How do you know what filter/strength to use for a sunrise shoot?

[occifer nick]

I’m not even sure strength is even the right terminology when describing a filter. I know it relates to the number of stops you lose in light but I have no idea how you work out what one you need. I have seen that some people have the same one or 2 stacked every time but how do you know what one you need? I have recently purchased the cokin p series for wide angle so can only fit one filter in at a time and i have the 121m GND. I used it on my recent trip to the Sunshine Coast and subsequent sunrise shoot at Dicky Beach. I know you can also hand hold another filter in front of the one in the holder but is there any need? Is there a formula, do you need a light meter to work it out? I just bought the grad as I knew that if I wanted to balance the light from the sunrise to my foreground and get a better exposure then i would need a grad but that’s as far as my understanding goes. Any explanation in layman’s terms would be appreciated haha

[ricktas]

experience and practice!

Basically the brighter the sky, compared to the foreground, the stronger the filter needed. What you are trying to do is balance the light brightness between the sky and ground to ensure that the dynamic range of the scene is able to be captured by your sensor. You can do some metering of the sky and foreground and see how many stops difference there is and calculate the filter needed. But I generally go on my own personal visual 'feel' as to which one(s) to use.

If you have an ND set, 2.4.8. Start with a 4 and take a test shot, and examine the histogram and result on your LCD, then adjust from there. As you do more of this shooting (sunrise,sunset) you will learn to reasonably well guesstimate the needed filter(s)- remember you can stack them and put a 2 and 4 on together to make a 6, etc.

[occifer nick]

Thanks again Rick and bricat as I keep forgetting that there is a thank you tab that I can click ;)
I only have the one filter at the moment so I think that I will be getting a couple more so I can get out and have a practice.

[lay-z]

My shooting workflow goes along the lines of this when I intend on using a graduated filter:

Setup camera on tripod
Attach filter holder
I set my camera to aperture priority mode, aim only at the fore/midground.
Take the shot, look at hisotgram. A
im at the sky, take the shot, check the histo.
Check the difference in shutter speed.
Calculate the exposure difference.
Select and fit the most appropriate filter.
Set to manual and use the fore/midground exposure settings.
Naturally, sometimes slight exposure adjustments are required and changing light conditions would require me to stack filters as I go.

Of course this sounds somewhat easy but add the factor of the light rapidly changing with a sunrise and you realise you'll need to work quick! So you need to know your camera intimately and be able to calculate the exposure diffference fairly quickly before the light changes.

[lay-z]

If you have an ND set, 2.4.8. Start with a 4 and take a test shot, and examine the histogram and result on your LCD, then adjust from there. As you do more of this shooting (sunrise,sunset) you will learn to reasonably well guesstimate the needed filter(s)- remember you can stack them and put a 2 and 4 on together to make a 6, etc.

Just to clarify my understanding Rick, I always thought the number of stops goes like this 2. = 1 stop, 4. = 2 stops and 8.=3 stops. So by stacking a 2 and 4, you'd effectively be making an 8?

[ricktas]

Just to clarify my understanding Rick, I always thought the number of stops goes like this 2. = 1 stop, 4. = 2 stops and 8.=3 stops. So by stacking a 2 and 4, you'd effectively be making an 8?

You are correct. I was simplifying the numbering system used for nd filters, which are generally 2 4 8 10