The Inverse Square Law (part 2) - in plain English

Having had a few days to mull over the concepts I introduced in the last post, now - I want to explain the practical application of this principle.  In place of the first beer bottle, lets use a model and instead of the second bottle, we'll use the wall of my imaginary studio as a backdrop...


The back wall of my studio is 6 metres behind the model, and the model is 1 metre from the softbox.  If you note the exposure for the model, and then do the same for the back wall, you should find that there is a little bit over 5 stops difference between them.  So if you take the picture exposed for the model, the back wall will only be receiving about 1/36th of the light, and will look pretty dark.

Now- leave the light where it is (and the back wall - obviously... I don't want the roof to collapse), but move the model back, so that he/she is just 1 metre from the wall - and therefore 6 metres from the softbox.  NOTE - our distance multiple unit is now 6 metres, and therefore the wall is now only 1/6th of a unit behind the subject.  In our examples above, we lost 2 stops of light in the first movement of 1 distance unit, so we should lose considerably less than that in just 1/6th of a unit - maybe even less than half a stop.  This means that if you expose the picture perfectly for the model, the back wall will only be half a stop darker, rather than the 5 stops we saw before - hardly even noticeable.

Now a final experiment - bring the softbox back up close to the model again - to 1 metre.  You now have 1 metre from the light to the model and 1 metre from the model to the back wall.  So bringing the light that much closer - surely, it will make the wall brighter, won't it?  Let's see - adjust your exposure for the model and, uh-oh... the wall just got darker again!  Why?  Remember in our first experiment, we lost 2 stops of light when we moved the subject back 1 distance unit, and this should be exactly what we see here - the model will be perfectly exposed, and the wall will be 2 stops darker, as the wall is 1 distance unit behind the model.

And here are a few test shots I did, just to prove the theory...

So, the upshot of all this is 3 simple rules...

• If you want your subject against a really dark background, have the light source close to the subject, and the subject far from the background.  
• Alternatively, if you want the subject and background with similar exposure, then have them relatively close together, and the light source some distance away (maybe 5 to 10 times the distance between the subject and background).  
• Finally, if you want the background just a little darker than the subject, then have the background a similar distance behind the subject as the light source is in front.  

Sounds simple when you say it like that - so simple in fact, maybe I'll start the post off with these rules.

Happy snappin'
Grum

PS - That's it, you can leave my studio and go back home now... dream's over, go on, go home!

The Inverse Square Law (part 1) - in plain English

When it comes to flash photography, or studio lighting, you won't get very far before someone mentions the dreaded 'Inverse Square Law', and then starts quoting lighting ratios and f-stops of dropoff, and all sorts of frightening sounding stuff.  I must admit, I was full of trepidation when I first tried to understand it, and I was left with only a feeling of vague understanding, and lacking that 'eureka' feeling that I had completely grasped the concept.

It is a hard subject to describe without getting bogged down with all the technical details, but the concept itself is actually very easy to understand.  Once you get the concept clear in your mind, then attacking the technical side becomes a whole lot less scary.  So - that's what this post sets out to do - explain what it means in a practical sense, explain the concept, and finally explain (in simple terms) the technical bit with real examples.  I'll split it into two parts, so as not to fry your brain...

I'll start by stating the basic rules of application, and then explain why these work the way they do.

• If you want your subject against a really dark background, have the light source close to the subject, and the subject far from the background.  
• Alternatively, if you want the subject and background with similar exposure, then have them relatively close together, and the light source some distance away (maybe 5 to 10 times the distance between the subject and background).  
• Finally, if you want the background just a little darker than the subject, then have the background a similar distance behind the subject as the light source is in front.

The rules above won't mean much to you until you either try them out and see them working, or read on to get an appreciation of how these results come about.

In order to help visualise this, try an experiment.  Get a light source of some kind - anything will do, a desk lamp, a torch, anything.  Now, in a darkened room, set your light source up next to a light coloured wall, pointing along the wall.  Step back and observe the brightness of the light falling on the wall at various distances from the light itself.  Close to the light, it will be very bright, but it will quite rapidly get less bright, and then less bright again, and again... Obviously, in real life, this is a gradient rather than 'steps', but to help understand the concept, let's break up this gradient up into four imaginary brightness areas - "really bright", "quite bright still", "getting darker", and "pretty dim".

OK - here is the important bit.  Let's measure the distance from the light that falls into the category of "really bright", and for argument's sake, say it is 30cm.  Now measure the distance from there to the end of the "quite bright still" area, and this might be 1 metre.  The length of the "getting darker" area might be 3.5 metres, and the "pretty dim" area might extend for another 8 metres.


