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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 10 May 2018 (Thursday) 20:43
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determining strobe strength

 
Ltdave
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May 10, 2018 20:43 |  #1

im contemplating putting up strobes in my local hockey arena to enhance the quality of lighting we have. the quantity isnt bad but its very very flat and needs some punch...

what do i need in terms of numbers besides distance from strobe to subject (i.e. ice surface) to plug into my calculations?

im currently shooting ISO 3200 at 1/800th and f2.8. this works for most of my shots but can be as much as a stop underexposed depending on how the high pressure sodium lights are cycling and what their color temp is at the time the picture is made...

i DONT know the exact measurement of height but im going to go with 50' from catwalk to ice. i will find out though. right now, im just trying to see what i would need and what i could get away with...

most pro arenas have up to 6 strobes in each offensive end (or so ive been told)...




  
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Wilt
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Post edited 3 months ago by Wilt. (6 edits in all)
     
May 11, 2018 14:05 |  #2

Flash computation before the days of flashmeters needed Guide Number equation...

Guide Number = Distance * f/stop

For example if a flash unit had ISO 100 Guide Number 160, then with a 16' light-to-subject distance you set f/10 on the lens.

The Guide Number will double when the ISO goes up by a factor of 4x. So with the same flash, the ISO 1600 Guide Number becomes GN 320.

So what you need to know is the manufacturer's claim for Guide Number (usually at ISO 100).

Assuming that you were shooting with ISO 3200 and f/2.8 and assuming your lights were 50' from the subjects mid-body, your current flash's ISO 3200 Guide Number is 50 * 2.8, or GN140. Your current flash's ISO 1600 guide number is 140 / 1.414, or GN99. At ISO 100, Guide Number 50.
That's a rather low power flash...no wonder your shots are often underexposed!


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FJ ­ LOVE
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May 11, 2018 14:16 |  #3

A local photographer used to leave these mounted on the catwalk in the local arena, you might even find some older used ones cheap

https://www.paulcbuff.​com …lightning-flash-unit.html (external link)


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Ltdave
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May 11, 2018 17:27 |  #4

Wilt wrote in post #18623980 (external link)
Flash computation before the days of flashmeters needed Guide Number equation...

Guide Number = Distance * f/stop

For example if a flash unit had ISO 100 Guide Number 160, then with a 16' light-to-subject distance you set f/10 on the lens.

The Guide Number will double when the ISO goes up by a factor of 4x. So with the same flash, the ISO 1600 Guide Number becomes GN 320.

So what you need to know is the manufacturer's claim for Guide Number (usually at ISO 100).

Assuming that you were shooting with ISO 3200 and f/2.8 and assuming your lights were 50' from the subjects mid-body, your current flash's ISO 3200 Guide Number is 50 * 2.8, or GN140. Your current flash's ISO 1600 guide number is 140 / 1.414, or GN99. At ISO 100, Guide Number 50.
That's a rather low power flash...no wonder your shots are often underexposed!


im not shooting with flash now. this is ambient and not "often" as in more than not, but often as in more than id like...

MOST of the lower leagues (AHL or NHL and DOWN) only shoot with ambient rink lighting. my team is in the Federal HL and we are the lowest of all professional leagues. i think all of the teams are in municipal owned arenas and as far as i know, im the only professional (okay, SEMI-professional photographer) working for any of the teams.

if i could just get the city to pitch in for $100,000 for new lighting id not have to ask this question lol....




  
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Ltdave
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May 11, 2018 17:29 |  #5

FJ LOVE wrote in post #18623982 (external link)
A local photographer used to leave these mounted on the catwalk in the local arena, you might even find some older used ones cheap

https://www.paulcbuff.​com …lightning-flash-unit.html (external link)

yes, thats exactly what i would do, but they would need to be way cheaper than what these cost now...

i figure id need minimum of 4




  
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Wilt
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May 11, 2018 18:30 |  #6

Ltdave wrote in post #18624088 (external link)
if i could just get the city to pitch in for $100,000 for new lighting id not have to ask this question lol....

Naw...instead you'd be asking 'Which flash should I buy?' ! :p


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May 12, 2018 14:55 |  #7

For a lot of sports images, simply high powered, very quick duration strobes are the ones you should be seeking.. For a lot of the NBA arenas, they used multi-tube Dyna-Lites and Speedotrons. I used the Elinchrom 500 with the speed or action flashtubes when I shot roller derby With a lot of arenas... They are just very dark and have high ceilings which can eat a lot of light.

Whatever you choose, I would steer you to a sports reflector that is compatible with your strobes. Some of them can really increase the light levels since they are highly reflective. PCB used to have this retro laser reflector that works wonders for indoor sports like basketball or hockey since it is shiny and focusable, but it is discontinued. The Elinchrom fireball reflector works well too.

