|Strobing with lens wide open at f/2 in bright sunlit background.|
We all love bokeh backgrounds in our portraits, don't we? It effectively separates our subject from the background with that blurred and creamy effect. It's one of the reasons why portrait lenses are usually fast with their f1.2 to f/2.8 maximum apertures. It's also why we buy those fast long lenses that are primarily designed for action photography (sports or wildlife). But for a lighting photographer, shooting outdoors under bright sunlight, it is almost impossible to get that bokeh without blowing out the background. We are generally limited by our DSLR shutter's maximum flash sync speed which is 1/250 at best, 1/200 for the lower end models. Mirrorless cameras (yep, even the mighty X-Pro1) can only sync up to 1/180. As we have learned in the past, shutter speed controls ambient, so if our ambient is really, really bright, our shutter speed needs to be faster than 1/250.
|Here's the EXIF data for the picture above. The built-in 3-stops ND filter was used here so that 1/500 is virtually 1/4000.|
We can, of course, control ambient with aperture but we don't do that because it affects our flash exposure too. Anyway, the main reason why we want to shoot wide open with our fast lenses is BOKEH. But like we said, 1/250 with f/2 is not fast enough. 1/500 may be just enough to properly expose your background but what you want to do really is underexpose it further by 1 to 2 stops so that when you light your subject, your subbject would stand out. That means you need to be at around 1/1000 to 1/2000. This is one of the main reasons I love my X100S. It can sync at virtually any shutter speed.
|And here's the behind the scenes shot of the above photo.|
Can this be possibly achieved with our DSLR's and their lowly 1/250 maximum flash sync speed? Of course. ND filters up to 10 stops are available for every lens diameter. But then, you will need some serious flash power to penetrate that ND. Why? Because ND affects your aperture too. Yes, it will remain at f/2 but with an ND-4 you are cutting down light by 4 stops. That f/2 virtually becomes f/16! The one thing ND filters do not affect is bokeh.