# Effect of ND filter



## mikecox (Feb 13, 2018)

I added a ND filter because I am doing a lot of videos and was advised to use a shutter speed of 30-60, and a wide aperture, the idea being to get a shallow DOF, though I haven't figured out why that is so desirable,  since it limits the amount of zooming that can be done in post-processing, except on the subject. But I decided to go for it and bought a variable ND filter.

While shooting stills I went to "no filter", or as close as I could get, as there is no density level indicator on the ring.

When I imported my stills they were all thin, slightly tan, with a kind of soft focus.  I checked my settings and was using f/stops, on average, of 8-10 with shutter speeds of >100, and an ISO of from 300-400 on a slightly grey day.

I didn't expect the ND filter to do anything except maybe force me to make some minor settings adj.

Is it possible that the ND filter, even in it's least dense position, is affecting my still shots as I've described?


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## Umberto Cocca (Feb 13, 2018)

mikecox said:


> I added a ND filter because I am doing a lot of videos and was advised to use a shutter speed of 30-60, and a wide aperture, the idea being to get a shallow DOF, though I haven't figured out why that is so desirable,  since it limits the amount of zooming that can be done in post-processing, except on the subject. But I decided to go for it and bought a variable ND filter.
> 
> While shooting stills I went to "no filter", or as close as I could get, as there is no density level indicator on the ring.
> 
> ...



It is possible that a cheap ND filter has a color cast that could result difficult to remove in post-processing.

From what you wrote I understand you bought a variable ND, which means it is most likely to be a double polarizer, and you can adjust one of them to match the desired light blocking. However, even if you align the polarity of the two filters, you will still suffer from the color cast.

No idea of the cause of the soft focus issue, but it could as well be because of poor filter manufacturing. 

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## mikecox (Feb 13, 2018)

Thanks for taking the time to respond.


> It is possible that a cheap ND filter has a color cast{/quote}
> 
> I don't know if it would be considered cheap, I paid $25 for this K&F Concept 67mm ND Fader Variable Neutral Density Adjustable ND Filter ND2 to ND400.
> 
> ...


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## Umberto Cocca (Feb 13, 2018)

Yes I think it is on the cheap side. Check this one for example:

SLR Magic Variable ND Filter

I am not an expert on variable ND filters and I do not shoot video. But I have a set of ND filters in my bag and some graduated ones too. I learned the hard way that quality has its price. 


P. S. I haven't heard any filter with 400 stops capability! 

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## Johan Elzenga (Feb 13, 2018)

Umberto Cocca said:


> P. S. I haven't heard any filter with 400 stops capability!


That filter is normally called 'lens cap'.


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## mikecox (Feb 14, 2018)

> I learned the hard way that quality has its price.


You were right, my filer was cheap! I sent it back.  




> P. S. I haven't heard any filter with 400 stops capability!


 The ring didn't have any stops, it just turned all the way in either direction.

Thanks for the link


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## mikecox (Feb 14, 2018)

JohanElzenga said:


> That filter is normally called 'lens cap'.


I thought a "lens cap" was an opaque cap the protected the lens when it wasn't in use.


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## Umberto Cocca (Feb 14, 2018)

Mike,

The stops is a  term to measure in a photographer friendly way how much light is "stopped" by the filter. By convention every 3 stops the amount of light is reduced by half. So a 6 stop means only a quarter of the original light is passing through the filter.

 The "darkest" filter I know of is the Lee Big stopper and it has 10 stops. I have heard them developing a 15 stops, but I do not know if they have commercialized it. None of them is a variable one. 

Therefore the sarcasm of Johan saying that a 400 stop being a lens cap. 


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## mikecox (Feb 14, 2018)

Umberto Cocca said:


> Mike,
> 
> The stops is a  term to measure in a photographer friendly way how much light is "stopped" by the filter. By convention every 3 stops the amount of light is reduced by half. So a 6 stop means only a quarter of the original light is passing through the filter.
> 
> ...


Thanks for the explanation (-:  As I said, the ND lens I had didn't even have stops, or numbers on the ring, so I had to use guesswork, and live view on the LED display, to determine the 0 position.  I had no idea what a cheap filter I had!


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## Johan Elzenga (Feb 14, 2018)

Umberto Cocca said:


> Mike,
> 
> The stops is a  term to measure in a photographer friendly way how much light is "stopped" by the filter. By convention every 3 stops the amount of light is reduced by half. So a 6 stop means only a quarter of the original light is passing through the filter.
> 
> ...


Actually, a single stop is already half the light passing through, but the numbers used to describe an ND filter are not stops. There are three different notations: Neutral-density filter - Wikipedia


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## mikecox (Feb 14, 2018)

JohanElzenga said:


> Actually, a single stop is already half the light passing through, but the numbers used to describe an ND filter are not stops. There are three different notations: Neutral-density filter - Wikipedia


Thanks.  It is very clear, after reading that, that the colors in my images should not have been affected the way they were.


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