Long Exposures in Sunlight using ND Grad

lauy

lauy

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Allen
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Hi

This has probably been asked many times before, but wondering if you lot could help me. I've just purchased a set of Cokin P ND Grad filters, which I know aren't the best but it is my first venture into ND Grads.

I went out into a field and tried each of the 3 different stop filters, and even the darkest one didn't really help much. I stopped down to f/18+ and ISO100 but anything above a second of exposure just resulted in complete blown out white image. I tried under-exposing on the meter bar and it still did this. I also stacked the 3 filters, which lead to a purple tint in the sky, but again any sort of long exposure of seconds would result in white image.

What am I doing wrong? I suspect I'm not metering correctly? Is it possible to have long exposures in the day time?

When I've tried indoors or not under sunlight, it is not a problem.

Apologies if this seems very dumb, I've read the tutorials on long exposures and metering, but clearly I'm not getting it right.......

Thanks for your help

Allen
 
ND Grads are used under normal exposures to get the colour back into the sky to stop blown out skies.

ND Filters that are NOT graduated are used to make the exposure longer in daylight such as 1 or 2 seconds even more in the case of a 10-stop ND filter.
 
Thanks for the reply! Okay, stupid me! So to use long exposure in daytime, it is necessary to use a standard ND Filter (non Grad)?

For a really long exposure, like 30 seconds for example, I assume a 10stop would be needed then?
 
You are correct. Something like an ND4/ ND8 is great for lower light conditions for a second or two.
But a ten stop filter is perfect for those very long exposures. Dont know if you've seen but search on here for welding glass :) I use one myself and it's the equivelant of a 10 stop filter, even more in some cases. And costs £1 rather than £80
And I made my own tutorial on how to use it so check that out too :)

Hope that helps
Jamie
 
Thanks for the tip, that is a big saving! I may have to get one off fleebay and give it a go :D
 
On ebay have a look for someone called DarkMutton, he's the guy who nearly all people on here have purchased from.
You can make him an offer of £1.10 apparently, but I just paid the buy it now price at £1.90.

But it does have a strong green cast too it, but if you follow my tutorial you will not have ay colour cast at all :)
 
J4MIE_P said:
You are correct. Something like an ND4/ ND8 is great for lower light conditions for a second or two.
But a ten stop filter is perfect for those very long exposures. Dont know if you've seen but search on here for welding glass :) I use one myself and it's the equivelant of a 10 stop filter, even more in some cases. And costs £1 rather than £80
And I made my own tutorial on how to use it so check that out too :)

Hope that helps
Jamie
Click to expand...

Just for clarity, I'm sure you know this Jamie, an ND4 filter is only two stops, and ND8 is three stops - it's the exposure factor. They are also known as 0.6 and 0.9 in terms of optical density.

Ten stops ND is 3.0. As a guide, ten stops takes 1/1000sec down to 1 second, or 1/60sec down to 16 seconds.
 
You may be able to use your ND grads as regular ND. Push them right down in the holder so the clear portion is entirely out of shot if you can.

Sounds like your problem is that your filter is not strong enough. Rather than try to pick a long shutter speed for it put your camera on aperture priority and pick a narrow aperture. Your camera will meter and tell you what is the longest exposure it can manage in that light.

If you've not read it yet, take a look here: http://www.talkphotography.co.uk/forums/showthread.php?t=169649
 
Thanks for all the info guys, much appreciated! Gonna go out and have a play now! :thumbs:
 
Okay, so I was testing out my Cokin filters, and it seems it gave a red colour cast to the photo. I've read online that they have the tendency to do this, but I didn't realise it was so apparent. Is there any way to get around this? I'm kind of regretting not shelling out for a a Lee filter set now
 
lauy said:
Okay, so I was testing out my Cokin filters, and it seems it gave a red colour cast to the photo. I've read online that they have the tendency to do this, but I didn't realise it was so apparent. Is there any way to get around this? I'm kind of regretting not shelling out for a a Lee filter set now
Click to expand...

Do a custom white balance with the filter/s on. But if you're talking about a grad effect with the filters, with only the darker area tinted, you'll have to adjust that in post processing - and best of luck to you ;)

Try HDR technique - works better than grads. Basically take two exposures (or more) - one two stops over exposed and another two stops under exposed - and merge them in post. Plenty on HDR (High Dynamic Range) if you search.
 
Also re the purple tint in the sky, that is partly because cokin filters aren't neutral, resulting in a slight colour shift. Lee filters are neutral, more expensive.
 
Hi Allen,

You have received some useful advice. The only extra I can add is make sure you move the ND Grad so it is on the horizon and I hate to say the next bit as I am sure you have got it right, but you did have the dark part of the grad on the sky didn't you;)

As suggested go to aperature priority and adjust for whatever dof you want.

The tint is as has been explained a product of the cheaper filter, but although you should go to Lee if you are serious I would suggest getting it right before you start spending serious money.

Best regards

Chris
 
Thanks for all the advice everyone, much appreciated as I'm a complete beginner to all this extra filter stuff. I've only attempted it a couple of times so far and the weather wasn't too great. I did have the dark part on the top yes, where the sky is, but for some reason the rest of the shot under the horizon still seemed to have a red tint? Maybe I didn't place it correctly but I would have thought it would have been more neutral than that at least..........

I will keep playing around with these ones until I get the feel of using filters, but I can see myself growing out of them very quickly and wanting to upgrade. If I decide to upgrade to Lee, will I need to buy new everything, i.e. holders, adapter ring etc ?
 
lauy said:
Thanks for all the advice everyone, much appreciated as I'm a complete beginner to all this extra filter stuff. I've only attempted it a couple of times so far and the weather wasn't too great. I did have the dark part on the top yes, where the sky is, but for some reason the rest of the shot under the horizon still seemed to have a red tint? Maybe I didn't place it correctly but I would have thought it would have been more neutral than that at least..........

I will keep playing around with these ones until I get the feel of using filters, but I can see myself growing out of them very quickly and wanting to upgrade. If I decide to upgrade to Lee, will I need to buy new everything, i.e. holders, adapter ring etc ?
Click to expand...

Hi Allen,

In a word yes!

Lots of us can advise you when the time comes.

Regards

Chris
 
One alternative to Lee is Hitech filters. I use them based on recommendations by others, and so far I think they are pretty good. I bought the 85mm size and these are compatibile with the cokin holder and rings etc.
 
Hi wiseman, thanks for suggestion on the Hitech filters. Do they produce any colour cast like the Cokin? How much difference is there between the Hitech and Lee?
 
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