Flash & long lens

Ady N

Ady N

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Will an SB600 with a Sigma 100-300 lens have any impact on a subject around 50 feet away?

Or not?

Or would the more powerfull 800 or 900 do the trick?

Remote won't do the job in this instance so it's either high ISO in low light or a stab with the flash........
 
Am I being too optimistic then?

Subject would be dog sixe.
 
Looks promising, thanks. SB600 fit on backorder!!
 
Guide number of SB600 is 42 (in meters at ISO 200)

So if it were dark then at 20 metres at full power it would give you f2 ish. ISO 800 and you'd have something close to f5.6.

You can increase the "power" a little by zooming the head (Nikon quote GN at 35mm - at 85mm setting it throws the light a little more) and of course if you only want fill you may find that you need less power. And 50 feet is less than 20 metres.

Bottom line: yes.

BTW it's slightly disingenuous (aka "a big fat lie") for Kirk to say their extender increases your flash output by 3 stops. It MAY have that effect but that statement ain't true. It's a variation on the zoom head built into the flash.
 
JonathanRyan said:
Guide number of SB600 is 42 (in meters at ISO 200)

So if it were dark then at 20 metres at full power it would give you f2 ish. ISO 800 and you'd have something close to f5.6.
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Can you explain why it's close to f5.6 and not f4. I thought doubling the sensitivity twice (200->400->800) would give 2 stops extra - I can't see how you'd get the 3 stops from f2-f5.6 :thinking:
 
arad85 said:
Can you explain why it's close to f5.6 and not f4. I thought doubling the sensitivity twice (200->400->800) would give 2 stops extra - I can't see how you'd get the 3 stops from f2-f5.6 :thinking:
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Cos it's a bit more than f2. ;) It's something like f/1.8.5 and so you'll end up at f4.5 which given all the errors in there will be pretty close to 5.6.
 
arad85 said:
Can you explain why it's close to f5.6 and not f4. I thought doubling the sensitivity twice (200->400->800) would give 2 stops extra - I can't see how you'd get the 3 stops from f2-f5.6 :thinking:
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Bit of guestimating. Taking those numbers, it is actually f/2.1 plus two stops, which is f/4.2, but then 50ft is only 15.4m and a lot less than 20m, so f/5.6 sounds about right.

I think it's also a bit unfair to say that Kirk is telling porkies, because the X-tender does in fact increase the brightness of the light. While the total flash output is obviously not increased, by concentrating the beam it is indeed brighter, but over a smaller area.

Changing the ISO or f/number is another way of increasing range and that is a bit of a cheat. The effect on the exposure can be the same though, but the drawback is that it doesn't alter the brightness of the flash in relation to the ambient light, if that's important.

I have a Kirk X-tender and it works as advertised - a good two stops extra, which is an effective doubling of range. Popular for birding on dull days as a bit of fill-in :thumbs: If it's the only light source, it can be harsh though, and prone to red-eye, so getting it up on a bracket helps a bit with that. There are a few reviews on the web.
 
JonathanRyan said:
Cos it's a bit more than f2. ;) It's something like f/1.8.5 and so you'll end up at f4.5 which given all the errors in there will be pretty close to 5.6.
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Sorry, still not getting it... 42/20 = f2.1, going from ISO200->ISO800 is 2 stops which means x 2 = 2.1 x 2 = 4.2... Surely that's a bit closer to f4 rather than f5.6 or are you saying you add another stop as a rule of thumb to ensure you don't oversaturate?
 
HoppyUK said:
Bit of guestimating. Taking those numbers, it is actually f/2.1 plus two stops, which is f/4.2,
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Well kind of. But f2 isn't a real stop. 1.8 is. f4.2 can mean different things but often it means "2/10 of the way between f4 and f5.6" where f2.1 would actually mean something like "1/3 of the way between f1.8 and f2.8". Double f2.1 would therefore be f4.6 or f4.7 ;)

I guess Kirk aren't really lying - but saying it's 3 stops over the 55mm position is almost as misleading as it would be to say it's 3 stops over half power. According to their numbers it would double the maximum range of a flashgun. But many people reading their copy would assume it was more.
 
