ND filters, how, what, why?

I been hearing about ND filters, what excactly would one use one for? and how?

Also what number would you need?

I have the same questions.

Put simply ND filters are dark and neutral density (shouldn't give your images a colour cast). There are two types, ND (solid) and ND grad.

ND grads are graduated from dark at the top to clear at the bottom. You can get them in a number of different strengths. Eg 1 stop, 2 stop or 3 stop. This means at the darkest, they reduce the light by 1, 2 and 3 stops respectively. But as I said they are all graduated to fully clear at the bottom. They are useful for landscape photography where the sky is much brighter than the foreground, so are used to ensure the sky isn't blown out. You can get ND grads in hard or soft, and this refers to how sudden the graduation is. A hard is more suited where there is a very clear and distinct horizon whereas a soft is better if it's less clear cut (general mountain landscape for example).

Solid NDs have no graduation - ie they simply uniformly reduce the amount of light entering the camera. These are used for a couple of reasons. 1: where you want to use a large aperture (small f number) for a desired background blur but it is too bright to do so (even at the lowest ISO setting the shortest shutter speed is too long). 2: where you deliberately want a long exposure in a setting where you would not normally get one (eg. a shot of the sea during the day to make the water appear very smooth, or to blur moving clouds). You can get these in a wide range of strengths, from 1 stop to over 10 stops! A 10 stop ND only allows 1/1000th of the light to enter the camera.

Also, different manufactures use different nomenclature for NDs. Eg. 1 stop can be 0.3, 2 stops 0.6, 3 stops 0.9.

nekrosoft13 wrote in post #10715044
I been hearing about ND filters, what excactly would one use one for? and how?

Also what number would you need?

ND filters are used to reduce the amount of light reaching the sensor under strong lighting conditions. Portrait photographers rely on ND filters in order to use a large aperture in bright light for DOF purposes. Landscaper shooters use them to lengthen the shutter speed to slow down moving water (silky effect or smooth-as-glass effect).

The "number" depends entirely on the available light at the time...there isn't a "one size fits all". Brighter light requires more ND (higher number of steps), not-so-bright light requires less.

ok, for example ND Grad, what would be a good number on very sunny day around 11-5pm?

top of the filter would be darker, how excactly would that affect lets say a tree that is visible on horizon?

nekrosoft13 wrote in post #10715123
ok, for example ND Grad, what would be a good number on very sunny day around 11-5pm?

top of the filter would be darker, how excactly would that affect lets say a tree that is visible on horizon?

Your question brings something important that is often overlooked about graduated filters: You can do the same digitally.

A graduated filter is just like a gradient mask between two layers in any photo-editing software. You can take two shots with different exposures and blend them digitally using a mask, in the way you want.

If the tree occupies both sky and ground a GND filter is going to create a problem as it will darken the top part of the tree only.

I use both grad NDs and digital blends and I don't have a rule about when to go one way or the other.

Another tip: For sunsets and Sunrises the horizon is the brightest part of the shot so you need a reverse grad ND, one where the horizon is dark and then fades to clear on top.

Solid ND filters, polarizers, Infrared can't be done digitally.

nekrosoft13 wrote in post #10715123
ok, for example ND Grad, what would be a good number on very sunny day around 11-5pm?

You meter the sky and the foreground separately and determine the difference in stops (say 5 stops). You then decide what you would want the difference to be (say 2 stops). This implies using a 3 stop ND grad to cover the difference.

Like with solid ND's, this is not a one size fits all kind of decision. It depends on the conditions and your preferences.

luigis wrote in post #10715223
Your question brings something important that is often overlooked about graduated filters: You can do the same digitally.

A graduated filter is just like a gradient mask between two layers in any photo-editing software. You can take two shots with different exposures and blend them digitally using a mask, in the way you want.

I prefer to spend my time in the field, instead of behind the computer. And GND's allow me to see the final result through the viewfinder.

On the other hand, digital blending gives you more flexibility in the placement of the transition area between the two exposures.

rvdw98 wrote in post #10715621
You meter the sky and the foreground separately and determine the difference in stops (say 5 stops). You then decide what you would want the difference to be (say 2 stops). This implies using a 3 stop ND grad to cover the difference.

Like with solid ND's, this is not a one size fits all kind of decision. It depends on the conditions and your preferences.

being a noob, how do you "meter" stuff seperatly

nekrosoft13 wrote in post #10715797
being a noob, how do you "meter" stuff seperatly

Using your camera's light meter. Either zoom in to separate parts of the scene, or use the spot meter setting if available.

Say you set your camera to aperture priority (Av) mode and dialed in f/16 as your aperture. Point towards the sky and half press. Take note of the shutter value selected by the camera. Do the same with the foreground.

If it's hard for you to determine the number of stops from those two shutter values, carry a printed copy of all shutter speeds as a reference. Or use a calculator: each stop is either half or double the value of the adjacent stop.

Anyone have a preferences to what ND filter they like to use?

nekrosoft13 wrote in post #10715797
being a noob, how do you "meter" stuff seperatly

you point it ... take note of the numbers... then point it to the next one.

Young_Werther wrote in post #10715953
Anyone have a preferences to what ND filter they like to use?

Brand, type or density?

Brand: I use B+W and Lee, but there are several good quality brands such as Hoya, Hitech, Heliopan and Singh Ray.
Type: I prefer slide-in (panel), but due to the lack of useable densities, I'm making do with screw-ins.
Density: whichever allows me to achieve the shutter speed I need.

So once you have those numbers down which shutter speed and Aperture do you use since you have two different field. What do you shoot at.

Young_Werther wrote in post #10715953
Anyone have a preferences to what ND filter they like to use?

For solid NDs I use a Hoya ND400 (9 stops) and a couple of ND8 (3 stops). Stacking I can go 3,6,9 or 12 stops.

For Grad NDs I use Singh-Ray's, specially the Reverse ND series. Top Quality (IMO). Usually 3 or 2 stops.