Getting everything in focus–the hyper focal distance

In last week’s post we talked about the factors that effect depth of field and how to use them to increase and decrease it (let’s face it, mostly decrease, everyone just loves to blur the background those days).

But some times you want to get everything in focus, a typical example is when you are taking a picture of a person in a nice landscape and want both the mountains in the background and the family member in the foreground to be in focus (and even if you don’t take vacation snapshots it’s still common to have some object close to the camera in landscape photos because it makes the photo more interesting).

When faced with such a challenge you can focus on the foreground subject and blur the background, you can focus on the background and blur the subject, you can use the techniques we discussed in the last post to increase depth of field (use a wider lens, stop down the aperture, get farther from the foreground subject) – or you can learn about a useful concept called “hyperfocal distance”.

What is hyperfocal distance and why should I care?

The diagram below shows what happens when you focus close to the camera, the red triangle is the point of focus and the yellow bar is the distance range that is in sharp focus – when you’re focusing close to the camera the in-focus are is small and relatively symmetric (the sharp area before the focus point is the same size as the sharp are after the focus point).

As you focus farther from the camera your in focus area grows, but the area behind the focus point grows more than the area in front of the focus point, in the next diagram you can see that focusing on the person leaves a wide (but not wide enough) are in focus behind the person.

As you focus even farther the are behind the focus point continues to grow until it reaches infinity – that is everything behind the focus point is in focus – that exact focusing distance is called hyperfocal distance.

When focusing to the hyperfocal distance (or behind) the area of sharp focus starts at exactly half the distance between the camera and the point of focus and never ends (everything from halfway to the focus point and farther will be in focus).

In the diagram below you can see that by focusing to the hyperfocal distance you can get both the person and background in focus – by focusing a bit behind the person.

How do I know what the hyperfocal distance is?

The hyperfocal distance is effected by all the factors that effect depth of field:

  • Focal length – wider lenses (smaller focal length) makes the hyperfocal distance closer.
  • Aperture – smaller aperture (larger f number) makes the hyperfocal distance closer.
  • Distance – well, we are trying to calculate the distance.
  • Circle of confusion – Smaller sensor makes the hyperfocal distance closer.

Like depth of field there are many on-line calculators as well as calculators for every smartphone platform (actually, most depth of field calculators also tell you the hyperfocal distance).

How can I focus to the hyperfocal distance?

If you have a lens with a distance scale you are in luck, after you get the distance from a calculator switch the lens to manual focus and turn the focus ring until you see you are focused just behind the hyper focal distance using the distance scale.

If you don’t have a distance scale you need to find something that is approximately at the correct distance from you and use that to focus.

Quick Tip: focus a little behind the hyperfocal distance because if you accidently focus a little closer the background will be blurred.

Real life example:

I wanted to take a picture where both the subject near the camera and the background are in focus, I started my depth of field calculator app and entered a focal length of 35mm (my favorite focal length) and an aperture of f/8 (for a nice middle of the road aperture) – The calculator tells me the hyper focal distance is 8.20 meter (or ~27 feet).

Armed with this information I went out to a park just across the street from where I live and took this picture I call “dog looking at path” (if you want to buy prints just e-mail me):

In this picture I used the lamp posts to focus, since the posts are more-or-less evenly spaced they give us a nice way to measure distance – I know the post behind the dog is more than 8.2 meter away so I focus on it, I know the post the dog is tied to is about half way between the post I’m focusing on and the post I’m standing next to (it’s out of frame) so by making sure the post near me is in front of me I know the dog is more than half way between me and the focus point.

If I focus on something that is farther than the hyperfocal distance than everything farther than halfway between me and the focus point will be in focus – so that means both the dog and the background.

To prove the point I took 3 pictures, one focused on the dog, one on the background and one on that second lamp post,

Here are 100% crops from those pictures:

The left part is from the picture focused on the dog, the dog ear is sharp but the background is blurred.

The center is focused on the background, the background is sharp but the dog is soft (look at the darker area of the ear that is so clear in the other pictures).

And finally on the right, the right picture is focused using hyperfocal distance and you can clearly see both the dog and the background are in focus.

That’s it for today, hope that helps the next time you want to photograph something close while keeping something far away in the distance sharp.

When auto focus fails/ Easy manual focus

What do you do when auto-focus fails? well, there are two ways auto focus can fail, either it focuses on the wrong thing or it doesn’t manage to focus on anything at all, we talked about what to do when auto-focus locks on the wrong subject last week, today we will talk about what to do when the camera can’t auto-focus at all.

