The World Through Filtered Eyes

Abbreviations are plentiful in photography these days. Some of the more common ones that had me searching wiki for definitions include : ND, GND, HDR, CPL. As it turns out, except for HDR, these are all filters of some sort and the topic of the following discussion is based on Marianne and my collective experiences. I’m by no means a gear-head when it comes to photography, so much of this will be based purely on limited field experiences with these filters of varying quality and prices. Sadly, with few exceptions, the quality did tend to rise proportionally to the price. However, be mindful that price doesn’t always guarantee a good result.

Now for the abbreviations and simple real-world definitions.

ND: Neutral Density. A uniformly dark piece of glass that allows you to lengthen exposures (slow shutter speeds). These come in various strengths.

GND: Graduated Neutral Density: A piece of glass that’s dark at one end and clear at the other with a gradual (soft-stop) or sudden (hard-stop) transition. Allows you to take pictures of scenes that are bright at one end and dark at the other with varying degrees of transition.

CPL: Circular Polarising Filter: A screw on filter that minimises reflections and glare, and also enhances natural colour and contrast.

HDR: High Dynamic Range : A process of using several exposures (either from several exposures taken at the scene or from several simulated exposures generated from the single file) to allow visualisation of highlights and shadows that would otherwise be featureless in a single exposure.

Some people have asked me how I go about determining what filter to use and how many stops of light to adjust for. Unfortunately, photography is not one of the areas where I have progressed from theory to practical. Rather, I’ve learned almost entirely from practical experience while filling in some holes in the theory along the way. ‘Gut feeling’  and the use of ‘live view’ modes would be the most honest and recommended way I could answer these theoretical questions. Reflecting on my practice though, I do seem to have an algorithm when it comes to filters.

1. Would the scene benefit from the use of a circular polarising filter? (the default answer is yes since the CPL lives on the end of my lenses)

2. Do I want to slow the shutter speed enough to require the use of a neutral density filter? (beyond what I can do by lowering theISO and making the aperture as small as possible)

3. Is the lighting contrast enough that I will need to use a graduated neutral density filter? – If  yes, what strength and what strength of transition? Will I need to stack more than one filter?

4. Would capturing the scene be better off achieved with blending exposures rather than filter use?

(5.) Should I get a functional filter holder? I tend to hand hold my filters but more on that later.

With those questions in mind, here are some examples:

Example 1: Godafoss Iceland: Marianne’s image

EXIF data : 80 second exposure, F16, ISO200, 16-35mm F2.8 II lens, 5dmkII

The questions answered:

1. Would the scene benefit from the use of a circular polarising filter?

– Yes. This image demonstrates two advantages of using a polarising filter. Firstly, it reduces the glare of wet surfaces reflecting ambient light (eg. rocks). Secondly, it allows a see through effect in water. Without the polariser, the colour of the water would have been a reflection of the sky.

2. Do I want to slow the shutter speed enough to require the use of a neutral density filter? (beyond what I can do by lowering the ISO and making the aperture as small as possible).

– Yes. When capturing waterfalls, very long exposures result in the dreamy look of water flowing smoothly. The exposure of 80 seconds was achieved with a 10 stop Heliopan filter. At F16 and ISO200 without this filter, the exposure time would have been a fraction of the final result. (To be exact, 2^(-10) of 80 seconds which approximates to about 1/10)

3. Is the lighting contrast enough that I will need to use a graduated neutral density filter? – If  yes, what strength and what strength of transition? Will I need to stack more than one filter?

-Yes. The end result may look like smooth lighting, but in reality, the sky and waterfall were significantly brighter than the foreground water. The transition across the water isn’t abrupt, so I would have chosen a GND with a soft (gradual) edge. Marianne in this instance didn’t use an ND filter but simulated the effect by holding a black object (hence blocking out light) over the top half of the lens and gradually lifting it off during the exposure. This technique is probably best used when exposure times are over 10 seconds.

4. Would capturing the scene be better off achieved with blending exposures rather than filter use?

– Probably not. A similar result could have been achieved by exposing the the water for 80 seconds, and then the sky for 20 seconds and then blending them manually afterward. I don’t believe that in this case, this would have achieved a better result than what was done in the field. Moreover, 20 seconds of exposure for the sky  may have resulted in less cloud movement. Finally,  at a pragmatic level, the manual blending of exposures would have required more post processing time.

