Posted by Jon Leibowitz on February 12, 2007 at 10:21 PM
I have read two predominant ways of using ND filters. The first is to meter the foreground, and then meter the sky, both without the filter. Then find the difference between the two metered areas, pick the appropriate filter, place the filter on, and use the metered numbers for the foreground.
The other way is to place the filter correctly, then meter the photo for the sky (with the filter already placed) and shoot.
Two questions, which method do you use?
Second, does anyone have a link (or is willing to explain) how to correctly measure the difference of two exposures?
I ask because I have ALWAYS only used a 3 stop GradND, and perhaps that is why sometimes it works, and sometimes it doesn't. I have been using the correct filter only some of the time!
Posted by Tony Bouchard on February 12, 2007 at 10:40 PM
I usually just go by feel - if the foreground seems particularly dark, or if I want the foreground to end up on the brighter side in the final image, I use a 3-stop. If the foreground isn't so dark, or if I don't care about seeing lots of detail in it, I go with the 2-stop. I add 1 stop to my exposure for the 2-stop filter, 2-stops for the 3-stop filter. I may also choose a 2-stop or no filter if I want a faster shutter speed for some reason.
It may not seem scientific, but I have used this method to expose Fuji Velvia for several years with sucess.
Posted by Don Grall on February 12, 2007 at 11:27 PM
When shooting film, I bracketed in 1/3rd stops from -2/3rds to a + 1/3rd using matrix or center weighted metering. With digital, I just chimp it (look at the lcd screen) ! I rarely use a 3 stop because it seems to darken clouds a bit too much for my tastes. 2 stop filters are used 90% of the time.
Don
Posted by Kalin Wilson on February 12, 2007 at 11:55 PM
Jon, Are you asking about graduated ND or full ND?
For digital, I place the filter on the lens and meter through the filter. I adjust the transition of the graduated ND to where it is appropriate for the scene. With matrix metering both the non-stopped and stopped regions are factored in. If you're spot metering you probably want to meter several spots or a nuetral area and decide on the exposure before putting the GND filter on or you'll end up metering through part of the transition area which might not be what you want.
I use full NDs to knock down the light for slower exposures. This usually across the whole frame although with Cokin filters I may slide the filter to only cover a region. Again, for digital I'll usually meter through the filter. As Don said, the histogram is king for me with digital!
For film I meter the highlights and shadows and determine if the scene is in the dynamic range of my film (3-5 stops). If not, I pick the appropriate filter density to bring the scene into range (or live with blocked shadows. The tough part for me, with LF, is to remember to include the filter factors in the exposure.
If you're shooting digital it's definately worth experimenting to see what works for you!
Another way is to spot meter the light and dark areas, determine the number of stops difference, select your filter, hold it front of the lens and matrix/evaluative meter the whole scene. It's so easy now with digital's immediate feedback that any of these methods will give great results.
Posted by Timothy Tonge on February 13, 2007 at 3:33 PM
Question, which (what brand) neutral filters are you using, thinking of getting some myself for use with digital. Thanks.
Posted by Rick Dunn on February 13, 2007 at 5:15 PM
You need to start with understanding the latitude of your film (or digital sensor). The goal is to provide enough filtering to bring things within the range of the film or sensor, but not go overboard.
With digital, I mostly bracket and then combine shots in PS rather than using grads; that approach offers more control than a fixed grad line. On the rare occasion when I do use a grad with digital, I rely on the histogram to tell me if I've got things within the range of the sensor, and confirm with a quick view of the image on the LCD. I rarely bother to take meter readings of light and dark areas as the histogram tells me what I need to know. In most situations, I try to push the histogram as far right as possible without clipping it. Assuming that the darks aren't pushed off the left end, I'm good. If not, I'd go with a stronger grad to further compress the histogram.
When shooting LF, I do meter the bright areas and dark areas and make an assesment of whether I need a 2-stop or 3-stop to reduce the range throughout the scene to ~3-4 stops (that's a good range for Provia 100; other films will be different). I use the exposure settings from my meter reading of the dark area (i.e., unfiltered area) to select the proper exposure. So, I'm basically placing the darks in the desired zone, and the brights fall where they fall; I do make sure that the brights don't fall beyond the range of the film of course.
Like Don, I find that a 2-stop is the appropriate filter far more often than the 3-stop. If that's all you've been using, I'd expect that you'd have quite a few overly darkened images.
Posted by Jon Leibowitz on February 13, 2007 at 6:00 PM
Discussion
7 repliesThe other way is to place the filter correctly, then meter the photo for the sky (with the filter already placed) and shoot.
Two questions, which method do you use?
Second, does anyone have a link (or is willing to explain) how to correctly measure the difference of two exposures?
I ask because I have ALWAYS only used a 3 stop GradND, and perhaps that is why sometimes it works, and sometimes it doesn't. I have been using the correct filter only some of the time!
It may not seem scientific, but I have used this method to expose Fuji Velvia for several years with sucess.
Don
For digital, I place the filter on the lens and meter through the filter. I adjust the transition of the graduated ND to where it is appropriate for the scene. With matrix metering both the non-stopped and stopped regions are factored in. If you're spot metering you probably want to meter several spots or a nuetral area and decide on the exposure before putting the GND filter on or you'll end up metering through part of the transition area which might not be what you want.
I use full NDs to knock down the light for slower exposures. This usually across the whole frame although with Cokin filters I may slide the filter to only cover a region. Again, for digital I'll usually meter through the filter. As Don said, the histogram is king for me with digital!
For film I meter the highlights and shadows and determine if the scene is in the dynamic range of my film (3-5 stops). If not, I pick the appropriate filter density to bring the scene into range (or live with blocked shadows. The tough part for me, with LF, is to remember to include the filter factors in the exposure.
If you're shooting digital it's definately worth experimenting to see what works for you!
With digital, I mostly bracket and then combine shots in PS rather than using grads; that approach offers more control than a fixed grad line. On the rare occasion when I do use a grad with digital, I rely on the histogram to tell me if I've got things within the range of the sensor, and confirm with a quick view of the image on the LCD. I rarely bother to take meter readings of light and dark areas as the histogram tells me what I need to know. In most situations, I try to push the histogram as far right as possible without clipping it. Assuming that the darks aren't pushed off the left end, I'm good. If not, I'd go with a stronger grad to further compress the histogram.
When shooting LF, I do meter the bright areas and dark areas and make an assesment of whether I need a 2-stop or 3-stop to reduce the range throughout the scene to ~3-4 stops (that's a good range for Provia 100; other films will be different). I use the exposure settings from my meter reading of the dark area (i.e., unfiltered area) to select the proper exposure. So, I'm basically placing the darks in the desired zone, and the brights fall where they fall; I do make sure that the brights don't fall beyond the range of the film of course.
Like Don, I find that a 2-stop is the appropriate filter far more often than the 3-stop. If that's all you've been using, I'd expect that you'd have quite a few overly darkened images.