The course notes ask us to experiment with maximum and minimum apertures. This is probably meant to demonstrate the visibility of the graduation step. I would expect f/16 with its wider depth of field to show this step but in my testing against f/2.8 I could see no difference. I suspect this is due to the soft gradation against a hard, and while I would like to see the effects I have no need for a hard grad, so this will have to go undemonstrated.
An excursion into The Fens of North Cambridgeshire one evening provided a good opportunity to use the ND grad in a overt situation that will demonstrate how well or otherwise this filter will hold some detail in a bright sky. WE need not limit ourselves to the sky, equally valid use of the ND grad could hold detail in water. Waves breaking into white water in a seascape often suffer from over exposure due to dynamic range and the filter used upside down would deal with this.
No 1 - No Filter
No 1 - No Filter is typical of a scene where the DR is too wide for the camera sensor. I knew when shooting that the sky was at least 2 - 3 stops too bright. The exposure has been set to under expose the shadows and recover them later in CS5.
No 1 - No Filter - Modified in CS5
No 1 - Modified in CS5 has taken me from the Raw file towards an image that is more acceptable. The shadow detail in the stubble has been recovered and the sky has also been manipulated with some burning and selective colour. The disappointment is that there is too large an area that is white. I think a small area of white would be acceptable. However, this is about as far as we can go with the file.
No 1 - With ND Grad
No 1 - With ND Grad has taken me closer to solving the burnt out sky that the Modified in CS5 could do. The basic file is still not unpleasant but the foreground and shadow detail can be improved.
No 1 - With ND Grad and modified in CS5
The last image in the set is the combination of the ND Grad and post processing in CS5. There is still a small potion of the sky (back lit cloud) near the sun that cannot be retrieved.
Conclusions for No 1.
The use of the ND Grad (Soft 2 stop) has improved how we can process the sky while retaining enough workable detail in the shadow. The option for further improvement would be to shoot the scene with HDR in mind. This would require 5 or 7 bracketed exposures form -3 stops to + 3 stops and some experimentation with combining the ND Grad.
Example No 2 is of a similar shot and included to demonstrate the technique.
No 2 - No Filter
No 2 - ND Grad and modified in CS5
So far I have looked at the effects of using a 2 stop graduated ND filter. In addition I will show the effect of using a 10 stop ND filter. The 10 stop filter is used exclusively with a tripod and long exposures. Typically a normal exposure of say 1/60 sec will become 15 seconds. If the lens is stopped down and the exposure is 1 sec, then 10 stops of filtration will require 16 minutes. During this time any movement with the frame will become blurred.
No 3 - 10 minute exposure f/32 - 5x4 Field Camera