flash speed??

[KingsHockeyFan]

I am looking at trying out a flash extender for use while shooting sports. In order to avoid motion blur, I typically shoot at least 1/640. If I put a flash extender on my camera will I be limited to 1/250 (which I understand is the fastest synch speed for the 70d), or can I still effectively use the flash at higher shutter speeds?

[Loose Canon]

Hi Kris,

Unless you fire your flash in high speed sync mode you will be limited to your camera’s max sync shutter speed. I’m not exactly sure what you are asking but a flash extender has nothing to do with x-sync speed or high speed sync.

If you use HSS you will experience a dramatic loss of flash power. If you need an extender because of the distance involved in shooting across a field, for example, your flash will most likely won’t be effective.

[Manfred M]

Kris - while I do a lot of flash photography (I own 2 speedlights, 4 studio flashes and a 300 W-s battery powered portable flash), I'm not a sports photographer, so can't get into an real specifics here other than I can't think of anyone that shoots sporting events that way. The ones I know shoot burst mode, at high ISO, using fast lenses and do they do not use flash.

Maybe a bit more information on what you are trying to do (lighting levels, distance to the subject, the equipment you are thinking of using) would be useful. My initial thoughts suggest what you are planning to do won't work, simply because I don't see people out there doing it.

[KingsHockeyFan]

I am really just looking to experiment at this point.
I shoot a lot of youth ice hockey, so I get poorly lit rinks with a high speed game. I use a Canon 70d with a 70-200 f2.8. My shots usually come out pretty good, but because I use a high iso, I deal with plenty of noise.
I have seen examples of bird photographers using flash extenders to provide some fill light when using a zoom lens through the shade of trees with good results. My thought is that if I can use a similar technique to provide some fill light at the rink I may be able to lower my iso and resulting noise.
I don't have any knowledge about flash sych speeds, so I guess my concern is if my flash can synch at higher shutter speeds to capture the moving subject 100' away.

[KingsHockeyFan]

Hi Kris,

Unless you fire your flash in high speed sync mode you will be limited to your camera’s max sync shutter speed. I’m not exactly sure what you are asking but a flash extender has nothing to do with x-sync speed or high speed sync.

If you use HSS you will experience a dramatic loss of flash power. If you need an extender because of the distance involved in shooting across a field, for example, your flash will most likely won’t be effective.

I need to learn more about HSS. I am not looking for very much power to reach the distance, just enough to maybe take the edge off some noise--- I have heard that with the extenders too much power results in hot spots.

[Shadowman]

interesting conversation, where exactly are you positioned when photographing? If you are behind the glass how do you plan to use flash, if you are in an elevated position how much reach do you expect the flash to have to make a difference in your shot? If you are on the ice.....wow?

[Manfred M]

I need to learn more about HSS. I am not looking for very much power to reach the distance, just enough to maybe take the edge off some noise--- I have heard that with the extenders too much power results in hot spots.

In a nutshell, HSS pulses the flash so quickly that for all intents and purposes you are throwing out a continuous beam of light. Both the camera and Speedlite need to be HSS compatible. It lets you shoot at shutter speeds up to the maximum that your camera has. The main downside of HSS is that you lose around 2 stops of light versus normal operation singleflash operation.

[William W]

You need to provide more specifics.

I can assist you with the calculations to give you a ballpark theoretical answer.

What's the typical ISO that you use?

What Speedlite do you have?

I assume you shoot wide open = F/2.8?

We will assume farthest Subject Distance is 100ft?

Are you shooting through Glass or Perspex?

We will assume a light modifier such as the Better Beamer?

Is 1/640s the Shutter Speed you need to freeze Subject Motion?

WW

PS Unlike the bird Photographer example that you gave, you are NOT looking to provide "Fill Light" because your Subjects are not in shade.

You need the Flash Power to be at or greater than the Ambient Light because you want to lower the ISO - that is not using the Flash as "Fill" - that is "Key".

PPS - on another note, you probably need to be aware of "the rules": I shoot (indoors) competition Swimming and also Gymnastics, one quick way for me to lose my accreditation would be to use Flash on Pool Deck or Mat side.

Even if your Association allows Spectators (I assume you are a spectator) to use Flash - as you pointed out, Flash Modifiers that "Focus" the Flash might create Hot Spots - so its sensible to be aware that you might cop some stick from player's who might be momentarily blinded by the light.

