Full time manual focus (FTM) is the ability to manually re-focus the lens after auto-focusing has completed, without having to change the lens to manual focus mode.
“Full time manual” focussing or FTM is a feature built into many Canon EF lenses: if your lens has FTM then you can use full-time manual focussing with any EOS film or digital camera body. Learning to use FTM can help both your analog and digital photography.
Except I could never get FTM to work. So recently I spent considerable effort researching FTM to determine how it works, when it works, and why it sometimes doesn’t work (for me anyway).
The EF Lens AF/MF Switch
Almost all Canon EF lenses have an AF/MF switch that changes between auto and manual focus modes. On lenses without FTM the lens can only be manually focussed with the switch set to MF; when set to AF the focussing ring is disconnected and spins freely. Lenses without FTM have an autofocus mechanism that can be damaged if the lens focus is manually adjusted focus while it’s auto-focussing.
Lenses with FTM can be focussed manually at any time without damaging the autofocus mechanism, so the focussing ring is connected in both AF and MF mode switch positions. Lenses with FTM use Canon’s ring ultra-sonic motor (USM). Initially only Canon’s most expensive fast telephoto lenses offered FTM, but from the early 1990s Canon began making more USM lenses with full-time manual focussing. From 2012 Canon introduced a new autofocus mechanism using a stepping motor. these STM lenses also offer full time manual focussing. Table 1 below lists the Canon EF lenses that offer full time manual focussing at the time of writing.
Using Full Time Manual (FTM)
To use full-time manual focussing with lenses that offer the FTM feature:
- Set the camera to ONE SHOT AF mode and set the lens to AF.
- Half-press the shutter and auto-focus on the subject.
- Keeping the shutter button half-pressed, manually adjust the focus.
- When focus is adjusted, fully press the shutter button to take the picture.
FTM sometimes lets me down when I need it the most, which is in low light conditions or difficult subjects when the AF fails to lock on. When set to ONE SHOT mode, the shutter won’t release unless the AF locked onto something. In these situations, even if I have used FTM to refocus the lens, the shutter won’t release. Urrgh, I missed the shot!
Well, I worked out what the problem is, and what can be done about it. First, some background… Canon EOS cameras have two focussing modes: AI SERVO and ONE SHOT.
AI SERVO auto-focus mode
In AI SERVO mode (called SERVO mode on the EOS 650 and 620; the EOS 630/600 added the AI part) the camera continuously focusses the lens while the shutter button is half-pressed, trying to get something in the AF sensor sharp. It never stops adjusting and will keep re-focussing for as long as the shutter is half-pressed. AI SERVO is intended for sports and moving subjects. A picture can be taken at any time even if nothing is sharp, so with AI SERVO you never miss a shot, but the shot may not be in focus.
ONE SHOT auto-focus mode
In ONE SHOT mode the camera focusses until something in the AF sensor appears sharp, then it stops focussing and allows the picture to be taken. Auto-focussing only starts again after a picture is taken, or after the shutter button is released and half-pressed again. If the camera cannot focus on anything it won’t let a picture be taken, so in ONE SHOT mode every picture will be in focus, but you may miss a shot.
FTM only works in ONE SHOT mode
If you try using FTM in AI SERVO mode the camera will change focus immediately after you finish your manual adjustment. For this reason, full time manual (FTM) only operates correctly in ONE SHOT mode.
ONE SHOT mode only lets a picture be taken after something has been in focus.
This is the trouble I have been having!
It’s not enough to manually focus the lens to get something sharp, you must make sure the AF sensor has locked-on to something before the camera will take a picture. You can use FTM to re-focus but the shutter will not release until the AF has locked-on to something, either before or after your FTM adjustment.
Now that the problem has been correctly identified, a solution can be determined. Here are three solutions to the problem:
- switch off auto-focus and manually focus
- lock the AF point on something, then refocus with FTM; or use FTM to focus on something, lock the AF onto that point and re-frame
- use back button focus (BBF) to have separate control over auto-focus and releasing the shutter. (Oooh you didn’t see that coming, did you.)
