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Then have a look at Dustin Diaz's article on 'How To Pwn The Inverse Square Law'. 
Good read for many flash users, could perhaps be seen as a bit basic for some but very well explained.
What is 'pwn' ?
As i said it is a good explanation, but really just double the distance/quarter the power, or half the distance/quaduple the power.
is all you need to know.
One point though, this works for any type of electromagnetic radiation from a point source in free space, any electromagnetic wave, of which light is just a fraction. (sound, UV IR, X-rays and Gamma rays) will conform too.
The bit about free space is important as you will get varying results in enclosed spaces due to reflection or absorbtion, and the inverse square law ceases to work.

LOL, just read the Wiki on pwn, I assumed that it was just a typo, so you can learn something new everyday.

Thank you for the link Tomas, Will read it later with a glass of JD and coke.![]()

It isn't so much basic - nothing wrong with that - as simplistic, because although it does mention that the ISL applies to point sources of energy it doesn't define a point source, so people might assume that flashguns are studio lights are point sources when in fact they aren't.
Looks like something from a Greek scripture to me!This wouldn't be another biased and disproportionate dig at hot shoe flashes would it Garry? :nono:
No - and I don't think I'm biased against hotshoe flashes anyway - I'm very happy with my SB-800s, use them whenever a hotshoe flash helps.This wouldn't be another biased and disproportionate dig at hot shoe flashes would it Garry? :nono:
No - and I don't think I'm biased against hotshoe flashes anyway - I'm very happy with my SB-800s, use them whenever a hotshoe flash helps.
I just recognize the need for the right horse for the right course, and prefer to use studio flash when studio flash does the job better - i.e. in the studio, where it's better IMO to use flashes that allow the use of effective light shaping tools.
I mentioned hotshoe flashes only because they're small, and the nearest thing you can get to a point source of energy.
Man flash makes my head hurt! :shake:
It's just light mate, shaping it and applying it to enhance or accent a scene in a way that assists your creative vision and imagination.
I think this is initially where many folk (including myself) seem to get a little distracted, or confused.
It's simply light all in all, whether it's a 60 watt second hot shoe flash, a 1600 watt second profoto flash head or a gazillion watt motion picture fresnel or flood.
It's all light and the fundamental principles remain the same.
Won't let it beat me though. I will get there. I will get there. I will get there......
forgive my ignorance but it's almost as if you were implying that the inverse square law doesn't apply to hot shoe flashes or anything else 'small' :shrug:

photography is mathematical ?
i screwed then![]()
I use flash for about 70 per cent of my magazine work and even though i've been doing it for years, i still have moments when I get brain fade and everything I know (or think I know) dissapears and I'm left feeling like a noob again....Getting the damn flash to actually look natural though is melting my brain and keeping Duracell in business! Full power, half power, ETTL, manual, exposure comp., remote trigger, yadda yadda yadda.....
One point though, this works for any type of electromagnetic radiation from a point source in free space, any electromagnetic wave, of which light is just a fraction. (sound, UV IR, X-rays and Gamma rays) will conform too.
*snip*
Simmotino, don't fret *snip*

I'm with Garry & I love my speedlights too - so no bias there
You only have to use a flashmetre with any form of flash to soon realise the ISL is pants in the real world when discussing lighting (other than the top of Everest of course)
DD
Here's a slight unrelated blog post that has some real world useful information.
http://jrfarrar.blogspot.com/2009/06/mixing-flash-with-ambient-part-3.html
I doubt whether anyone will be interested![]()
.....but let me explain WHY I get a bit wound up about these 'tutorials' that pump out misleading info about the Inverse Square Law, or at least info that's misleading in the real world...

Todays' generation of digital photographers don't know they're born![]()
Todays' generation of digital photographer...
...... don't know they're born![]()
Fantastic response .... Mr Whitehouse
and so far the sb900 in iTTL is giving me that. Once that fun element has gone then its for the real work to use and understand in manual.Of course it has its uses. All I'm saying is that people need to actually read and understand it, not just quote it as an immutable law of physics. All I've tried to do is to point out that the ISL is a law of physics that applies to point sources of light in free space, and we hardly every use lighting in free space and never use point sources of light, therefore the ISL is just a guide that explains WHY the intensity of light diminishes over distance.Because of the tests that you have done Garry 'back in the day', you find that the inverse square law is non applicable to lighting?
Furthermore, any photographer that suggests it has it's uses, is incorrect or misleading?
As usual when you quote me, you seem to misunderstand what I'm actually saying.Quote:
Originally Posted by Garry Edwards View Post
Todays' generation of digital photographer...
Whether your picking up a camera for the first time in the digital age or if you have 'earned your stripes' back in the good old days of film, a fair few elements still separate the greats from the not so great, and the following but, albeit rough equation is unarguable.
No matter how aggressive or how rapidly technology advances in the world of the arts, you cannot subtract the human element.
Anyone who spews this 'Technology Has Made It Too Easy' manure around the place is in dire need of highly critical self analysis.
It merely quickens the pace and increases accessibility. Nothing more.
As usual when you quote me, you seem to misunderstand what I'm actually saying.
What I'm saying is that 'back in the day' we had to carry out detailed, time consuming and expensive tests to find out whether the textbooks were right. Digital photography makes this testing process much easier but the downside of it is that a lot of people don't seem to see a need to put theories to the test, they just experiment to see what works and use a trial and error approach rather than a testing approach. That can't be a good thing because knowledge gained from testing is real knowlege and it sticks.
Todays' generation of digital photographers don't know they're born![]()
Having it easy isn't a bad thing, it's good. It makes photography more accessible and it makes it easier to learn quickly and cheaply. But new technology doesn't replace the need to learn
Of course the ISL law has its uses.
I reckon you're being a touch over sensetive here Tomas. Garry has put plenty of smillies in his posts indicating a touch of sarcasm or humour needs to be applied when reading it. You seem to have taken everything too literally and personally.
Your attitude towards Garry's opions on ISL are no better than what you claim he is saying about the source you referenced. He's got an opinion based on his own tests rather than readings someone elses work and you're not even slightly accommodating because it conflicts with your source.
As for his remark about digital photography being easy, it is. Good digital photography isn't.
I believe that to be a good digitial photographer is easier and quicker than it would have been when film was the only option. Now that isn't to say that it doesn't require hard work and skill but you can't deny the advantages to learning of instant feedback and virtually zero cost (excluding hardware and software, I'm talking materials here).
You get the hump with anyone who has shot film pointing out the difficulties involved with it as a learning process but as someone who confesses to having never used a film camera you'll find it hard to fully understand why they're saying it.
PM me your address in Finland if you want, I'll send you the Lubitel when Joxby has finished with it, loaded with a roll of slide film and you can have a go at film photography for yourself to see the other side of the fence.

![]()
Fantastic response .... Mr Whitehouse
![]()