Project 35 : using a polarising filter

The course note for this project describe a number of situations where to try out the filter and the results to expect. Without doubt the main requirement is a bright sunny day with some blue sky.The science and detailed explanation of polarised light is perhaps not required although some understanding of whats going on will not go a miss. I resort here to Wikipedia as my source.

"Some of the light coming from the sky is polarized (bees use this phenomenon for navigation). The electrons in the air molecules cause a scattering of sunlight in all directions. This explains why the sky is not dark during the day. But when looked at from the sides, the light emitted from a specific electron is totally polarized. Hence, a picture taken in a direction at 90 degrees from the sun can take advantage of this polarization. Actually, the effect is visible in a band of 15° to 30° measured from the optimal direction." (http://en.wikipedia.org/wiki/Polarising_filter)


A recent opportunity in Menorca, while looking for landscape images that would satisfy assignment 5 (Edward Weston style) did bring about the use of a PF. The first two examples below were taken with a very wide angle lens though so the effect on sky and reflection is graduated, which looks natural in the sky by producing receding tones.The two photographs below are "straight" images and have had no post processing. The filter used is a B+W C-POL MRC. 77mm. The time was 15:00 and the sun is to my right at about 90 degrees.

 

No.1

Nikon D3 17-35 f2.8 AFS - 22mm FL
ISO 400 1/200 sec f14
 Filter at maximum effect.

 

No.2

Nikon D3 17-35 f2.8 AFS - 22mm FL
ISO 400 1/200 sec f14

Filter at minimum effect.

Careful inspection shows that apart from the darkening of the blue sky the most significant change is in the reduced reflection in the rock pool, mush as I would expect.

At right angle to the rock pool scene I tried the following image to see if there was any significant difference due to the camera being at a different angle now to the sun. The sun is now behind me.

 

No.3
Nikon D3 17-35 f2.8 AFS - 25mm FL
ISO 400 1/125 sec f14

Filter at maximum effect.

No.4
Nikon D3 17-35 f2.8 AFS - 25mm FL
ISO 400 1/125 sec f14

Filter at minimum effect.

 

The difference in the sky is not that striking. In fact No.4 has a slightly darker sky, which is interesting. However, the rock pool refection has almost been completely removed and is an improvement on reflection removal, than seen in No.3.

Conclusion.

While having owned a couple of polarising filters, it has not been a habit to use one, or indeed to test the effects of one, while shooting that often. The reason  (excuse maybe) is that I am a habitual user of a lens hood and on the current crop of Nikon lenses the hoods fit on a bayonet at the outside of the lens barrel and not the 72mm thread. With hoods fitted on the filter thread, it was simple to rotate the hood and the filter. A Gobo (small square card maybe) on a support held onto the camera base could bet around the lens shading issues and give access to the filter.

All the science and the relationship of me, the sun and my subject is likely to be of a secondary consideration when in the field and making landscape images. The primary concern will always be the composition of the image based on some previsualisation in my head of the finished photograph.