(Mixed Metaphors and Puns intended)

[William W]

I gotta go to a job I'll call in later and check if he has come back

[KingsHockeyFan]

interesting conversation, where exactly are you positioned when photographing? If you are behind the glass how do you plan to use flash, if you are in an elevated position how much reach do you expect the flash to have to make a difference in your shot? If you are on the ice.....wow?

If at all possible I get above the glass. If I am stuck behind the glass I would not use the flash, I have another tool for that situation (glare reduction not light providing). I don't know what to expect for reach, I have seen internet examples where birds were captured well lit at some distance. If possible I would like to reach the other end of the rink---about 200ft.

[KingsHockeyFan]

In a nutshell, HSS pulses the flash so quickly that for all intents and purposes you are throwing out a continuous beam of light. Both the camera and Speedlite need to be HSS compatible. It lets you shoot at shutter speeds up to the maximum that your camera has. The main downside of HSS is that you lose around 2 stops of light versus normal operation singleflash operation.

That makes sense---I would guess the lower power means reduced wait time in between flashes??

[Manfred M]

That makes sense---I would guess the lower power means reduced wait time in between flashes??

No, it simply means that with the light on "continuously" for the duration of the shot, the flash can only push out a lower amount of light. Recycle time; I can't really address as I have never checked out how that goes when shootin HSS. I use an auxiliary battery pack when I need faster recycle time on my Speedlight.

I've only shot with HSS to test it and have never actually found a "real life" situation where I would want to use it. Most of my flash shots are relatively stationary people or totally stationary products, so shooting at synch speed is fine.

[KingsHockeyFan]

You need to provide more specifics.

I can assist you with the calculations to give you a ballpark theoretical answer.

What's the typical ISO that you use?

What Speedlite do you have?

I assume you shoot wide open = F/2.8?

We will assume farthest Subject Distance is 100ft?

Are you shooting through Glass or Perspex?

We will assume a light modifier such as the Better Beamer?

Is 1/640s the Shutter Speed you need to freeze Subject Motion?

WW

PS Unlike the bird Photographer example that you gave, you are NOT looking to provide "Fill Light" because your Subjects are not in shade.

You need the Flash Power to be at or greater than the Ambient Light because you want to lower the ISO - that is not using the Flash as "Fill" - that is "Key".

PPS - on another note, you probably need to be aware of "the rules": I shoot (indoors) competition Swimming and also Gymnastics, one quick way for me to lose my accreditation would be to use Flash on Pool Deck or Mat side.

Even if your Association allows Spectators (I assume you are a spectator) to use Flash - as you pointed out, Flash Modifiers that "Focus" the Flash might create Hot Spots - so its sensible to be aware that you might cop some stick from player's who might be momentarily blinded by the light.

(Mixed Metaphors and Puns intended)

Typical iso is 4000

speedlite is a cheap knockoff (Allura) I just looked at it and do not think it is HSS capable

I sometimes shoot wide open, and when I do I reduce the iso to 3200. Recently I have moved to shooting 3.5 at 4000 in order to have an increased focal range.

farthest distance would be closer to 200ft

No flash through the glass

Yes, I am looking at the better beamer or a diy of the same design using a fresnel lens

I need at least 1/640

-----
Understand the need to have flash power greater than ambient. That is a great point and one I had not considered.

Rules....they are pretty lenient at the rinks. Sometimes at tournaments there will be a photog that has strobes set up around the rink for use during the game. Although having the light concentrated on a person is just a bit different than using strobes pointed in general directions---but either way there is a flash occurring. My plan was to experiment during a practice and ask the players if it bothered them.

[KingsHockeyFan]

Even if your Association allows Spectators (I assume you are a spectator) to use Flash - as you pointed out, Flash Modifiers that "Focus" the Flash might create Hot Spots - so its sensible to be aware that you might cop some stick from player's who might be momentarily blinded by the light.

(Mixed Metaphors and Puns intended)

I was going to play around with the Fresnel lens distance from the flash---an attempt to reduce hotspots by slightly reducing the focus of the flash light

[inkista]

Here's also an old Strobist blog entry about lighting basketball with speedlights. Might spark some ideas.
.

[Manfred M]

Here's also an old Strobist blog entry about lighting basketball with speedlights. Might spark some ideas.