Example 2: The Tarkine Coast , Tasmania: Dylan’s image

EXIF : 4 seconds. F16, ISO50, 16-35mm F2.8 II lens, 5dmkII

1.Would the scene benefit from the use of a circular polarising filter?

– Probably Not. Polarising Filters have their maximum effect 90 degrees to the source of light (imagine pointing at the sun with your index finger ; the polarising effect is maximal in the arc created with your outstreched thumb as you rotate your hand). The CPL may have some effect reducing glare off the metal surface. In this situation, I wanted the light reflected off the water rather than trying to ‘see through’ to the sand below. The desired effect here is subjective I think.

2. Do I want to slow the shutter speed enough to require the use of a neutral density filter? (beyond what I can do by lowering the ISO and making the aperture as small as possible).

-No. As it is, I think I allowed for too long a shutter speed. In seascapes, when waves are crashing, if I’m aiming to catpure motion but not freeze it, I usually aim for a shutter speed of 0.3-0.5 seconds.  A very long shutter speed gives an entirely different look of almost mist like water floating through the scene. As it turned out, 4 seconds was not quite long enough to get rid of the sense that water was flowing around the pylons but I did take a series of further images with a higher iso and wider aperture to allow that faster shutter speed.

3. Is the lighting contrast enough that I will need to use a graduated neutral density filter? – If  yes, what strength and what strength of transition? Will I need to stack more than one filter?

– Yes. As you can imagine, the lighting in the sky was very significantly greater than that of the foreground. Also, the transition of light occurs very abruptly at the horizon where the sun was setting. The clouds above gradually faded off  in light. The effective use of a reverse graduated ND filter (darkest at the point of transition) requires these two conditions to met. If there are objects protruding above the horizon, using this kind of filter results in a very unnatural black line through the middle of that object! To smoothen the very harsh transition of a reverse GND, I often stack a second GND with a soft edge. Beware the dangers of stacking GNDs though – this can result in a colour cast for certain filter brands (Lee filters give the least cast) and it will also lengthen your exposure time which may or may not effect your desired composition.

4. Would capturing the scene be better off achieved with blending exposures rather than filter use?

– Probably not. Once again, the same result can be achieved with blending images exposed for the sky and foreground respectively. However, manual blending of scenes with such harsh transitions takes a skill and alot of patience  to end up with a result that looks as natural as a well placed filter.

Example 3: Dove Lake & Cradle Mountain, Tasmania: Marianne’s image

EXIF: 20 seconds, F16, ISO100, Sigma 10-20mm lens, 7d

1. Would the scene benefit from the use of a circular polarising filter?

– Yes. Without the polarising filter in this example, the foreground rocks under the still water would not have been visible. There will always be a degree of reflection in the distance despite the use of a CPL. In this example, Cradle Mountain’s reflection is still present as well as some foreground underwater rock detail

2. Do I want to slow the shutter speed enough to require the use of a neutral density filter? (beyond what I can do by lowering the ISO and making the aperture as small as possible)

– No. Given the still conditions and the lack of any appreciable movement, there was no need to have a long exposure. The exposure of 20 seconds was the result of the requirement for a large depth of field (F16) and low iso to reduce noise on the 7d. If anything, for this kind of image with plants in the foreground, it may be desirable to shorten the shutter speed such that there is no motion blur on the foreground plants. This can be done for this given scene by either increasing the ISO or perhaps using a slightly wider aperture up to F11 (without compromising depth of field significantly). We were fortunate that the evening was dead still.

3. Is the lighting contrast enough that I will need to use a graduated neutral density filter? – If  yes, what strength and what strength of transition? Will I need to stack more than one filter?

– Yes. In at dusk, the foreground lighting was minimal while the sky was relatively bright; hence the need for a GND. The point of transition of light is not a straight line , hence a GND with a soft edge was used. For this image, the ‘guestimate’ was 4 stops of light which resulted in this look. It would not have been wrong to use a 2 stop or 3 stop GND – the difference in result would have been a brighter sky. A hard edged filter would have resulted in an abrupt line across the already shadowed mountains.

