# Are filters needed?



## jvgig (Apr 4, 2008)

Can filters fix problems and create effects that post processing cant?  I was looking into a few different filters and the difference between the pictures seems within reach of a software filter, but I do not know.

Thanks


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## Big Mike (Apr 4, 2008)

There are a couple filters...firstly, a polarizer.  This filter does things that no simple software effect can do.  Some of it's effects can be done with software, but it's much easier to just use the filter.

Grad (gradient) or split filters.  A camera (or film) is limited to how much of a range it can capture in one photo.  By using a grad/split filter, you can effectively darken part of the scene, thus bringing the tones closer together and allowing you to capture that in one photo.  
Of course, you can use software to selectively edit areas of a photo, or even take multiple shots at different exposures and use software to combine them.

ND (Neutral density) filters are often used to simply block light which can allow you to use a longer shutter speed than you would be able to use otherwise.  This is often used for things like waterfalls or moving water.  That's not something that can easily be duplicated with software.

The effects of most other filters can be easily duplicated with software...and doing it with software allows for an infinitely more adjustable effect.


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## Garbz (Apr 4, 2008)

wow Mike that would have been my reply almost word for word.

The NDGrad filter is really only needed in the absence of a tripod, or when you're photographing a moving subject, in which case 2 frames combined with a gradient map would lead to irregularities.


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## skieur (Apr 12, 2008)

Garbz said:


> No, a grad ND filter in scenics is used to even the exposure between a very bright colourful sky and a foreground which is much darker in comparison.  Shooting without one would give you a foreground that is underexposed with little detail and a correctly exposed sky or a washed out sky and a correctly exposed foreground.  They are often a requirement for a good sunset shot.
> 
> A grad ND filter will also improve a shot with a clouded sky from any angle, whereas a polarizer works best at 90 degrees from the light source.
> 
> skieur


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## Garbz (Apr 13, 2008)

Errr yeah. That's what I said. 

2 frames, one brighter one darker (HDR style), overlay them in photoshop, gradient map between them. It's the poor mans ND Grad filter, and it is adjustable in post. Providing they line up and there is nothing moving in the transition between the 2 exposures you will not be able to tell it apart from an image taken with an ND Grad.


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## skieur (Apr 13, 2008)

Garbz said:


> Errr yeah. That's what I said.
> 
> 2 frames, one brighter one darker (HDR style), overlay them in photoshop, gradient map between them. It's the poor mans ND Grad filter, and it is adjustable in post. Providing they line up and there is nothing moving in the transition between the 2 exposures you will not be able to tell it apart from an image taken with an ND Grad.


 
Too much work, time, and effort.  The real thing is faster.

skieur


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## Garbz (Apr 16, 2008)

... I can see straight away that we're at 2 minds about this and we won't agree, but seriously it would take me longer to screw the filter on the camera than it would to do this effect in photoshop.

But then we normally use it in landscapes anyway where time is not so constraint. In reality anything worth doing is worth taking some time to do. This method love it or hate it is simply $150 cheaper, customisable without changing filters, and works in every situation I've tried it in.


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## Helen B (Apr 16, 2008)

I completely agree with Garbz. An ND grad is generally less precise and significantly less versatile than exposure blending, and there may also be issues of filter quality - few (if any?) ND grads are multi-coated, and they are often used with uncovered edges (possibility of contrast reduction by light piping). Exposure blending usually produces better results, in my opinion. I avoid ND grads if at all possible. I only use them for cinematography (the Schneider rectangular grads), where exposure blending is usually not a practical option.

Oh, and the good rectangular ND grads are very expensive.

Best,
Helen


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## skieur (Apr 16, 2008)

With exposure blending or software filters you cannot bring back detail that is not in the image you have already taken.  With camera filters you are working at the source and with live view and a large LCD it is not difficult to adjust a linear filter.

There is no consensus on filter quality with Singh Ray and Cokin being either outstanding or poor.  Some top pros would not be without them.  Others do the computer thing.  Bottom line I think is that different camera colour settings, different lenses, and different cameras add some variables to the use of filters and their effect.

On one of my cameras, my Cokin grad ND filter produced better shots overall than my polarizing filter in dealing with wide scenics.

skieur


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## Garbz (Apr 17, 2008)

Do you understand what we are saying at all? The point of taking 2 images is so you do get that detail. It's like HDR except without the (IMO) crap heavily processed look.


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## Helen B (Apr 17, 2008)

Exactly. The other thing is that an ND grad has a linear graduation. The real world is rarely that uniform, and it is often difficult to get a natural-looking transition. Sometimes it is completely impossible - in a wooded scene, for example. In addition, each filter has a fixed exposure effect and a fixed rate of change of effect (hard/soft grad). The rate of change has different appearances on different focal lengths. Those limitations don't apply to exposure blending.

