Focusing question

[Hans Sandstrom]

I'm struggling with my 600D trying to learn to handle it. After three years with Canon HV30 I miss the autofocus...
My question is more about how autofocus works — does it measure the average distance to what I see in the viewfinder or...? If so, it must mean that everything is out of focus, more or less.

Please share your wisdom

Hans S

[Murray Christian]

The 60d (and most dslrs I think) uses phase detection for focus, which judges the image on the sensor in clever ways against a copy from a slightly different angle.
Autofocus - Wikipedia, the free encyclopedia
So when two points in the given ..er focus point match, that is in focus. You could probably triangulate distance from this system, vaguely, but I don't think it does (since it wouldn't be very accurate, depending on the lens and so forth) . Hence you can get that hunting of autofocus in low light or low contrast situations.

The HV30 has an infrared rangefinder, like a lot of video cameras, and may use a hybrid of the two (I can't find my manual right at the minute).

[Hans Sandstrom]

Thanks, this is more complicated than I expected and, according to the link, very close to rocket science.

My main problem with manual focusing is the short distance between focus and unfocus — feels like a fraction of a millemeter. Does a follow-focus use a "gear-box" to handle this?

[Jon Fairhurst]

The best way to get sharp focus in Live View is to zoom in by 10x before recording and set your focus point. If the actor will move to a second location, do this twice and mark the two positions on the lens or follow focus. Then, when you do the take, you can really nail the focus. Focus on the eyes.

For live work, use a loupe or monitor and stop down the lens to f/4 or tighter. This will increase the depth of field and make it easier to hit focus.

Another method is to go with a fast, wide-open lens and embrace the feeling of being in and out of focus. Rather than focus with the lens, you can focus handheld shots by moving your feet.

[Murray Christian]

Originally Posted by Hans Sandstrom

Thanks, this is more complicated than I expected and, according to the link, very close to rocket science.

My main problem with manual focusing is the short distance between focus and unfocus — feels like a fraction of a millemeter. Does a follow-focus use a "gear-box" to handle this?

How fine that is depends on the usual stuff; brand and model of lens, focal length, aperture. But you can end up with very fine adjustments necessary in a lot of situations. Some are better than others, but it's also that using photography equipment for video isn't always the neatest fit in terms of usability (eg: if you went to "video school" like me you might have been taught that a good way to focus is to zoom in on the subject, focus and zoom back out to the frame you want. What they didn't mention was that this is a design feature, not an intrinsic property of optics, and a lot of cheaper photography gear doesn't keep focus very well when zooming in and out --- edit: I should make clear this has nothing to do with Jon's advice, merely my schooling not including a certain breadth of information). But it's all about the picture and if you've got to stand on your head to get the best resolution and operate focus with your teeth we probably will.

Anyway, can't say I've ever seen a gearbox sort of system (and I shudder to think what it'd cost. Better off making it yourself out of Technic Lego, I'd say). Mostly you swap to a different ratio'd drive wheel though, I think.
Just the difference in changing the axis of movement helps a lot in fine adjustments though. Also if focus is so critical it becomes impossible to keep the subject in for any length of time, generally people just change the shot. So it depends what you're doing.

[Hans Sandstrom]

Thank you both — I suddenly realize how much I have to learn before actually using my DSLR.
Or I can switch to my iPhone again...

vimeo.com/29743254

Hans

[David Knaggs]

Originally Posted by Hans Sandstrom

I suddenly realize how much I have to learn before actually using my DSLR.

Hi Hans.
I don't know if you're a member of Lynda.com or not but, if you are, they've got a brand new set of tutorials called "Shooting with the Canon Rebel T3i (600D and Kiss X5)" and he covers some good points about using the autofocus.

I come from a 100% video background (I was never interested in taking still pictures, only motion pictures) and have always focused by turning on the peaking, zooming all the way in, setting focus and then zooming back out to my desired framing. Like Murray, I'm unsure whether the cheaper stock lens can really hold the same focus while zooming in and out and so I studied the autofocus tutorials (on Lynda.com) with great interest last week.

Basically, the camera has a number of automatic focus points spread around its field of view. By default, it automatically tries to identify which one of those points is sitting on your subject. There is a way to override that automatic mechanism, in case the camera has chosen the wrong point, by manually choosing the focus point yourself.

I chose the center focus point when I did some executive portraits last week (stills) and the auto-focus worked great. I took shots of each person in front of two different backgrounds (each with its own lighting set-up). I took portraits of 30 people in about 3 hours (I'll spare you the long backstory of how this circumstance came about). With the two different set-ups, that meant I had to focus 60 times during that period and achieved a good focus every single time.

The simple method I used was to slide the button on the lens barrel to AF, frame my subject, tilt slightly to get my centre point in the subject's face, half-press the shutter button until focus was achieved, slide the button to MF (manual focus), re-tilt to my proper frame and then take my shots.

This was with a Rebel T3i (the same model as your 600D) and this focusing method worked so well (and fast!) for stills that I'm pondering using it with the video mode on the T3i.

