I encountered some ideas on web discussions like - you don't need filters with digital, or the only filter you need is a polarizer, the rest can be done in post processing.... however, the Big Six filters that are useful to most photographers, cannot adequately replace with digital techniques.....
One - The Polarizer
This is so obvious I shouldn’t need to get into "why" you need it, but Im me, and that means Im going to talk about it anyway. Any time light moves from air to a transparent substance, some of the light doesn’t penetrate into the transparent substance and is reflected away. Whether the light hits water on a lake, the natural oil on human skin, clear cellulose and wax on plant leaves and flowers, lacquer on a car or a guitar, or glass on a building, there are reflections. The reflections are lights they fill in the color and reduce saturation. They reduce the detail visible under the clear substance. The blue of the sky is also polarized, and a polarizer can deepen the blue, and keep it from blowing out and rendering your sky a cloudless white or a drab gray.
You can fight this with post processing, but you won’t win. When you boost saturation, you fix the things that were "robbed" of contrast, but you also oversaturate the things that weren't suffering from contrast robbing reflections. And you can’t replace the lost detail.
Two - The 80A "Color Balancing"
Most cameras have sensors that are "daylight balanced". They have nice, balanced red, green, and blue channel responses in neutral colored scenes lit by daylight. They achieve their incandescent white balance by amplifying the blue channel over two full stops relative to the red channel. That adds a great deal of noise to the blue channel, so you see some pretty ugly shadows. It also makes it very easy to blow the red channel, especially when shooting red dominated subjects (human skin, cosmetics, and fall colors near dusk and dawn when the light is warm).
Using an 80A will often let you get an interior architecture image in a single shot that would have taken multiple shots and HDR to do otherwise. It also makes it much easier to shoot incandescent or candlelit scenes without blowing the red channel.
Three – The Neodymium Enhancing
Sensor manufacturers (like film manufacturers before them) spend a lot of effort trying to get the red, green, and blue filters in the camera to do a tolerable job of seeing colors the same way a human eye sees them. Normally, this is a "good thing", it reduces an annoying phenomena we techno-geeks call a "failure in observer mesmerism", where colors that look identical to one "observer" (a human) look different to another observer (a camera, for example). The neodymium filter disrupts the nice "mimic the eye" characteristics of a sensor, and causes large-scale failures of observer mesmerism. Neodymium (sometimes called didymium) does it in a way that is very pleasing in a landscape or fall color photograph: browns that would be identical in the picture (or to the eye) suddenly separate, with one turning red, another going yellow.
Again, this cannot be done in post processing, because without the filter, the camera sees all those browns as identical in hue. There's no way Photoshop can know to turn one brown into red, while another, apparently identical brown should be colored yellow, and a third identical brown should be left as "brown". Same thing happens in other colors, seemingly identical oranges separate into deeper oranges, reds, ambers, etc.
Four - The "Soft Focus"
Using a Gaussian blur can only make a good-looking soft focus effect on things that are not overexposed. For my own soft focus work (and the majority that I see from other photographers) the "prettiest" soft focusing is the glow surrounding blown highlights: candle flames, sparkling dew on flowers, the catch-lights in a woman’s eyes, the glint of jewelry. You can't get that right in Photoshop.
A soft focus filter in front of the lens gives you a glow with size and density that are proportional to how blown the blown area really is. So the glow around candles, specular reflections, water drops, etc varies with the brightness and the size of the blown area. And the transition from blown to not-blown on skin is much more natural with a filter or lens than with a PS blur. You can get this same effect with the soft focus lenses offered by Nikon, Canon, and Sony, but that’s an expensive route taken only by serious soft focus aficionados. The Tiffen soft focus or center spot(a personal favorite) or Zeiss Softer are much less expensive than a soft focus lens, and you can use them at a variety of focal lengths’.
Five - The Neutral Density
Many people like the look of a stream, waterfall, fountain, or brook with the water blurred into a soft "cotton candy" substance, flowing over rocks and plants. To do this, you have to shoot with a long exposure (anywhere from a second or two to a minute or two). In daylight, there's just too much light to do that, even at ISO 100 and f22, the longest exposure you can use is 1/50 sec. The "neutral density" lets you shoot much longer exposures. You can also use this technique to "blur away" all the moving people and vehicles in a street or architectural scene. Architectural photographers have been doing this for decades.
One "digital way" to emulate the neutral density long exposure technique is to shoot a whole bunch of those 1/50 sec exposures, then blend them together so that they "average out" to a much longer exposure. But that means taking 20 shots just to get one view of a waterfall. Recompose, and that's another 20 shots. It gets boring after a while...
Six - The "Split Grad"
OK, the big "buzz" these days is HDR, "High Dynamic Range" techniques of taking multiple exposures, and combining ones that get the highlights right with others that get the shadow detail. But light that "scatters" in a lens (our old enemy "veiling flare") can cause the highlights of a sunset to "fill in" and destroy the shadow details. The filter that is part clear and part neutral density can "hold back" the highlights so that they can’t damage our shadows.