1) Use manual focus
Use manual focus by setting the switch on the lens to MF. When using manual focus you control the focus and the camera will let you take a picture any time you want, whether something is in focus or not. No more missed shots, but maybe more blurry ones…
MF is not really a solution to the FTM problem (in a way it’s giving up on FTM altogether) but I mention it for completeness. MF is an option for lenses that don’t offer FTM
2) Re-focus and lock AF, or lock AF and re-focus
The camera will not take a picture until AF has been locked, so you need to either lock AF on something then re-focus with FTM, or use FTM to focus on something, lock the AF onto that point then re-frame and take the picture. Note that in ONE SHOT the AF system “memory” is held as long as the shutter is half-pressed, so you could get AF-lock on a something in good light, keep the shutter half-pressed to re-frame and re-focus then take the picture any time as long as the shutter has remained half-pressed (ie. hold it down for minutes if necessary).
With lenses that offer full time manual (FTM) focussing, turn the focus ring to refocus the lens, but make sure the in-focus subject is recognised by the AF system and focus locks on. This may require moving the AF point over the in-focus subject, waiting for the AF to lock on, then re-framing to take the picture. Practise doing this and it will become second nature, but there is a faster method…
3) Use Back Button Focus (BBF)
WHAT? During this research I also learned about back button focussing (BBF) and how it can help solve full-time manual focussing problems, particularly focussing in difficult light.
BBF was introduced in 1989 with the Canon EOS 630/600 film camera, and many subsequent EOS film cameras offer it as an option. Most DSLRs have BBF as an option too. (See table 2 below for a list of EOS film cameras with BBF.)
Modern cameras like the Canon EOS have two-stage shutter buttons: half-press (a light touch until resistance is felt) is stage 1; pressing the button all the way down (until it stops) is stage 2.
The half-press (stage 1) usually does two things: it activates the light meter to make the camera work out the aperture and/or shutter speed necessary for correct exposure; and it activates the auto-focus system to start adjusting the lens to get the subject in focus. Pressing the button all the way down (to stage 2) releases the shutter and takes the picture.
Back button focussing (BBF) moves the auto-focus system activation to a different button, usually the * button on the back of the camera (hence “back button” focussing). The * button usually activates exposure lock or partial metering depending on the camera. With BBF, half-pressing the shutter button only activates the light meter and full-pressing releases the shutter. Auto-focus isn’t activated until the * button is pressed. The neat trick with BBF is that the camera will allow a picture to be taken at any time, even in ONE SHOT mode, even if the subject isn’t in focus and hasn’t been in focus (so it operates more like AI SERVO mode).
I will discuss setting setting up back button focus (BBF) in the next post, and talk about when and why you might use it, and when and why you might not.
Table 1: Canon EF Lenses with FTM
Below is the list of Canon EF lenses with full time manual (FTM) focussing list by year of release (up to 2019).
