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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Iris Rack?

Joshua Brown

Joshua Brown

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Anybody use this? Heard of it. Only recently have I heard about this technique. It sounds a bit technical to me given the challenges it presents.

Basically, the camera op (or whoever) adjusts the iris during the shot the change the depth of focus.

But wouldn't that change the exposure? I think this would be really cool for a couple shots I'm envisioning. But I'd like to see how other people handle this type of shot.

So what do you guys do?

-J.A.Brown
 
Josh, we did this on the short you helped on, the close up of the girls stomach was too hot so I had Sam do an Iris rack (he opened it up a stop after the camera panned up). Yes, the DOF increases, but that isnt nearly as noticeable as the change in exposure.
 
Shawn Nelson said:
Josh, we did this on the short you helped on, the close up of the girls stomach was too hot so I had Sam do an Iris rack (he opened it up a stop after the camera panned up). Yes, the DOF increases, but that isnt nearly as noticeable as the change in exposure.
Click to expand...

Haha. Thats great, I didn't even notice.

So I guess that confirms my suspicions, it changes the exposure considerably. But even if you could rack the shutter speed also, that would completely change the feel of the shot/frames. So do you just live with the exposure change?

I imagined it for a reveal type shot. Where the person or object to be revealed in the classic Horror style (behind the character). Except we can see them, just horribly out of focus given the DOF. Then when the character whips around to face the horrific... thing... the iris is racked to include both of them in relative focus. BUT then the exposure would be radically shifted.

Is this just pipe dreams or is this actually done. I guess I'm specifically talking about going from WFO to F16 or so.

-J.A.Brown
 
Might be better handled with a tilt shift lens. Or a simple edit to another lens- you could even morph between the two if you're sneaky enough.

Noah
 
If I was told to get this shot, I'd shoot the front guy (who starts in focus) in front of a green screen, then make the back guy (who starts OOF) as the background plate, shot clean the whole time. Then, in post I'd time the blur to rack clean as the front element turns and looks.

I read that Speedracer shot things on different plates and used greenscreen to get shots that are optically impossible
 
So I'm basically going about it the hardest possible way. :p I've been in stills land for too long... starting to forget.

Thanks for the tips guys.

-Josh
 
Joshua Brown said:
Is this just pipe dreams or is this actually done. I guess I'm specifically talking about going from WFO to F16 or so.
Click to expand...

Can be done with lens control and camera control systems on film cameras however you might be best to shoot it clean and do it VFX.
 
Curious as to what the story point would be that would motivate this...not challenging, just genuinely curious, because generally I would simply envision this as a focus rack, and be fine with the person in the foreground going out of focus once they had turned to see the intruder. Anyway, if nothing else, this would be really cool to experiment and play with.
Peace,

-Harry
 
Harry Lipnick said:
Curious as to what the story point would be that would motivate this...not challenging, just genuinely curious, because generally I would simply envision this as a focus rack, and be fine with the person in the foreground going out of focus once they had turned to see the intruder. Anyway, if nothing else, this would be really cool to experiment and play with.
Peace,

-Harry
Click to expand...

No story yet to incite motivation of camera moves. Just imagining and testing to add things to my arsenal. I was just thinking about it being used and wondered if it can/had been done. I just imagine it having some interesting new feel to it given I havn't really seen it before. A rack gives a certain feel, and I'm curious what this move would feel like.

-J.A.Brown
 
Joshua Brown said:
So I'm basically going about it the hardest possible way. :p I've been in stills land for too long... starting to forget.

Thanks for the tips guys.

-Josh
Click to expand...


You might be able to reveal him with a dolly move combined with a rack focus that lands the camera an equal distance from both characters thereby rendering them both focus with no exposure change. You might have to make one character or the other move during the shot. Maybe speed the move up in post if you want to be stylized about it.

If the rear character is far away that probably wouldn't work real well. Then I'd probably just rack to the rear guy and cut to a wide with both in focus.

You could simply have the bad guy in the left rear of the frame and have our hero walk from close to the camera back to right rear of the frame without noticing the bad guy. The bad guy slowly comes into focus with the rack on our hero.

