What are your settings?  -  a question that I am often asked about various images. 
And quite often, the answer is surprising  -  it doesn’t really matter.   
Sometimes the specific settings are of importance, but usually much less so than the method of getting to correct exposure of the ambient light and the flash.

This is the photographic equivalent of teaching someone to fish, versus just slapping a fish down on a dinner plate.  Just telling my settings will reveal very little about the how.  And yet, the how is far more important than just a listing of seemingly random figures.

Let’s look at this recent image from one of my workshops on flash photography - especially since it is exactly the kind of thing which I teach during the course of the day.

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1/100 @ f1.6 @ 1000 iso

“Dragging the Shutter” is a term used to describe the technique of using a slow enough shutter speed to allow a measure of ambient light to register when using flash.

This term originates from an era when photographers would determine correct flash exposure for on-location photography by :
 - setting the ISO speed according to the film used,
 - setting the aperture according to subject distance  (depends on flashgun’s guide number),
 - then using the shutter speed as the ONLY way of independently allowing more ambient light in, slowing the shutter speed far lower than max sync speed when shooting in low light.

(This worked fairly well for colour negative film, because the labs took up the slack in exposure miscalculation when printing the images.)

However, with TTL flash on a D-SLR, you have more flexibility than this.  And I’m of the opinion that the phrase “dragging the shutter” is archaic in the era of TTL flash photography.

As explained on these two previous pages …
 - Manual flash vs TTL flash,
 - juggling the three controls
… TTL flash exposure will follow your chosen aperture and ISO.
This means that your choice aperture and ISO effectively becomes ‘transparent’ to your flash exposure.

Hence you can equally well use your aperture and your ISO and your shutter speed, to allow more or less available light in, independent of your (TTL) flash exposure. (Obviously we have to work within reasonable ranges.)

So it would be of great benefit not to get locked into the idea of “dragging the SHUTTER” to control your available light, when you could equally well use any of the three controls when you use TTL flash.

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Many photographers seem to have a hard time wrapping their heads around this idea - that with TTL flash it isn’t only the shutter speed that you can control, but that you can now use all three settings (shutter speed, aperture, iso), to control how your available light registers .. and still not affect your flash exposure.

Let’s look at all of this in relation to some images:

1/100  @  f1.6  @  1000 iso
Canon 1Dmk3 / Canon 85mm f1.2 II / Canon 580EX

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1/125  @  f1.6  @  1250 iso
Canon 1Dmk3 / Canon 85mm f1.2 II / Canon 580EX

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1/100  @  f2.0  @  1600 iso
Canon 1Dmk3 / Canon 85mm f1.2 II / Canon 580EX

If you look at my settings for all three images, my shutter speeds weren’t all that slow, BUT if you look at the images you’ll notice that the available light most definitely did register.  And this was because of my choice of aperture and ISO.  With a wide aperture, and a high ISO,  I allowed ambient light to register, and give context to my photographs.  And then I added TTL flash to it, and exposed correctly for my subjects, opening up shadows and controlling contrast and cleaning up skin tones.

I didn’t need to specifically “drag my SHUTTER” to get to this point.

What is at the very heart of this, is the idea that you get better results with on-location flash photography, when you make sure your ambient light registers to some extent - whether you use your aperture, ISO or shutter speed.

So in trying to understand this technique, don’t stare yourself blind against the idea that shutter speed is the only thing which allows you to independently control your ambient light, separate from your flash exposure.  With modern (ie, TTL) flash photography, this technique has become a lot more interesting and versatile.

The breathtaking sight of lightning splitting the evening sky has to be one of the more dramatic subjects to photograph… and also surprisingly easy.

A vivid burst of purple lightning over this store, framed by the arch of the verandah I was sheltering under, contrasts perfectly with the yellow cast of the man-made light. Of a series of 10 photos I took here, there were 2 usable images with lightning.  The strong colour cast are from the street-lights, and having used daylight-balanced film.