Now - I just made these numbers up to illustrate a point - and that is that the rate at which the light fades is not constant.  It drops off very quickly at the start, and then less and less quickly.  The key thing to understand here is that if your subject is quite close to the source of light, somewhere in the "really bright" area, and you move it away from the light by 30cm, it will have a radical affect on the exposure, as the level of light is changing very quickly at this distance, and the subject will now only be in the "quite bright" area.  However, if your subject is 5 metres from the light, and you move it back by 30cm, it will have much less impact on the exposure, because the light level is changing much slower at this distance, and the subject will have been in the "pretty dim" area the whole time.

Let me just state that again - in fewer words this time, without the explanation.  A small change in the light to subject distance when close to the light source, will require a big difference in exposure.  The same change in distance when further away from the light source, will require only a small difference in exposure (if at all!)  Savvy?

Now that (I hope) you have begun to grasp the concept, let's give you some real figures so you can appreciate what it means to your camera settings, and start to understand the real life scenario.  But first of all, close your eyes, and drift into dream mode, and come on over to my studio, where I have a nice strobe in a big soft box set up for you, with Cactus V5 radio triggers, and you'll have a great camera in your hands (of course, that would be a Nikon D3000, wouldn't it?) Pssst - now, open your eyes again so you can carry on reading!!

So here in my studio, sitting 1 metre in front of the softbox, is your subject.  It could be a beautiful girl, a handsome guy, or a bottle of beer someone brought to Australia for you from England (hic!) - yes, let's go with that one.  You set up your camera to expose the bottle perfectly, and take the shot.

NB - From now on, all the distances we talk about will be in multiples of the distance from light to subject (which in this case, is nice and conveniently 1 metre).  I'll call these 'distance units', but remember, it is just the distance from the light source to the subject.

Now place another bottle of beer 1 distance unit (e.g. 1 metre) behind the first, and take another shot without changing any settings, and... whoa - where's my second beer gone!?  Being 1 distance unit further away, there is only 1/4 of the light reaching the second bottle - that is 2 stops of light lost over the first unit of distance.

Now let's move the second bottle back another distance unit, so it is now 3 distance units (3 metres) from the light.  At this distance, only 1/9th of the light is reaching the it.  Now the interesting thing is that although you doubled the distance, you have only lost a little over 1 stop of light this time.

Another metre (or distance unit) back, and now just 1/16th of the light is reaching the second bottle, but this unit cost you even less than one stop of light.

From here on, the loss of light is becoming more and more negligible.  You can now go another FOUR distance units, and only lose 2 stops of light.  Remember - you previously lost 2 stops of light just in that first unit!

Hopefully, you are getting the idea...?  Good.  Now, take a break, and come back in a few days for part two (when I've had a chance to create a few more graphics).

TTFN
Grum

PP - Example 2 : Twice the taste

Over the last few days, I've been looking into retouching and have learned a few new techniques, and also noted that even the pros can spend an hour or more, tweaking an image to perfection.  So I gave my beer bottle another go.  Here are the results - original on the left and tweaked on the right.

First of all,I took two pictures - one with the main label lined up, and then a second with the neck label lined up.  The first job was to cut and paste the neck off one to the body of the other.  This went quite easily, with only a minimum of healing brush and cloning required to disguise the join where water drops were suddenly cut in half.  I think that just having the labels aligned makes a huge difference!

After merging these two into a single layer, I then used a mask to mask the bottle and reflection, while I painted the background white, discarded it as too clinical, and then applied a uniform gradient of a very pale blue (could have been a bit stronger in retrospect).  I then masked everything but the reflection part, and applied a white gradient to tone it down a bit.

The final step was to do some light sculpting.  This involves adding a new layer at the top, switching it to overlay mode, and filling it with 50% neutral gray.  Because it is 50% neutral and in overlay mode - this has no visual affect on the image.  However, if you then paint on it with either a black or white brush, it has the effect of darkening or lightening the image. So, I masked off everything except the bottle, and then I used a very soft large brush at about 5-10% opacity with white, to run up and down the middle of the labels and eliminate that mid-line shadow, then with black down the right hand side to tone down that flash highlight.  The image to the right shows what that gray layer looked like if I took away the actual image, so you can see the areas that were darkened or lightened.

OK- the difference I made was nowhere near as pronounced as those of the pros doing the demos I watched, but I was quite pleased with it as a first effort.

