Project 34: using a graduated filter

For this exercise I opted to take the required images and then employ the ND grad feature in Lightroom 4 as it is so good and doesn't give the  problems with colour casts that I experience with my cokin filters.  These tend to give a magenta cast, especially if I use more than 1 in combination.  Maybe one day I will push the boat out and invest in some Lee filters.  In retrospect, perhaps I should have completed the exercise using the physical features in order to see the subtle difference between  wide and narrow apertures.  In all cases I bracketed the exposures by 1 1/2 stops either way and when filtering used a 1 stop filter.

Completely overcast day with a featureless sky.

It is suprising how difficult it is to get these conditions when you need them.  I grabbed the opportunity and photographed from our loft window rather than going out and having the sky clear on me.

    F4 Images

• Images taken with the aperture set at f4 and at the meter reading

f4 unfiltered

f4 filtered

• Images under exposed by 1 1/2 stops

Underexposed by 1 1/2 stops and unfiltered

Underexposed by 1 1/2 stops and 1 stop ND Grad

• Overexposed images at f4

Overexposed by 1 1/2 stops and unfiltered

Overexposed by 1 1/2 stops and 1 stop ND grad applied

Although the sky appeared to be featureless it can be seen that there is some detail even without filtration although the use of the ND grad does both darken the sky and bring out the cloud detail.  Without any other post processing, perhaps the meter reading filtered image is the best but with a 2 stop ND grad the over exposed image would probably be the best.

       F22 Images

• Images taken at the meter reading

unfiltered

Filtered

• Images underexposed by 1 stop

unfiltered

filtered

• Images overexposed by 1 stop

unfiltered

filtered

The results here can be seen to be very similar to the images shot at f4.  Again the picture that was overexposed slightly seems to be the best and would have been even better with a 2 or 3 stop ND grad.  The foreground certainly has a better exposure.

Clouds which show some difference in tones.

I took these shots whilst out walking in the Lincolnshire Wolds on a day of mixed cloud and sun.  I waited until the sun was obscured and then took these shots.  The clouds showed a great deal of structure.

F4 Images

• Meter reading

unfiltered

filtered

• underexposed

unfiltered

filtered

• overexposed

unfiltered

filtered

Of the above images, I prefer the filtered meter reading one, although I think that the one that is slightly overexposed would be the best with heavier filtration.

F22 Images

• meter reading

unfiltered

filtered

• underexposed

unfiltered

filtered

• overexposed

unfiltered

filtered

Again I noticed the same difference between images.  This time I think the meter reading and filtered shot is the preferred one.  I like the sky on the underexposed image best but here the foreground is too dark.  One major difference was in the sharpness of the images.  When the trees on the skyline are observed at 100% the f22 images are distinctly sharper.

The best image from each situation with post processing.

In both cases I worked on the meter reading image.

Here I increased the filtration to 3 stops and slightly increased the clarity, vibrance and saturation of the image.  I set the white balance to cloudy.

Again the filtration was increased to three stops and the clarity, vibrance and saturation increased slightly.

A few days later we experienced a truly featureless sky and so I repeated this part of the exercise but have only displayed here the meter reading images at f22.  It can be seen that when a sky is truly without detail no amount of filtration can help and it only succeeds in darkening the sky.

unfiltered

filtered

Sunset Images

F4

• meter reading

unfiltered

filtered

• underexposed

unfiltered

filtered

• overexposed

unfiltered

filtered

Again it can be seen that the ND grad filter darkens and increases the detail in the sky.  The underexposed and filtered image gave the most dramatic sky but the foreground is too dark unless the aim is to produce a silhouette but as the metering was taken from the houses in order to show some detail in the foreground.  I have shown a further image below where I have started with the f22 image taken at the meter reading on the houses.  I used the ND grad on the sky but the houses were still too dark so I used a second ND grad in Lightroom to increase the exposure on the houses whilst leaving the sky unaffected.  Just increasing the exposure also reduces the drama in the sky.  I also slightly increased the saturation, vibrance, clarity and also colour temperature.

Telephoto Pictures.

Whist out in the Wolds I zoomed in to 85mm at f22 and reproduce here a filtered and unfiltered image.

unfiltered

filtered

Although the detail has been increased in the sky, the effect is less marked.  Of course, the 1 stop ND grad could have been replaced by a 2 or even 3 stop one to increase the effect.

What Have I Learned.
Often, especially in cloudy conditions the sky can be rendered featureless in a landscape image.  In this situation an ND Grad can be used to both darken and increase detail in the sky.  The effect has to be tempered, however, otherwise the effect can be too dramatic.  If the sky is too featureless filtration doesn't help.  ND Grads can be used in sunset images if detail is still required in the foreground rather than a silhouette effect.  If a silhouette is preferred it is satisfactory to meter off the sky.  A variety of exposures can be taken in order to select the preferred image.