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How to zoom and focus at the same time on a DSLR


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#1 Ale Capo

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Posted 26 January 2016 - 05:55 AM

Hi everybody,

I was making an amatorial short film for school and I had this shot where the character was seated on a chair reading a book. The camera was at his back and I wanted to change the focus from the character's head to the page of the book while at the same time zooming in it. Since I was using a cheap DSLR I couldn't hold the camera and at the same time deal with zoom and focus of the lense. How this shoot should have been done?

Ps: I'm not a native English, I'm sorry for some grammatical errors!

Thanks
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#2 Brian Drysdale

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Posted 26 January 2016 - 06:08 AM

You need a parfocal zoom lens to do that, the varifocal design as used on most stills zooms don't allow you to pull focus and zoom at the same time (or at least easily). Having said that breathing when pulling focus on many parfocal zooms can make it ugly when zooming at the same time.


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#3 Mark Dunn

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Posted 26 January 2016 - 06:21 AM

For a start you need the camera on a tripod or other support, otherwise you need about 4 hands.

Older stills zooms let you zoom and focus with one movement, but they fell out of favour because they were unsuitable for autofocus. You might be able to get one and adapt it to your DSLR. Twist to focus, push/pull to zoom.

You need something like this.

https://www.flickr.c...ino/16116285933

Professionally it would be done by two people, one on focus and one on zoom, or one with a remote unit.

As Brian says, unlike cine lenses stills lenses don't necessarily hold focus when you zoom. They don't need to. But as you are pulling focus anyway, it doesn't matter in this case.


Edited by Mark Dunn, 26 January 2016 - 06:25 AM.

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#4 Ale Capo

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Posted 26 January 2016 - 06:43 AM

Thanks, I didn't know what a parfocal lense was, now it's clear. By the way, on that shot I couldn't use a tripod because it was a 50 seconds shot with a movement from the front of the character to his back and then to the book. Maybe too hard to realize with no equipment!
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#5 Satsuki Murashige

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Posted 26 January 2016 - 08:01 PM

Definitely sounds like a challenging shot, even for a professional crew. To start with, you absolutely must have a parfocal lens that holds focus when you zoom, or at least shoot at a deep enough aperture so that the depth of focus of the lens holds throughout the zoom, making the lens effectively parfocal.

Next, if the shot must be handheld or on a Steadicam, then you need a way to control the zoom remotely. Usually, to do this you would use something like a Preston Microforce Zoom Control with the zoom handle replacing one of your handgrips, or a Preston FIZ3 wireless lens control system and let your 1st AC perform the zoom. Finally, you would also need wireless focus control and a 1st AC to pull focus. If you were only shooting handheld, then your AC could also use a manual follow focus and a whip.

If the camera can instead be on a dolly and circular track, then you can perform all of this manually by having the 1st AC pull focus, the 2nd AC pull zoom, all while you operate the camera. In that scenario, all three of you would be riding the dolly, so you would probably need two dolly grips to push since it will be so heavy. Or you can still choose to use the Microforce and do the zoom yourself by putting the zoom handle on pan bar of the tripod head, necessitating only two people to ride on the dolly. That's probably what I would do.
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#6 Ale Capo

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Posted 27 January 2016 - 05:09 AM

It's nice to learn from you guys, thanks again. I have a doubt, does the parfocal lens still let you make the focus-shift effect (from character's head to the book) or is the whole scene already on focus at the same way?

 

I wanted the scene to end with the zoom and focus to the book and the rest of the details in shot blurred but I'm not sure wether you can get the blur effect with this lens or not. Do you see the idea?


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#7 Mark Dunn

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Posted 27 January 2016 - 05:20 AM

'Parfocal' refers to a particular aspect of lens design. It isn't a special lens as such. What is and isn't in focus depends on sensor size, distance, focal length and aperture. It would be very difficult to get an entire scene, from near to far, in focus without a small aperture and a great deal of light.

