Best way to use a Graduated ND filter...

theMusicMan

theMusicMan

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I was thinking last night in prep for some shots I want to take shortly - of how I should best use the graduated ND4 filter I have, and wondered which way would be best. I know I could try out both methods to see the difference - if any - but I also thought I'd post here.

Simple question really... do I simply get shots by placing the GND in the holder, position it accordingly, then simply let the camera do the auto exposure and get the shot... or alternatively, do I first take an exposure reading, lock the EV, then position the filter and get the shot...?

Which way would yield best results here folks...? which way would you use yours...?
 
Personally I position the grad to get the result I want, take a test shot. Evaluate it, normally via the histogram, but also check the grad is having the desired effect, then re shoot if necessary
 
...but you don't state which method I suggested above you actually use Chappers? Do you let the camera auto expose with the grad in place, or meter first, lock it, then place the grad...?
 
Position the filter, take the pic. Bracket exposures 1/3 of a stop each side just to make sure.

It might be a different matter with a 3 stop ND grad though.

Otherwise, if there's a problem, there's plenty of leeway with digital to correct exposures.:)
 
Sorry MM thought it was implied. I position the filter first, then meter. The filter will have an influence on the way the camera meters, so it needs to be in place.

You are trying to reduce the the amout of light recorded in part of the image, by using the grad. If you meter without the filter in place the camera will take the "excessive" light into account when it meters and the result with the filter will be underexposed.

Hope this explains things
 
When i use mine i spot meter for the area i want to be correctly exposed - then switch to manual and dial in the settings (make sure ISO is not set to Auto) stick the grad on line up the grad line with the horizon and take the picture, to get the correct exposure you may need to use different strengths of ND grads or you can bracket the shots, or you can do it properly and meter for the sky also and work out the difference between the sky and foreground then use the correct ND Grad in the first instance !
 
Most of the time I look at the scene then stick the ND grad on and let the camera look after the metering.
 
Knikki said:
Most of the time I look at the scene then stick the ND grad on and let the camera look after the metering.
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If you do this surely you will just end up with an incorrectly exposed shot :thinking: the ND grad will stop some light entering the camera the camera will then adjust either the shutter or the aperture (depending on the camera settings) to compensate for the reduced light ?
 
Wont this be right.. because the reason your put the nd on in the first place was because your foreground would be too dark? so therefore if you meter aftewards you will get it right?
 
Janice said:
Wont this be right.. because the reason your put the nd on in the first place was because your foreground would be too dark? so therefore if you meter aftewards you will get it right?
Click to expand...

The idea of a ND graduated filter is to control the exposure difference between the sky and the ground- if you only meter after putting the filter on the camera the camera will adjust the settings to compensate for the reduced light and either alter the shutter or aperture to compensate for the reduced light - you will see a difference between the sky and the foreground by the whole shot will be incorrectly exposed. - the camera evaluates the whole scene, it cant tell you have a ND grad on the lens.

Before you put the filter on point the camera at the foreground (make sure the whole foreground fills the frame) take a reading , then do the same but point the camera at the sky (make sure the whole sky fills the frame) take a reading. Then work out the difference between the 2 readings this is how much light you need to stop from the sky to end up with a correctly exposed shot - (2 stops would need a 0.6 ND) set the camera to manual dial in the settings you metered for the foreground stick the ND grad on and take the picture - The ND grad will stop 2 stops worth of light from hitting the sensor where the sky is on the frame but all the light metered for for the foreground will hit the sensor - correctly balanced image will be captured :)

Thats the theory - as i understand it anyway.;)
 
There is a really good book from Lee filters about how to use various filters, it is well worth a read.

FWIW I though the correct thing to do was before putting any filters on, meter both what you want exposed as it is (usually ground) and what you want darkened (usually sky), work out the difference in stops between them, select the corresponding ND grad and expose for the ground. Obviously bracketing and checking the histogram are good ideas.
 
Dogfish_magnet said:
The idea of a ND graduated filter is to control the exposure difference between the sky and the ground- if you only meter after putting the filter on the camera the camera will adjust the settings to compensate for the reduced light and either alter the shutter or aperture to compensate for the reduced light - you will see a difference between the sky and the foreground by the whole shot will be incorrectly exposed. - the camera evaluates the whole scene, it cant tell you have a ND grad on the lens.

Before you put the filter on point the camera at the foreground (make sure the whole foreground fills the frame) take a reading , the do the same but point the camera at the sky (make sure the whole sky fills the frame) take a reading. Then work out the difference between the 2 readings this is how much light you need to stop from the sky to end up with a correctly exposed shot - (2 stops would need a 0.6 ND) set the camera to manual dial in the settings you metered for the foreground stick the ND grad on and take the picture - The ND grad will stop 2 stops worth of light from hitting the sensor where the sky is on the frame but all the light metered for for the foreground will hit the sensor - correctly balanced image will be captured :)

Thats the theory - as i understand it anyway.;)
Click to expand...
You type faster than me!
 
See... :) I am so glad I posted this question, I feel better now knowing that I am not the only one who uses an ND grad in different ways. I have used the filter both ways to be honest, but wondered which was the 'correct' way to do it.