You could rack your brain on this one forever but I'm not sure the shot is worth it. Change the idea up a bit IMHO. :Angel_anim:
 
Or you could do the classic dolly counter zoom out/vertigo effect that was very popular in the '70s. That's a pretty spooky thing.

http://www.youtube.com/watch?v=Y48R6-iIYHs

I'm a big fan of in-camera effects. :)

-Noah
 
Joel Kaye said:
You could simply have the bad guy in the left rear of the frame and have our hero walk from close to the camera back to right rear of the frame without noticing the bad guy. The bad guy slowly comes into focus with the rack on our hero.
Click to expand...


I like this bit a lot. Very interesting idea. That, combined with your afore mentioned dolly in would be very cool.

Not to beat a dead horse, it seems this shot has not practical purpose and I'd have to agree at this point. But being that it's theoretical I don't mind exploring it a bit more:

How do you feel about calculating the light falloff from the iris rack and fading up the lights to match the falloff? I don't know, I just think it would add a very eery sense about it to have EVERYTHING suddenly come in focus.

Maybe it could go from a locked off shot to a sudden iris rack and Dolly Pull out for a wide reveal (for a group of baddies), using the light fading technique.

-J.A.Brown
 
Noah Kadner said:
Or you could do the classic dolly counter zoom out/vertigo effect that was very popular in the '70s. That's a pretty spooky thing.

http://www.youtube.com/watch?v=Y48R6-iIYHs

I'm a big fan of in-camera effects. :)
Click to expand...

Yeah. I was thinking changing focal length could work too. Start with the camera back and zoomed in (include both characters). Dolly in, zoom out and the background comes into focus as you do it.

That may be the best route. Well VFX where the whole room is CG would and shots of the background got at different F-Stops that could be blended with a CG iris rack or morphs might nail it exactly as described. You gotta want that pretty bad though. :-)
 
Or just set focus close so the bad guy can walk into focus from being way out of focus- that's spooky too...

Noah
 
Joshua Brown said:
How do you feel about calculating the light falloff from the iris rack and fading up the lights to match the falloff?
Click to expand...

I don't know that you'd need to do a whole lot of math. Light the room for the max aperture with all the lights on dimmers and that's MARK II. Dim the lights to until the meter reading in the same spot matches your wide open aperture for MARK I.

Probably something like a 20mm lens with our Hero 3 feet from the lens with an Iris rack from F2 to F11. Add a pinch of salt for taste - LOL. F11's a lot of light though. Obviously all your shadows change and things get more contrasty - which might fit just fine. Maybe everyone dies in a wide contrasty scene and that's how you get there.
 
Joshua Brown said:
No story yet to incite motivation of camera moves. Just imagining and testing to add things to my arsenal. I was just thinking about it being used and wondered if it can/had been done. I just imagine it having some interesting new feel to it given I havn't really seen it before. A rack gives a certain feel, and I'm curious what this move would feel like.

-J.A.Brown
Click to expand...

Right on dude. I'd love to see footage of some camera tests if you ever get a chance.
Peace,

-Harry
 
"Or just set focus close so the bad guy can walk into focus from being way out of focus- that's spooky too..."

Much prefer that to the Vertigo thing, which is so played out. And it's too much human activity to control the image shift. I don't like that effect.

It worked well in Jaws (probably the last time I care to see it) because of how the scene was cut -- masterfully. Brody is extremely tense, watching through the beach bodies as they cross in front of his vision. Each time someone crosses, the zoom ratio changes. It's jarring as he jumps closer, farther, looking all around as he knows the high stakes. His sense of responsibility and his diligence in trying to fulfill his responsibilities is perfectly shown without words.

Then -- the big zoom rack. That's the money shot after a harrowing build up.
 
I used it on a short I did (Prairie Odyssey) quite a
few years ago. Context; Dying old man dreaming
about when he was a kid on a FARM: we dolly in,
from med wide to close up of young boy's face as
he has a revelation about the meaning of an old compass,
and we very slowly creep focus out and open up aperture-
moving through nice high key images that give the kid an ethereal look,
to a blown out image that merges into a cloud scene. Dreamy.
Would be safer to do in post, but that's no fun.
 
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