Feb 272015

Check out my landscape photography video and hopefully you will learn one or two new tips….

 

Oct 212014
Virgin River-0827

The Virgin river close to the Zion junction shuttle stop.

Zion National Park is one of my favourite national parks in the US, it is also one of the busiest. For example, if you want to take classic photographs at sunrise and sunset of The Watchman, then you will probably find yourself shoulder to shoulder with fellow photographers.

However, come back to the same spot an hour later and all will be quiet. Admittedly the light on The Watchman may not be as dramatic but the same area still offers fabulous photographic opportunities.

The key is finding open shade. Shady areas where nice light is being bounced in to the scene. This can solve the problem of dealing with high dynamic range and you can create beautiful and more unique photographs at a time of day when most photographs have gone home.

For the photograph on the left I also used a 4 stop graduated neutral density filter. No polarizing filter was used.

The Virgin river near Temple of Sinawava

The Virgin river near Temple of Sinawava

Below are two more photographs taken on the same morning. No filters were used, my friend Dave and I simply walked up the river looking for nice shady spots. These photographs were taken around midday!

It is always tempting to take classic landscape scenes when travelling to places like Zion National Park, if you look around, you may be surprised at how nice the light is even though it is not the “magic hour”.

The Virgin river and trees near Temple of Sinawava.

The Virgin river and trees near Temple of Sinawava.

Aug 222011

In this second part of ‘Understanding Depth of Field’ I will look at the problems associated with using very wide and very small apertures. The main problems that I will look at are:

  • Why can’t I see the depth of field in the viewfinder?
  • Problems with using a wide aperture (focusing and lens softness)
  • Problems with using a small aperture (diffraction and shutter speed)

Why can’t I see the depth of field in the viewfinder?

This is a question that I am asked a lot!

Let’s imagine that you are using aperture priority mode and you change the aperture from f4 to f11. If you look through the viewfinder as you change the aperture you see absolutely no change in depth of field (DOF). However, when you take a photograph there is a big difference in DOF between the f4 photo and the f11 photo.

So why, when the camera is set to f11 do you see the DOF for f4 in the viewfinder and not the DOF for f11?

The reason is that when you mount a lens on to the camera, the camera automatically sets the lens to the widest aperture. This is to give you the brightest possible image in the viewfinder for composition and focusing. It is only when you press the shutter release that the camera sets the lens to your chosen aperture.

If you do want to see the depth of field before you take a photograph then many digital SLR’s have a ‘depth of field preview’ button. Pressing the button sets the selected aperture and you can see the depth of field, the viewfinder image also goes very dark!

Problems with using a wide aperture

 

This photograph of my daughter Erin was taken with a 50mm f1.4 lens at f1.4. Only her left eye is really sharp. Using a smaller aperture such as f4 would allow me to get her face in focus but maintain the blurry background.

From last week’s blog you will remember that a very wide aperture will produce a shallow depth of field. If the depth of field is too shallow then your focusing needs to be very accurate. This can be very difficult to achieve if your subject is moving!

Another problem is that not all of your subject will be in focus. E.g. If your subject is not looking directly at you, then one eye may be in focus but the other eye is soft.

Another problem with using a wide aperture is that many lenses are only sharp in the centre of the frame when they are used at their widest apertures.

If you have plenty of light to work with, then trying using a smaller aperture to overcome focusing problems and lens softness. E.g. if you are taking a portrait with a 50mm f1.8 lens, then try the shot at f2.8 or f4. You will still see a blurry background but your subject will be sharper and you will have fewer problems focusing.

If you don’t have plenty of light to work with then try one of these solutions:

1. Increase your ISO and use a smaller aperture.

2. Move further back.

3. Prefocus on a point that you expect your subject to pass and take multiple frames as the subject passes that point.

Problems with using a small aperture

Probably the biggest problem with using a small aperture is the slow shutter speed you will get when taking a photograph in low light conditions. The easiest solution is to mount the camera on a tripod and use a remote shutter release. If using a tripod is not possible then increase the ISO but beware of noise!