And you can fit around four basketball courts into a hockey rink. The only plus for the rink is that the floor and boards are white and are somewhat decent reflectors..

200 ft is a long way to throw your light.

[William W]

Rules....they are pretty lenient at the rinks. Sometimes at tournaments there will be a photog that has strobes set up around the rink for use during the game. Although having the light concentrated on a person is just a bit different than using strobes pointed in general directions---but either way there is a flash occurring. My plan was to experiment during a practice and ask the players if it bothered them.

OK, I understand. I run you through a few points that should form a basis for your experiments.

*

Understand the need to have flash power greater than ambient. That is a great point and one I had not considered.

Good. That’s important for you to understand. You should see why it is so important in, a few minutes.

*

> Typical iso is 4000
> speedlite is a cheap knockoff (Allura) I just looked at it and do not think it is HSS capable
> sometimes shoot wide open, and when I do I reduce the iso to 3200.
> moved to shooting 3.5 at 4000 in order to have an increased focal range.
> farthest distance would be closer to 200ft
> No flash through the glass
> looking at the better beamer or a diy of the same design using a fresnel lens
> need at least 1/640

OK. Thank you.

Couple of minor points:
1. “speedlite is a cheap knockoff (Allura) – TYPO? “Altura Photo” ?
2. “moved to shooting 3.5 at 4000 in order to have an increased focal range.” – assume you mean increased DoF (Depth of Field)?

*

For the sake of this conversation we need to assume a “typical” exposure that you use for the AMBIENT LIGHT.

From the information you have provided we will assume that you are pulling the shot at:
F/2.8 @ 1/640s @ ISO3200.

***

Consideration of using the Flash that you have (Altura), without and with a “Beamer” on its head.

You do NOT have HSS available.

You need to FREEZE the SUBJECT MOTION by using the FLASH EXPOSURE. To do this you will need to have the FLASH as the KEY exposure. This means the FLASH Exposure MUST be greater than the AMBIENT Exposure. Remember this point.

Also (in simple terms) the faster the SPEED of the Subject Movement, then the greater the DIFFERENCE between the FLASH Exposure and the Ambient Exposure is required. Remember this point too.

Data attained from the User Manual (Altura_Photo_Flash-CANON_USER_GUIDE)
Guide Number for your Flash Unit: GN = 68 (Meters)ISO100 @ FL 105mm

This Guide Number is the key to this discussion and to discovering what might or might not be possible. The Guide Number is a GUIDE. (Note: also sometimes Manufactures will ‘embellish’). The Guide Number above is when the Flash Head is fully zoomed in to cover only the FoV of a 105mm lens on a (135 format) Camera. If you are using a Wide Angle Lens or a Normal Lens and the Flash Head is zoomed wide to cover that FoV, then the Guide Number will be a lower number.

At this point the light globe might have gone and the man in your head is saying “OK now I get how the beamer works, it is just adding more ‘zoom in’ to the Flash Head so therefore the GN will get bigger . . .” . . . yes that’s how it works – and that’s why you might get an “hot spot” – for example, if you Flash head is zoomed to cover the FoV of a 400mm lens’s and you only have a 200mm Lens mounted on your camera - what you want in this situation is for the hot spot to be in the centre of the frame and your player to be in that hot spot.

The Guide Number divided by the APERTURE used will give you the MAXIMUM FLASH WORKING DISTANCE. So: GN/A = MFWD.

Note the Guide Number (68Meters) is for ISO 100. As you increase the ISO the Guide Number gets bigger by a factor of √2 for each Stop of ISO, or more simply the Guide Number doubles for each 2 STOPS of ISO increase. If you are adept at mental arithmetic, √2 is about 1.4.

*

Now back to the two points I asked you to remember:
> Flash Exposure has to be KEY over Ambient Exposure
> Faster Subject Movement ≡ bigger difference between Flash Exposure and Ambient Exposure

You can experiment and find the correct answers - I’ll make experienced guesses to put you in the ballpark:

I reckon the Flash Exposure will need to be FOUR STOPS over the Ambient Exposure as your starting point for the Flash to Freeze the SUBJECT MOVEMENT of the speed of typical Ice Hockey Play.

