Complete Guide for Manual Focus

[Haitham Lawati]

It is well known to every individual dealing with professional cameras and particularly cinematography types that the manual control of focus is a very challenging task.
From this point, it is necessary for every camera operator to have thorough knowledge about the theoretical and technical aspects related to focusing, and superior skills to deliver the appropriate image for the human eye to feel convenient.
ِAs far as manual focus for video shooting is concerned, I am very keen to improve my knowledge about lens focusing and the techniques of measurement and calibration. I will be very grateful if anyone can guide me to some educational resources and complete guidance in this regard.

[Haitham Lawati]

Any Reply ?

[Battle Vaughan]

Patience, patience! The nature of this forum is such that it usually takes a few days for enough people to pass through that someone has a cogent answer for you. Also, your question arrived very early on a Sunday morning in North America, where many of our members live....

The only help I can offer is my experience, in which as a still photographer I practiced follow focus for hours, following automobiles on the street behind my house, practicing to cover sports events. It helped. There are some technical details of setting up your camera's backfocus which will be specific to your brand and model, and that information should be available from the manufacturer. Other than a basic knowledge of depth-of-field, focus is about eye-hand coordination, which only extensive practice can give you. Hope that is some help....

[Jon Fairhurst]

One challenge for video is to know the "curve" of the lens. When the subject is far away, you barely turn the lens ring. When the subject is close, you need to turn it quickly. Getting that feels takes practice.

One trick that stills photographers use is to pre-focus to a specific point in space. When the subject reaches that point, shoot! This was especially important for wedding photographers with medium format cameras before SLRs and autofocus. The bride gets to the third pew and - snap!

A trick for handheld video is to adjust the focus coarsely with the lens and finely with your feet. If you move in and out with your subject, you'll hold focus without needing fine motor control or predicting the curve of the lens.

Of course, good equipment is important. This includes a good loupe or viewfinder and a good follow focus. With DSLRs on narrative shoots, we can zoom to x10, adjust our focus points, and mark them on the follow focus with gaffers tape. With a film camera where we can't zoom and the ground glass view screen might be ever so slightly out of position, it's best to use a calibrated lens and tape measure.

There's an irony when you stop down the aperture for live focusing. On one hand, it's more forgiving. On the other hand, it's hard to know if you are in the middle of the focus range or at its edge. When the DOF is shallow, you'll sometimes see the details pop and know that you've nailed it.

Speaking of which, there are some firmware tools either in the camera or in the monitor that can help. Some will simple amplify sharp edges. Some will replace sharp edges with red pixels. Some let you zoom the center of the screen.

I'm sure that there are more tips, but those come to mind.

[Chris Harding]

Definitely practice and it might sound silly but get in your mind which way the focus ring turns!! As the subject moves closer it's pretty important to know whether you need to turn it clockwise or counter clockwise!!

Also it's really useful to know what depth of field you are working with! The DOF at F1.8 is tiny but assuming the same distance, F4 has a lot more DOF so you have more latitude!

Use this to find your DOF at various settings/distances Online Depth of Field Calculator

Lastly if your camera has focus peaking then use it ...there is nothing more re-assuring than seeing your picture full of yellow hi-lights showing you what is in focus!! (my peaking is yellow but whatever colour you choose)

Chris

[Haitham Lawati]

Originally Posted by Use this to find your DOF at various settings/distances [url=http://www.dofmaster.com/dofjs.html

Online Depth of Field Calculator[/url]


Chris

That's what I really need to understand. The following terminology are not clear to me as far as focusing is concerned: Hyperfocal, Far limit, near limit and Depth of Field

[Jim Andrada]

All the terms you list are closely related and sort of refer to the same thing

I'll try to make it simple

Let's start by assuming that we have a perfect lens (there really isn't any perfect lens, but that's a topic for the advanced explanation- for now just assume that the lens is absolutely perfect) and what it does is make a perfect image of all the points one one plane on another plane at some (usually closer) distance. In the case of a camera, we would say that the lens is FOCUSED at 10 feet if it every point on a plane 10 feet in front of the camera.showed up as a perfect point on the surface of the film

The key here is that there is only one plane that will be exactly in focus and a point even a tenth of an inch closer or further away won't be imaged as a perfect point on the film/sensor, but as a slightly larger spot.

Fortunately, the way the human eye works, we can't distinguish between a perfect point and a spot as long as the spot is very very small. This means that there is a range of distances closer and further from the lens within which things LOOK acceptably sharp or IN FOCUS. This is what's called the "DEPTH OF FIELD". Images of things that fall within within the "depth of field" will look sharp, or IN FOCUS, Images of things outside of this range of distances will look "fuzzy" or OUT OF FOCUS.

