Depth Of Field

Aperture is a key feature of DSLR cameras and one of the reasons they are so popular. They offer massive depth of field due to a large sensor size and lenses that have fast apertures.

Inside every DSLR lens there are aperture blades that control the amount of the light that can come through the lens and its then focused onto the sensor.

Here are some examples of the ways in which DOF can be used to enhance a photo:

To achieve shallow depth of field (blury subjects among sharp subjects) you need to be using an aperture of around f/4 and below. This is where the aperture blades are letting a lot of light in and will give you brighter images. When your aperture is around f/22 there will be a lot less light coming in and everything in your image will be in focus. Both a wide open and closed aperture have pros and cons.

Most lenses will be soft around there fastest aperture and you will often have to stop up to get sharp results. When your lens is at f/22 you need to compensate for the fallout of light by either slowing down your shutter speed or increasing your ISO. All three of these things are related and have a knock on effect when one is changed, but more on that later.

The below images were shot around between f/1.4 and f/4 as you can see some parts are in focus and some are not. This is what I was hoping to achieve by using such a fast aperture. Plus I was indoors so needed to let as much light as possible into the sensor so I could keep my shutter around 1/60 sec to avoid camera shake.

In this photo I was using a fast aperture so that the foreground was blurred to emphasise the leading lines of the wall and also draw your eye towards the human subject on the right of the image by blurring the left.
f/1.4
1/250
ISO 200
30mm

This was shot through a security door which had lines going through but because of the shallow depth of field and the fact I've focused on the background you can barely see the foreground. This is another use of aperture.
f/2.5
1/160
ISO 200
30mm

My Final Images

After experimenting with depth of field I have selected a few images which demonstrate the use of DOF and the different ways in which it can be used.

This shot demonstrates the use of foreground V background in DOF. This is a popular technique as you can be selective with what you want the user to focus on. For this particular photo you can tell there is a corridor in the distance but visually you can't see much about it so your imagination can wander.

The use of shallow DOF in this shot creates a nice blurred background and some nice bokeh from the lights. 

In this shot I used DOF to separate the 3 foreground subjects from the background as I wanted them to be the entire focus of the image. I think it helps create a sense of atmosphere and helps to add a sense of mystery to the location.

Shallow

This shot was about making only one element in focus. I chose something that was in the centre as I wanted a blurred foreground and background. This is often used to create a sense of visual hierarchy as you can choose what elements you want visible and what you want to be blurred out. The point of these shots was to select a point of focus that was around the centre of the image so that the foreground and background were both blurred.

Background V Foreground

This technique involves using a shallow DOF but focusing on an element in the background so that any foreground visuals are blurred. To achieve these shots I was shooting at around f2.8 on a sunny day this means I had to put my shutter speed up to around 1/800 and ISO 100

Foreground to background

This shot demonstrates my knowledge of aperture by being able to select an f stop that allows everything to be in focus. This is useful in many situations especially when used alongside leading lines as the audience can see everything in the photo. It also provides a sharper image as most lenses tend to be soft around large apertures but as they get smaller the image quality becomes sharper.

Aperture Range

The series of photos below were taken on a tripod and the exposure was kept the same. I was taking a shot each time I increased my aperture by a stop. The results is several images showing the graduation between small and large DOF. The first image was shot at f1.4 and as you can see there is only a very small part in focus. As the shots go on and the aperture increased up to f16 the background elements become more in focus. This is easier to demonstrate outdoors where there are several objects along the focal place that I can throw in or out of focus. This will be my next experiment.

Shutter Speed Continued

This post is going to be about the previous photos I posted about shutter speed. These are the two images that I combined in post production using a layer mask. There wasn't much more editing to it apart from adding some contrast and playing with the colour balance.

As I mentioned in my previous post the overall exposure of the subject is okay but the light trails from the flashguns power LED presented a problem. I could have avoided this by taping it up but this is the first time I've encountered such a problem but it's a lesson learnt. 

The key to getting these 2 images identical was using a tripod and mirror lock up to minimalise the change of camera shake meaning the images wouldn't line up in post. Once they were both in the same window in photoshop I created a layer mask and simply painted in the car and any other areas I wanted lit up eg. the floor.

Overall I'm very happy with this photo and it wouldn't have been as easy to achieve if I hadn't have used a slow shutter speed because I would have had to use at least 4/5 lights to expose the subject more than the background and then remove the stands in post production etc.

This is a very popular technique used in car photography as the dynamic lighting gives the car a much needed edge in comparison to most photos in natural light.

I also been experimenting with light painting as this uses a long shutter speed and a light source.

I used a glass bottle as this lets like through and gave interesting results. I placed my camera onto a tripod and set my exposure at 10sec, f16, ISO 100 and focused onto the centre of the bottle. I then turned off all the lights and used a torch to literally paint the bottle with light.

As you can see the bottle is much brighter than the background because I was moving a torch around it. In some shots you can see streaks of light behind the bottle, this is where the torch was facing directly at the camera similar to when people light paint words. I like this technique and it helps me understand long shutter speeds and how to use light with it.

After receiving a small assignment based around shutter speed I decided to go and do some long exposure night photographs but with my own twist.

Instead of doing the usual light trails etc I decided to photograph a subject and use the longer exposure to my advantage to get creative with lighting rather than letting the ambient light dominate the photograph. I exposed for the background and then lit the subject (in this case a car) using a speedlight off camera firing multiple times which gives a creative lighting effect which I would have needed several lights firing at once if the exposure was shorter.

I ran into some problems early on because the car is a reflective surface the light would often bounce from it and onto me meaning I was ghosted into the image. The key with any long exposure image is movement. If you don't want something to be in your image keep it moving and it will either not appear or you will see the trail of it's movement. This depends on how long your exposure is and what kind of photograph you are trying to achieve.

These final shots are a combination of 2 photographs. A 30 second exposure at ISO 200 f/16 or f/8 to get a base exposure and then another photograph using the same settings but with the car being lit by a flashgun. I was running around the car firing the flash several times in one photo giving the illusion that several lights we're used.

I then stacked the 2 photos in photoshop and used the first base exposure as a layer mask to paint out unwanted elements such as light trails from the LEDs on the flash or where I was ghosted into the image.

This is a fairly common technique often used in architecture photography amongst other fields. It's something I would like the investigate more and see how far I can push the boundaries subject wise.

I will be posting the initial shots that led up to the final 2 photos very soon as well as commenting on what I think worked and what I can improve on for future shoots.

Matt Stuart

Matt Stuart is a British street photographer who's work relies heavily on composition. His clever use of his camera creates scenes that you think would only be possible through being staged. He has the ability to make links in a single photograph, I think this is good practice as the best photographs aren't always the one that are presented right in front of you. Sometimes you have to look a little deeper into a scene to establish why it was photographed.

I will definitely be referencing his work when completing my first assignment as I feel composition is the foundation for any good photograph.

http://www.mattstuart.com/

This blog is where I'll be posting all the thoughts, processes and techniques I'm developing while on my BA Hons Photography Course.

My first set of tasks is to fully investigate shutter speed and aperture whilst maintaining basic photography principals such as composition and exposure.

I'll be researching into different photographers who use a range of techniques that demonstrate the use of shutter speed and apertures.