But bear in mind that I am probably the least experienced person on this board when it comes to DSLRs. Those portraits were the first time I'd tried to use a DSLR for stills, so you can take what I say with a large grain of salt, if you wish.

[Hans Sandstrom]

Hi David,

First I have to correct you — I am the least experienced person in this forum when it comes to DSLRs :-)

Thanks for your tutorial. I used the same way as you when shooting in manual mode on my HV30 trying to get a more shallow DOF.
A question — why did you leave AF-mode when taking those stills? Couldn't this be done staying in AF all the way?

[Hans Sandstrom]

Sorry, I ment MF.

[R Geoff Baker]

This is not an answer to your question Hans, but a comment on the video you linked:

Your iPhone video demonstrates an often overlooked fact -- skill trumps equipment most any day of the week.

I hope you get comfortable with the expanded options the DSLR will give you, and I look forward to watching more of your work.

Cheers,
GB

[David Knaggs]

Hi Hans.

We may have to call it a draw on being "least knowledgeable" concerning DSLRs. Although, coming from a purely video background, I didn't even know what "ISO" meant until two weeks ago!!!

And that was a big reason why I got the T3i (besides its video capabilities). This new breed of larger-sensor cameras around the $10,000 to $15,000 range (F3, C300, Scarlet) really demand a very solid grounding in the principles of stills photography, I think. Especially when it comes to the selection and purchase of lenses. So I've probably been using the T3i more for stills than video at this point, while studying the various Lynda.com tutorials (they've also got some great tutorials by Douglas Kirkland, the noted celebrity portrait photographer) and an excellent textbook recommended to me by a veteran DP.

As to your question, which I take to mean, "Why did you leave MF-mode when taking those stills? Couldn't this be done staying in MF all the way?"

Two reasons: 1) The large volume of people to photograph in such a short time left me with only 2 or 3 minutes to get the shots in each set-up. So focusing had to be really quick and certain. But I would always slide it back to MF immediately after focus was achieved, so that I could then take the actual shots smoothly and quickly.
2) I'm only using the stock lens on the T3i and so I'm not entirely sure whether it holds the same focus when you zoom in and out (I'm not quite sure if that's what's meant by the term "breathing"). I trust my fixed lens (to maintain focus after zooming back out) on the PMW-EX1R when I'm shooting video. Not so sure, until I get more knowledgeable, with the T3i stock lens.

But the good news is that the AF works great, so long as you manually select a single focus point for the AF to use beforehand.

[Hans Sandstrom]

Hi David,

Ha, so you know what ISO means - I don't have a clue...

Besides the stock lens, 18-55, I only have one lens - Tamron 10-24. Today I went to try the Tamron for the first time but, when arriving to my location, I had forgotten to bring it with me. So I ended up recording some 200 people with torches (it was a demonstration) downtown Stockholm using the stock lens. This was at 3 pm meaning that it was dark outside.

I shot everything in full automatic mode (with Quick focus mode) and am very impressed by the result. But so far I have only seen the footage in the viewer of the 600D.

When focusing I only used the center point of the nine available and then framed the scene as I wanted it. This seems to me to be the quickest way of focusing as you don't have to change focus point for every clip.

[Jon Fairhurst]

I recommend avoiding auto mode for a number of reasons, such as avoiding stuttering video, avoiding mid-scene exposure changes, and in getting the intended colors. Also, when filming similar scenes, you don't want inconsistency on different takes.

The settings you want are:
* Shutter: 1/50 (almost always. The exception is when you want a stutter effect.)
* ISO: 100 or 160 in the day; 640 or 1250 when the light is low
* Aperture: set as needed to get the right exposure. (If you want shallow depth of field when it's bright, you will need to use an ND filter. A 0.9 provides three stops and is good for bright days.)
* White Balance: Simply select sunny, cloudy, tungsten or fluorescent as needed. (For instance, choose sunny or cloudy for sunsets; otherwise, auto will remove the red from the sky!)
* Picture Style: Choose Normal. Set the contrast and sharpness at minimum. Put the saturation at one tick below mid-position.

Regarding setting the exposure, in manual mode, there are two methods. The quick and easy way is to center the exposure indicator. The more accurate way is to look at the histogram and make sure that nothing (or nothing important) is clipping.

You can print this out or make yourself a cheat-sheet for making these settings. Within a couple of days, it will become second nature. It seems daunting when it's all new. Like anything, it's simple after you know it. :)

[Hans Sandstrom]

Are you joking? If I had done that all the torches had burned out before I was ready to shoot...

But you are probably right — I have to be more familiar with the settings so I'll check the Lynda course.

Thanks for the list. I'll try it tomorrow even if I, so far, is quite happy with the quality i've got from the auto mode.

Hans

[Greg Fiske]

Hans,
Depending on your ambitions there are tools that are available to aid with focusing. You can install magic lanter (a camera hack) that provides focus peaking features. What it does is outlines in yellow the areas that are in focus. More expensive options include bigger monitors. The stock monitor on the camera is too small to accurately focus. With a bigger screen you can more reliable rack focus, and the monitors have focus peaking features to assist with focusing. And it just takes practice.