Jump to content


Photo

Portholing? can i get some help


  • Please log in to reply
1 reply to this topic

#1 Zachary Baney

Zachary Baney

    New

  • Basic Members
  • Pip
  • 1 posts
  • Student

Posted 28 June 2008 - 02:04 PM

I have recently been discussing what portholing (dark center and brighter center) is and how it pertains to digital photography and cinematography.

From what I understood it is mostly caused by the size up the rear element. digital sensors are inherently more reflective than the emulsion of film. I was told that if the rear element is too small then the rear element will reflect light bouncing off sensor and create a hot center. If the rear element is larger than the sensor then this problem will not ocur.

If this is true then I assume that rear element size/coating in the primary differnce with digitally optimized cine lens

This all makes sence to me except the fact that digital still lens often have very small rear elements and do not exhibit portholing. at least from what I can tell. Havnt really tested that statement however.

could someone tell me if I am completely wrong or at least clarify why dlsr lens have resilien to portholing
  • 0

#2 Stephen Williams

Stephen Williams
  • Sustaining Members
  • 4708 posts
  • Cinematographer
  • Europe

Posted 28 June 2008 - 02:09 PM

Hi,

Digital optimized lenses are telecentric, with film the angle that light hits the film is unimportant.

Stephen

I have recently been discussing what portholing (dark center and brighter center) is and how it pertains to digital photography and cinematography.

From what I understood it is mostly caused by the size up the rear element. digital sensors are inherently more reflective than the emulsion of film. I was told that if the rear element is too small then the rear element will reflect light bouncing off sensor and create a hot center. If the rear element is larger than the sensor then this problem will not ocur.

If this is true then I assume that rear element size/coating in the primary differnce with digitally optimized cine lens

This all makes sence to me except the fact that digital still lens often have very small rear elements and do not exhibit portholing. at least from what I can tell. Havnt really tested that statement however.

could someone tell me if I am completely wrong or at least clarify why dlsr lens have resilien to portholing


  • 0


Aerial Filmworks

Visual Products

Willys Widgets

The Slider

FJS International, LLC

Metropolis Post

Wooden Camera

Gamma Ray Digital Inc

Rig Wheels Passport

rebotnix Technologies

Technodolly

Abel Cine

New Pro Video - New and Used Equipment

CineTape

Broadcast Solutions Inc

Tai Audio

Glidecam

CineLab

Ritter Battery

Paralinx LLC

Media Blackout - Custom Cables and AKS

Wooden Camera

Glidecam

CineLab

Media Blackout - Custom Cables and AKS

Broadcast Solutions Inc

Ritter Battery

Technodolly

Willys Widgets

CineTape

rebotnix Technologies

The Slider

Visual Products

Metropolis Post

New Pro Video - New and Used Equipment

Aerial Filmworks

Rig Wheels Passport

FJS International, LLC

Tai Audio

Abel Cine

Gamma Ray Digital Inc

Paralinx LLC