The second major problem with using a small aperture is diffraction. When rays of light pass through a small aperture they diverge and interfere with another and create a diffraction pattern. In simple terms; if the diameter of the diffraction pattern is larger than your camera’s pixel size (pixel pitch) then the resolution of your photograph will be reduced.

When is diffraction really a problem? To be honest you will only notice diffraction when you are producing large prints.

There are four ways to solve diffraction problems:

  1. If you are using a small aperture to get a slow shutter speed then use a neutral density filter instead of small aperture. E.g. use f8 and a 3 stop ND filter instead of f22.
  2. If you are using a small aperture to get a large depth of field then focus at different distances and use either Photoshop or Helicon Focus to combine the different photographs and increase depth of field.
  3. Alternatively, if you are using a small aperture to get a large depth of field then use a tilt-shift lens and tilt the lens to move the plane of sharpest focus. I will explain in a separate blog post in the very near future!
  4. Perhaps the easiest alternative, if you are using a small aperture to get a large depth of field is to use a wider angle lens.

Below are two photographs which show diffraction. These are cropped photographs from a Nikon D3x with a 105mm macro lens. The lens was manually focused.

In the first photograph, the Nikon D3x sensor has resolved a fine hair in the centre of the photograph, in the second photograph there is greater depth of field but the fine hair has almost disappeared because the diffraction pattern at f32 is much bigger than the D3x’s pixel pitch and therefore the sensor can no longer resolve the detail.

Macro photo of a paint brush at f11. Notice the fine hair near the centre.

Macro photo of a paint brush at f32. Compare the fine hair near the centre with the previous photograph.

Aug 112011

I have decided to write several articles on depth of field. The articles will range from ‘What is depth of field?’ to ‘Problems and solutions associated with shallow and large depth of field’, the latter is detailed as it includes useful information on diffraction.

This week we’ll start with the basics. What is depth of field and how is it controlled?

Depth of field (DOF) is essentially how much of an image is in focus. Shallow DOF means that only the distance you have focused on will be in focus. A large DOF means that most of the photograph is in focus.

The combination of a telephoto lens (600mm), wide aperture (f4) and large, full frame sensor give this photograph a very shallow depth of field.

Depth of field is controlled by the following:

1. The size of the aperture in the lens: Small or shallow DOF = wide aperture = low f number (e.g. f2.8). Large DOF = small aperture = large f number (e.g. f16)

2. The focal length of the lens: Wide angle lenses give a much greater depth of field than a telephoto lens.

3. How close you are to the subject: Close = shallow depth of field. Far away = greater depth of field.

4. The size of the sensor: Small sensors = large depth of field (e.g. compact cameras), large sensors = shallower depth of field (e.g. medium format cameras)

The combination of a long focal length (105mm) and close distance to this flower means that it is very difficult to get a large depth of field despite using an aperture of f11.

Why use a shallow depth of field?

The advantage of using a shallow depth of field is that you can turn a distracting foreground and background in to a complete blur. This makes your subject really jump out, such as the photograph on the left. Therefore, a shallow depth of field is very useful when taking portraits and photographing animals.

A wide angle lens (20mm) and small aperture (f32) give this photograph a large depth of field.

Why use a large depth of field?

A large depth of field is used when you want both the foreground and background of the photograph to be sharp. This is traditionally the case in landscape and architectural photographs. This is typically achieved by using a combination of a wide angle lens and small aperture.

It is important to note that when you use a small aperture, the only area of the photograph that is truly ‘in focus’ is the part of the photograph that you have actually focused on. E.g. if you have focused on a point 10 feet away, then everything at 10 feet is critically sharp.

With digital cameras using a small aperture (usually smaller than f11 on dSLR’s) can cause a problem called diffraction. Diffraction can be a considerable problem if you create large prints. I will look at what diffraction is and to solve the problem in a future blog posting.