There are 3 common reasons for auto focus failure:

  1. You are too close – each lens has a “minimum focusing distance” and it’s just can’t focus light from something closer (for interchangeable lenses cameras that distance is usually printed on the bottom of the lens) – if you are using a point and shot camera you can go into “macro” mode (that usually has a flower icon) for camera’s with interchangeable lenses you need to switch to a macro lens, move back or read next week’s post about how to take macro pictures with no extra equipment.
  2. You are pointing you camera at something that is just a flat color – the camera need something to look at, if you point your camera at an evenly lit single color wall (for example) it can’t find focus because the in focus picture looks the same as the out of focus picture – in this case you can hold something next to the surface you are photographing, focus and then remove the object and take the picture.
  3. The third and most common case is not enough light – the camera is not as sensitive as our eyes (at least when auto-focusing) and can’t focus on something it can’t see – in this case a simple flashlight can help (light the subject, focus, turn off the light and take the picture) but sometimes that’s just not possible and you have to focus manually.

Some people can just look trough the viewfinder and set perfect manual focus every time, I’m not one of those people – so what do people like us that don’t have perfect eyesight can do?

Turn on live view, use the live view zoom function to zoom all the way in and turn the focus ring until the zoomed in picture is sharp – it’s that easy.

It’s easier to do this if the camera is on a tripod and the subject is not moving, but if we are in low light condition than you need a tripod and a stationary subject anyway.

That’s it, this was a shorter tip than usual, next week, as I said before we will talk about cheap macro photography.

Controlling the point of focus

I was walking around the countryside when I turned a corner and seen the most amazing site – a farmer fighting a real life dragon! so I took out my camera and quickly snapped a picture before the dragon has a chance to fly off (or set me on fire), I got home with the picture that would make me rich and famous, quickly loaded the picture on the screen and – the farmer and dragon are both completely blurry because the camera focused on this stupid cow at the distance – so much for fame and fortune  and back to blogging about photo techniques.

A more common version of the same problem (for people who don’t get a chance to meet a dragon) is a photo of a couple at a wedding or similar event where the couple is blurry but some aunt in the distance that is visible between the two people you are trying to photograph is crystal clear.

There are actually two easy ways to completely control the camera’s point of focus:

Focus and recompose

“Focus and recompose” is the oldest, quickest and simplest way to control the point of focus.

You start by setting your camera to always focus on the center point of the picture, check your camera manual about how to do that – for simple cameras and cell phones that don’t let you preset the focus point you can skip to the next technique.

Now, to photograph a lion wandering into a quiet farmyard point the camera strait at the lion (the composition is way off and we see stuff that is supposed to be out of the frame – but we don’t care at this point we’re not taking the picture just yet):

Half press the shutter button and hold- this will make the camera focus but not take the picture:

Now, with the shutter button half pressed, move the camera so that you see the picture you want to capture (but don’t move closer, back up or zoom in/out as those will change the focus) and press the shutter all the way:

And we get the exact picture we are looking for – the lion is in sharp focus and the farm animals blurry – who are both closer to the camera and near the center – so if we leave it to the camera they will be the most obvious point of focus (note that resizing pictures to smaller size makes them sharper and so the farm animals don’t look so blurry in the small version, to better see where the focus is note the difference in the level of detail between the face of the lion and the face of the cow).

It’s important to know this technique does fail miserably in one situation – when you have a very shallow depth of field (when the subject is very close the the camera, you set a very wide aperture or you are using a long lens) in this case the area of focus is so small that by moving the camera you are moving the focus enough to blur your subject – for those cases we have the next technique.

Choose the focus point

Here instead of focusing and then moving the camera we just tell the camera exactly where we want it to focus.

For cellphones, point and shoot cameras, DSLRs in live view mode usually focus by using the image captured by the sensor, there will be a frame on the screen that tells you where the camera will focus, just move this frame (usually by using the arrow keys, or tapping the screen for touch screens) so it covers the area of the picture you want to be in focus:

For DSLRs using the viewfinder and other cameras that have the faster and more accurate “phase detect” auto focus method the camera has actual multiple special focusing sensors and you can choose which of those sensors to use – if you look trough the viewfinder you will see black dots on the image, each of those dots represent an auto focus sensors, and when you half press the shutter button a dot that is in focus will glow red, you can tell the camera to use just one specific auto-focus sensor) (or, in more expensive cameras, to use only part of the sensors) – here is the focus point selection screen on my camera with the top left point (that is right on the lion) selected :

This technique is more accurate than “focus and recompose” but is slower because you have to mess with the camera settings.

That’s it for today, next week we will talk about what you can do when auto focus doesn’t work at all.