diffraction? Using nd filters at DVinfo.net

Luke McMillian · March 28th, 2007, 08:35 AM

Hey,

I've heard some people say to use an ND filter on a camcorder to avoid difraction (using the narrow f stops?) I just picked up a ND6 for my GS400 and now in day light, my auto exposure reads 6.8, and at 5.6 depending on the light. I've been told to shoot in these apertures to get the sweet spot of the lens. Do I have my information right? I know there's automatic ND filters also in my cam, but I don;t know when they kick in.

A. J. deLange · March 29th, 2007, 11:36 AM

HD cameras with 1/3" chips are at the diffraction limit at about f/8 thus sharper pictures (though with less depth of field) will be obtained by using wider (smaller f number) apertures. A neutral density filter requires a larger aperture, ceteris paribus, to make up for the light lost to the filter. Thus a neutral density filter is one way to stay away from the diffraction limited lens apertures. Another is to reduce the exposure time (increase shutter speed).

Heiko Saele · April 3rd, 2007, 03:25 AM

"I know there's automatic ND filters also in my cam, but I don;t know when they kick in."

I really doubt your camera has something like automatic ND filters. If your camera has ND filters then you have a switch or a filter wheel. You can clearly see a filter being put in front of the chip, this can't be an automatic process or it'd ruin your shots

A. J. deLange · April 3rd, 2007, 06:17 AM

Forgot to mention it: If your camera throws in ND filters automatically it should tell you that it has done this by giving an indication in the view finder AND you should be able to turn this feature off. If hazy recall is correct the Canon XL1 worked that way.

March 28th, 2007, 08:35 AM	#1
Luke McMillian Regular Crew Join Date: Dec 2005 Posts: 62	diffraction? Using nd filters Hey, I've heard some people say to use an ND filter on a camcorder to avoid difraction (using the narrow f stops?) I just picked up a ND6 for my GS400 and now in day light, my auto exposure reads 6.8, and at 5.6 depending on the light. I've been told to shoot in these apertures to get the sweet spot of the lens. Do I have my information right? I know there's automatic ND filters also in my cam, but I don;t know when they kick in.

March 29th, 2007, 11:36 AM	#2
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	HD cameras with 1/3" chips are at the diffraction limit at about f/8 thus sharper pictures (though with less depth of field) will be obtained by using wider (smaller f number) apertures. A neutral density filter requires a larger aperture, ceteris paribus, to make up for the light lost to the filter. Thus a neutral density filter is one way to stay away from the diffraction limited lens apertures. Another is to reduce the exposure time (increase shutter speed).

April 3rd, 2007, 03:25 AM	#3
Heiko Saele Major Player Join Date: Mar 2007 Location: Wurzburg, Germany Posts: 316	"I know there's automatic ND filters also in my cam, but I don;t know when they kick in." I really doubt your camera has something like automatic ND filters. If your camera has ND filters then you have a switch or a filter wheel. You can clearly see a filter being put in front of the chip, this can't be an automatic process or it'd ruin your shots

April 3rd, 2007, 06:17 AM	#4
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	Forgot to mention it: If your camera throws in ND filters automatically it should tell you that it has done this by giving an indication in the view finder AND you should be able to turn this feature off. If hazy recall is correct the Canon XL1 worked that way.