With that as our starting point let’s look at your Ambient Exposure:
F/2.8 @ 1/640s @ ISO3200 ≡ F/2.8 @ 1/320s @ ISO1600 ≡ F/2.8 @ 1/250s @ ISO 1250

BUT – we need Flash Exposure to be FOUR STOPS over the Ambient Exposure.
Therefore we need to DROP (underexpose) Ambient by FOUR STOPS.
Hence: [F/2.8 @ 1/250s @ ISO 1250] – [4 Stops] ≡ F/11 @ 1/250s @ ISO 1250 ≡ F/10 @ 1/250s @ ISO 1600


So now let’s look at the Flash’s GN for ISO 1600:
100 > 200 > 400 > 800 > 1600
ISO 100 to ISO 1600 4 Stops, therefore we can multiply the GN (for ISO100) by 4
Hence: 68 x 4 = 272

So we can now work out how far you can shoot:
272/10 ≈ 27

*

Summary using Flash without Beamer:

> Without any “beamer” you can use you Flash “naked”, and you’ll have a MAXIMUM FLASH WORKING DISTANCE of about 27metres (about 90 ft) at ISO 1600.

> To do this you would pull the shot at: F/10 @ 1/250s @ ISO1600

> That cribs you one stop of ISO and less noise.

> In a nutshell you’re stuffed for any play beyond 90ft

> AND you HAVE TO WAIT FOR THE FLASH TO RECYCLE BEFORE YOU CAN SHOOT AGAIN (isn’t this last point gut wrenching! ?)

> We can extrapolate at ISO 3200 the GN would be about 380 (i.e. 272 x 1.4) And: 380/10 = 38, therefore without any “beamer” you can use you Flash “naked”, and you’ll have a MAXIMUM FLASH WORKING DISTANCE of about 38metres (about 125 ft) at ISO 3200, and to do this you would pull the shot at: F/10 @ 1/250s @ ISO3200

NOTES -

The above ballpark theory assumes the following:
> The Manufacture was not ‘embellishing’ the GN data
> The Flash is within Specification
> The Flash has recycled fully for each shot
> The guess that “4 Stops over ambient” is about correct (That guess might be wrong: if you need fewer than 4 Stops of Flash over Ambient then that's good, if you need more than 4 Stops of Flash over Ambient, then that's bad. Also note the amount of BLUR noticeable which is caused by Subject Movement is related to the SUBJECT DISTANCE and the DIRECTION OF MOTION in relation to the Lens's Axis and also the amount of Enlargement of the image and the Viewing Distance.

***

Using a Beamer:

A Flash Beamer will get you about another “1~2 Stops worth of flash power”. I like to think in GN. So that means a really REALLY good Beamer will give me 2 Stops and thus double the GN.

Let’s assume that it does give us 2 stops more "power" and we will b shooting at ISO1600 with your Altura Flash: F/10 @ 1/250s @ ISO1600, but now with an enhanced GN = 272 x 2 = 544.

So: 544/10 ≈ 54

So: WITH a really good “beamer” you’ll have a MAXIMUM FLASH WORKING DISTANCE of about 54metres (about 180 ft) at ISO 1600, and to do this you would pull the shot at: F/10 @ 1/250s @ ISO1600 . . .

Oh – but – remember:
You HAVE TO WAIT FOR THE FLASH TO RECYCLE BEFORE YOU CAN SHOOT AGAIN

***

High Speed Sync:

High Speed Sync is even more fun. What Manfred wrote – you’ll lose about 2 Stops worth of “flash power” (halve the GN) just by engaging HSS.

But HSS will really cause you grief apropos MFWD if you need you get the TV (Shutter Speed) much faster than HALF the X Flash Sync. Your X Flash Sync is 1/250s, so any Tv faster than about 1/800s will likely rip the guts out of your MFWD, depending upon the Speedlite that you use.

Oh – but – remember:
You HAVE TO WAIT FOR THE FLASH TO RECYCLE BEFORE YOU CAN SHOOT AGAIN

Also with HSS, even though most (all) have a cut-out switch to stop the Flash from frying, sometimes (not often but sometimes), it doesn't work: I had a colleague fry two 580's on the one shoot.

WW

N.B. I did quick mental arithmetic for all calcs and I haven't time to carefully proof read so - E. & O. E. if you find an error, please let me know, ta.

[KingsHockeyFan]

OK, I understand. I run you through a few points that should form a basis for your experiments.

*



Good. That’s important for you to understand. You should see why it is so important in, a few minutes.

