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graduated neutral density exposure question

Don Ferguson Jr.

Don Ferguson Jr.

Well-known member
''Imagine a scene with a snowy mountain peak under sunlight. Assume a grassy patch near to the camera with some flowers but these are in the shade. The meter reading of the snow peaked mountain is 1/250 at f/16 and the green grass (which is medium tone) is at 1/60 at f/4. This means there is a four-stop difference. If we take the shot at 1/60 f/16, the mountain will be rendered properly but the grass will be two stops below medium tone and hence will be extremely dark (underexposed). In a situation like this an one-stop grad ND filter can be used to compress the brightness range to three tops thus recording both snow and grass properly. Digital cameras offer much more flexibility allowing taking two exposures one over, one under and merge both in Photoshop. Only necessity is a tripod since accurate alignment of two images is needed.''
http://www.betterphotography.in/showstory.php?storyid=533


I understand the stops and all what I do not get is you would you ever switch to f 4 to first meter the foreground ? Why would you ever pick f4 ? Doing landscape I would think you use f11 or f 16 .I guess the author is trying to show a case and I should not take it too literal but it bugs me how you would know to meter at f4 . Does that make sense ?
Thanks
Don
 
Cem_Usakligil

Cem_Usakligil

Well-known member
Don Ferguson Jr. said:
''Imagine a scene with a snowy mountain peak under sunlight. Assume a grassy patch near to the camera with some flowers but these are in the shade. The meter reading of the snow peaked mountain is 1/250 at f/16 and the green grass (which is medium tone) is at 1/60 at f/4. This means there is a four-stop difference. If we take the shot at 1/60 f/16, the mountain will be rendered properly but the grass will be two stops below medium tone and hence will be extremely dark (underexposed). In a situation like this an one-stop grad ND filter can be used to compress the brightness range to three tops thus recording both snow and grass properly. Digital cameras offer much more flexibility allowing taking two exposures one over, one under and merge both in Photoshop. Only necessity is a tripod since accurate alignment of two images is needed.''
http://www.betterphotography.in/showstory.php?storyid=533


I understand the stops and all what I do not get is you would you ever switch to f 4 to first meter the foreground ? Why would you ever pick f4 ? Doing landscape I would think you use f11 or f 16 .I guess the author is trying to show a case and I should not take it too literal but it bugs me how you would know to meter at f4 . Does that make sense ?
Thanks
Don
Click to expand...
Hi Don,

If I'm not mistaken, in case the author had kept on using f16 for the foreground the shutter speed would then go down to 1/4 sec. If he is not shooting from a tripod this would be a problem, hence the choice of the 1/60 speed.

Besides, the metering system in the camera (when shooting in P mode) will offer the best exposure combination, thus will shift the aperture and stutter at the same time like in this example. So you don't have to do anything explicit to meter at f4 or f16 for that matter. If you use the aperture priority mode, OTOH, you can then set the aperture at f11 or f16 and measure from there. This would then result in 1/500-1/250 for the mountain and 1/8-1/4 for the grass.

And lastly, the text is wrong since there is a difference of 6 stops, not 4. Like this:
f16 -> f11 -> f8 -> f5.6 -> f4 are already 4 stops and then
1/250 -> 1/125 -> 1/60 are yet another 2 stops => total is 6.
 
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