GND filters


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winzee

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Apr 17, 2008
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#1
Hey guys

what does one mean by GND2 (2 stops), GND4 (4 Stops) and GND8 (8 stops)

Thanks in advance!
 

MRSAMO

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Nov 17, 2008
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#2
* Warning - layman explanation!

I did some research on this recently and basically :

GND2 - dark filter
GND4 - darker filter
GND8 - darkest filter

Think of sunglasses for your lenses, at first I was curious why people would want such dark filters but if you set your shutter speed to something like 1 second or more then you'll notice that the picture gains a lot of brightness. People usually do this for night shots to get as much light in as possible but not for day shot, however it is a technique used to capture something slowly like waterfalls and the sea, creating a smooth effect. The GND filters is used to sustain that brightness so that it won't appear too bright.

So with a GND8 filter, you can take a much longer capture of your photo like 1 minute or something. GND4 will maybe allow 30 seconds and the GND2 is probably around 10 seconds. I'm just guesstimating since I haven't got any of these to speak from experience. Just did a bit of research because I'm getting one myself.

Maybe some others can explain it in more technical details.
 

giantcanopy

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Feb 11, 2007
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#3
This applies to the dark part of the GND filter / the ND filter as well

1 stop filter - allows 50% light transmission
2 stop filter will only allow 25% of light transmission
3 stop filter will only allow 12.5% of light transmission
and so on and so forth

Hi MRSAMO

I think you might be referring to ND filters for the " smooth " effect that you talked about.

For GND filters :


( Picture from bobatkins.com )

The darker half is like an ND filter, and is placed across the scene to reduce the bright areas of the scene that will otherwise overwhelm the ( dynamic range ) digital sensor. Very useful and I always carry them around.

Ryan
 

simranjits

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Apr 11, 2008
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#4
The darkest filters will also allow you to make moving objects invisible , to create a ghost town etc.
 

MRSAMO

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#5
Ryan, thanks for that, now I'm confused. So the GND filters are only half tinted and NDs are fully tinted?
 

giantcanopy

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Feb 11, 2007
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#6
The Graduated Neutral Density filters have a gradient. Depending on the type of GND, the transition can be from the middle, or in some cases it starts from one end and is darkest at the other.

Neutral Density filters reduce the light evenly. No gradient.

Ryan
 

winzee

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Apr 17, 2008
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#8
This applies to the dark part of the GND filter / the ND filter as well

1 stop filter - allows 50% light transmission
2 stop filter will only allow 25% of light transmission
3 stop filter will only allow 12.5% of light transmission
and so on and so forth

Hi MRSAMO

I think you might be referring to ND filters for the " smooth " effect that you talked about.

For GND filters :


( Picture from bobatkins.com )

The darker half is like an ND filter, and is placed across the scene to reduce the bright areas of the scene that will otherwise overwhelm the ( dynamic range ) digital sensor. Very useful and I always carry them around.

Ryan
Hello Ryan!

Do you carry ND and GND together with you all the time?

I've just got GND (for my sunrise/sunset shots).. thinking of getting ND...
is it realllyyy that useful? any recommendations for ND stops?
 

CokaCola

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Dec 9, 2008
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#9
Hello Ryan!

Do you carry ND and GND together with you all the time?

I've just got GND (for my sunrise/sunset shots).. thinking of getting ND...
is it realllyyy that useful? any recommendations for ND stops?
For sunrise/sunset shots, you are better off with the Singh Ray reverse GND http://www.singh-ray.com/reversegrads.html

I dun noe if any other brand have the same thing as well.
 

giantcanopy

Senior Member
Feb 11, 2007
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#10
Hello Ryan!

Do you carry ND and GND together with you all the time?

I've just got GND (for my sunrise/sunset shots).. thinking of getting ND...
is it realllyyy that useful? any recommendations for ND stops?
Yes i always carry them. ( for the kind of shots i take )

ND is good when u need longer exposures, and some examples include smoothening out motion, having interesting light streaks, shooting wide open for that thin airey dof in bright scenes etc. If there is no need for such "effects" then it is not really useful. Sometimes u can double up the circular polariser as a sorta 2-3 stop "ND" filter ( depends on the brand, different CPL cuts light by different stops. )

Recommendations hard to tell. I got a variable ND filter that packs an adjustable 1 to 8 stops in one. I guess if you want to get a pretty long exposure u can get an 8 stop ND filter.

I was using my ND filter to even out waves when i was shooting sunset yesterday at labrador too :p ( will post up the pic when i am done working on it )

Ryan
 

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Octarine

Moderator
Staff member
Jan 3, 2008
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Pasir Ris
#11
what does one mean by GND2 (2 stops), GND4 (4 Stops) and GND8 (8 stops)
1 stop = reducing the amount of light by 50%. It is the same as if you close your aperture by one full step which also called 'stopping down aperture'. And there you see the one purpose of ND filters: reducing the amount of light without changing aperture. In return you'll get very low shutter speeds which enables long-term exposure pictures (light trails, silky water etc.)
GND do the same, but only partially depending on how the gray part of the filter is designed.
 

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