ND Custom White Balance
Neutral density filters leave colour casts on your images. What that colour cast is depends on your neutral density filter because they’re all different. I use a Lee Big Stopper, which adds blue to everything.
If like me you shoot RAW and make your own jpgs this isn’t a problem because you can easily correct it in Lightroom when developing the file. But when shooting jpg you’re leaving this to (to my mind crucial step) the pre-programed parameters of your camera.
Your camera can’t know what colour you want the image to be and can only make it’s best guess about colour casts. Even auto white balance can get it very wrong – especially when shooting with a very strong 10 stop nd filter, like the Lee Big Stopper.
It’s easy to set a custom white balance to counteract your filter’s colour cast, but as they’re all different, there’s no definitive setting. You have to go experiment and find one that’s right for you.
I’ve never used a variable filter, but have been told by people who do the colour cast can vary according to the strength they set. This means you have to find several custom white balances. Maybe a light – medium and full strength then save them as pre-sets. This is why I shoot RAW – it’s so much easier!
So how do you set up custom white balance and where do you begin?
First go out somewhere and, set up a test shot using a tripod so the shots are identical. You’re not trying to win awards with this so don’t get all precious about subject matter. This is a test to find the nearest custom white balance only. Once complete, delete the images.
- Set a white balance preset to match the conditions you’re shooting in such as cloudy, sunny etc to act as a control image. Take a shot without the ND filter.
- Add your ND filter, adjust exposure as necessary and take another shot using same white balance as the previous one. (If you don’t see any difference in colour cast, your filter is neutral and there’s no need to go any further.)
- In white balance settings go to manual degrees Kelvin setting and dial in 10,000 degrees as a starting point. Take a shot and compare it to the 1st image, the one without the filter.
- If the colours match, 10,000 degrees Kelvin is enough. If still blue, dial up to 11,000 Kelvin and test again. If it’s warmer then dial down to around 9,000.
Keep adjusting and shooting test images until the 1st shot matches the one you just took. Whatever custom white balance you have is the one for your filter, so make a note of it and set that custom white balance when shooting with your neutral density filter.
Important: Ensure the light doesn’t change during the test. If it goes from sunny to cloudy for example, the colour of available light will change and give you false readings. If it’s a cloudy day and your exposure changes during the test, it means the cloud thinned and it’s likely to have changed the colour of the available light.
Even though your eyes can’t see that change, it happened. You must do this in constant light.
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I like the video, but as a Canon user there is an in-camera way to set up a custom white balance (I don't know if Nikon or any other make has this facility as I only use Canon cameras). You can take a photograph of the grey card with the big-stopper in front of the lens just as you did, then in the menu you can assign the colour that is recorded of the grey card to the custom white balance. Then by selecting custom white balance the camera will subtract any colour cast on the image of grey card from any further photographs taken with this custom white balance selected. The customer white balance can be used in for other circumstances by simply assigning another photograph of the grey card to the custom white balance. This works on JPG images, but it also sets the initial white balance seen in lightroom if you take your photographs in raw too.
However, not all colour casts are due to the dark grey tint of the big-stopper type filters (I refuse to call this set of filters "neutral density filters" because they impart a colour cast and hence they are not neutral!). Some areas of the cast is due to infra-red light. to combat this, Tiffen produce a range of three big-stopper type filters: one has a dark grey tint only; one has an IR block filter in addition to it's dark grey tint, and the other has an IR block filter and an IR reflection layer in addition to it's dark grey tint. Since IR light is basically heat, this light imparts an additional tint on any elements of the image that were warmer than the others. This makes producing an overall white balance a nightmare if it is possible at all.
I have taken IR photographs of the lighthouse where I live with a camera that had been converted for IR photography, and items like the black sea-weed drying in the sun turned out bright pink while the concrete causeway were rendered as dark grey with little or no pink colouration. A man jogging up the causeway dressed in black was also pink but his dog, who was wet after being in the sea was not. The clouds were pink but the blue sky was white! When using a big-stopper type filter on my camera to blur waves etc. The overall cast seemed to be yellow-brown. I noticed that by changing the white balance in Lightroom I could get the colour of the water to look natural, but then some of the rocks turned out to yellow-green, and I also needed to use the green-cyan slider in addition to the yellow-blue slider (which was marked in degrees Kelvin, 2000K to 10,000K).
I must confess that I haven't yet bought a Tiffen ND 3.0 with either of the two methods of IR reduction yet, but I do intend to in the near future. Then I will return to the lighthouse at low tide and take some more shots with my friend's IR converted camera and my camera with the Tiffen filter for comparison. Maybe this could be an interesting subject for a future video Mike. I'm sure some photographic outlet would provide you with a set of the ND filters for this purpose. Unless, of course, you don't see this issue that I have have with my Tiffen ND3.0 AXENT without IR Absorption.