Jump to content


Photo

Flange distance on the K-3


  • Please log in to reply
4 replies to this topic

#1 Antonio Bunt

Antonio Bunt
  • Basic Members
  • PipPipPip
  • 134 posts
  • Cinematographer

Posted 16 October 2014 - 10:33 AM

Hello,
I measured the distance between the mount and the gate and approximately it has a 46 mm length. This means the flange distance is almost 5 cm so a C-mount 25 mm lens will render it into a slight telephoto? Do I need a 20mm instead to make it a true normal lens.
Can someone explain? Am I right?
Thanks!
  • 0

#2 Rafael Pankratau

Rafael Pankratau
  • Basic Members
  • PipPip
  • 61 posts
  • Other
  • Belarus, Europe

Posted 16 October 2014 - 10:51 AM

Hi, Antonio!

K3 (M42 vesion) has standard 45.46 mm FFD.

C-mount has 17.52 mm FFD.

This means that C-mount lens will work at very close distances (few centimeters) from object only, without any chance to focus to infinity or even a portrait.

FFD isn't related to a crop factor (depending on sensor/frame size).

Thanks.

Raf.


  • 0

#3 Antonio Bunt

Antonio Bunt
  • Basic Members
  • PipPipPip
  • 134 posts
  • Cinematographer

Posted 16 October 2014 - 04:42 PM

Thanks Rafael!
I do own an M42 K-3 camera.
So, let me get this straight. If I use the C-mount lenses, it will be like a macro lens?
Why does the kit zoom lens work fine to infinity?
Do you recommend to use only M42 mount lenses?
Thanks again!
  • 0

#4 Rafael Pankratau

Rafael Pankratau
  • Basic Members
  • PipPip
  • 61 posts
  • Other
  • Belarus, Europe

Posted 16 October 2014 - 05:05 PM

1. If I use the C-mount lenses, it will be like a macro lens?
2. Why does the kit zoom lens work fine to infinity?
3. Do you recommend to use only M42 mount lenses?

1. Yes.

2. Because kit zoom has correct FFD (flange focal distance) for this camera. To focus C-mount lens to infinity on an M42 camera you need to insert this lens about 28mm deep into the camera that is just impossible for reflex cameras, and useless for non-reflex ones since you'll lose access to lens control rings.

3. Yes, due to long FFD of M42 mount specification you are very limited in lens mount choice. T2 lenses (M42x0.75) will work fine with corresponding adapter though. So, you may use M42 and T2 lenses easily, and there are literally hundreds different lenses available in these mounts. So, you'll be able to find all what you need without going to C-mount.


  • 0

#5 Antonio Bunt

Antonio Bunt
  • Basic Members
  • PipPipPip
  • 134 posts
  • Cinematographer

Posted 17 October 2014 - 07:38 AM

Rafael, your tips have been incredibly useful. I am very grateful for this information. All the best!
  • 0


Gamma Ray Digital Inc

CineLab

Glidecam

FJS International, LLC

Media Blackout - Custom Cables and AKS

Rig Wheels Passport

Ritter Battery

Abel Cine

Technodolly

Broadcast Solutions Inc

The Slider

CineTape

Tai Audio

Aerial Filmworks

Paralinx LLC

rebotnix Technologies

Visual Products

Metropolis Post

Wooden Camera

Willys Widgets

Metropolis Post

Broadcast Solutions Inc

rebotnix Technologies

Paralinx LLC

CineTape

Glidecam

Gamma Ray Digital Inc

Technodolly

Aerial Filmworks

Media Blackout - Custom Cables and AKS

Tai Audio

Willys Widgets

Visual Products

Wooden Camera

The Slider

CineLab

FJS International, LLC

Ritter Battery

Rig Wheels Passport

Abel Cine