Photography in practice – Variable ND filter or Polarising filter.

Or both together?

Essentially I am not in favour of combining filters for the simple reason that the additional glass surfaces, regardless of coating, create flare and reflections and will reduce the brilliance and sharpness of your picture, this is, unless you want this deliberately.

So which filter and why?

Honestly, I do not work that much with variable ND (Netral Density) filters, as they can restrict your creativity and forces you to make vertical alignments at the wrong position.

In this case I prefer to work in Affinity Photo, Photoshop or Lightroom and make the required changes to the image afterwards.

It is portant is to ensure that your exposure does not wash out the highlights, something you can check well on the right side of the histogram, which can be shown in most of the decent cameras, while taking pictures. (also refer to my article about exposure compensation)
The right hand bar should never reach the top of the field. Washed out, or overexposed pixel can never be corrected, while slightly dark ones can be coaxed to a good and often low noise brightness.
Modern sensors, do have a fantastic latitude, compared to early versions, even if they are not as good a analog film. But they are getting closer and image processing has adanved in leaps and bounds.

High dynamid range. The whites are borderline, but details in the shadows.

Back to the filter.

In countries, like Australia, with bright sun and dark shadows, a polarising (Pol) filter can be essential. Not only let the Pol filter increase the blue sky colour, but also reduces faint casts over colours and make them overall more intense, apart from other things.

For me the pol filter is a good way to balance highlights and shadows out, by darkening the blue sky and forcing the camera exposure to shoot up in the shadows.
Of course you need to ve careful not to overdo it, as otherwise the blue sky turns grey.

As a rule of thumb, turn the polfilter to a position, which you think makes a great picture. Then turn it back by maybe 25%. It now looks less dramatic in the viewfinder, but will get you the better pictures. Why? Our eyes have a fantastic capability to deal with light and shadow and even adjust as we scan the image. Our brain than interprets what we see and tell us the sky is blue, while the camera shows it is grey. Try it out.

Polarising filters are also great as ND filters. By closing the filter, you darken it overall and thus forcing the lens aperture open, reducing the depth of field, which can be desirable to separate a subject from the fore-and-background. But, be aware that this does not always works, depending on the time of day, how the sun stands and how much polarised light exist in the atmosphere.
So if you are after reducing the depth of field, a ND filter may still be required.

The ND filter of course is also great, if you want to be able to extend the exposure time to get blurred movements or the creamy looking, flowing creek or water fall.
One of the ‘problems’ with digital cameras is, that they normally do not have a very low sensitivity setting. 100 ASA is often the lowest.
In the past we used Kodachrome with just 25 ASA and had longer exposure times. But you needed a tripod for best results.

So what about variable ND filters?
Let’s say you are taking a wide, open landscape shot.
While it looks good on site, later is appears flat. In particular if you shoot from eye level.
By changing your position, like getting down to your knees, you will get some foreground into your picture and/ or more sky. This can make the image much more interesting.
However, you may find with wide angle lenses, that your foreground and your background are both equally sharp.
This reduces the ‘depth’ effect, you were trying to create.
Using a variable ND filter allows you to darken the sky and force the camera to a more open aperture and a shallower depth-of-field.
This shallow depth-of-field allows you to get creative and work out, where you want the viewers eyes to focus on.

Here the foreground is shapr, while the background blurred and make it appear even further removed. Taken with 10mm fisheye.

Nearly every scene has different levels of subjects. Very close, mid-range, far away. And anything in between. This you can use to your advantage.

In audio visual we often used a two-or-three shot setting, provided you used a tripod.

Shot one was close focussed, shot two, mid-range and shot three far. In the presentation we blended from one image to the next, moving the viewers eyes, through the image.
No, this is not like zooming through the landscape, as you may do with video. We did not change the perspective, which happens when you zoom from wide to tele nor the angle of vision.
By shifting through different focus layers, the overall impression changed and in the end, in the viewers mind a complete ‘landscape’ appeared, even if it was made out of three, separately projected images.
This approach can be used with almost any subject to great effect.

Back to the variable ND filter. It allows you to change the brightness of image parts and subsequently the exposure ratio speed/ aperture. This can be used highly creatively.

By the way, if you use a tripod and use the multi-shot approach, you can later combine the images in layers and play with opaqueness, etc. You could even extract subjects and have them sharp against s ‘naturally’ out of focus background.
All a great deal of fun and ways to make your images more interesting.

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