If your priority is to affect the focus of the image then you may need to balance the brightness of your image by using the shutter and/or the ISO.

For example - 1/500 / f22 / 100 is 2 stops too dark but by adjusting the shutter speed to 1/125 lets the correct level of light into the camera and maintains a small aperture to achieve the creative effect of a long depth of field.

So, first and foremost get the light right but in doing so make the adjustment to create the effect you want to achieve.

Shutter Speed Freezes Movement, or creates Motion Blur, the Aperture affects the Focus and the ISO creates Noise.

Phew! Be sure and post a question if you need greater clarity.

Monday Week One

Great to meet you all and welcome back those that attended the previous 8 week block.
What a beautiful evening, it was great to get out and about - to put theory into practice outside the confines of the classroom.

This evening we explored exposure using the Fully Automatic setting. On this setting the camera essentially works everything out for you, however as you found there are certain things you can do to affect the brightness of your image.
Most/all cameras (including film) have an inbuilt light meter that measures how bright the scene you aim your lens at. By default it takes a number of measurements within your view finder and makes an average reading that will present as much detail in your image as possible, but being selective about the reading you take can offer you a variety of results. For example, taking a reading for a light area in or near you frame of view by pressing the shutter half way and holding it down to recompose, then firing the shutter darkens the image by deepening the shadow areas.
This technique has a number of uses, it can make your image/s more graphic, change the mood of the image and therefore the meaning and also introduce detail into areas of your image that didn’t have them before. Shooting a landscape for example may result in the sky being washed out due to the contrast between the ground and the sky, but by altering your light reading may re-balance that exposure and introduce detail in the form of clouds.
For sake of simplicity we used the Auto setting but in future sessions will use exposure settings that offer more control.

As I mentioned the course structure and content has yet to take shape, as I have indicated the course is fairly flexible and can respond to your individual needs, the following areas may be something that could be introduced along the way or inform the structure of the course, we could...

Investigate different themes such as, environment, structures, relationships, time and what they could represent.
Explore different specialist fields such as, Documentary, Portraiture, Street, Architecture, Still Life and Landscape, the aesthetical and technical needs they require.
Publishing such as, creating a Photo Book, exhibiting and taking part in Social Networking sites such as, Flickr, Blogger and Facebook.
Selling your Work
Image manipulation from simple enhancing techniques to simple art work outcomes such as collage
Specialist Equipment including lenses, tripods, to what memory card to buy and where to buy it
Presenting your work such as mounting and framing

Exploring different lighting situations and Macro were a few of the suggestions made, fell free to make any suggestions.

Look forward to connecting with you virtually or in person in a couple of weeks.


Photograph by Danielle (I hope you don’t mind me using it I thought it did a good job of representing the evenings activity!)