I tend to agree with the 'meter first, then place the grad on' approach as allowing the camera to do the metering just seems to allow it to override the exposure you are after. Surely you want the sky area less exposed than the rest of the scene...? by placing the filter on after allowing the camera to calculate the correct exposure, allows less light to hit the sensor from the part obscured by the filter - which is what you want... yes??
 
Dogfish_magnet said:
If you do this surely you will just end up with an incorrectly exposed shot :thinking: the ND grad will stop some light entering the camera the camera will then adjust either the shutter or the aperture (depending on the camera settings) to compensate for the reduced light ?
Click to expand...

You know I am not 100% sure TBH (you explanation of the ND filter is good):thinking:

But with modern multi pattern mettering systems, sticking the ND Grad on then letting the camera work it all out it would adjust accordingly. I mean cameras these days seem to work in less than 1/3 stops, so it should work it out.

That is how I have used the ND Grads and it so far has worked out for me. But after reading your explanation I will give it more thought. :thumbs:
 
Ideally you should meter both the sky and the land, see how big a difference it is, and use the appropriate strength ND on the sky

Then, the meter can work perfectly well with the filter in place as you've balanced the sky to the land

If you just pick any old ND filter and meter after putting it in place, then yes the exposure could easily be out

Example...

Land is f5.6 sky is f16. Put a 3-stop ND in and the land & sky will both be f5.6

But if you just dropped in the only ND filter you had, and it's a 2 stop, then metering with it in place will underexpose the land a bit and overexpose the sky

HTH

DD
 
Surely it depends on your metering mode as to how the NDG will affect?

Exposing for land and sky then chosing the filter is fine for evaulative metering but if you spot or centre weight isn't it affected by framing?
 
Uneducated_Rick said:
Surely it depends on your metering mode as to how the NDG will affect?

Exposing for land and sky then chosing the filter is fine for evaulative metering but if you spot or centre weight isn't it affected by framing?
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I don't get you m8 :thinking:

To meter for either the sky or land you remove the other, which could be zooming in for example

Then, any type of metering will work ok assuming either the land or sky is fairly uniform - but even if not, you're simply metering for the 'correct' exposure to each and then using that as a guide to choosing your ND strength

Or have I completely missed your point ???

DD
 
Sorry, I was talking about if you put it on and let the camera do the work afterwards.

Spot metering would have to be through clear glass to avoid overexposing wouldn't it?
 
You shouldn't let the camera do it afterwards as you may not have put the right strength ND on

A Spot metering through a filter will still give the right exposure for the bit it's aimed at, it's just that overall it could still be wrong - but then that's true of any use of Spot readings

DD
 
Hey dave - great to have your expertise input on this, thanks. (we're not talking about birds, so you;re good to go!!) hehehe...

Re: spot metering - this is exactly how I have been doing NDG images up to now. I usually have the filter raised, then I take a spot meter reading on the non-sky or non-bright part of the image (the area I don't want darkened), then I lock that EV, drop and position the filter to where I want it, refocus and take the shot.

This method seems to work OK, and I was wondering if this was the best way to accomplish great ND Grad shots.
 
theMusicMan said:
Hey dave - great to have your expertise input on this, thanks. (we're not talking about birds, so you;re good to go!!) hehehe...

Re: spot metering - this is exactly how I have been doing NDG images up to now. I usually have the filter raised, then I take a spot meter reading on the non-sky or non-bright part of the image (the area I want darkened), then I lock that EV, drop and position the filter to where I want it, refocus and take the shot.

This method seems to work OK, and I was wondering if this was the best way to accomplish great ND Grad shots.
Click to expand...

Hi MM

That's still relying on only 1 filter, so if the range from sky to land happens to be the same number of stops as your filter then that's fine

The idea with NDs is to have a range of them and pick the right one AFTER you've metered and know which strength to use

I'd do such shots on manual too, just in case your finger slips off the lock button

DD
 
This is slightly off thread, but trying to get my head round metering.
If you want to meter for partic part of shot, ie dark areas so they are not too dark, do you have to use manual focus, cos when Ive have tried this with auto, as soon as you move camera to focus on area of picture that you actually want sharp, the camera alters the exposure to suit.
Is that right?

thanks
x
 
guyfawkes said:
This is slightly off thread, but trying to get my head round metering.
If you want to meter for partic part of shot, ie dark areas so they are not too dark, do you have to use manual focus, cos when Ive have tried this with auto, as soon as you move camera to focus on area of picture that you actually want sharp, the camera alters the exposure to suit.
Is that right?

thanks
x
Click to expand...


have a read here
 
guyfawkes said:
This is slightly off thread, but trying to get my head round metering.
If you want to meter for partic part of shot, ie dark areas so they are not too dark, do you have to use manual focus, cos when Ive have tried this with auto, as soon as you move camera to focus on area of picture that you actually want sharp, the camera alters the exposure to suit.
Is that right?

thanks
x
Click to expand...
Not quite right if you have a camera that can lock the exposure. One simply takes a reading, lock the exposure (however this is achieved on your camera - if it has this feature) then refocus on the part of the image one wants leaving the exposure as previous.
 
Thanks for that - helpful and will also have another read of my manual about the AE-L now I know what its for!

x
 
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