For general photography in digital or on film there are several filters that are most frequently used to improve the rendition or alter the possible range of exposure values.

Make colors snap…

If I had to have only one filter it would be a circular polarizer. I use the polarizer on most of my nature photographs.
The only time that I do not use it is when I am photographing rainbows or handheld in low light. When photographing reflections the filter does not need to be removed just rotated to the correct orientation so that you get the desired degree of reflection. This can be useful in controlling the amounts of reflection from bodies of water as some reflection is nice but the natural amount is usually too much. Rainbows suffer from the polarizer and it must be removed to fully render the rainbows subtle colors.
The polarizer will darken the sky a variable degree depending on its setting. Plants will be rendered with richer colors because the polarizer cuts the specular reflections off of the moisture in the leaves. Most colors will benefit from the polarizer’s effect. This is different from turning on the vivid switch in your camera. In-camera processing is always a bad idea as it is better to enhance color saturation and sharpness interactively in post processing.
The exposure compensation for a polarizing filter is +1 2/3 stops. This has been standard across all the polarizers I have owned over the years.

The second filter I carry is an ND or neutral density filter. ND filters are marked with the opacity value as if they were being read on a transmission densitometer. .10 is 1/3 of a stop, .30 is one stop and .90 is three stops. I like the ND .90 as it gets me into a different range of aperture and shutter speed combinations.

Making the water move…

If I have two filters the second is a neutral density filter. At EI 100 the BDE, basic daylight exposure, for direct sun is 1/100 at f16. As many lenses only support f22 as the maximum aperture this makes the slowest shutter speed available 1/50 (at f22).

Good movement in flowing water happens at shutter speeds between 1/15th and 1 second. 1/15th gives you lots of texture and good movement. As you head towards 1 second the water becomes less detailed and more unsubstantial. At about 5s the water seems to be simply a cloud in the channel. With the preceding assumptions you will see that using a polarizer with its 1 2/3 stop compensation factor will give an exposure of 1/30 at f16 or 1/15 at f22. You are exactly at the top of the range of good motion effects.

Using the ND .90 and the polarizer I get an exposure value of about 1⁄4 at f16 or 1⁄2 at f22. This filter allows me to really hit that window of good motion that happens between 1 second and 1/15th second and to have some choices as to how I want to render the water rather then just being stuck at 1/15th at f22 with the polarizer.

I find that the ND filters will change the white balance of the picture slightly and I have a custom white balance that I use for the filter. This amount of color shift is certainly not much and can be easily corrected in post processing.

When you use more then one filter the old wives tale is that your focus will suffer a very small amount. I do not feel this is even noticeable and will not hesitate to use the second filter, especially as you cannot get to this range of exposure values without it....

The third filter is the UV0 or 1. I use these to protect an exposed front lens element. As I rarely remove the Polarizer this is only for that time. A good example is photographing in low light where the polarizers density makes it too hard to see through the camera and there is not a direct light source to produce specular reflections.

It is critical that whatever filter you are using that you use a lens shade. This prevents lens flare, which robs your pictures of contrast and color saturation. Unlike the difference between 1 and 2 filters, which I cannot identify in a photograph, I can usually tell you weather your picture was shot with or without a lens shade.

I use a lens shade and my fedora type hat, which I hold over the lens to cut that last bit of flare when looking into the light. If you look at most pictures of Ansel Adams working you will not that he is wearing a fedora, there is a reason for this…

When the wind conditions are to high for me to wear the fedora I carry an 8x10 piece of black mat board that I use as the additional shade. I cannot stress too much the importance of a good lens shade and making the extra effort to do some additional shading. You can usually see the effects of the additional shading in the finder because it really makes a big difference.

Watch The Quicktime Video - Part 1 Filters for Digital



Watch The Quicktime Video - Part 2 Filters for Black and White

Knowing the film speeds can be useful in applying filter factors and making general exposure calculations. Following is a listing of the film speeds (E.I.'s) in 1/3 of a stop increments.

To calculate the exposure correction for a filter simply take the amount of in stops and subtract that from the E.I. using the table below and then use that re-calculated film speed to make your exposure calculations.

