Beginner ND grads & lens focal length

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299
Name
Simon
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Yes
#1
Good afternoon,
At what focal length do ND grads become ineffective? Obviously, the longer the lens, the less effective they become, but would, say, a two of three stop soft grad work on a lens set at 70mm?

Thank you
 
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8,129
Name
wayne clarke
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Yes
#2
It should work at 70mm. I dont have one here in the studio to check. Certainly other ND/colour grads work ok at 70mm
 
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22,918
Name
Richard
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No
#5
Grads work at all focal lengths, but the effect gets progressively weaker with longer lenses, as the lens is looking through an increasingly small section of the filter in the middle. Eg, a two-stops grad will reduce exposure by two stops in the darkest area at the top, but obviously a lot less lower down. There are some other less significant factors too.

For the full effect, a wide-angle lens is necessary. As focal length increases, say above 50mm equivalent as a very rough guide, the grad effect can be enhanced by using a darker filter with a harder transition. Above 100mm equiv, I'd say don't bother and look at a post-processing solution.

In post, none of these problems apply and there are other advantages too. With some of the latest cameras with high dynamic range, a popular alternative is to under-expose so that highlights in the sky are retained, then darken the sky with a grad effect in pp and brighten the foreground.
 
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