Daylight exposure and fill in flash

<p>Picture the scenario: I want to take a photo of a person who is in full sunlight outdoors. They are wearing a hat so their face is in shadow. I set the camera (D90) to expose the scene correctly for sunlight - which will require a fast shutter speed - and use fill in flash (SB-400) to illuminate the face. My problem: with the optional flash attatched the camera settings are automatically overidden and the fastest shutter speed of 1/200 sec is set. This means the shutter speed is too slow for sunlight and the scene will be over exposed. Is there anything I can do? Am I missing something? Surely I can balance daylight exposure with fill in flash?</p>

<p>Make your aperture smaller.</p>

<p>The SB-400 flash is very limiting. The higher-end flashes from the SB-600 and up have the FP sync feature so that you can use the flash as higher shutter speeds.</p>

<p>Well the camera's flash sync is 1/200 sec,so when using flash you cannot use shutter speeds over 1/200 sec. With sb-400,I think your only option is to close down the aperture. If you don't do that, you will only get overexposure. For now,it will probably be good enough,but if you want shallow DOF with large apertures,you need SB-600,800 or 900 since they are better for fill flash(as I understand),and can be used at faster shutter speeds,and when used like that,they lose their maximum power. I don't know much about sb-400. I am also a newbie when it comes to fill flash,I only used my pop-up as a fill,and only few times,but I am reading about fill flash whenever I found a thread about it. Don't take my words 100% correct because I sad I'm not an expert at this,I am just trying to help. Cheers :)</p>

<p>Using the sunny f/16 rule you'd expect to get a correct exposure at f/16, 1/200 sec. using the optimum setting of ISO 200. If difraction is now a problem you could use an ND filter. You could use the 100 ISO setting at about f/11 but that may well give lower dynamic range than the 200 setting.<br>

Failing that trade in for a D40 which syncs. at 1/500 sec ;-) With this I find fill flash works just fine using the built-in flash!</p>

 

<p>This is the reason high sync speeds are coveted by photographers. Any way around the problem, like ND filters or FP mode, greatcly reduces the relative power of the flash. Those are the options, though, if you want narrow depth and fill flash in the same shot.</p>

<p>An ND filter, like reducing the ISO, does <em>not</em> reduce the relative power of the flash since it reduces both flash and ambient energy by the same factor. FP mode <em>will</em> reduce it however. This is because the flash fires a sequence of low power flashes during the time that the shutter takes to travel across the film/sensor. It's confirmed by the low guide number for these modes.<br>

Of course the sync. speed does control the relative power of the flash. The flash lasts a very short time, perhaps 1/2000 second, so changing the shutter speed will not change the affect the flash has. The shutter speed affects the ambient exposure however so a short exposure time means that the flash power is relatively high. This is why you can use the low power built-in flash on the D40/D50/D70 for daylight fill.</p>

 

<p>The flash has to provide a certain share of the total light in order to give a good result. The exact amount is restricted by the maximum sync speed imposed by the camera and the f-value. Higer f-value, e.g. f/16 instead of f/5.6, may bring the shutter speed back into the limit , but you would need more power at the flash then. Hence, if the ambient light is too bright, there is not much you can do other than to use a stronger flash.<br>

Alternatively use a flash that is able to "high-speed sync". That would be stronger then anyway...</p>

<p>Joseph, it's a very good question. Thanks for posting it. This is a situation where using the Aperture Priority exposure mode could be a bad idea.</p>

<p>Set your ISO to 200 (which you should always use when the light is bright), then rotate the D90's dial to P and let the camera select BOTH the f-stop and shutter speed. Then you won't have to worry about it.</p>

<p>Forget about FP mode unless you have a pressing need to use it (e.g. professional sports photography).</p>

<p>If stopping down isn't something you want to do I'd say a reflector is a good option. If buying a reflector is problematic then any large white poster board will do in a pinch. The glossy side (if it has one) of the poster board will be more reflective but may also cause focused hot spots. Try the matte side first and see how that goes. This may not be the best solution for you but it's low cost and can help with the shadows. </p>

<p>You'll also need a stand of some kind to place the board on or a helper to hold and angle it for you. I'd say the extra person is best since there's really no limit to the positioning compared to a fixed easel or something similar.</p>

<p>Good luck!</p>