Focusing and Depth of Field
This tutorial is primarily for BookTubers with a DSLR (short for Digital single-lens reflex camera). BookTubers mostly have DSLR’s – with changeable lenses – or Compact Cameras. The camera in your mobile phone also count as a Compact Camera.
Autofocus or manual focus
All physical rules for light and photography are of course the same whether you use a Compact Camera or a DSLR, but the Compact Cameras are based on autofocus (AF) — an optical system that uses a sensor and a motor to focus fully automatic — where DSLR’s can both be operated by autofocus or manual focus.
(Picture: On Nikon DSLR’s there are three different focus choises. M for Manual focus, S for Single (this is Autofocus and focuses only one time, good for objects that stand still), C for Continous (Also Autofocus, that focuses continous, which is great for moving objects).
While working with this tutorial, set your DSLR to M: Manual Focus.
Manual focus avoids autofocus-accidents
(Picture: When you decide to control the focus, you also avoid tragic accidents where autofocus thinks it’s your potted plant to the left of you that’s going to be the star in your video – and therefore in focus.)
To fully understand photography and to control your own BookTubes, manual focus is an ernormous advantage. With manual focus, you decide what’s going to be sharp and what’s going to be blurry in the picture.
Also, the motor that controls the cameras autofocus is noisy. So recording a BookTube with a naughty autofocus will result in motor noise over the sound of your voice. Just another good reason to choose Manual Focus during BookTube recordings.
The focus ring
With your DSLR’s focus set to ‘M for Manual’, you have sacked autofocus, and only you have the responsibility for a BookTube with yourself in focus!
If you have always used your DSLR’s autofocus, you may never have touched your focus ring on your lens.
You do the job by turning the focus ring until your object appears sharp. You can recognise the focus ring by the feet (ft) and meter (m) units for the distance between the camera and the object you want to photograph.
(Remember the focus ring has nothing to do with your zoom ring, if you have a zoom lens on your DSLR. The zoom ring doesn’t have feet or meter-units on it. It has focal lengts, and they are specified in millimetres (mm), e.g. 35 mm – 50 mm – 70 mm – 105 mm – 200 mm. Sometimes they doesn’t even have the mm unit, but are just written like: 35 – 50 – 70.)
Controlling the Aperture makes you PRO!
“Hey! Aperture!? That sounds really technically and boring! I dont need to know that to shoot a good BookTube!”
Well, you don’t need to know it — if you just wanna shoot mainstream BookTubes anyone could have done with a cheap Compact Camera or a mobile phone.
But you actually bought an expensive semipro DSLR with a great lens. If you use its aperture in a smart way, you could make remarkable pictures and videos. So why not make a five minute investment and learn this?
The aperture blades in your lens creates a hole, where the light can get in. To know exactly how much light the aperture blades lets in, wise people has invented aperture stops. Aperture stops are several positions where the aperture blades stop and creates a fixed sized hole.
The aperture stops are known by their prefix ‘f/’. E.g. f/1.8 or f/22
On the illustration above, you can see that an aperture stop named f/1.4 creates a really big hole and lets almost all light into the lens, while an aperture stop named f/16 lets very, very little light into the lens.
And hang on! It’s wasn’t just tecnically stuff for nerds. You’re actually going to use it now …
Depth Of Field (DOF)
Not all pictures are sharp. You know that. But do you know that you can put unsharp pictures into two categories? Well, you can: Shaken pictures and pictures out of focus.
In shaken pictures (picture to the left) everything is … shaken! 🙂 That’s the way you know them. There are motion blur, and nothing is in focus. To avoid shaken video, put your camera on a tripod. To avoid shaken pictures (still photography), choose a quicker shutter-speed or use a tripod.
In pictures out of focus (picture to the right), there are blur, but no motion blur! And it’s very possible that something is sharp and in focus — just not the object you wanted to be in focus. 😉 On this picture the potted plant is in focus, instead of the girl.
“Can’t video or a picture be both shaken and out of focus?” Yeah, actually, it can! A double whammy, but unfortunately it doesn’t end up like two wrongs make a right. It’s just double crap! And you will be send back to kindergarten in Hogwarts School of Photography. 😉
It’s like playing ‘The Floor is made of Lava’
To get yourself sharp in a BookTube, you need to move yourself into the Depth of Field (DOF) range. Also if you show books in front of you, they need to be in the Depth of Field (DOF) range to appear sharp.
Actually you get to play ‘The Floor is made of Lava’, because you can only operate within your DOF! Anything outside your DOF, is lava. 😉 If you move outside the DOF or just stick an arm or a book outside your DOF, you’ll get burned – because you yourself, or the books you show your viewers, will appear out of focus.
Sharp or blurry birds? DOF decides!
- Everything within your Depth of Field range always appears sharp.
- Everything in front of and behind your Depth of Field range, always appears blurry.
Aperture stops with small numbers, like f/1.4, f/1.8, f/2.8, f/3.5 lets a lot of light into your lens and makes the Depth Of Field (DOF) low.
(Top illustration: Only one bird in the middle appears sharp.)
(Bottom illustration: All birds appears sharp.)
Conversely, an aperture stops with high numbers, like f/16 or f/22, lets in very little light and creates a high Depth Of Field (DOF).
Recording a BookTube with different DOF’s
Three things decides your Depth Of Field (DOF):
- The focal legth (the one you set with your zoom ring on the lens)
- The distance between the camera and the object you want to photograph
- The aperture
But, unless you live in the great hall of a castle, you can’t change the distance to the object and the focal length much. BookTubing in a normal bedroom just has its limits.
So, you control the DOF in a BookTube-setup in your bedroom with — ta-dah — the Aperture!
Here we will show you how different results you’ll get in the same set-up, just by changing the aperture:
Error e.g. 1: Back-focus with f/2.8
Error e.g. 1: Back-focus with f/2.8: “Why would I focus on my potted plant instead of myself?”
Well, first, when you focus manually yourself, you’re standing behind the camera and therefore you can’t focus on your own eyes, because your not sitting in front of the camera. A tip for focusing is to place you BIG teddybear on the chair or on the floor, where you’re supposed to sit during recording. Focus on teddys eyes, start recording and then exchange teddy with yourself. 😉
Also, when shooting with low DOF like this at aperture stop f/2.8, DOF is maybe only 20 centimeter. You just have to turn your focus ring on your lens one or two millimeters wrong and your potted plant becomes the star in your Booktube. So adjusting focus before recording a BookTube demands fine motor skills.
Error e.g. 2: Front-focus with f2.8
Try it yourself with this Camera Simulator
This DSLR camera simulator is a great way to check your knowledge about Depth of field (DOF) http://camerasim.com/apps/camera-simulator/ It’s easy to make the girl sharp, because the focus has alread been set, but can you choose an aperture that makes the background blurry? And can you choose an aperture that makes the background as sharp as the girl? Can you take a picture, where the mill is frozen perfectly, without blurry wings?
Remember to choose ‘Aperture Priority’ first in the simulator!
Also remember to choose ‘A = Aperture Priority’ on your own DSLR camera, when your working with apertures like in the BookTube example above.