The NEAR limit and the FAR LIMIT are the distances between which things look IN FOCUS. Things closer than the NEAR LIMIT or further than the FAR LIMIT will look soft or OUT OF FOCUS.

If the FAR LIMIT is really really far away. we would say the FAR LIMIT is at infinity. If for example we focused the lens at 15 feet and everything from 15 feet to "infinity" looked sharp, we would say that 15 feet was the "HYPERFOCAL DISTANCE"

And as an extra bonus, not only would everything from 15 feet to infinity be in focus, everything from 7.5 feet (half of the hyperfocal distance) would also be in focus, and the DEPTH OF FIELD would be from 7.5 feet to infinity.

Hope this helps. Things are actually a bit more complicated and this wasn't EXACTLY the right explanation, but it's pretty close to correct.

[Chris Harding]

That's a pretty good explanation Jim!

For basic focussing you don't really need to know much more than that I reckon! In the field as long as you have a rough idea of near and far limits for your most used apertures then you can focus manually pretty well especially with similar events like weddings. I can cruise around a reception with my 18-38 F1.8 and I have a pretty good idea of whether a guest table will be in focus or not as most tables are the same size and I know how far to stand back to utilise the depth of field to my advantage ... again it all comes with practice.

Haitham? What camera and lenses are you using ...if you let us know we could probably issue a little more advice!

Chris

[Jim Andrada]

I was a Chemistry and Physics major in college (from which I graduated 50+ years ago) so I'm surprised I remember even this much.

It's sort of getting to where when I go to a party I wear my "Hi, I'm Jim" tag upside down so I can read it myself and remember who I am.

[Chris Harding]

Hi Jim

Yeah getting old really sucks! However we do have experience on our side and at least over here we get very generous tax rebates if you are working and are over retirement age.

We can also boast that we actually know what Super8 film is and while all these purists are struggling with trying to get the cinematic film look we simply picked up our Bolex Super8 camera wound up the spring and we were in business!!

Gotta get me an upside down name tag too I think!

Chris

[Jim Andrada]

It's all relative. Getting old sucks relative to some things but compared to the final alternative, it isn't so bad. Had a rather near miss a few years back. ICU, full blown life support, etc. Quite a fascinating, if miserable, experience, really. Did a lot of thinking about the meaning of life and all that.

Never quite made it to Perth, unfortunately. Lots of trips to Melbourne and Sydney and Brisbane though.

I have to admit that until I tried to write my little primer on focus just how complex a subject focus really is. I think most of us here have grown up with an understanding based on doing a lot of photography (even 8mm B&W!!) and just kind of absorbing the concepts as we went along, but there's an awful lot of physics lurking in the background.

Hope you're enjoying your autumn while we here in the desert are getting ready to enjoy (if that's the word) summer.

[Haitham Lawati]

Originally Posted by Chris Harding

Haitham? What camera and lenses are you using ...if you let us know we could probably issue a little more advice!

Chris

I am using Canon 6D along with EF 24-70mm f/2.8L

[Jon Fairhurst]

I see that the focus ring throw for the 24-70/2.8L is 105 degrees. That's on the tight side but is normal for many autofocus lenses.

Canon EF 24-70mm f/2.8 L II USM Lens Specifications and Measurements

Canon's EF 50/1.4 lens has a 204 degree throw but also has significant play. It's all good when focusing in one direction, but once you change direction you need to turn the ring about 5 additional degrees to get back to a previous point.

The Zeiss ZE 85/1.4 takes focusing to another level with 245 degrees and virtually no play. The ZE 50/2 Makro has a 305 degree throw. Keep in mind that the Makro can take you down to a very close 2:1 focus distance while the ZE 85/1.4 only gets as close as 39 inches, so that 305 degrees has to roll a lot further than the 245 degrees in the 85.

Regarding play, a follow focus will add a small amount of additional slop, so get a good one. The teeth of the focus ring add a bit of a zipper feel to the motion.

For solo shooting, I find a small focus handle on the follow focus to be a necessity. First, it allows you to turn the focus further in one move as you can twirl your finger round and round. Without the handle, you twist to the limit of your wrist, re-grab, and twist again. Also, you can feel the position of the handle, so without looking at it, you can turn from/to set points. Well, kind of. It's harder than it seems to turn a handle to a given, precise angle by feel alone. But at least it gives you a rough target.