One - The Polarizer
This is so obvious I shouldn’t need to get into "why" you need it, but Im me, and that means Im going to talk about it anyway. Any time light moves from air to a transparent substance, some of the light doesn’t penetrate into the transparent substance and is reflected away. Whether the light hits water on a lake, the natural oil on human skin, clear cellulose and wax on plant leaves and flowers, lacquer on a car or a guitar, or glass on a building, there are reflections. The reflections are lights they fill in the color and reduce saturation. They reduce the detail visible under the clear substance. The blue of the sky is also polarized, and a polarizer can deepen the blue, and keep it from blowing out and rendering your sky a cloudless white or a drab gray.
You can fight this with post processing, but you won’t win. When you boost saturation, you fix the things that were "robbed" of contrast, but you also oversaturate the things that weren't suffering from contrast robbing reflections. And you can’t replace the lost detail.
Two - The 80A "Color Balancing"
Most cameras have sensors that are "daylight balanced". They have nice, balanced red, green, and blue channel responses in neutral colored scenes lit by daylight. They achieve their incandescent white balance by amplifying the blue channel over two full stops relative to the red channel. That adds a great deal of noise to the blue channel, so you see some pretty ugly shadows. It also makes it very easy to blow the red channel, especially when shooting red dominated subjects (human skin, cosmetics, and fall colors near dusk and dawn when the light is warm).
Using an 80A will often let you get an interior architecture image in a single shot that would have taken multiple shots and HDR to do otherwise. It also makes it much easier to shoot incandescent or candlelit scenes without blowing the red channel.
Three – The Neodymium Enhancing
Sensor manufacturers (like film manufacturers before them) spend a lot of effort trying to get the red, green, and blue filters in the camera to do a tolerable job of seeing colors the same way a human eye sees them. Normally, this is a "good thing", it reduces an annoying phenomena we techno-geeks call a "failure in observer mesmerism", where colors that look identical to one "observer" (a human) look different to another observer (a camera, for example). The neodymium filter disrupts the nice "mimic the eye" characteristics of a sensor, and causes large-scale failures of observer mesmerism. Neodymium (sometimes called didymium) does it in a way that is very pleasing in a landscape or fall color photograph: browns that would be identical in the picture (or to the eye) suddenly separate, with one turning red, another going yellow.
Again, this cannot be done in post processing, because without the filter, the camera sees all those browns as identical in hue. There's no way Photoshop can know to turn one brown into red, while another, apparently identical brown should be colored yellow, and a third identical brown should be left as "brown". Same thing happens in other colors, seemingly identical oranges separate into deeper oranges, reds, ambers, etc.
Four - The "Soft Focus"
Using a Gaussian blur can only make a good-looking soft focus effect on things that are not overexposed. For my own soft focus work (and the majority that I see from other photographers) the "prettiest" soft focusing is the glow surrounding blown highlights: candle flames, sparkling dew on flowers, the catch-lights in a woman’s eyes, the glint of jewelry. You can't get that right in Photoshop.
A soft focus filter in front of the lens gives you a glow with size and density that are proportional to how blown the blown area really is. So the glow around candles, specular reflections, water drops, etc varies with the brightness and the size of the blown area. And the transition from blown to not-blown on skin is much more natural with a filter or lens than with a PS blur. You can get this same effect with the soft focus lenses offered by Nikon, Canon, and Sony, but that’s an expensive route taken only by serious soft focus aficionados. The Tiffen soft focus or center spot(a personal favorite) or Zeiss Softer are much less expensive than a soft focus lens, and you can use them at a variety of focal lengths’.
Five - The Neutral Density
Many people like the look of a stream, waterfall, fountain, or brook with the water blurred into a soft "cotton candy" substance, flowing over rocks and plants. To do this, you have to shoot with a long exposure (anywhere from a second or two to a minute or two). In daylight, there's just too much light to do that, even at ISO 100 and f22, the longest exposure you can use is 1/50 sec. The "neutral density" lets you shoot much longer exposures. You can also use this technique to "blur away" all the moving people and vehicles in a street or architectural scene. Architectural photographers have been doing this for decades.
One "digital way" to emulate the neutral density long exposure technique is to shoot a whole bunch of those 1/50 sec exposures, then blend them together so that they "average out" to a much longer exposure. But that means taking 20 shots just to get one view of a waterfall. Recompose, and that's another 20 shots. It gets boring after a while...
Six - The "Split Grad"
OK, the big "buzz" these days is HDR, "High Dynamic Range" techniques of taking multiple exposures, and combining ones that get the highlights right with others that get the shadow detail. But light that "scatters" in a lens (our old enemy "veiling flare") can cause the highlights of a sunset to "fill in" and destroy the shadow details. The filter that is part clear and part neutral density can "hold back" the highlights so that they can’t damage our shadows.
Sohailnazish (dubai photographer)
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