Thanks Richard/Jonathan... As long as it's a guesstimate and a bit of rounding here or there, I can understand that :)
 
JonathanRyan said:
Well kind of. But f2 isn't a real stop. 1.8 is. f4.2 can mean different things but often it means "2/10 of the way between f4 and f5.6" where f2.1 would actually mean something like "1/3 of the way between f1.8 and f2.8". Double f2.1 would therefore be f4.6 or f4.7 ;)

I guess Kirk aren't really lying - but saying it's 3 stops over the 55mm position is almost as misleading as it would be to say it's 3 stops over half power. According to their numbers it would double the maximum range of a flashgun. But many people reading their copy would assume it was more.
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You've lost me JR :thinking: F/2 is a full stop position, f/1.8 isn't. And one stop higher than f/2.1 is f/2.97, and two stops is exactly f/4.2, no more and no less.

But no matter, whatever you're starting with, the X-tender gives a minimum of two stops more light and that's exactly double the range (inverse square law). A smij more if you're lucky, depending on the flash/zoom setting etc.
 
HoppyUK said:
You've lost me JR :thinking: F/2 is a full stop position, f/1.8 isn't. And one stop higher than f/2.1 is f/2.97, and two stops is exactly f/4.2, no more and no less.
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Oh right. I should probably stick to taking pictures.

Any truth in the rumour you ca make your own flash extender out of an old people's page magnifier and 2 elastic bands?
 
Well, all those "flash extenders" are freznel (sp?) lenses, but as we all know, not all lenses are about the same thing :)
 
Why bother, all makers guide numbers are wildly optimistic. I think they have a room with mirrored walls.
 
You could try the Better Beamer - its a freznel lens thingy used by birders, only usable at 300mm or greater but claims to add 2.6 stops and has a version for the SB600.

Its about US$48
 
HoppyUK said:
I have a Kirk X-tender and it works as advertised - a good two stops extra, which is an effective doubling of range. Popular for birding on dull days as a bit of fill-in :thumbs: If it's the only light source, it can be harsh though, and prone to red-eye, so getting it up on a bracket helps a bit with that. There are a few reviews on the web.
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Sounds just the thing - dim conditions not dark so a good dose of fill should do the trick for me.

My intended settings will be TTL, 1/320th with auto ISO on an f/4 100-300 lens. Do I need to do anything specific other than the settings outlined?
 
Ady N said:
Sounds just the thing - dim conditions not dark so a good dose of fill should do the trick for me.

My intended settings will be TTL, 1/320th with auto ISO on an f/4 100-300 lens. Do I need to do anything specific other than the settings outlined?
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It's easy enough to use, just like zooming the flash head out (a lot) further. Just clip it on and the camera works as normal - doesn't know the X-tender is there.

1/320sec sounds like you'll be in FP sync territory, which will instantly lose you about three stops of flash power - you'll never make 50ft. Knock it back to 1/250sec max and all will be well.

It's Fresnel BTW, after a French bloke. And the 's' is silent :p :D
 
Thanks for all your help. The proof of the pudding and all that will come out when the item comes off back order and it arrives although the shooting season could well be over by then!
May try the flash without the fitment on Saturday if dogs within 30' or so although may be snowed in given the weather reports...............but then again given the location this Saturday I would not mind being snowed in for the weekend!
 
HoppyUK said:
1/320sec sounds like you'll be in FP sync territory, which will instantly lose you about three stops of flash power
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Yeah what he said (though I'm not sure it's 3 stops right away - it tails off rapidly).

Keep at 1/250 for longer throw.
 
JonathanRyan said:
Yeah what he said (though I'm not sure it's 3 stops right away - it tails off rapidly).

Keep at 1/250 for longer throw.
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It's worse than that. Just tried it.

Fire the 580EX flash at normal full power, I get correct exposure at 1/200sec at f/16. Switch on HSS, I need to drop the f/number to f/5 with the same shutter speed to match the exposure. 3.3 stops. (HSS disengages at 1/160sec on a 5D2.)

And for every stop of shutter speed above max x-sync, you lose an extra stop of flash with HSS, so at 1/1000sec for example you're getting on for six stops down on regular flash at 1/200sec, eight stops at 1/4000sec :eek:

HSS is great for fill-in and close range shooting, works brilliantly especially with E-TTL - couples and small groups etc - but quickly runs out of puff at greater range, or if you the push the shutter speed too high.

Edit: to be fair, I think there is a step-change with some Canon guns (580EXII?) at around 1/1000sec, where it reconfigures the HSS pulse to make it (a bit) less inefficient, so might not be quite that bad.
 
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