4. Would capturing the scene be better off achieved with blending exposures rather than filter use?

-Possibly. Any situation where there are jagged lines of light transition or patches of light, forces me to consider the use of exposure blending rather than (or combined with) filters. Once again, it does take skill, practice and patience to achieve a natural result when exposure blending this kind of image. A common mistake would be to give to much ‘lightness’ to the shadowy mountains resulting in a halo at the transition between land and sky.

Example 4: St Giles Cathedral, Scotland: Dylan’s image

EXIF: 3 exposures, F16, ISO 100, 16-35mm F2.8 II lens, 5dmkII

1. Would the scene benefit from the use of a circular polarising filter?

– Not likely. I’ve found interior shots rarely enhanced by the use of a polarising filter.

2. Do I want to slow the shutter speed enough to require the use of a neutral density filter?

– No. There’s no requisite in a still scene like this to increase shutter speed. Having said that, providing that you have a steady tripod, there’s no real reason to compromise intended picture quality by increasing iso or reducing the depth of field to shorten the shutter speed either.

3. Is the lighting contrast enough that I will need to use a graduated neutral density filter?

– There is a big difference of exposure between light and shadow but the light source is coming from multiple directions. There was no effective way that I thought I could use GNDs to benefit in this scene.

4. Would capturing the scene be better off achieved with blending exposures rather than filter use?

-Yes. I took several exposures exposing for the bright light and for the shadowed recesses in the wall and blended them through manual methods as well as incorporating an automatic image produced by photomatix pro.

Example 5: Quality Control Testing!

Brighton Jetty, South Australia.

EXIF Data : 70 seconds, ISO100, F16, 16-35mm F2.8 II lens, 5dmkII

1. Would the scene benefit from the use of a circular polarising filter?

– Debatable. I chose not to use it for this image because I wanted the light reflected off the water rather than a see through effect. The image would have looked different had I used one, but not necessarily better.

2. Do I want to slow the shutter speed enough to require the use of a neutral density filter? (beyond what I can do by lowering the ISO and making the aperture as small as possible)

– No. At that time of day (predawn) , there was little enough light that I could achieve the smooth water effect through long exposure simply by using a small aperture and low iso.

3. Is the lighting contrast enough that I will need to use a graduated neutral density filter? – If  yes, what strength and what strength of transition? Will I need to stack more than one filter?

– This image was a test of GNDs. I held a ‘Hitech ‘(AUD40) 2 stop hard edged GND over the left of the image and a ‘Lee’ (AUD100)  2 stop hard edged GND over the right of the image. If I was taking this image for a smoother transition of light, I would have used soft edged GNDs. The aim of this set up was to test the colour cast that the filters were likely to produce. As you can see, on the left of the image, the Hitech filter has produced a magenta cast. On the right of the image, the Lee filter has maintained the murky blue hour colours of the day. Sometimes, I will exploit the cast of the Hitech filters  if I want to produce an image with that magenta cast in mind.

4. Would capturing the scene be better off achieved with blending exposures rather than filter use?

– Probably yes. Holding two filters at strange angles can result in grief from either scratching or, worse still, dropping them into the sea. I like to hand hold my filters so that I can easily change the angle at which they are held but those are the 2 constant risks I take by doing so. The disadvantage of using an exposure blend method is that the shorter exposure for the bright sky may not be of sufficiently long shutter speed to produce the blur of cloud motion or water motion.

To sum up my recommendations :

– Try all of the techniques available to you and find something that suits your style.

– I would recommend starting off with a few of the ‘cheaper’ filters. If you find that you get good results that are better than your exposure blending efforts, – I would then move on to purchasing the more expensive Lee (or Singh Ray) filters and expanding your repertoire of filters.

– MOST IMPORTANTLY :  Know the theory but realise that nothing replaces experience in the field for finding out what works and in what situation. Go out and shoot!

Thanks for reading and good luck with the new-age old dilemma 🙂

Canon 5dmkII, 16-35mm F2.8 II lens, ISO 50,F16, 15 seconds, 3 stop reverse GND

-D