It's perfectly right that everyone should make their own minds up about which technique they use, but  it's better to make that decision based on good information rather than misinformation. It's even better to make the decision from experience, but good grads are expensive. My experience is that it is easier to get natural looking results by using exposure blending than by using an ND grad. If you use negative film, you will rarely need either technique, of course.

Best,
Helen

Best,
Helen


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## skieur (Apr 20, 2008)

Garbz said:


> Do you understand what we are saying at all? The point of taking 2 images is so you do get that detail. It's like HDR except without the (IMO) crap heavily processed look.


 
Of course, I do, duh!  You are saying that you can capture absolutely all the detail in the scene from the brightest highlights to darkest shadows in 2 shots and then blend them together absolutely perfectly, whereas someone with an on-camera filter will produce a lesser quality shot because of a "possible" (depends on the contradictory opinions of a variety of pros) issue with the quality of a filter.

I have seen no lab data related to tests of filters on different cameras and any quantitative measure of their so-called negative effect on image quality.  Most pros use filters and their use shows up in photo and other magazines.

So, I am not convinced that filters should be avoided.

skieur


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## Helen B (Apr 20, 2008)

skieur said:


> Of course, I do, duh!  You are saying that you can capture absolutely all the detail in the scene from the brightest highlights to darkest shadows in 2 shots and then blend them together absolutely perfectly, whereas someone with an on-camera filter will produce a lesser quality shot because of a "possible" (depends on the contradictory opinions of a variety of pros) issue with the quality of a filter.
> ...



Er, no. You do appear to be misunderstanding us. Filter quality is a _possible_ side issue, not the main issue.

My exact words were: _"An ND grad is generally less precise and significantly less versatile than exposure blending, and there may also be issues of filter quality..."_

As my previous post explained, the graduation of an ND grad is linear and fixed. Nature does not always comply by providing a neat line between the areas needing different exposures.

Best,
Helen


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## Jim H (Apr 20, 2008)

In addition to all the great advice and discussion regarding filters, use and pitfalls thereof, it is also important to note that you have to know how to white balance and expose correctly. If you have your camera set to Auto it will try to defeat the filtering effect you are striving for.


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## skieur (Apr 20, 2008)

Helen B said:


> Er, no. You do appear to be misunderstanding us. Filter quality is a _possible_ side issue, not the main issue.
> 
> My exact words were: _"An ND grad is generally less precise and significantly less versatile than exposure blending, and there may also be issues of filter quality..."_
> 
> ...


 
You seem to be saying that a ND grad filter is "less precise" "linear and fixed" and that nature does not always comply by providing a neat line..."

That sounds extremely contradictory to me.  Moreover since you can move the placement of a ND grad filter to suit your preview, how is it "fixed"?  Grad filters do not have any neat line either.

skieur


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## Helen B (Apr 20, 2008)

skieur said:


> You seem to be saying that a ND grad filter is "less precise" "linear and fixed" and that nature does not always comply by providing a neat line..."
> 
> That sounds extremely contradictory to me.  Moreover since you can move the placement of a ND grad filter to suit your preview, how is it "fixed"?  Grad filters do not have any neat line either.
> 
> skieur



We both know exactly what ND grads are. As I mentioned earlier in this thread, I have a set of rectangular Schneider ND grads.

What is 'fixed' about them, you ask. I know that they can be moved along the long axis, and rotated. That's obvious. The number of stops of difference between the clear part and the full ND part is fixed. As I explained in a previous post in this thread: _"In addition, each filter has a fixed exposure effect and a fixed rate of change of effect (hard/soft grad)." _You need different filters for different densities. 

The graduation is in a straight line, ie linear. Surely you aren't arguing with that?

The lack of precision is in comparison with exposure blending. Exposure blending can be applied very precisely in terms of both exposure and position in the frame. You can match the transition between the exposures to the image very precisely. You can't do that with a graduated filter.

Best,
Helen


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## PaulBennett (Apr 23, 2008)

jvgig said:


> Can filters fix problems and create effects that post processing cant? ...



Hate to get in the way of a good fist fight but feel you question deserves an answer.   

And the answer is:  YES.    

For example, consider horizontally polarized light reflecting from a car fender in your picture.  It cannot be removed digitally, no way, no how, but is easily removed by a polarizer before it enters the lens.  Samo samo for unwanted light of a particular wavelength.  Once it enters the lens, it's inextricably mixed forever.


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## theadamsociety (Apr 23, 2008)

I just wanna say to the original poster that  even if you aren't using filters I would say at least an A1/UV is necessary, in a logical sense. The glass in your lens is worth alot of time and money, an A1 is 10-40 bucks (depending on filter size) and who cares if you scratch it.


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