What Causes "Grain?"

[LINVS]

I have heard that shooting with a fast shutter causes grainy pictures. I know that higher speed film is more prone to "graininess" too.

But what really happens? Do the chemicals in the film need a longer exposure to light to "sear" the image into the picture? Is there a simple answer in regards to the whole chemistry of "grain?"

 

[480sparky]

The 'grain' are actual grains.......... granules of silver halide crystals. In order to be more sensitive to light, they must be physically larger.

Using high shutter speeds does not cause grain. It's function of using higher-ISO film.

 

[Ysarex]

More than anything

The 'grain' are actual grains.......... granules of silver halide crystals. In order to be more sensitive to light, they must be physically larger.

Using high shutter speeds does not cause grain. It's function of using higher-ISO film.

Yep, Sparky nailed that one -- that's the single best answer. Here's a secondary concern: The developer used to process the film can leave the grain substantially intact or take the edge off. There are fine-grain developers (sodium sulfite added) that reduce the appearance of grain by ever so slightly starting to dissolve those crystals. The original size of the crystals remains as Sparky noted the dominant factor.

Joe

 

[LINVS]

Using high shutter speeds does not cause grain. It's function of using higher-ISO film.

Why then do some pictures come out grainier than others - while using the same film? Could it be because of the camera or lens?

 

[Dave442]

I have never heard of shutter speed having an effect on grain size.

I expect that underexposure can lead to an image that will give a print showing more grain in the underexposed areas. How are you looking at the grain, I would look at the negative with a grain focuser to compare the different negatives. If you scan or print it can add another variable.

I often preferred Pan-X over Tri-X as I felt it gave a smaller or less pronounced grain. That helped when enlarging a 35mm negative to 11x17 inch size prints. If you use a larger film size you have less enlargement to have the same size print so the grain will also enlarge less.

 

[480sparky]

Using high shutter speeds does not cause grain. It's function of using higher-ISO film.

Why then do some pictures come out grainier than others - while using the same film? Could it be because of the camera or lens?

You can 'push-process' B&W film. Meaning, you can take, say, an ISO 400 film and shoot it at ISO 1600, then develop it longer (and/or at a higher temperature) than normal to bring out the shadow detail. The side effects are more grain and much higher contrast.

 

[Gary A.]

Using high shutter speeds does not cause grain. It's function of using higher-ISO film.

Why then do some pictures come out grainier than others - while using the same film? Could it be because of the camera or lens?

Nothing at all to do with camera or lens. Many factors affect grain, the higher the ASA the greater the grain, the type of developer will affect grain, over development and over agitation will affect grain, high developer temperature will affect grain, exposure of film to high temps will affect grain.

 

[LINVS]

Thanks for your help everyone.