Comparing ND Filter and FP-sync in bright ambient

There are two ways to use a studio or hybrid strobe in bright ambient light outside. One depends on the capabilities of the strobe, the other works with any strobe.

Recently hybrid strobes have been appearing on the market that include an FP-sync capability that, similar to a speedlite’s HSS, permits using shutter speeds greater than the camera X-sync. (There is another article on the site describing how that works using Cheetah Lights.) Its reasonable to expect that more and more hybrid, and eventually studio strobes will have a similar capability. Until then, the only viable option is using neutral density (ND) filters.

I have a Tiffen variable ND filter. I selected the filter for its versatility since I don’t use it often. I selected a size that fits my three largest lenses and then a step up ring for those that are smaller. One disadvantage with the variable version is that it requires leaving the lens shade off the lens for access to the lens, that increases potential for flare.

Below is a matrix of 6 images. They are the base exposure for strobe with bright ambient. The sun wasn’t out but still fairly bright. That exposure, with a CL-360 in a 30″ umbrella framed octa box (One of my favorite modifiers for hybrid strobes.) was F11, 1/160, ISO 100. The light was 5 feet away at 1/4 power. There are captions under each image in the matrix describing the exposure and in the second row, describing what Lightroom adjustment were required to get the ND and FP-sync images corrected to the base exposure for color balance, as well as overall exposure and contrast.

 

FP-ND-COMP-LRG

 

The base image illustrates why photographers want to be able to open up a lens, even in bright ambient. The edge of the bluff and the plants are distractingly sharp, even though out of focus. They are probably 75 feet behind Manny yet still a distraction. Opening the lens to F2.8 at 70mm softens the background, but, without some way to control light would over expose the shot. The numbers in the caption in the first row are F stop, shutter speed, flash power, along with Lightroom slider reading for color/tint/exposure/contrast. For all the images the tone curve in Lightroom was left at linear.

The captions in the second row are Lightroom adjustments necessary to balance the images. The Lightroom color balance eye dropper was used on the second white square in each image to set the color temp and tint sliders. The exposure and contrast sliders were used in the HD and FP-sync images to set the same reading as the base image for the white and black squares.

Its obvious that the ND filter introduced a color cast and flattened contrast. Both are easily correctable in Lightroom. I expect that constant value ND filters would be much less likely to have these attributes. If planning to use ND filters a lot in my work, I’d probably consider getting constant value filters for at least a bright sun situations.

As for controlling the light balance, both the variable ND filter I have and the CL-360 will handle bright sun.

Here are two test images shot with the CL-360 in a 90x90cm umbrella frame soft box in bright sun.

This is the test shot with the ND filter, ISO 100, 1/200, F2.8;

ND-COMP-9158

 

 

And this is the image shot with the CL-360 in H mode at 1/2 power;

1 360 1/1 diffusion +.25 EXP

 

As illustrated, both techniques work. The ND filter approach is much more widely used and understood simply because that’s the way photographers have had to solve this problem for a long time. The FP-sync solution is much more recent, just the last year or so, Until the availability of FP-sync capable strobes like the Cheetah Light this option was only available with speedlites and High Speed Sync. While it works, there are significant limitations because of a speedlite’s limited power output.

 

If you want to see some examples shots with ND filters in the sun have a look at this thread on Photography-on-the-Net. Especially shots done by Scott (abandon31).

 

Have fun shooting.