Question about Neutral Density filters

**Mike Buckles** · July 18th, 2002, 12:37 PM

I've seen this brought up from time to time....I want to buy some ND filters for my super 8...is there an "ideal" strength to use? Or should I buy several....an ND 8 to use in strong bright sunlight, and an ND6 to use in more moderate sun? Is ND8 too much? I know that nd filters allow a wider aperature, affecting the depth of field....has anyone noticed a different look using them? Increase in sharpness or brighter colors? Thanks, mike

**Alex** · July 19th, 2002, 02:07 AM

I think f 5.6 is the sweet spot on most lenses. Since your film stocks may vary by a couple of f-stops worth of sensitivity, you probably need both an ND9 and an ND6...

I believe every 3 is equal to one f-stop, but I'm not sure.

You could probably get away with an ND6 and an ND9. If an ND3 is only one stop, that isn't that great a difference.

One disadvantage to Nd's is that they do make the image darker through the viewfinder. Don't overlook the power of the polarizer, since a polarizer cuts light AND adds color saturation.

**Mike Buckles** · July 19th, 2002, 02:22 AM

Hmmmm....a polarizing filter, eh? What does that do? Does an ND filter only really help when you're trying to affect the depth of field? On my minidv camcorder, an ND filter does make the picture sharper, and the colors a bit more vibrant..do ND filters have the same effect on film? If i'm not trying to affect the depth of field, and just trying for a sharper, more brilliant image, would a polarizing filter work better, and do they come in different strengths too, and which of those is best? (questions, questions!) Mike

**cameraguy** · July 19th, 2002, 10:06 AM

ND filters simply cut down on light and are not suppose to affect anything else.

Polarizers cut down some light and reduce glare off non metallic objects. For a camera with a beam splitter viewfinder you have to use a circular polarizer so that the internal meter can work correctly.

**Alex** · July 19th, 2002, 10:59 AM

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">Originally posted by cameraguy:
ND filters simply cut down on light and are not suppose to affect anything else.
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Perhaps you are referring to "Neural" Density Filters. [img]graemlins/devil.gif[/img]

ND filters will definitely affect the depth of field.
A film stocks "look" and color response characteristics could be affected by depth of field, but how noticeable would that effect be, probably not very.

However, if a 5.6 f stop truly makes better use of the optical elements inside of a glass, perhaps that has an effect on your final image's "look".

**cameraguy** · July 19th, 2002, 11:09 AM

Again that is an indirect affect. The image itself (colors, contrast etc..) should not be affected at all by a ND filter.

Isn't it a little too early in California to be disscussing filters? [img]graemlins/coffee.gif[/img]

**Alex** · July 19th, 2002, 11:38 AM

The way the silver is exposed by incoming light will be different depending on depth of field/f-stop opening.

It would be interesting to do a test where in very quick fashion (to minimize lighting changes), one were to keep the Super-8 camera in automatic exposure, shoot outdoors without an ND filter at let's say f-16, then quickly put on a 9x ND filter, (being careful to reset focus after the Nd filter has been attached.) and then shoot the exact same shot at f 5.6 and see if there is any difference in the image that is generated by the larger f stop-opening of f-5.6 instead of f-16.

And yes, it is very early in the morning in Calfornia, I am actually asleep and this message is being "sleep-posted".

<font color="#a62a2a" size="1">[ July 21, 2002 03:03 AM: Message edited by: Alex ]</font>

**Alex** · July 19th, 2002, 03:28 PM

Your opening up a huge cans of worms!

The biggest can has to do with the word "sharpness". Sometimes an image looks "sharper" because the objects in front and in back of the subject that is in focus appear clearly out of focus...emphasis on clearly!

You can clearly make out what the out of focus image is, but it has been muted by the softness to support, or emphasize what is the in focus subject.

Theoretically, f-11 should be an overall sharper image than f5.6. (Unless the lens has light inefficiencies that can be seen at higher f-stops because the amount of light being let in is through a much smaller aperture opening)

But f 5.6 will probably be a more efficient use of the lens glass, and will probably result in a more pleasing yet smaller depth of field.

Is the color better at f5.6 versus f 16.0? I don't know for sure, I but I think your overall reproduction of the image, on film, will look more pleasing to the eye.

A polarizer can reduce glare off of windows, blue up a pale blue sky, and cut down light by up to 2 f-stops.
It can be a hinderance in telephoto mode close-up shots of faces, as it may cut much needed light, and there is nothing blue to "blue-up".

**Actor** · July 19th, 2002, 08:09 PM

<BLOCKQUOTE><font size=2 face="Verdana, Helvetica, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="Verdana, Helvetica, sans-serif">
Neutral-density (ND) filters are gray in color and serve to decrease the intensity of the light passing through the filter without altering its color balance. They are useful in both black-and-white and color photography. ND filters are manufactured in unit increments of 0.1 ND, which corresponds to one-third of a lens stop or a comparable decrease in exposure time. A 0.3 ND filter is equivalent to one full exposure stop. Neutral-density filter effects are additive. Thus, a 0.3 ND filter used with a 0.1 ND filter reduces exposure by 1 1/3 stops (1 + 1/3 = 1 1/3).

A neutral density filter can come in handy in a situation where the lighting conditions are bright but you want to use a large aperture to limit the depth of field -- for example, if you are taking a portrait in full sunlight. Such conditions would normally require you to use a small aperture and a fast shutter speed, but with a 0.9 ND filter you will need to increase the aperture by three stops in order to achieve the correct exposure -- while you decrease the depth of field.

Basic Techniques of Photography by John P. Schaefer; pp 112-13; Little, Brown and Company; Boston
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