Provided you can cope with some unsteadiness you may be able to achieve your shot with a lens of the type I described earlier, but with a modern DSLR zoom it would be extremely difficult unless you can figure out a way to use the autofocus.

Ask your tutors about depth of field.


Edited by Mark Dunn, 27 January 2016 - 05:24 AM.

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#8 Satsuki Murashige

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Posted 27 January 2016 - 06:01 PM

does the parfocal lens still let you make the focus-shift effect (from character's head to the book) or is the whole scene already on focus at the same way?
 
I wanted the scene to end with the zoom and focus to the book and the rest of the details in shot blurred but I'm not sure wether you can get the blur effect with this lens or not.


Yes, absolutely you can. Still photo lenses work just like cinema lenses, so you can still rack focus with the manual focus ring and control depth of field with the aperture settings. The main difference with zoom lenses is that a non-parfocal lens (most stills lenses) will shift focus as you zoom. This is no good if you want to have full control over what is in focus and what is out of focus during the shot. So that's why you would only use parfocal zooms lenses (all cinema lenses and some stills lenses) if you were trying to make this type of shot. Otherwise, there would be no way to guarantee correct focus moment to moment.
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#9 Jan Tore Soerensen

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Posted 07 February 2016 - 07:24 PM

Wouldn't it be easier to just move the camera forward and pull focus?


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#10 Ale Capo

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Posted 11 February 2016 - 06:28 AM

Actually, yes. I also tried to do it but i couldn't pull focus well while moving forward for two reasons:

 

1) I was using the cheapest DSLR and i couldn't see well the LCD

2) I am a newbie and maybe even with the best DSLR of the world I couldn't realize the shot


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#11 Sabyasachi Patra

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Posted 11 February 2016 - 01:11 PM

You should try the Canon 70D with Dual pixel autofocus.

 

With any other model of Canon you may try the Canon's 24-105 lens and zoom out from 105 to 24 mm. It will retain focus.


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#12 Jan Tore Soerensen

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Posted 11 February 2016 - 04:12 PM

Actually, yes. I also tried to do it but i couldn't pull focus well while moving forward for two reasons:

 

1) I was using the cheapest DSLR and i couldn't see well the LCD

2) I am a newbie and maybe even with the best DSLR of the world I couldn't realize the shot

You'll need MagicLantern software which has focusmarkers, and preferably a monitor, which will make the whole operation easier. It's usually about having the right tools for the job. Well, that or 15 takes, to get one usable.


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#13 Satsuki Murashige

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Posted 11 February 2016 - 04:35 PM

Actually, yes. I also tried to do it but i couldn't pull focus well while moving forward for two reasons:
 
1) I was using the cheapest DSLR and i couldn't see well the LCD
2) I am a newbie and maybe even with the best DSLR of the world I couldn't realize the shot


I think also there is a limit to how much one person can do. On a professional set, a good operator only worries about framing the shot. The 1st AC only worries about the focus. If there is a dolly shot, the dolly grip takes care of the movement. So when you have multiple specialized technicians who are really good at their job working together, then you can accomplish more complicated shots. It would be very difficult even for a professional to pull off the shot you described if they had to operate and pull focus by themselves. Maybe you could automate parts of the shot by using a good autofocus system and using an image stabilized lens, but it's still a compromise compared to working with a talented crew.
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#14 Jon Kline

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Posted 16 February 2016 - 12:45 PM

You'll need MagicLantern software which has focusmarkers, and preferably a monitor, which will make the whole operation easier. It's usually about having the right tools for the job. Well, that or 15 takes, to get one usable.

Fifteen takes for a shot like this seems like not nearly enough.

 

There comes a point where the cinematographer has the right, or obligation, to turn to the director and say: "I think there is a better way to tell the story." A cut, a fade, a camera move, or blocking change can all be considered. There are a lot of tools in the visual storytelling toolbox.

 

DSLR filmmaking is usually about creating the "film look" illusion. You can't maintain that illusion when your camera operator is doing the job of three people, with the equipment of none of them.


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