Monday, 21 November 2011

Project 34 : graduated filter

I am a regular user of the ND grad. and while this project asks for certain photography to take place it will repeat much of what has been done, and probably gone unnoticed elsewhere. ND grad. filters come in a number of guises, some with more ND and others with varying amounts of graduation. For the landscape photographer using of a DSLR and wanting to include any sky that has clouds, it is tool that will save the highlights and make the processing simpler. I do not believe though that it saves everything and there are issues with metering that need careful use. My filter (Lee System)  is the 2 stop soft gradation and is mainly used with my 77mm filter lens. The 100mm x 100mm size is too small to cover the front of the larger fast telephoto glass and for those there is no solution, and probably no need.

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


  1. Interesting. I haven't used a grad' filter, I got a big stopper in March this year and apart from a deep red for mono work never really used filters - so this has been informative. How do you rate the grad' filter in ACR - which I have used occasionally as compared to the real thing?

  2. This comment has been removed by the author.

  3. I have never really got on that well with the Grad in ACR or in CS5. The problem is that once its 255 white in the raw file its never going to be anything else and a ND grad does extend the range to cope with that (but not all the way as I found here). I think for belt and braces its 7 frames of bracketing and tone mapping. I have Photomatix Pro 3 but have only used it once. I think a combination of SEP and tone mapping would be great for a monochrome workflow but its starting to get long winded. Maybe for level 3.