*



OK. Thank you.

Couple of minor points:
1. “speedlite is a cheap knockoff (Allura) – TYPO? “Altura Photo” ?
2. “moved to shooting 3.5 at 4000 in order to have an increased focal range.” – assume you mean increased DoF (Depth of Field)?

*

For the sake of this conversation we need to assume a “typical” exposure that you use for the AMBIENT LIGHT.

From the information you have provided we will assume that you are pulling the shot at:
F/2.8 @ 1/640s @ ISO3200.

***

Consideration of using the Flash that you have (Altura), without and with a “Beamer” on its head.

You do NOT have HSS available.

You need to FREEZE the SUBJECT MOTION by using the FLASH EXPOSURE. To do this you will need to have the FLASH as the KEY exposure. This means the FLASH Exposure MUST be greater than the AMBIENT Exposure. Remember this point.

Also (in simple terms) the faster the SPEED of the Subject Movement, then the greater the DIFFERENCE between the FLASH Exposure and the Ambient Exposure is required. Remember this point too.

Data attained from the User Manual (Altura_Photo_Flash-CANON_USER_GUIDE)
Guide Number for your Flash Unit: GN = 68 (Meters)ISO100 @ FL 105mm

This Guide Number is the key to this discussion and to discovering what might or might not be possible. The Guide Number is a GUIDE. (Note: also sometimes Manufactures will ‘embellish’). The Guide Number above is when the Flash Head is fully zoomed in to cover only the FoV of a 105mm lens on a (135 format) Camera. If you are using a Wide Angle Lens or a Normal Lens and the Flash Head is zoomed wide to cover that FoV, then the Guide Number will be a lower number.

At this point the light globe might have gone and the man in your head is saying “OK now I get how the beamer works, it is just adding more ‘zoom in’ to the Flash Head so therefore the GN will get bigger . . .” . . . yes that’s how it works – and that’s why you might get an “hot spot” – for example, if you Flash head is zoomed to cover the FoV of a 400mm lens’s and you only have a 200mm Lens mounted on your camera - what you want in this situation is for the hot spot to be in the centre of the frame and your player to be in that hot spot.

The Guide Number divided by the APERTURE used will give you the MAXIMUM FLASH WORKING DISTANCE. So: GN/A = MFWD.

Note the Guide Number (68Meters) is for ISO 100. As you increase the ISO the Guide Number gets bigger by a factor of √2 for each Stop of ISO, or more simply the Guide Number doubles for each 2 STOPS of ISO increase. If you are adept at mental arithmetic, √2 is about 1.4.

*

Now back to the two points I asked you to remember:
> Flash Exposure has to be KEY over Ambient Exposure
> Faster Subject Movement ≡ bigger difference between Flash Exposure and Ambient Exposure

You can experiment and find the correct answers - I’ll make experienced guesses to put you in the ballpark:

I reckon the Flash Exposure will need to be FOUR STOPS over the Ambient Exposure as your starting point for the Flash to Freeze the SUBJECT MOVEMENT of the speed of typical Ice Hockey Play.

With that as our starting point let’s look at your Ambient Exposure:
F/2.8 @ 1/640s @ ISO3200 ≡ F/2.8 @ 1/320s @ ISO1600 ≡ F/2.8 @ 1/250s @ ISO 1250

BUT – we need Flash Exposure to be FOUR STOPS over the Ambient Exposure.
Therefore we need to DROP (underexpose) Ambient by FOUR STOPS.
Hence: [F/2.8 @ 1/250s @ ISO 1250] – [4 Stops] ≡ F/11 @ 1/250s @ ISO 1250 ≡ F/10 @ 1/250s @ ISO 1600


So now let’s look at the Flash’s GN for ISO 1600:
100 > 200 > 400 > 800 > 1600
ISO 100 to ISO 1600 4 Stops, therefore we can multiply the GN (for ISO100) by 4
Hence: 68 x 4 = 272

So we can now work out how far you can shoot:
272/10 ≈ 27

*

Summary using Flash without Beamer:

> Without any “beamer” you can use you Flash “naked”, and you’ll have a MAXIMUM FLASH WORKING DISTANCE of about 27metres (about 90 ft) at ISO 1600.

> To do this you would pull the shot at: F/10 @ 1/250s @ ISO1600

> That cribs you one stop of ISO and less noise.