April ‘91 .. Colesberg; South Africa
Pentax Super-A;  Pentax-A 24-50mm f4
15 sec @ f8.0 .. Fuji RD 100 .. tripod.
 

the essentials:

• A camera with a wide to medium-range zoom.  (Composition is easier with a zoom.)
• A sturdy tripod.
• Your camera should have shutter speeds longer than a second or two, or should be able to take a cable release, since exposures are often going to be in the region of 4 to 30 seconds.
• A dry sheltered place from where to photograph. A verandah or some such to keep you and your equipment dry.  Especially if the lightning flashes aren’t merely far-off on the horizon, but somewhat closer.
• Lightning (of course.)

the method:

You might be under the impression that it takes great skill and reflexes to take the picture at the exact brief instant of the flash of lightning. Not so. Most times, you will be using a slow shutter speed in dim light, allowing the lightning to take its own photograph so to speak. The lightning flash is short-lasting, but your camera’s shutter will be open for at least a few seconds. (There are also devices available that will trigger your camera’s shutter at the very instant it detects the lightning flash.)

Since you can only anticipate where lighting will occur, you can only point your camera (on the tripod), at the approximate area of the most intense display of lightning.

Interesting foreground detail will add to the appeal of your photograph - city lights in the distance; or street lights closer up, perhaps some buildings in the picture with the lightning; lights of cars streaking by on a nearby road; or anything else to give a sense of scale and place.

metering & exposure

Most lightning will be seen at night or in the evening when the light level is fairly low due to weather condistions.  This low ambient light will necessitate a slow shutter speed of a few seconds or up to a minute or so.  But this works to your advantage.  More time for a bolt of lightning to appear.

On 100 ISO film, an aperture of f8 should expose the lightning fairly well.  A stop or even two wider perhaps if the lightning is distant or faint due to rain.  With an aperture of f8, you need to decide on the length of exposure, and this will be determined by the ambient light or how bright the scenery is that you’re including.

In other words, you need to expose for the rest of the scene using f8 (or your chosen aperture.) How intensely the flash of lightning will record on film or digital, is controlled by the aperture and not the shutter speed. (This is similar to using flashguns on manual output.)  This is due to the short duration of the flash.  So the eventual shutter speed that you use will not dictate the lightning intensity, but only how bright the entire scene will appear in your final image. However, the shutter speed will dictate how many flashes of lightning appear on the single frame of film.

Meter for the rest of the picture in the usual way.  If, for example, you are including a street-lit building in the foreground, take a meter reading of this building or an appropriate area that you would like to expose for.

If the scene is too dim for the range of your camera’s metering display, try metering at a large aperture or a higher ISO setting.  (Eg. f2 at 800ISO is 7 stops away from f8 at 100ISO.  A 1/4 sec reading at f2 and 800ISO will translate to 30 seconds at 100ISO.)

Since the lightning will not be predictable in how often and where it strikes, you will need to take a series of photos at your chosen shutter speed, to make sure you do get to record a lightning strike.

The matter of reciprocity failure with film never really bothered me in this type of photography.  With strangely coloured illumination from artificial light sources, and dark areas all round, exact exposure of foreground objects is not so critical. If anything, under-exposure is far more acceptable to the eye than even slight over-exposure of night-time shots.

One of the most astounding lightning photographs I have ever seen, was one where the photographer must have used a lens around 24mm while shooting upward to catch a crazed pattern of jagged lightning overhead in a delicately tinted evening sky.  Magical! 
There is always something to aspire to.

I want to explain a bit more about how I use fill-flash, by using a specific example - and compare the results with and without fill-flash.

The image above is of clients of mine (Erik & Carla) whose engagement shoot took place in Vegas earlier this year.  This part of the shoot took place outside The Venetian. I bounced the flash into that open ceiling of the Venetian, and half behind me into the walls. And anyone who has been there, knows how large a space it is … but enough light bounces back from the walls and ceiling to lift the shadows and reduce the contrast.

The image as shown above, had some post-processing done to it.
Specifically, I ran the Prettyizer and Rusty Cage actions by the Boutwells.
(Highly recommended, btw)

But here on the left is the image as it comes out of Canon’s DPP (which follows the camera settings for image quality), with only a minor WB correction done to it, and exposure pulled down -0.3 stops in raw processing.
On the right is an image taken shortly after where I tripped the shutter before the flash had enough time to recycle. ie, no flash. Exposure at 0EV, and the same WB correction as the left-hand image.