The settings I have for roller derby was 1/640 at F/9 at ISO 320. This allows me to get in focus shots with good foreground and background so the players around the main subject is also in focus. I had the strobes on 13 foot stands so it wasn't in the way of the fans and your hockey ice can reflect some of the light spill to light up under their chin, so you might be able to get away with less power.




  
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F2Bthere
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May 14, 2018 00:01 |  #8

Good points above. A couple notes to add:

Whatever you get needs to support HSS or the equivelent for your camera if you are using a shutter speed faster than your synch speed.

The Elinchrom Maxilite ("fireball") is a good reflector option. The Maxispot has the same design but a more reflective surface, so it is even more efficient.


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sincity
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May 14, 2018 14:32 as a reply to  @ F2Bthere's post |  #9

My input to the HSS reply from F2Bthere is for sports is that HSS isn't all that necessary.. Arenas are already dark by nature, so if you have a fast duration strobe. The fast duration will freeze the action even if the shutter speed isn't at the same speed. For example, Dyna-Lites aren't HSS at all, but their head is 1/3200 of a second at full power, so it can be used for arena lighting.

EDIT~~ There is a science of the Fast Duration flashes Versus the Long tail/HSS flashes.. Each have their pros and cons.. I am on the camp of the fast duration since it isn't dependent on the camera system or protocols of the flash firmware. With the HSS/Long burn, they are using a 'slice' of the decaying flash to match the speed of the shutter {up to 1/12,000 sec} , but it needs to know the timing in order to get all of the fading light at speed.




  
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Ltdave
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May 14, 2018 16:14 |  #10

another poster here shoots for the AHL Rockhogs (Chicago affiliate) and they strobed the rink last year...

hes getting action stopping shots at 1/200 ss with the strobes, so i thought i could probably do okay




  
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Ltdave
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May 18, 2018 20:48 |  #11

so playing around with some numbers i have this:

the JTL 160s (they were being discussed in another thread i was following) have a guide number of 120.

the distance from the catwalk where i would be mounting to the middle of the ice is NO MORE THAN 85'. in fact probably a little bit less. my thoughts were a strobe on each side of the rink so the light would not have to try and reach all the way across.

at ISO 3200 (where i normally shoot) at f4 (where i sometimes shoot depending on lens) i would have sufficient light out to 170' (169.7 actually). does this sound right to anyone? this makes it look (in my mind) that i could cut my ISO to 1600 and still have enough illumination. while i currently am not lacking in QUANTITY of light, the QUALITY is lacking. my goal would be to have better quality light vs the old high pressure sodium stuff they currently have...




  
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sincity
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May 20, 2018 04:59 as a reply to  @ Ltdave's post |  #12

I don't know anyone who has the JTL strobes, so one can ask.. How is it??? I am thinking the JTL strobes do not have enough power to overcome the HPS in the arena to take advantage of the strobe flash duration in order to freeze the action. Since the ISO of 1600 SS~1/800 at F/2.8 doesn't inspire confidence in me compared to the natural light settings.. In the previous post, I stated I shoot at ISO 200 F/9 and got shots

The only thing I can say is to try it out and report back to us..




  
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gonzogolf
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May 20, 2018 05:36 |  #13

You should be looking at watt seconds not guide numbers. Guide numbers are how you measure hotshoe flash units, because the lens of the flash and the distance are a factor. If a "studio strobe" is selling itself using a GN be wary. You should be able to find used Alien bee 400s which would work well for your purpose, plus they are pretty durable for field work.




  
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Ltdave
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May 20, 2018 13:08 |  #14

gonzogolf wrote in post #18628851 (external link)
You should be looking at watt seconds not guide numbers. Guide numbers are how you measure hotshoe flash units, because the lens of the flash and the distance are a factor. If a "studio strobe" is selling itself using a GN be wary. You should be able to find used Alien bee 400s which would work well for your purpose, plus they are pretty durable for field work.

the JTL 160s i was looking at (as discussed in another thread) have in the specs, GN 120' and 180WS...

maybe not enough, but i didnt think GN was restricted so to speak, to only speedlites...




  
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F2Bthere
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May 20, 2018 19:22 |  #15

Ltdave wrote in post #18629078 (external link)
the JTL 160s i was looking at (as discussed in another thread) have in the specs, GN 120' and 180WS...

maybe not enough, but i didnt think GN was restricted so to speak, to only speedlites...

It isn't "restricted." But, as in the case you mention, only a low-powered unit is likely to give a guide number. And 180 WS is quite low for a strobe unit.

Guide Number has to be calculated using a specific reflector. If you use a sports reflector (a long throw reflector) on a strobe unit, you will get much better output with a narrower beam.

The Elinchrom Maxi Spot, for example, has a 29 degree spread, about the same as the angle of view on an 85mm lens on full frame. Knowing this information for your reflector can help you visualize when you place your strobe.


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determining strobe strength
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