Thursday, 4 June 2009

Flash photography - The Hot Shoe Diaries

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I've just finished reading The Hot Shoe Diaries by Joe McNally and highly recommend it to those who love lighting with flash. It's written in a very casual, chummy style (in a similar vein to Scott Kelby's books) which I found a little grating at times, but it's packed full of useful information, with plenty of case studies and detailed notes on set-ups. Joe comes across as a very likeable, down-to-earth chap.

He has a no-nonsense approach to shooting: aperture priority with evaluative metering, letting the camera get him into the correct ballpark for exposure and then using exposure compensation to adjust; using TTL metering for flash and then flash exposure compensation as required. Those who regularly read my blog will know that that's exactly how I like to shoot.

One last observation. As I always suspected, but never liked to explore in too much detail, Nikon's creative lighting system (CLS) seems to have a real edge over Canon's system. One feature I would love to have with my Canon set-up is a single button to be able to disable flash for a shot, as opposed to having to turn the flash unit off - simple but incredibly practical. If there is a way to do this, please feel free to enlighten me!

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zeno said...

Hi David,

Can you explain to me what the guide number scale means on my speedlite in real terms? Sometimes it only shows 6m or another single distance rather than a range - does that mean, unless my subject is at 6m the flash will be too much or too little?

I'm also confused in that when I put my iso up for indoor shooting, to get a decent shutter speed, the flash becomes way to powerful for close (1-2m) use - it just nukes the scene even with -2 FEC. And what I find more strange is that if I put the flash into Manual at minimal 1/128power it still nukes the scene indoor no matter what the distance?

As an exmaple ISO 1600 / F1.8 = 50 shutter. Subject 6ft away. If I turn on the flash and set the flash to Manual 1/128power it nukes the scene, ETTL however seems to work the math. It doesn't seem possible with direct bare flash to reduce the flash power enough to just add a kiss of light.

Am I doing something wrong here?


David said...

Hi Zeno,

The scale indicates the range in which the Speedlite thinks it can correctly expose a subject.

It sounds like your unit is trying to act as the key, rather than fill, light in some of these scenarios. It's putting out light to try and illuminate the whole scene rather than just the subject. FEC is normally the way to tackle it. Remember you can dial in -3 stops via the unit itself (but only 2 stops if you use the camera).

When you've set the flash to manual try reducing the ISO and stopping down the aperture (let's forget about ambient light for the moment) to see at what point 1/128 power gives an acceptable exposure. It might be that 1/128 power will always overwhelm the camera with these settings and the scene you're trying to shoot.

What zoom setting have you got your unit set to? Is it in auto or manual?

Try setting your unit to 24mm manual and engaging the built-in wide-panel to spread the light more widely. Or using a gobo (go-between: an object that limits the light between your flash and subject).

Please keep me posted with your progress.

All the best,


Zeno said...

"It might be that 1/128 power will always overwhelm the camera with these settings and the scene you're trying to shoot."

I think you are right, dropping the aperture and iso way down works. However, I want the bokeh and the faster shutter speed so I had ruled those options out. (I realise that flash freezes the action but if the shutter is slow it leaves a nasty ghosting around people I don't like) It just seemed strange to me that in ETTL the flash can reduce power way down to expose such a scene nicely, but the lowest power setting in manual flash mode is unable to provide just a hint of flash to a correct ambient exposure. So there is no way to force your flash not to act as a key light? - is this because ambient levels are so low?
I guess that in manual flash the guide number becomes critical and I should match that with my focused distance as indicated on the lens barrel. It seems to me that in ETTL mode the guide number doesn't matter, as it compensates the power output accordingly.

My solution has been to bounce the flash off the wall in manual flash mode to soak up the power. Setting the flash to a wide 24mm setting also helped as you suggested.

I'm sure you're wondering why I want to use manual flash and not ETTL anyway in these conditions - I don't , just curious :)

I'd love to know if other people can replicate this issue!

a) typical home living room scene in the evening with low tungsten light.

b) Wide aperture and high iso to get a good ambient exposure/shutter speed.

c) Direct Manual flash 1/128 power. Does it nuke the scene?

(I was using 85L /580EXII / 5DMk2)

Thanks all.