Understanding dof Part 2: Time to go Hyperfocal

I think that when the auto focus was a feature of a camera lens more than twenty years ago, a great many photographers never got to understand depth of field and hyperfocal distance.

Take this quick true or false test to see how you go.

1. The only way to have an object in focus is to use the auto (or manual) focus to focus on it.
2. The depth of field does not change with distance from the object.
3. The depth of field does not change when you focus on different parts of a scene.
4. The only way to ensure everything is in focus is to use the largest f-stop possible eg f29, f32 etc, and use a tripod.

How did you go, here are the answers: False, False, False, False ....

let me clarify all this for you.

We know that the depth of field depends on three things: 1. focal length of the lens your are using (17mm, 40mm, 70mm, 90mm, 200mm etc) 2. Where we focus within the scene ie the distance this object is away from us. 3. The aperture setting we have set ie f4, f8, f16 etc.

With today's cameras having auto zoom and auto focus, it is no wonder why it is easy to forget about depth of field (since the dof is changing as we zoom in as well as what we focus on).

Imagine that for a given lens (say 90mm)  it has a "window" of sharpness. When I point at a spot and focus, there is a window of sharpness around this spot. The size of the window (aka dof) will depend on how near or far the spot is from me as well as the aperture setting.

Here is a table of distances (in feet) for my 90mm lens

 

Distance to Subject		f/4	f/8	f/16
10 feet		9.6-10.5	9.2-11	8.5-12
50 feet		41-64.5	34.5-90	26-490

 
A couple of things stand out:
1. As the f-stop increases the window (aka dof) grows.
2. The further into the scene I focus the greater the dof.

 My question now is, what is the distance I need to focus at within a scene to get the biggest possible dof? That distance is called the hyperfocal distance. 

 Here are the hyperfocal distances (in feet) for my lenses.   

 

Lens: 17mm		f/4	f/8	f/16
Hyperfocal distance		8	4	2
	dof	4- ∞	2- ∞	1- ∞

 

Lens: 40mm		f/4	f/8	f/16
Hyperfocal distance		44	22	11
	dof	22- ∞	11- ∞	5.5- ∞

 

Lens: 70mm		f/4	f/8	f/16
Hyperfocal distance		134	67	34
	dof	67- ∞	34- ∞	17- ∞

  

Lens: 90mm		f/4	f/8	f/16
Hyperfocal distance		220	110	55
	dof	110- ∞	55- ∞	28- ∞

 

Lens: 200mm		f/4	f/8	f/16
Hyperfocal distance		1094	547	274
	dof	547- ∞	274- ∞	137- ∞

Some things to note:
1. With a 40mm lens, you can get infinite dof with f16 if you focus 11 feet from you.
2. When focusing at the hyperfocal distance, the dof starts half way between you and the focal point and extends to infinity. Now that is cool!!
3. fast zoom lenses are cool bis of glass but they dont give us much dof.
4. Since there is a nice pattern in the data, I just remember the hyperfocal distance at f/4 for each lens and go from there.

The final part to this study on depth of field will look at how to create super sharp images with deep depth of field when we are close to an image, or the lack of light means we must use a small f-stop say f4 or if our lens gives too much diffraction at large f-stops (f22, f29, f32 etc) but we still need a sharp image with large depth of field.

 If you want to know the hyperfocal distance of your lens, here is a cool calculator I use. hyperfocal calculator

 have fun! ☺  

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Texture ...

When was the last time you took a photo that had real texture?

Taking photos with texture is all about the time of the day: the angle of the sun and the strength of the sun's rays. Shallow angles dancing across a rough surface can bring out the texture. Just watch you don't over expose the shot as the shadows are needed to create depth to the texture.

have fun! ☺

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Movies and Munchies

I was watching I am Legend recently, I love the introduction to the movie where the character played by Will Smith is driving his red Mustang through the streets of NY. Many different perspectives were used with cool effect.

This also got me thinking about when I grab some fast food. When choosing from the menu, we are looking at the work of some of the best food photographers in the business. Studying how they compose their images and emulating some of those elements when we compose images with people etc will raise our standard.

The world is a visual place, and gifted photographers and cinematographers enhance our experience. Studying their work whenever we see it will make a difference to our own work.

Here are two quick shots using my phone to show you the difference.   Yes the chips tasted so good!


  

have fun!  ☺

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Is your camera a hammer or a scalpel?

Look at a scene, point the camera and shoot... and you  probably have a reasonable image. But you have just used the most expensive hammer you own. Did you set the exposure yourself? Did you set the white balance or use AWB? Did you know what parts of the scene were in focus and what wasn't? Did you move yourself into a better position or shoot from a different angle or perspective? Have you ever taken a shot whilst lying down?

Have fun taking the time to learn how to use your camera as a scalpel, artistically removing unwanted elements from a scene to reveal the beauty you saw subconsciously. Here are some ideas to get you started:

1. Learn how to adjust the focal length of each lens you own to control the depth of field in a scene. You can practise this by shooting along the railing of a staircase.

2. How does the perspective of a scene change when you crouch down or lay down? How about experimenting with images that are taken from waist height only?

3. If you usually take big picture shots, how about experimenting with small scale images.

4. Find a scene with a large tonal range and explore black and white photography.

5. Take a  risk and turn your camera off manual. Set the time for an exposure and play with the ISO and focal length to see what happens.


Here is a shot I took - the subject matter is a little left of center. After thinking for a while I decided to turn these sweet potatoes into a conversation, so I worked hard to make sure that only the middle part of the scene was in focus and hopefully the result is the viewer focusing in on this  "conversation".

I would love to hear how you went with your project.


have fun :-)

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Should your images be on a diet?

Less is so much more.

I recently spent a week working on a project. Every day I would shoot with the early morning light and the late afternoon light, all for really one or two images. I didn't have a clear vision of how I wanted it to look, only how I wanted it to feel. I shot hundreds of images, thinking about the light, the shadows, where the focus should be and the narrative. After a week of shooting, I realized something: my story was not clear, but rather too muddled. I tried to do too much with the images, or I had elements in the shot that detracted the viewer from the story. So I put my images on a diet: paired them down, used simple elements, gave my story more clarity by getting closer. Guess what? I got a better result.

Do your images need to be on a diet too?

have fun :-)

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Clouds and Light

I love clouds :-)
As I turned into my driveway I saw this image, so I quickly took out my phone to take it. Clouds and light are amazing things, they add an intense dynamic to photography, and if you are patient enough to wait until the sun finds its way through the denseness, you can be rewarded with rays of light. If you set the exposure off the light you will lose details in the low tones, it's best to play it safe and get the exposure off a mid tone and bracket the shot one stop either side of the setting.

 
have fun :-)

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How to be your own critic ...

If photography is subjective, then why do we have critics, competitions and awards?

Before I answer that question, here is how I critique my own work. I think of the acronym E.A.T. If you are a good photographer then you will be able to E.A.T. if not, then ... Ok, so E.A.T. stands for emotional, artistic and technical.

Emotional: does my image create the emotion I am looking for? It is hard to create a sombre mood in full sunlight if there is nothing to give the viewer the cues to feel sad or reflective. What story am I telling and is it working?

Artistic: How have I composed the image or elements within the image to produce an effect? How effectively have I used either my camera or the space around me to create the image? Has the use of Photoshop been effective?

Technical: Is the image sharp? in focus? bokeh? noisy/artifacts? overdone the use of Photoshop?


Here is an image ... I would love you to critique it for me.

Getting back to the question about competitions and awards; I can see the need to award photographers who create awesome images that can tell a powerful story and possessing artistic and technical brilliance - how about you?

have fun :-)

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