| Canon EF Lenses with Full Time Manual (FTM) | Year |
| EF 300 f2.8 L USM | 1987 |
| EF 200 f1.8 L USM | 1988 |
| EF 28-80 f2.8-4 L USM | 1989 |
| EF 50 f1.0 L USM | 1989 |
| EF 85 f1.2 L USM | 1989 |
| EF 35-135 f4-5.6 USM | 1990 |
| EF 70-210 f3.5-4.5 USM | 1990 |
| EF 100-300 f4.5-5.6 USM | 1990 |
| EF 14 f2.8 L USM | 1991 |
| EF 14 f2.8 L USM | 1991 |
| EF 200 f2.8 L USM | 1991 |
| EF 28-80 f3.5-5.6 USM | 1991 |
| EF 20 f2.8 USM | 1992 |
| EF 20 f2.8 USM | 1992 |
| EF 28-105 f3.5 USM | 1992 |
| EF 20-35 f3.5-4.5 USM | 1993 |
| EF 28-70 f2.8 L USM | 1993 |
| EF 35-350 f3.5 L USM | 1993 |
| EF 50 f1.4 USM | 1993 |
| EF 28 f1.8 USM | 1995 |
| EF 70-200 f2.8 L USM | 1995 |
| EF 135 f2 L USM | 1996 |
| EF 200 f2.8 L USM II | 1996 |
| EF 17-35 f2.8 L USM | 1996 |
| EF 24-85 f3.5-4.5 USM | 1996 |
| EF 24 f1.4 L USM | 1997 |
| EF 300 f4 L USM IS | 1997 |
| EF 35 f1.4 L USM | 1998 |
| EF 28-135 f3.5-5.6 USM IS | 1998 |
| EF 100-400 f4.5 L IS USM | 1998 |
| EF 300 f2.8 L USM IS | 1999 |
| EF 70-200 f4 L USM | 1999 |
| EF 100 f2.8 USM Macro | 2000 |
| EF 16-35 f2.8 L USM | 2001 |
| EF 24-70 f2.8 L USM | 2002 |
| EF 17-40 f4 L USM | 2003 |
| EF 28-300 f3.5 L USM IS | 2004 |
| EF 24-105 F4 L USM IS | 2005 |
| EF 50 f1.2 L USM | 2006 |
| EF 85 f1.2 L USM II | 2006 |
| EF 14 f2.8 L USM II | 2007 |
| EF 16-35 f2.8 L USM II | 2007 |
| EF 24 f1.4 L USM II | 2008 |
| EF 200 f2 L USM | 2008 |
| EF 100 f2.8 L USM IS Macro | 2009 |
| EF 8-15 f4 L USM | 2010 |
| EF 70-300 f4 L IS USM | 2010 |
| EF 300 f2.8 L USM IS II | 2011 |
| EF 300 f2.8 L USM IS II | 2012 |
| EF 28 f2.8 USM IS | 2012 |
| EF 35 f2 USM IS | 2012 |
| EF 40 f2.8 STM | 2012 |
| EF 24-70 f2.8 L USM II | 2012 |
| EF 24-70 f4 L USM IS | 2012 |
| EF 16-35 f4 L USM IS | 2014 |
| EF 24-105 f3.5-4.5 STM IS | 2014 |
| EF 100-400 f4.5 L IS USM II | 2014 |
| EF 35 f1.4 L USM II | 2015 |
| EF 50 f1.8 STM | 2015 |
| EF 11-24 f4 L USM | 2015 |
| EF 16-35 f2.8 L USM III | 2016 |
| EF 24-105 F4 L USM IS II | 2016 |
| EF 85 f1.4 L USM IS | 2017 |
Table 2: Canon EOS Bodies with BBF
Below is a list of Canon EOS film cameras with back button focus (BBF) listed by year of release. The first camera to offer back button focus was the Canon EOS 630/600 released in 1989. Each of these cameras has a custom function that moves AF from the shutter button to the * button.
All Canon EOS Digital bodies EXCEPT the EOS 300D and EOS 350D have an option for BBF. Many EOS digital bodies released since 2007 have an AF-ON button dedicated to back button focus; those without an AF OB button have a custom function that moves AF from the shutter button to the * button.
| Canon EOS Film Cameras with Back Button Focussing (BBF) | Year |
| EOS 600 • EOS 630 | 1989 |
| EOS RT | 1989 |
| EOS 1 | 1989 |
| EOS 10 • EOS 10S | 1990 |
| EOS 5 • EOS A2 | 1992 |
| EOS 1n | 1994 |
| EOS 1n RS | 1995 |
| EOS 50 • EOS 55 • EOS Elan II | 1996 |
| EOS 3 | 1998 |
| EOS 1v | 2000 |
| EOS 30 • EOS 33 • EOS 7 | 2000 |
| EOS 30v • EOS 33v • EOS 7s | 2004 |