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  #1  
Old 07-09-2012, 06:53 PM
mjw364 mjw364 is offline
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Question ND grads help

Hi

I need some help with exposure settings for soft nd grads... I am new to this and a little confused.

As I understand it a 0.3 nd grad equals one stop under, 0.6 two stops, 0.9 three stops etc...

So I set up my camera without filter at f5.6 1/60 sec... In aperture priority mode. I slide 0.6 2 stop filter into position and the camera stops down to 1/30 sec ( which is only one stop) I take a shot and compare with image without filter and yes the clouds have darkened slightly. However, this is a two stop filter so I switch to manual mode and stop down to 1/15 sec keeping aperture at f 5.6, two stops down from the original reading of 1/60 sec @ f 5.6. But this time the sky doesn't darken it actually gets lighter and the histogram shows the exposure is too far to the right with highlights off the chart so to speak.

What am I doing wrong and why is a two stop filter showing a better image when only stopped down by one stop?

Any help welcome.

Thanks

Mike
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  #2  
Old 07-11-2012, 01:58 PM
Vato_Law Vato_Law is offline
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Default ...

Hi Mike,

I'm not a great "technician" myself, but it must be because you kept the F-amount but lowered the speed and the amount of light that got thru is higher.

A tip, if available in your camera, switch the live view on and like this you are able to preview live, what the results should be.

If you want to use longer exposures you might consider increasing the f-stop so that in combination with the lower speed the images doesn't get over exposed.

Or, buying those filters that allow "monster exposures" even in broad daylight, it all depends on what you want to achieve with those filters.

Hope this helps in some way.
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  #3  
Old 07-11-2012, 06:05 PM
mjw364 mjw364 is offline
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Default Hi

Hi Paulo

Thanks for the information. It is another way of achieving the same results that makes sense to me so I will have a little play around - I do have live view...

Its all trial and error at the moment! More error than anything!

I had some other tips from another site that may also shed light on the matter so I'll post it below for general consumption until one of the obviously talented photographers on Trek Earth decides to chip in and enlighten us...

One guy said:

"ND Grads still allow for normal exposure for at least half of the scene, and the camera meters the entire scene (in matrix mode) so that half that is not covered by the ND Grad is still giving normal exposure and the camera is averaging between the two.

Also, exposure settings are not fixed. If 1/30s gives you a better image than 1/15 use it, just as long as you realize what you see in the small lcd screen at the back of your camera is not always the best representation of what you see on a larger computer screen. Same for ND filters, they are not exact either, they are created within tolerances. Therefore a 2stop ND filter could actually be 1.8 or 2.2 stop instead."

This makes sense to some extent but how do I trust my calculations when using an ND filter for say three stops if they are not exact... ultimately it all becomes guess work and I can't really trust the accepted "theory" of how to use these things... that's something they don't tell u in the instructions or the "how to" section!

I also realised that another complicating factor may have been the fact that I had Active D lighting set to Auto - this is a feature on Nikon cameras (I use a D7000) - may have lightened the darkened areas when I stopped it down further... I'll try it on a normal setting...

I'll just keep going until I get there!

Thanks for taking the time to reply.

Mike
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  #4  
Old 10-12-2012, 11:00 AM
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feather feather is offline
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Default

Hello Mike
I'm late to see this, so you've probably figured it out by now, but I thought I would add my twopenn'orth.
I've been using ND grads for a while now and find that I get the best results by using manual exposure mode and spot metering.
Manual exposure because you control the aperture and the speed. With aperture priority the speed will automatically change as soon as you add the grad.
Spot metering because you can metre on the foreground choosing something you think is 18% grey....grass usually. If no grass, the palm of your hand is said to be roughly 18% grey. Only add the grad after you fix the settings.
Using the spot metre also lets you check out the reading for the sky and figure out which grad you're likely to need, although it still requires a bit of guesswork. When using matrix metering the meter takes an average of the entire scene including the sky, but to use grads successfully you're accepting that the sky and the ground require different exposures.
Hope this helps.
Kath

Last edited by feather; 10-12-2012 at 11:02 AM. Reason: missed word
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  #5  
Old 10-13-2012, 07:30 AM
delpeoples delpeoples is offline
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Smile Grads

Hi Mike...

And Kath, so nice to see you here and thank you for your advice on the filter, I always learn something new from you. Also good that you made it back from Italy in one piece, so sorry to have missed you.

Sorry I've only just noticed this post in the Forum. Kath has said just about everything I wanted to say, but she said it better.

ND Grads are so interesting; no two ever seem to be the same, and each make seems to have a different caste to them (Cokin seems to go a bit purple etc). My 0.6 Cokin and my 0.6 Lee require completely different light values. Out of interest, what type are you using? There is always going to be a variance in stops, between brands, between cameras and of course depending on what type of metering you use(spot, centreweight, average etc). So half the fun is muddling about with them.

I can't say that there is one successful recipe for using them. All I can tell you is what I do:

1. Like Kath, I always use Manual mode;
2. Will usually use Spot Metering;
3. Sturdy tripod;
4. Mirror lock;
5. Will usually compose the scene, meter the shot and then put on the grad filter (although lately I've been getting lazy and composing/metering with the filter already on
6. Also like Kath, I'd never use an aperture of f/5.6 for a landscape/seascape and will always use between f/11 and f/20 - the sharpness of my lens tends to fall off after about f/18;
7. I use Lee hard edged filters (0.3, 0.6 and 0.9), but am coming round to the idea that I should have bought the soft-edged versions.

I've spoken with André (Inasiajones) about the use of filters. He doesn't use them at all and so will meter for the foreground, take a shot, then meter for the sky, take a shot and merge the two in Photoshop. This is beyond my skills, but is certainly helpful when there are things which break the line of the grad filter, such as cliffs, lighthouses etc.

I've just recently bought a B+W Big Stopper something like 15-30 stops so you can use it during the day. This definitely requires composing the scene, metering and then putting on the filter. I'm still playing around with it but having alot of fun.

So I wish you lots of fun and lots of interesting photos.

Cheers
Lisa
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