Wednesday, 21 January 2009

Wedding Photographer Kent - Using flash

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Another good question that deserves a post of its own.


When using flash in AV mode, but trying to capture ambient light in backgrounds, do you take your meter reading from the background (without the main subject) then recompose with the subject and let the flash balance itself? Or just meter the whole scene, and adjust EV?


When lighting for portraits, photographers talk specifically about key and fill lights. In the simplest scenario, the key light is the principle light source and determines shadow placement, and the fill light is used to reduce the contrast between highlight and shadow, by 'filling in' the shadow regions with light. A similar situation exists when you have to balance ambient and flash light - your flash can act as either the key or fill light. This is pertinent to the above question, since if you shoot in an automated flash mode, you have to be aware that the camera is making this decision for you, and can get it wrong.

90% of my shots are taken in aperture priority mode, with evaluative metering, and I use my flash in E-TTL II mode (the other 10% of the time I use manual mode). This requires me to make both exposure and flash exposure compensations and requires me to think about what I'm doing. In fact, although there is no best method for using your camera, to expose shots correctly in a wide range of lighting conditions will require you to think, whatever the process you use. Cameras are not yet clever enough to do it all for you, although I hope one day they will be. In the meantime, it's all about finding a reliable and efficient method that works for you.

So in the above example I would typically (alas, there are always exceptions) meter the whole scene and then apply exposure compensation to adjust the ambient light to the level I required, followed by flash exposure compensation to control the level of flash light. The ambient light is easiest to get right. Getting the right level of flash can occasionally be tricky, particularly when the camera has been fooled and is trying to use the flash as a key light rather than a fill light - it attempts to flash light the whole scene, resulting in your subject being massively over-exposed (nuked!). In this situation, you can either dial the flash right down (up to -3 stops) or use flash exposure lock on your subject.

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Reeves said...

what are you thoughts on using a ring flash for wedding portraits? I think you have one right?

Kent Wedding Photographer said...

I wouldn't use one as part of my standard repertoire. Ring flash is a very directional form of lighting that works well under very specific conditions - generally close-up glamour-style portrait shots. You can do something similar with a flash and softener (like the Lastolite micro Apollo) but can use this set-up for many other purposes too, unlike a ring flash.


Vince said...

Hi Davaid,

Please can I ask about FEC. Is this something you do based on distance to subject?

Also, when does the camera decide to use the flash as a main light rather than a fill light in AV mode.

I find it hard to judge FEC becuase it also effects my ambient light at high ISO.

Many thanks

David said...

Hi Vince,

The only way to get to grips with these techniques is practice. Persuade a friend to spend an afternoon with you and then try lighting them under various conditions. Change your settings and note the results. Annoyingly, FEC information is not recorded in EXIF data so you'll need to write this down.

Distance, balance of dark and light tones, location of light sources - all affect FEC.

A light subject in front of a dark background and light sources shining directly into the camera are classic situations where the flash can become confused as to its role.

Bear in mind when you shoot E-TTL you're using Canon's algorithms to balance ambient and flash. One way to circumvent this is to put them both into manual mode.