Topics

Circular Aspect Ratio

Justin Black
 

Hi all,

I had the thought of putting a lens meant to cover a small sensor on a large sensor camera, with the effect that it portholes so entirely that you get a circular aspect ratio. Seems like a fun way to shoot a music video. Obviously the intention here isn't optical perfection edge to edge, would be embracing the falloff.

Any suggestions on lens/sensor combinations that would work for this? 16mm lenses on a RED Monstro seems like it would do it? I imagine different lenses in a set would have different image circles which would need to be factored in, different size circles could be scaled in post so long as they're not big enough to touch the edges of the sensor...

I'm not experienced in how to look at image circles info and relate that to whether it would have this effect on a given sensor, basic information there would be appreciated.

Thanks for reading!

Justin Black
DP
Toronto

Po
 

Hi Justin,

You may found this movie interesting to you. 

On 29 Nov 2017, at 21:55, Justin Black <contact@...> wrote:

Hi all,

I had the thought of putting a lens meant to cover a small sensor on a large sensor camera, with the effect that it portholes so entirely that you get a circular aspect ratio. Seems like a fun way to shoot a music video. Obviously the intention here isn't optical perfection edge to edge, would be embracing the falloff.

Any suggestions on lens/sensor combinations that would work for this? 16mm lenses on a RED Monstro seems like it would do it? I imagine different lenses in a set would have different image circles which would need to be factored in, different size circles could be scaled in post so long as they're not big enough to touch the edges of the sensor...

I'm not experienced in how to look at image circles info and relate that to whether it would have this effect on a given sensor, basic information there would be appreciated.

Thanks for reading!

Justin Black
DP
Toronto

Jeff Barklage
 

We used to do a very similar thing [yet square/rectangular] with hard mattes that were too small for the taking lens.
Like placing a 100mm hard matte [with a very small opening] in the matte box whilst shooting with an 18mm lens....of course you can do this in post, but why not have fun in camera!
We also once did a hotel door peephole POV effect by using a Kinoptik 5.7mm lens on a 35mm camera...perfect!!

I am prepping a food shoot where we will need to occasionally window down to 2K [240fps] on a Dragon, using a Cooke 9-50mm zoom, [which, by the way DOES cover 2k & 2.5K on the Epics] had a similar "port-hole" look when bumping the chip out to 5K.

--

Bill Randall
 

Jeff, with the Cooke & the Kinoptik did the port-hole look get cropped on the top and bottom of the frame? When I put my Kinoptik 5.7mm on an APS-C sensor camera (23.6mm x 15.6mm size) the whole image circle won't fit. Spec sheet says the Epic Dragon sensor is 15.8mm tall by comparison.

I've used a 2/3" format TV lens to get a full porthole on APS-C with a c-mount adapter, a dirt-cheap Toyo 12.5-75 zoom. It gives a nice grimy edge on the circle.

--
best,
Bill Randall
www.williamrandall.net

Chuck Barbee
 

If we can assume that lenses cover no more than the diagonal of the target (sensor/film frame) for which they are designed, then the object/image math found in the American Cinematograher's Manual will give you the answers you want.  Any format, any lens, any focal length, any f-stop..  Some lenses will do exactly  that, and some will cover a larger area.  Bench testing is probably the best way to find out for sure.

 

But why go to all that trouble and expense for mount addaters, etc.?   I mean, I'm a guy who loves 'old school' techniques as much as anyone.  I love doing things 'in-camera'.  But Vignetting in post will give you the same thing and you'll have more control.  The best reason to do what you suggest would be if you want to mount a lens of a wider focal length than you could find for, say, the Red.  I.E. a 4mm or 5.5mm zoom for a 1/3" chip camera or an 8mm camera.  Then you would probably be able to zoom from a fairly normal looking shot inside the vignette, to a "fish-eye" look inside the vignette.  The 9.5-57'' Angenieux is one of the widest zooms for 16mm.  There is also the 5.7mm Angenieux prime.  An excellent piece of glass with almost no barrel or pincushion distortion in 16mm.  Mounts could be made for these, for the Red, if they don't exist already.

 

Good luck.

 

Chuck Barbee

Director of Photography (Retired)

Local 600 

 

 


From: cml-glass@groups.io [mailto:cml-glass@groups.io] On Behalf Of Justin Black
Sent: Wednesday, November 29, 2017 5:55 AM
To: cml-glass@groups.io
Subject: [cml-glass] Circular Aspect Ratio

 

Hi all,

 

I had the thought of putting a lens meant to cover a small sensor on a large sensor camera, with the effect that it portholes so entirely that you get a circular aspect ratio. Seems like a fun way to shoot a music video. Obviously the intention here isn't optical perfection edge to edge, would be embracing the falloff.

 

Any suggestions on lens/sensor combinations that would work for this? 16mm lenses on a RED Monstro seems like it would do it? I imagine different lenses in a set would have different image circles which would need to be factored in, different size circles could be scaled in post so long as they're not big enough to touch the edges of the sensor...

 

I'm not experienced in how to look at image circles info and relate that to whether it would have this effect on a given sensor, basic information there would be appreciated.

 

Thanks for reading!

 

Justin Black

DP

Toronto

Douglas Glover
 

Hi,
I used an old Angenieux 12-120 from the 16mm days on a Red Epic for a spot.  We were going for a vignette effect.  The lens produced very soft vignetted corners and the sharp area in the center of the frame went very soft and created a smear as it transitioned into the black of the vignette.  This is different from what you were going for but a very interesting look.

Douglas Glover
Cinematographer
Los Angele, CA