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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 :)

adjusting dof while shooting

H

Holger Rytter

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Is there any system that allows you, while shooting, change your depth of field without losing/gaining exposure? Perhaps something with an electronic lens with stepless aperture and have your camera change the aperture in, say, 1-stops while changing the ISO or shutter speed. Am I missing something here? To me it seems like it would be possible and perhaps be an "interesting" effect
Has any of you tried this or seen something similar or is it just not practically functional?

EDIT: or well.. stepless aperture is not really smart when ISO is not... :-)
 
Holger Rytter said:
Is there any system that allows you, while shooting, change your depth of field without losing/gaining exposure?
Click to expand...

Yes. It's called aperture ramping, and you can do it with Arricams and 435s, unfortunately no digital camera is able to do it, yet, afaik. Maybe the Alexa Studio and the F65 with the optional mechanical rotary shutter will be albe to offer such an option.
 
Oh I see. Could you enlighten me on why a mechanical shutter is necessary for that?
 
because when you change the aperture while rolling, you need to compensate for the change in the amount of light that gets through the lens. In other words, if you want to reduce the depth of field by opening the iris by, say, 3 stops, you either have a dimmer to decrease the light level (which is probably a way you could do it with digital cameras, *if* you have total control of the lighting, or use John's method of variable NDs), or you change the shutter angle, and you can change the "real" shutter angle only in cameras with a mechanical spinning mirror shutter. With the ARRI WRC is all automatic, you just choose what you want to ramp and how much, and how you want compensate it.

In theory, you could compensate by changing ISO in a digital camera (if there was an option to do so in a smooth way), but there would be some changes in the quality of the image (increase in noise levels, shifting/reduction of dynamic range, etc.).
 
New firmware request? Should be doable with Epic/Scarlet...
 
Michael Mayda said:
New firmware request? Should be doable with Epic/Scarlet...
Click to expand...
I know ISO is pure meta-data here, but wouldn't it be possible with a firmware upgrade? If there was something like a shockless ISO change, or whatever you would call it, it wouldn't be too hard to code, right?
 
Holger Rytter said:
Is there any system that allows you, while shooting, change your depth of field without losing/gaining exposure? Perhaps something with an electronic lens with stepless aperture and have your camera change the aperture in, say, 1-stops while changing the ISO or shutter speed. Am I missing something here? To me it seems like it would be possible and perhaps be an "interesting" effect
Has any of you tried this or seen something similar or is it just not practically functional?

EDIT: or well.. stepless aperture is not really smart when ISO is not... :-)
Click to expand...

Are you trying to fire you focus puller guy? LOL
 
I think in the original spec for epic there was external control for framerate, and shutter. i.e that we should be able to control the frame rate and shutter by the control port.

So I think it will come in future updates.

However if you have LDS into your meta data you could reverse the F stops in ISO adjustments in the other direction so you get a constantly exposure, as long as you are not pushing your image of the sensor.

Or you could just pull the Fstop and then just color match your sequence to a frame before the pull, or after...
 
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