To convert from filter factor to stops is a little less clear. A factor of 2 is a one stop increase, 3 is 1.5 stops and 4 is 2 stops. As it goes on 6 is 2.5 stops and 8 is 3 stops.

I always calculate the correction values of my filters in 1/3's of a stop not factors. Filter factors are the construct of a warped mind and are an unnecessary level of distraction and indirection.

No, no attitude… I really do love filter factors. /snark

It is just more direct to make a correction without having to calculate the factors difference in stops prior to making the correction.

Mark the correction amount on the filters case or some tape on your filter pouch. I call the thirds .3 and .6 so that a correction of 1.3 is an increase in exposure of 1 1/3 stops, 1.6 is an increase of 1 2/3 stops. Using this method a P1 circular polarizer has a correction of 1.6 stops.

Here is a quick way to calculate the bellows extension factor and exposure compensation amounts for large format view camera users in the studio.

To use the calculator follow this link.

However when you are working in the big room there is no computer or webbernet so the online calculator is not an option...

For years I have calculated my bellows comp in my head for large format. I always enjoyed using my RB-67 partially because of the bully bellows comp scale which made the bellows factor calculation into a non-issue.

I wanted to improve my large format production rate as it is a notoriously slow process. This was one of the points where I saw that it could be better, not that it took me that long to figure out the factor but just having to go into math mode detracted from the experience of vision and visualization.

I have carried a legal size xerox of a ruler which I coated with packing tape on two sides for years. When backpacking a 4x5 I try to keep the kit light.

I decided to make a scale that was like the RB-67 scale which covered the lenses in my kit while giving me an inch ruler as well.

I immediately noticed that there were not many simple calculators for bellows extension on line so I fixed that...

While I can't use the online version in the field it will certainly did enable me to make an excellent paper ruler.

I first made a 2 inch tall version and hindsight being 20:20 I decided I wanted it even smaller so I transformed it to make a 1 inch version. My Zone VI field camera has a 300 mm maximum bellows draw my ruler ends in that range. The ruler is around 14 inches long.

Here are links to the two rulers, the 2 inch and the slightly more compressed 1 inch version.

With inkjet prints there are occasional spots where the surface flecked off leaving a small white spot. While this happens rarely it usually happens on a larger print.

I guess that is just Murphey doing a really fine job of it!

To fix this problem I use the standard photo retouching methodology...

Marshalls photo retouching dyes take well on pigment inkjet prints and I find that all in all it works fine.

I have a 00000 (5 ought) brush with half the hairs carefully trimmed out and I use a pair of strong magnifying glasses. It is critical that you can see the work magnified.

I have all the colors of the dye dried in the compartments of a plastic palette. I put a few drops of water in the center and dip from the dried color spots to make an even small dot of water with my color match in it.

I test on a piece of the material I am retouching and wear a nylon glove on my left hand so I can touch the work freely.

I try to fill the white spot without overlapping the edges with a medium wet brush. I look for the brush to make a consistant line when gently stroked on the test sheet. If you touch it and it leaves a drop it is too wet and if it wont make a short consistant line it is too dry.

I want the brush to deliver dye the first time I go at a spot amd I may gently touch the sopt several times to make dots that fill it in rather then swabbing at it. Swabbing at the spot is death, you want to fill it with small several gently overlapping dots.

Like anything this is a skill and takes practice.

I would recommend that you make a black file in photoshop with some small white dots and practice on a printout. After you have done 20 or 30 you will get the hang of if and be spotting away...

A big part of success is the few hair brush and the magnifyer so you can really see the spot.

I was fortunate enough to have been able to get some training in retouching in the 70’s and although everything has gotten much better I still find spotting to be a useful abilitiy.

Now those Adams vibrating pencil retouch stations for negatives... Mine perished in a fire and I would much rather photoshop the face thank you :)

But those damn occasional flecks!

Actually we have it easy now because an absolutely clean wet photo print was rare if you were a critical worker, it seemed like everything needed a little touch.

Now I spot my dust once and it is gone-gone-gone and life is good!