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Reverse grad filter 100x150mm

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K&F Concept Reverse graduated ND filter

100mm x 150mm filter


Keith recently looked at the K&F square ND1000 filter and mounting holder. It’s useful for extending exposures to blur movement. However it’s a uniform filter, so darkens the whole image.

Using the same filter mount, Keith has had a look at a reverse graduated filter which can help deal with some lighting extremes.

For more details see the filter at K&F
or buy from Amazon UK

The reverse graduated filter

If you’ve ever photographed landscapes around sunset, you’ll be aware  of the significant difference in sky brightness near the horizon and higher up. If you want any detail in the landscape then you are dealing with a rang of brightness that challenges even the best of modern digital cameras.

A long standing solution to this is to have a graduated filter that darkens the sky but not the foreground. That’s OK for some situations, but near sunset, it can darken the sky too much. This is where the reverse grad filter comes in.

graduated filter and case

Note how the darkest band is just above the middle.

The filter fits the standard K&F frame. Shown here attached to the Canon TS-E24mm F3.5L tilt/shift lens.

filter on camera

The frame comes with adapter rings for different size lenses (see the ND1000 review for more info)

filter-adapters

The filter is 2mm thick glass, with anti-reflective coatings – noticeable by the lack of ghosting and reflections, from when I shot with the sun directly in front of me.

gnd-filter-100x150

Using the filter

Obviously the filter is quite specialised – something I’d more likely use when visiting the coast, where I’ve a clear horizon line, rather than in mountains, where I might not want the darkening to cut across trees or mountains.

Fortunately the gradation is quite soft, meaning you’ve quite a bit of latitude in moving the  filter up/down, or even rotating the whole unit.

Here are two shots taken with and without the filter, from a recent trip to the Yorkshire Dales, using the Canon TS-E24mm lens shifted upwards.

no filter

The bottom one, with the filter is a slightly longer exposure, as seen by the grass.

with filter

Note that I’ve made no other significant changes to the RAW files as shot. The images were exposed so as to only just be clipping in the sun area. With the bright but hazy sun I’ve managed to keep realistic colour in the area near it. You do need to experiment with exposures, and it really helps if you’ve a good feel for how much ‘overhead’ you’ve got with RAW files when the camera’s highlights warning is flashing.

The point of this is that using the filter is unlikely to ‘fix’ lighting issues on its own, but it does give you a file that is a lot easier to work with.

So, after just a bit more adjustment I’ve a photo that give me a much better feel for the scene, where the only noise was of the sheep and lambs biting off grass to eat.

Click to zoom to see more clearly

sheep sunset

Conclusions

There’s no signs of distortion or hue shifts from the filter and it handled the wide angle views just fine (24mm lens shifted). Do remember that it does potentially alter the relative intensities of different coloured parts of the scene, so could well throw off auto white balance.

This is a filter that I’d look at using to make files easier to work with rather than hope that it will apply exactly the adjustments needed to get things right in the camera – but it does help you head that direction.

One of those filters I’d not initially expect to use often in my day to day commercial work, but that I’d definitely include on a trip to the country or the coast.

Actually, in thinking of some of my architectural work, it’s potentially useful rotated by 90 degrees if I’ve the side of a building in shade – like many gadgets you don’t always think of using them until a particular situation arises…

For more details see the filter at K&F
or buy from Amazon UK

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