Jump to content


Photo

What is the physical difference between fast and slow stocks?


  • Please log in to reply
3 replies to this topic

#1 grantsmith

grantsmith
  • Basic Members
  • PipPipPip
  • 138 posts
  • 2nd Assistant Camera

Posted 05 November 2006 - 10:23 AM

hi,

What is the physical difference between fast and slow stocks?

Is it the size of the silver particles? or is it the amount? or something else?

I know slower stocks are referred to as having finer grain but I'd like to know the physics behind it.

thanks
  • 0

#2 John Pytlak RIP

John Pytlak RIP

    (deceased)

  • Sustaining Members
  • 3499 posts
  • Industry Rep
  • Rochester, NY 14650-1922

Posted 05 November 2006 - 05:03 PM

hi,

What is the physical difference between fast and slow stocks?

Is it the size of the silver particles? or is it the amount? or something else?

I know slower stocks are referred to as having finer grain but I'd like to know the physics behind it.

thanks


Mostly it is the size and shape of the silver halide grains. Kodak's invention of "T-Grain" technology in the early 1980's was a significant breakthrough in reducing graininess and improving sharpness. Likewise, Kodak's introduction of DIR couplers in the early 1970s. Here is a good tutorial:

http://www.kodak.com...html#graininess

And some of the technology in the Kodak VISION2 color negative films:

http://www.kodak.com...s/vision2.shtml
  • 0

#3 grantsmith

grantsmith
  • Basic Members
  • PipPipPip
  • 138 posts
  • 2nd Assistant Camera

Posted 05 November 2006 - 05:07 PM

thats great. thanks john. hope everythings going well with you
  • 0

#4 Dominic Case

Dominic Case
  • Basic Members
  • PipPipPipPip
  • 1357 posts
  • Other
  • Sydney Australia

Posted 05 November 2006 - 08:51 PM

A silver halide crystal needs to be struck by three or four photons to become "exposed' so that it will be developed into a part of the image.

However big or small the crystal is, it still only needs the same number of photon strikes.

If a certain area of the emulsion surface is lit by a certain intensity of light - that is, a certain number of photons per unit area strike it during the exposure time - it's clear that a large crystal is more likely to score the required hits than a small crystal. Or even a number of small crystals covering the same area as one large one.

So it follows that emulsions with large halide crystals are more sensitive to light (i.e. "faster") than ones with smaller crystals (more "fine grained").

Emulsions usually have crystals of a range of sizes, which extends the dynamic range (large crystals capture shadow detail, smaller crystals kick in in the highlight area as well as filling in some of the detail in the shadows.

T-grain technology essentially creates flat crystals and has them lying flat in the emulsion coating so that they present their largest face to the light, maximising their sensitivity for the same size of crystal.
  • 0


Broadcast Solutions Inc

Paralinx LLC

Rig Wheels Passport

Metropolis Post

FJS International, LLC

Technodolly

CineTape

Tai Audio

Gamma Ray Digital Inc

The Slider

Willys Widgets

rebotnix Technologies

Visual Products

Wooden Camera

New Pro Video - New and Used Equipment

Glidecam

CineLab

Ritter Battery

Abel Cine

Media Blackout - Custom Cables and AKS

Aerial Filmworks

FJS International, LLC

Wooden Camera

Ritter Battery

The Slider

Willys Widgets

Paralinx LLC

Abel Cine

Rig Wheels Passport

Gamma Ray Digital Inc

CineTape

Broadcast Solutions Inc

Visual Products

Media Blackout - Custom Cables and AKS

Glidecam

New Pro Video - New and Used Equipment

rebotnix Technologies

CineLab

Tai Audio

Metropolis Post

Aerial Filmworks

Technodolly