HD100 Rack Focus with standard Fujinon lens at DVinfo.net

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Old February 27th, 2006, 01:41 PM   #1
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HD100 Rack Focus with standard Fujinon lens

I'm preparing for a shoot this weekend, and the director is obsessed with rack focusing. and he keeps declaring the HD100 to be a 'crappy camera' because it 'can't rack focus'.

i've shown him some basic examples of rack with the camera, but he's thoroughly displeased, because he compares it with the Sony PD-150 and it's 'rack' capabilities.

I've tried to explain to him about the manual lens and a bit about the optics, but he remains displeased.

Unfortunately, I haven't been able to figure out the full capabilities of rack focusing with the HD100. I've managed to do some weird things by messing with the 'Back Focus' ring. but is that a good idea?

Any tips for racking with the HD100?

the main shots will be at NIGHT, car parked in front of a house, with the camera on the driver side looking at the driver through the car windows to the house. he'd like to first focus on the driver and then rack back to the house in focus.

(i hope i don't get bumped. this is a question about the HD100, so i think it's appropriate.)

:: efrain ::
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Old February 27th, 2006, 01:48 PM   #2
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If I'm not mistaken that lens has a macro on it? Focus on you're background "the house" then use the macro to make your close up subject in focus, that should give you the rack depth that the director is looking for.
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Old February 27th, 2006, 02:01 PM   #3
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Rack focusing is by definition the act of shifting focus between two planes (objects, people) within a frame. For a camera to be "unable" to rack focus, it would have to be unable to allow the user to control the speed and accuracy of the two focus points, which is the case with many of the electronically linked built-in lenses on video cameras. Any camera equipped with a manual lens (i.e. the focus element is mechnically operable) is thus capable of rack focusing, and that includes the JVC.

However, one complication that is common to all 1/3" cameras is the great depth-of-field that is a function of the size of the imager, which makes it more of a challenge to "see" the rack (i.e. have enough of the image out of focus to have the rack be visible when it occurs). Generally one will have to shoot substantially telephoto, with a significant distance between the two planes of focus. With the example you described, a focal length of around 20mm and a wide-open aperture combined with framing the gent in the car in a head-and-shoulders closeup should result in a "rackable" image.

It's been a long time since I used a PD150 but I know that that was a not a true manual lens, so I cannot see why it would be superior for this type of shot. From an optical standpoint, the depth of field should be the same with both cameras.

I hope you are able to convince your director, and that he is as equally obsessed with performances and telling the story as he is with rack focusing (which is a useful technique but can easily be overdone btw...)
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Old February 27th, 2006, 02:14 PM   #4
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The 16x stock lens breathes alot. If you can, I would suggest renting the Fuji Th13x3.5BRMU lens for your shoot. It hardly breathes at all by comparison.

I had a chance to review the 13x3.5 Wide Lens last week. I'm writing my review now, but here is a sneak peek at the breathing comparison of the two lenses.

http://timdashwood.com/.Movies/Breathing.mov
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Old February 27th, 2006, 02:22 PM   #5
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Great clip Tim. I got to use the 13x last month and I too am a big fan of that lens.

If anything, that clip does illuminate the point I was making about 1/3" imagers--it's hard to see the focus shift at all as the depth of field is virtually holding both subjects.

One way to cover breathing if present is to build a slight camera move like a pan into the move which will help mask the magnification.
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Old February 27th, 2006, 02:37 PM   #6
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spot on man..

yeah, the 16x lens was kinda bugging me because of the breathing.

thanks, i needed that convincing. because i'm a bit of a newbie-amateur, but from all the stuff i've learned, i know that the lens should be capable of racking - in theory. but because the of the depth of field range, it's a bit more difficult.
i told him about that, and he understood, but he was just bummed cuz it didn't look like he thought it would.

another option: i could back up the camera, closer to the middle of the street(if possible), and zoom in to the close-up of the driver, that should help with the racking.

i wonder if i'd lose a bit of light by having the lens zoomed in like that...gotta test it.
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Old February 27th, 2006, 02:44 PM   #7
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The further out you are on the lens the less breathing effect you'll get but you do not want to go beyond 40mm unless you want to risk CA on overexposed areas or highlights. It will rack focus nicely and if you're careful with lighting you can get dramatic focal events. True it's not the greatest lens in the world but you can achieve DOF effects. Following was out initial trial of rack focus with the HD-100 last year. Maybe the director can take a look.

Click here for wmv (45MB)
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Old February 27th, 2006, 02:45 PM   #8
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Quote:
Originally Posted by Charles Papert
If anything, that clip does illuminate the point I was making about 1/3" imagers--it's hard to see the focus shift at all as the depth of field is virtually holding both subjects.
True,
the best solution is to light well, use ND filter and stay at f2.8 and get as far away from the subject as possible to use the tele end of the lens. Also try to keep your subject as far away as possible to its background.

