flash speed??

[William W]

George,

I don't see that, but I am OK if you do.

And I don't recall ever stating that I don't like you (or anyone) linking to Niel's website.

For the record I have worked with Niel on Judging Panels and I hold him and his knowledge in high esteem.

WW

[george013]

George,

I don't see that, but I am OK if you do.

And I don't recall ever stating that I don't like you (or anyone) linking to Niel's website.

For the record I have worked with Niel on Judging Panels and I hold him and his knowledge in high esteem.

WW

With linking I meant showing content of his site directly in this forum. Like this diagram. I doubt he made it, he's using it too.
Anyway I added this diagram so the part of HSS will be easier to understand to others.

George

[Dave Humphries]

Very educational thread, thanks to contributors, especially Bill.

A thought crossed my mind; if beaming long distances and using tight angles of view, surely it won't take much slack in the flash mounting/aiming for the desired 'hot spot' to move outside the lens' field of view?

Particularly if it is a DIY ensemble and you shoot some landscape orientation and others portrait, meaning the weight distribution is being changed often.

[William W]

Hi Dave,

Your thought is my experience, the beam's aim can get more inaccurate, over greater distances. I sort of alluded to that in Post #17 but I didn't spell it out really clearly - glad you did (my bold now for emphasis):

"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."

BUT - more importantly, what I have found is that the Flash Units Guide Numbers and the 'Beamers' Claims are mostly always 'embellished'. That's why I was encouraging Kris to make his own experiments and firstly with his flash "naked" as that will establish two things:

> more accurate indicative of the GN of his flash

> more accurate indicative of the number of Stops overlay of Flash over Ambient exposure tom arrest the Subject Motion

Kris should also notice how the Direction of Motion is related to the Number of Stop of Overlay that is required.

WW

[William W]

With linking I meant showing content of his site directly in this forum. Like this diagram. I doubt he made it, he's using it too.

(Aside) Thanks for explaining what you meant George.

For clarity what I have pointed out a couple of times on previous threads is that I am uncomfortable with the general situation concerning copyright infringement, especially concerning images.

My views on this subject are pretty much summed up in Post #4 of this thread, extract below:

"Copyright infringement is rampant: it is as simple as that. I think that in the main, most people are not aware they do it, or if they are aware they think that it doesn't really matter all that much.

WW

[William W]

Some more points which I consider very important.

Concerning the difference between HSS and 'normal' -

I think it is important to understand the simple concept that, in HSS Mode the Flash is PULSATING quickly. It is sort of like "continuous light" but not exactly the same as continuous light. An important point is, this is different to how the Flash works in its 'normal' condition, i.e. in 'normal mode' the Flash exhibits one, relatively very short explosion of light. The Guide Number for the Flash is based on this one relatively short explosion of light and this is how the GN has always been calculated even for the simplest of the manual Flash Units.

From this basic computation of the GN, a few slightly more sophisticated computations can be made to adjust the Guide Number to suit the placement of the Flash's Zoom Head - this is where we get in the Flash User Manuals, a table of GN's for different Focal Lengths. These Focal Lengths are referring to the position of the Flash's Zoom Head (the 'beamer' bit inside the flash).

Hopefully it is an easy concept to understand that, if the one 'bucket of light' is to be spread across the FoV of a 35mm lens then that bucket full of light light 'won't go as far' as if it is 'beamed' narrower for the FoV of a 105mm lens.

However, when the Flash is into HSS Mode, there are many things that happen electronically.

The complexity of HSS renders the simplicity of a Guide Number MUCH less meaningful and MUCH less useful.

*

Advice:

It is best to NOT use any reference to Guide Number when using HSS.

I advise to NOT rely upon any details of the Guide Number for computations or as any exposure guide when using the Flash in HSS Mode.

WW

[george013]

Some more points which I consider very important.

Concerning the difference between HSS and 'normal' -

I think it is important to understand the simple concept that, in HSS Mode the Flash is PULSATING quickly. It is sort of like "continuous light" but not exactly the same as continuous light. An important point is, this is different to how the Flash works in its 'normal' condition, i.e. in 'normal mode' the Flash exhibits one, relatively very short explosion of light. The Guide Number for the Flash is based on this one relatively short explosion of light and this is how the GN has always been calculated even for the simplest of the manual Flash Units.

From this basic computation of the GN, a few slightly more sophisticated computations can be made to adjust the Guide Number to suit the placement of the Flash's Zoom Head - this is where we get in the Flash User Manuals, a table of GN's for different Focal Lengths. These Focal Lengths are referring to the position of the Flash's Zoom Head (the 'beamer' bit inside the flash).

Hopefully it is an easy concept to understand that, if the one 'bucket of light' is to be spread across the FoV of a 35mm lens then that bucket full of light light 'won't go as far' as if it is 'beamed' narrower for the FoV of a 105mm lens.

However, when the Flash is into HSS Mode, there are many things that happen electronically.

The complexity of HSS renders the simplicity of a Guide Number MUCH less meaningful and MUCH less useful.

