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Split ND (graduated ND) filter

Michael Shpuntov (Yahoo!, FZ10 group, 27 and 28th June 2005)...

I've finaly got graduated ND filter, or how they call it split ND. It's Tiffen Color Grad ND 0.6 (gradually reducing light by 2 stops in one half of the filter)...

When I metered test scene without this filter, I used spot meter on shadows and then highlights. I've got approximately about 7 stops difference in readings from f/3.3-1/80 to f/6.3-1/2000. This range was too big to be covered just by camera itself. Dynamic range of FZ is about 5 stops, I've tested it some time ago. In this situation to preserve details in shadows and highlights you have basically three options.

Take two pictures with spot metering on shadows and highlights and superimpose them in PS or PSP. PS CS2 has even special processing for this. Pros: that you can increase dynamic range for more then 2 stops. Cons: practically difficult in the field. Tripod, static scene, etc..

Use Split ND filter which comes with 1/2/3 stops light reduction. Pros: easy to use. Cons: generally only 2 stops coverage, need some scene alignment with the filter, no dynamic range increase (since it just reduces the light).

No filter at all. Expose to bright midtones and hope that shadow details will be good enough after PS processing with shadows/highlight tool. Pros: Even easier than with filter. Cons: Colors in shadows might to grainy after PS processing. A bit of unnatural look.

I hope that split ND filter will help me to keep both highlight and shadow details while taking a shot. Even the dynamic range of image still will be about 5 stops, it's looking more naturally to eye, since eye accommodate much wider range (I think it's about 10 stops).
John Lehman (Yahoo!, FZ10 group, 29 June 2005)...

The media in a camera only has so much dynamic range wheither it be film or a CCD. That is the range from max brightness to minimun darkemess is comtroled by the medium you are exposing. What a split ND will do for you is compress this dynamic range in to something that the camera media can handle more effectly. In other words increace the dynamic range buy 2,3 or 4 stops by putting the breaks on the highlights. You can't do this with f stop adjustment alone because all you are doing there is moving the mid range exposure point around and you are going to still be underexposed in the shadows and blow out the highlights or vice versa.

The only other way, other than a split ND, to acheive saving both the highlites and the shadows is to take 2 shots, one for the highlights and one for the shadows and combine the two in Photoshop or something similar. A simple way this could be done with software is to tahe two shots as described above and useing some panorama software to stich them together.

The bottom line here is you can't do it with the camera alone, you need some outside help. One solution I have used in the past is to take a bunch of nice cloud pics an the use them to inhance a picture that needs something in the sky. I remember spending hours in the darkroom trying to get it right..

next up previous index Link to 'photography' page
Next: White balance Up: Filters Previous: Polarizing filters   Index
David Fong 2009-09-04