Well, of course, now we run into a possibility of CA at this point.

Steve
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Old February 27th, 2006, 02:48 PM   #9
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Breathless, also comments on shallow DOF

Tim,

What a great link to post. Very, very well done. That is in line with my experience with the wide lens. Any breathing is virtually imperceptible. But as for rack focusing, that sucker is hard to throw OUT of focus!

Anyway, does anyone agree with me that focusing to change the focal plane to force the viewer's attention back and forth between two people in a conversation has become a cliche, and worse is an artifice that can shake you out of the story and suspension of disbelief by reminding you of technical process? Also, what if I want to see the reaction of the actor who isn't the one talking? With this artifice, I am deprived of this choice.

The director who uses this artifice is forgetting that the viewer's reaction is part of the creative chain. I favor giving the viewer the freedom to range around the frame as they wish, not be yanked by the nose toward what the director wants them to "focus on" with DOF manipulation.

Also, a director should make the most of other filmmaking tools, say acting for one, to gently nudge viewers where he or she wants them looking. If a director has to rely on something as heavy-handed as a rack focus to draw their attention to the speaker, that is a sad commentary on the filmmaker's overall skill set.

But then I think shallow depth of field is an over-rated artistic element in general, no doubt useful in certain instances but one that should not a primary determinant of composition.

Good advice about going full telephoto to blur the background, but even that has drawbacks. I was working on a doc and the DP did his talking head shots from over 40 feet away so he could go full telephoto and throw the background out of focus. Sure, that worked, but it also flattened out the features of the subjects who then looked significantly less lifelike.

I'd rather have a better looking foreground subject than compromise that for the background look. I know this is a bit of an extreme example verging on "strawman" but the fetish for shallow DOF is way over the top too.

It has also not ALWAYS been a cinematic convention. Watch "Citizen Kane" and remember the lengths that Orsen Welles went to for the huge DOF that was a signature aspect of the "Greatest American Film."

Okay, I'm putting on my nomex suit and having my wife stand by with a fire extinguisher so I don't get fried by the flames!

Tip
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Old February 27th, 2006, 02:49 PM   #10
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I'd be less worried about CA on the long end, and more worried about vignetting. I find the stock lens starts to vignette between 40mm and 88mm.
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Old February 27th, 2006, 02:51 PM   #11
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Quote:
Originally Posted by Tim Dashwood
I'd be less worried about CA on the long end, and more worried about vignetting. I find the stock lens starts to vignette between 40mm and 88mm.
True but the CA is unmistakable out there on anything near field.

Anyway, good luck..
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Old February 27th, 2006, 02:54 PM   #12
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Quote:
Originally Posted by Tip McPartland
It has also not ALWAYS been a cinematic convention. Watch "Citizen Kane" and remember the lengths that Orsen Welles went to for the huge DOF that was a signature aspect of the "Greatest American Film."

Okay, I'm putting on my nomex suit and having my wife stand by with a fire extinguisher so I don't get fried by the flames!

Tip
No need for extinguishers... you are completely right about Citizen Kane. Sometimes we do obsess a bit too much over DOF...
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Old February 27th, 2006, 02:58 PM   #13
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FOV comparison of 16x and 13x

Here's my measured Field Of View comparison between the 13x3.5 @ 3.5mm and the 16x Stock lens @ 5.5mm and 4.5mm (with 0.82 Wide Adapter.)

http://timdashwood.com/.Public/13xvs16xFOV.jpg

Just one more reason to rent this lens for dramatic work, especially in cars.
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Old February 27th, 2006, 02:59 PM   #14
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Quote:
Originally Posted by Stephen L. Noe
The further out you are on the lens the less breathing effect you'll get but you do not want to go beyond 40mm unless you want to risk CA on overexposed areas or highlights. It will rack focus nicely and if you're careful with lighting you can get dramatic focal events. True it's not the greatest lens in the world but you can achieve DOF effects. Following was out initial trial of rack focus with the HD-100 last year. Maybe the director can take a look.

Click here for wmv (45MB)
Stephen

Do even the best lenses produce CA if the shot is overexposed?

Tony
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Old February 27th, 2006, 03:08 PM   #15
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Quote:
Originally Posted by Tony Goodman
Stephen

Do even the best lenses produce CA if the shot is overexposed?

Tony
There is no perfect lens. Even Flourite lenses will have some CA, but will be less than non-flourite glass.

Even the 13x3.5 lens has CA. I compared CA between the lenses (results with frame grabs will be forthcoming) but it isn't as bad.

On either lens, if you open the iris up all the way you will get a purple to green gradation, top to bottom, over the whole image. We've seen this before from some people, but I've finally identified it as CA and not an electronic problem.
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