Advantages of a higher max flash-sync speed
A typical scenario we face, photographing people in bright sunlight – we have to add flash to balance them against the much brighter background. The thought-process or algorithm in deciding on camera settings, is carefully explained in this article: Controlling bright daylight w/ direct off-camera flash. What max flash sync speed is, and why understanding the impact of max flash sync speed is on balancing flash with ambient, is explained in that tutorial: Max flash sync speed.
Now that we have all that under our knee, the question might still remain – what are the advantages of a camera having a higher max-flash sync speed … compared to a camera with a lower max flash-sync speed, but with a lower ISO range.
Let’s consider two of the popular DSLR models that came out years ago, and helped make digital photography accessible to us – the Nikon D70 and the Canon 10D.
The Nikon D70 has a maximum flash sync speed of 1/500th, but only went down to 200 ISO. The Canon 10D has a maximum flash sync speed of 1/250th, but went down to 100 ISO. There were huge debates on the photography forums at the time, on whether the D70 had the advantage or not, since many argued that 1/500th @ 200 ISO is the same as 1/250th @ 100 ISO.
A quick bit of math comparing just the numbers, make it look like the two cameras are equals in terms of how you can balance flash with ambient light – but that’s too simplistic an explanation, and an entirely wrong way of considering this.
So here it is – the advantage of your camera having a higher max flash sync speed …
Let’s work through an example of camera settings
If the Nikon D70 boasts a higher maximum flash sync speed of 1/500th, but only has a minimum of 200 ISO … as opposed to the Canon 10D offering a lower max sync speed of 1/250th, but with 100 ISO as its base ISO … then it might seem that 1/500 @ 200 ISO = 1/250 @ 100 ISO.
It would be that simple if we were only regarding available light. But we’re bringing flash into this equation. So while a change in ISO affects both ambient light and flash exposure, shutter speed only affects available light. And that is where the difference comes in.
Let’s assume a certain combination of settings for ambient exposure:
1/250 @ 100 ISO @ f/5.6 (for the 10D), which is the same as:
1/500 @ 200 ISO @ f/5.6 (for the D70)
But let’s change the 10D settings to:
1/250th @ 200 ISO @ f/8 … which is still the same ambient exposure, compared to:
1/500th @ 200 ISO @ f/5.6
But now, when we add flash, we need to add f/8 worth of flash to the scene for the 10D, as opposed to only f/5.6 worth of flash for the D70. So our flashguns have an easier time with the higher maximum flash sync speed in situations where we are shooting in bright light conditions.
Just to be sure, let’s run through the explanation again
Let’s say we have light outside that gives you 1/250th @ f5.6 (100 ISO), for the background.
(ie, 1/250th @ f/8 for 200 ISO)
And let’s say our flash’s guide number tells us that, for the distance we are standing away from them,
(ie flash to subject distance), is such that we can squeeze f/4 maximum out of it at 100 ISO.
So now we have a flash that can only give us (at this distance),
f/4 (100 ISO) = f/5.6 (200 ISO) = f/8 (400 ISO)
So the photographer with 1/250th flash sync, can get
f/5.6 ambient, but only f4/ for flash, (100 ISO), or ..
f/8 ambient, but only f/5.6 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 @ f/4 (100 ISO).
Aaah, but you say he is limited to 200 ISO ?? Not an issue ..
this becomes .. 1/500th @ f/5.6 for ambient exposure in this example, for 200 ISO.
And our flash in this example, can give us … f/5.6 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.
Camera settings & photo gear (or equivalents) used
- 1/250 @ f/8 @ 100 ISO
- Nikon D4
- Nikon 24-70mm f2.8G AF-S /equivalent Canon 24-70mm f/2.8L II
- Lastolite EZYBOX 24″×24″ softbox
- Nikon SB-910 Speedlight controlled by PocketWizard FlexTT5 Transceiver & AC3 Controller
or alternately, the Canon 600EX-RT Speedlite controlled by Canon ST-E3 Transmitter
- Controlling bright daylight w/ direct off-camera flash (model: Molly)
- tutorial: Max flash sync speed
- tutorial: High-speed flash sync
- When to use high-speed flash sync / Auto FP (model: Aleona)
- How to overpower bright sunlight with on-camera flash
- Manual flash vs. TTL flash