*

Advice:

It is best to NOT use any reference to Guide Number when using HSS.

I advise to NOT rely upon any details of the Guide Number for computations or as any exposure guide when using the Flash in HSS Mode.

WW

I would like to add another practical difference with normal flash: you can't freeze motion.

George

[William W]

George, good point.

I concur.

When the Flash is in 'normal' mode, then with a single Flash Pulse it is easy to freeze Subject Motion. Not all Subject Motion can be arrested, though.

When flash is in HSS Mode it is the Camera's Shutter Speed which determines whether the Subject Motion will be arrested, or not.

WW

[Manfred M]

When the Flash is in 'normal' mode, then with a single Flash Pulse it is easy to freeze Subject Motion. Not all Subject Motion can be arrested, though.

Exactly. Ambient light can still sneak in and cause problems. This can be used creatively by shooting rear curtain / second curtain to show a bit of motion, yet freeze the subject with the flash.

[William W]

Relating this specifically to the OP and Ice Hockey:

When the Flash is in 'normal' mode, then with a single Flash Pulse it is easy to freeze Subject Motion. Not all Subject Motion can be arrested, though.

Exactly. Ambient light can still sneak in and cause problems. This can be used creatively by shooting rear curtain / second curtain to show a bit of motion, yet freeze the subject with the flash.

AVOIDING that tedious and problematic ambient light that "can still sneak in and cause problems" is the reason for the using the technique of overlaying the Flash Exposure on the Ambient Exposure by several stops (i.e UNDEREXPOSING the Ambient Exposure). This was described in Post #17.

*

If using Flash (for example for Ice Hockey) the point Manfred raised regarding using Second Curtain/Rear Curtain Sync, could be applied IN ADDITION TO underexposing the Ambient Light relative to the Flash Exposure.

I think that employing BOTH these techniques could mean that the underexposure of the Ambient might be a bit less than otherwise required if one were using First Curtain Sync. In which case the GN would be a bigger number and thus the MFWD would be farther and that would be good.

Although all the theory I've detailed thus far in this thread I have tested in the field; the extrapolation above (of using 2nd Curtain Sync to allow more threshold of Ambient Exposure in the scene) is something I have not attempted. I did think it through several times and I can't find a flaw in the idea.

***

Having stated much about Flash in this thread and I do encourage Kris to experiment: my expectation is that to shoot Ice Hockey effectively one really needs: a fast lens; good high quality, high ISO camera with a useful frame rate; and for the rink to be lit to Telecast Standards.

For a local Ice Rink (much like a local Gym or local indoor swimming pool which I sometimes encounter) the killer is the existing lighting rig, in situ. These Lighting Rigs are usually poor quality (apropos Colour Temperature/mixed lighting) and also low level (i.e. low EV).

One fix for a low light situation is make your own Bank of radio triggered Slave Flash Units. These are usually set high and arranged for "flood coverage". For example at a small gym the size of a BBall Court, we'd set 6 Flash Heads, one in each corner and one each at the halfway line looking downwars each set to a w/a position.

Without the availability of MULTIPLE Flash Heads or the permission to use Flash anyway, the only option is to suck it up and use the fastest Aperture the lens will allow; then set the slowest allowable Shutter Speed to arrest Subject Motion and then those two parameters determine the ISO that is required.

This is why it is very important to know the Limits of the Shutter Speeds required for the particular Sport one wants to Photograph.

A good de-noise Post Production Program is a benefit and also NEVER underexpose, is a good rule to follow.

***

Even seeming being prepared (as described above), one has to be ready to address unforeseen problems.

This story of how USELESS a 70 to 200/2.8 lens can be, just might be of interest.

I was happily shooting this swimming meet at around F/4.5 @ 1/1250s @ ISO1600. A circuit breaker tripped the floodlights. I needed a shot of the Swimmer in Lane 6 at a Backstroke Start.

I grabbed my 85 F/1.8. I crept as close as I could on the Pool Deck, almost situated laying under the ‘15metre Line Judge’.

I pulled this (terribly underexposed) shot: F/1.8 @ 1/800s @ ISO3200 (Note ISO 3200 was the max. on my DSLR’s in 2004/5 and 1/800s is close to the absolute limit to capture a Backstroke Start effectively for a National Level Swimmer)

Considering the lighting was so low level, that I had to UNDEREXPOSE a shot using F/1.8 to even make the safe Shutter Speed limit of 1/800s at the Max ISO 3200 - my 70 to 200 F/2.8L (great 'sports lens' though it usually is) was totally useless in this situation:


EF 85 F/1.8 Lens - F/1.8 @ 1/800s @ ISO3200

*

As luck would have it, she qualified into the final and I made a better shot of her under the full lighting:


EF 70 to 200 F/2.8L Lens - F/4.5 @ 1/1250s @ ISO1600

WW

All Images © AJ Group Pty Ltd Aust 1996~2015, WMW 1965~1996

[Rob Ekins]

Great thread, thanks to all involved..