And just to show what the flash does to the detail in the faces.
(And yes, they did give me permission to use the image here.)

For me, the difference is huge. The left hand image is flattering, there is detail, but the mood is retained. And it certainly does NOT look like flash.

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And NO, I did not modify the flash. A flash modifier would’ve thrown too much light forward and made it look like flash was used. Which quite often is ugly. (If only I could convince the world that using a flash modiefier is more often a bad idea than a good one.)

Re my specific settings … the shutter speed was 1/250th - maximum flash sync speed for this camera.

And this setting was chosen deliberately. There is something very sweet happening at max flash sync speed - and too many photographers aren’t aware of it. I touch on some of it in this blog posting - but if it doesn’t quite make sense why, let me elaborate:

Let’s say your background that is brightly light is at 1/60th @ f11 .. and you’re trying to push enough light from your strobe to light your subject which is in ’shade’. Now your strobe would have a really hard time trying to push out f11 if you’re bouncing it off the ceiling or wall in a large room.

BUT .. that same exposure setting, also translates to ..
1/125th @ f8 … and now your flash has a slightly better chance.
1/250th @ f5.6 … and now we’re getting into the realm of bouncable flash.

We could extend this to 1/500th @ f4 … but we’d have to go into high-speed sync mode.  And as soon as you do that, you lose more than half your flash’s range. 

You can double check this by watching what your strobe’s range indicator does as soon as you go 1/3rd stop over your max sync speed. For this, you would need to take your flash out of bounce position.
(5D users have a slightly different experience here wrt when high-speed flash sync kicks in.)

btw … I am explaining this as if your camera has a max sync speed of 1/250th. Of course it differs for different cameras, but the same thought process remains.

So we’re looking at 1/250th (or whatever your max flash sync speed is), offering us the widest possible aperture, at the most range / output we can get from our strobe. Less than max sync speed, and we’re making our strobe work harder than it probably needs to because we are using a smaller f-stop. (We’re still thinking in terms of balancing flash with a very bright background, or in bright conditions.)

For me, 1/25oth therefore becomes an easy default when working outdoors.
I have max efficiency from my strobe (in case I need it), and at the slightly higher shutter speed, I have less chance of camera shake or subject movement to register.

And in the instance where in bright conditions (or against a bright background), we’re settling on max sync speed giving us the widest aperture we can use for the most range from our strobe, but this also has the implication that ..
 - our batteries lasting longer, and
 - our flashgun recycles faster, and this in turn
 - we have more consistent exposures when shooting faster.
 

I frequently receive emails with questions which seem to vary in content, but essentially come back to the same point. For example:
 - how do the automatic exposure modes work on a specific camera, especially when flash is used ?
 - do I agree that a certain camera model tends to under-expose in matrix metering / evaluative metering when used in Aperture Priority ?
 - can I explain certain inconsistencies when using an auto mode such as Program / Aperture Priority?

Although the questions seemingly vary,  my reply is usually the same - that I don’t know the specific answer. And the reason is that, for the most part, any “answer” here is ultimately not of any consequence to me because … I shoot (nearly) exclusively in manual exposure mode.

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Histograms display the relative levels of the darker to brighter tones. As the histogram stands, it isn’t of much direct use to us, since the tonality of the scene that was captured will dictate what the histogram shows us .. without a direct indication of whether exposure is correct.

Some will say that a histogram should have an even bell-shaped curve, but this is too simplistic.   A light toned subject against a white wall will show a much different histogram that a dark toned subject against a dark wall .. even though the exposure might be correct in both instances.

In both those cases, the actual histogram display might be interesting to look at, but of no real direct use to us. But, here’s how I use the histogram to determine correct exposure …

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the effect of having a higher flash sync speed …

or

… why 1/500th @ 200 ISO is better than 1/250th @ 100 ISO

A question I often see asked on the internet forums, is whether having 1/250th flash sync at
100 ISO (on a camera like the Canon 10D), is the same as having 1/500th flash sync but being limited to 200 ISO, (such as with the Nikon D70).

In short, the answer is .. no, it’s not the same.
The camera with the higher flash sync has a distinct advantage.
Not only in being able to stop motion better, and giving you better control over depth of field,
but more importantly, the higher flash sync gives your flashgun greater range.