> In a nutshell you’re stuffed for any play beyond 90ft

> AND you HAVE TO WAIT FOR THE FLASH TO RECYCLE BEFORE YOU CAN SHOOT AGAIN (isn’t this last point gut wrenching! ?)

> We can extrapolate at ISO 3200 the GN would be about 380 (i.e. 272 x 1.4) And: 380/10 = 38, therefore without any “beamer” you can use you Flash “naked”, and you’ll have a MAXIMUM FLASH WORKING DISTANCE of about 38metres (about 125 ft) at ISO 3200, and to do this you would pull the shot at: F/10 @ 1/250s @ ISO3200

NOTES -

The above ballpark theory assumes the following:
> The Manufacture was not ‘embellishing’ the GN data
> The Flash is within Specification
> The Flash has recycled fully for each shot
> The guess that “4 Stops over ambient” is about correct (That guess might be wrong: if you need fewer than 4 Stops of Flash over Ambient then that's good, if you need more than 4 Stops of Flash over Ambient, then that's bad. Also note the amount of BLUR noticeable which is caused by Subject Movement is related to the SUBJECT DISTANCE and the DIRECTION OF MOTION in relation to the Lens's Axis and also the amount of Enlargement of the image and the Viewing Distance.

***

Using a Beamer:

A Flash Beamer will get you about another “1~2 Stops worth of flash power”. I like to think in GN. So that means a really REALLY good Beamer will give me 2 Stops and thus double the GN.

Let’s assume that it does give us 2 stops more "power" and we will b shooting at ISO1600 with your Altura Flash: F/10 @ 1/250s @ ISO1600, but now with an enhanced GN = 272 x 2 = 544.

So: 544/10 ≈ 54

So: WITH a really good “beamer” you’ll have a MAXIMUM FLASH WORKING DISTANCE of about 54metres (about 180 ft) at ISO 1600, and to do this you would pull the shot at: F/10 @ 1/250s @ ISO1600 . . .

Oh – but – remember:
You HAVE TO WAIT FOR THE FLASH TO RECYCLE BEFORE YOU CAN SHOOT AGAIN

***

High Speed Sync:

High Speed Sync is even more fun. What Manfred wrote – you’ll lose about 2 Stops worth of “flash power” (halve the GN) just by engaging HSS.

But HSS will really cause you grief apropos MFWD if you need you get the TV (Shutter Speed) much faster than HALF the X Flash Sync. Your X Flash Sync is 1/250s, so any Tv faster than about 1/800s will likely rip the guts out of your MFWD, depending upon the Speedlite that you use.

Oh – but – remember:
You HAVE TO WAIT FOR THE FLASH TO RECYCLE BEFORE YOU CAN SHOOT AGAIN

Also with HSS, even though most (all) have a cut-out switch to stop the Flash from frying, sometimes (not often but sometimes), it doesn't work: I had a colleague fry two 580's on the one shoot.

WW

N.B. I did quick mental arithmetic for all calcs and I haven't time to carefully proof read so - E. & O. E. if you find an error, please let me know, ta.

That is more than I ever expected from asking my question. Thank you very much. I just drank a bottle of wine and really need to sober up and re-read / absorb /learn all the information you just sent my way. Please give me a moment to digest and respond.

-Kris

[William W]

^ Yes on some Topics I get going and I just can't stop, anyway take your time digesting as I've just arrived home from a VERY early start and MOST successful shoot and so I have rewarded myself with a Glass of Adelaide Hills Riesling: it is very possible I might have a second before beginning to prepare dinner . . .

[george013]

^ Yes on some Topics I get going and I just can't stop, anyway take your time digesting as I've just arrived home from a VERY early start and MOST successful shoot and so I have rewarded myself with a Glass of Adelaide Hills Riesling: it is very possible I might have a second before beginning to prepare dinner . . .

I remember an earlier discussion on flashes where a link to Niel van Niekerk was used. http://neilvn.com/tangents/high-speed-flash-sync/
I know you don't like this, but I linked to a diagram he used in that article. Just to be sure people are reading it.



What I see here is that if the gap between the 2 curtains is getting smaller, the used flashlight is getting less.
When shooting slower as the sync speed, the GN of the flash is independent of thew shutterspeed. Using HSS the GN is directly dependent on the shutterspeed.

George