The reason for this is that a change in ISO will affect both ambient light exposure and flash exposure. As does your choice of f-stop. But flash exposure is not affected by the choice of shutter speed (as long as you remain within flash sync range). This higher shutter speed will enable us to get a wider aperture - and hence greater flash range.

At first glance, it seems logical that 1/250th @ 100 ISO might effectively be the same as
1/500th at 200 ISO, but it isn’t that simple. Here’s an example to help us step through this, and let’s base it on an actual scenario.

The actual EXIF data for this image, taken with the D2H says, 1/250th @ f6.3 @ 200 ISO,
but let’s keep it to round figures for simplicity’s sake.

In our example the couple is getting married inside a venue, and the sliding doors are open and you can see New York’s skyline in the background. And we want to balance them perfectly with the background skyline. We need to use flash, or else the background will wash out completely if we expose only for ambient light on the couple. Or, alternately, without flash, the couple will appear sillhouetted - a cool idea for a photo or two, but won’t be acceptable for an entire sequence.

Let’s say we have light outside that gives you 1/250th @ f5.6 (100 ISO), for the background.
(ie, 1/250th @ f8 for 200 ISO)

And let’s say our flash’s guide nr is such that at the distance we are standing away from them,
ie flash to subject distance, is such that we can squeeze f4 maximum out of it at 100 ISO.

So now we have a flash that can only give us (at this distance),
f4 (100 ISO) = f5.6 (200 ISO) = f8 (400 ISO)

So the photographer with 1/250th flash sync, can get
f5.6 ambient, but only f4 for flash, (100 ISO), or ..
f8 ambient, but only f5.6 for flash, (200 ISO).

It is important to notice here that the photographer with a max flash sync of 1/250th in this example, will always be one stop under for his flash exposure compared to the ambient light.
Or seen in another way, his background here will be one stop over-exposed compared to his flash exposures. It’s also very important to note that raising ISO up or down does nothing in terms of balancing flash with ambient .. simply because raising the ISO or lowering the ISO, affects ambient exposure and flash exposure equally.

Now, on the other hand, the proud owner of the D70 with 1/500th max flash sync, just bumps his shutter speed to 1/500th of a sec. His ambient light becomes .. 1/500th @ f4 (100 ISO).
Aaah, but you say he is limited to 200 ISO ?? Not an issue ..
this becomes .. 1/500th @ f5.6 for ambient exposure in this example, for 200 ISO.

And our flash in this example, can give us … f5.6 at 200 ISO.

Tadaaaaa .. in this instance we can perfectly balance flash with ambient ..
because we could raise our flash sync speed. ISO had nothing to do with it.

So someone who has only 1/125th top flash sync (like on the Fuji S2), has a very real (2 stop) disadvantage compared to the 1/500th flash sync speed like that found on the Nikon D70.

By the way, in the example photo above, I had to trigger other strobes for additional light
and to give some degree of modelling that straight-on flash wouldn’t have.

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Neil vN

I often get asked which metering mode I use - Matrix / Evaluative, or Center-weighted, or Spot-metering?

You’ll find different arguments on the various web forums as to which works better. Lots of advice there. But now I’m going to add something that might confuse you … it doesn’t really matter in the end which metering mode you use.

Since I’m shooting in manual exposure mode, no matter which route we take to get to the exact shutter speed / aperture combination that I’m using … I would be getting the exact same exposure regardless of which metering mode was used.

As I said on the page on metering techniques ..

For me, exposure metering has become an iterative process of:
- checking my camera’s meter,
- checking the histogram
- and blinking highlights display,
- checking the image on the LCD, (although this isn’t an accurate assessment of exposure),
- experience.

There is no fixed recipe in approaching metering in all kinds of situations.
It’s a mix-n-match of different techniques -
all used to make sure I get optimum exposure for my images.

With that iterative method, it doesn’t really matter which metering mode was used - I end up at the same place - the same aperture / shutter speed / ISO combination.

So which metering mode do I actually use ? I mostly keep the camera set to matrix /evaluative metering, but I occasionally switch to spot metering. When I do use spot metering, I am specific about the tonality of the area which I am metering of. That is a very important consideration when you use spot-metering.