Until next time
Happy Snappin',
Grum

A little taste of home

A family friend who has just been back to the UK for a visit, brought back a bottle of Spitfire for my son, so I figured I'd hijack it before he could drink it, and use it as a subject to practice my lighting on. This was the result of my first attempt - I can see some areas for improvement, so I'll have another go at it if I can persuade him not to drink it first...

I want to try and find some software that will allow me to do some setup diagrams - until then, I'll just have to try and describe the setup for you - but I've included a photo of it below.

The whole setup was done in the kitchen on the worktop, with a very DIY studio.  First off, I draped a white cloth across the worktop, with enough hanging off the back to form a backdrop.  Then I placed a sheet of glass (rescued from a broken scanner) on the cloth to provide a reflection.  I propped up a breadboard at the back and draped the rest of the white cloth over it as a backdrop.  I had the camera on the tripod level with the label on the bottle, giving a nice low angle so the rear edge of the glass wouldn't show.

For lighting, I used a speedlight off-camera with a radio trigger.  This was placed to the right of the camera, slightly in front of the bottle, to provide a bit of a highlight, but pointing past the bottle and onto the backdrop.  I used the omnibounce and flash spread set to 14mm to get an even spread across the backdrop which was less than 1m away.  The flash was set to 1/16th power.

I set the camera to 1/160th and f/5.6 in manual mode, and using my 18-55 lens, zoomed in to catch some space above the bottle, and an equivalent amount of the reflection below.  I took a test shot without the flash to make sure I had eliminated any ambient light, so that the only light in the picture would be from the flash - mainly being reflected back from the backdrop.  Unfortunately, being lit from behind, this put the front label in shade, so I used a sheet of white paper as a reflector right next to the camera lens on the left, to reflect some of that light from the background onto the label and illuminate the front of the bottle.

Of course, the most important detail was to leave the beer in the fridge for a few hours, to ensure I had some nice condensation on the bottle (though this could have been added at the end using a water spray), and that it was nice and cold when I drank it (oops, sorry son!).

Here's the setup picture...

So - I mentioned I felt there was room for improvement...

• The background is extremely white on the right, but has a slight blue cast top left as the light started to drop off - I'm wondering if I could exaggerate that a bit,by using a snoot or some other modifier to restrict the light from the flash, or zoom it in to 105mm rather than a wide 14mm spread, and have a more dramatic graduated background.  My son suggested having a Union Flag instead of plain white.
• The highlight on the right hand side is a little too bright, but taking the flash down a stop made the whole image too dark.  Perhaps a diffuser between the flash and the bottle would have helped.
• There is still a darker area right the way down the middle of the labels - especially noticeable on the Spitfire outline on the neck label.  Perhaps a bigger/better reflector would have put more light on the front.
• The neck label is not quite in line with the main label. I may be able to rectify this by taking a second shot after rotating the bottle slightly so the neck label is lined up with the camera,and then combining the two shots in Photoshop (10,000 miles is a long way to go to buy another bottle which IS lined up).

Let me know what you think, and if you have any ideas how to improve it.

Happy Snappin'

Grum

On display

I am really chuffed to announce that I now have two of my photos on permanent display at a small private gallery, in Swindon in England.  OK - perhaps I've glammed it up a bit...  by small private gallery, I mean someone's house, but they did specifically ask for two of my pictures that they 'fell in love with'.

They are my wife's brother's wife's parents, and they came out to Australia at the end of last year to visit various family.  They had seen one of my photos on facebook, as Karen had it as her homepage picture (in fact it is one of the early morning misty tree shots you can see in the 'Dabbling at dawn' post), and they asked if they could have a print of it to take home with them.  Of course, how could I turn down such a boost to my ego, so I had a 12x8 print made for them which I gave them on their last day here.

Earlier this year, we went to Tasmania for a few days, and while there, I took a shot of the moon reflecting across the bay where we were staying.  Ironically, Karen decided to use that as her facebook cover for a while, and once again, they saw it and commented about it - saying how they'd like a copy.  So, as we were travelling back to the UK for a visit in August, I had a 12x8 copy made for them as a surprise, and took it over.  We went to their house for a meal one evening, and I must say how proud I felt to see the misty tree picture hanging on their wall.  It would be great to go back and see them both up.

So, though I still haven't actually 'sold' a photo to a stranger, it's a step in the right direction (perhaps I should have left some business cards with them, and made them my UK agents?)

Happy Snappin'
Grum

Bad Blogger!

Oh dear - it's like going to the dentist... the longer you leave it, the harder it is to face up to how long it's been since the last check-up, and you just know it's gonna hurt!  Yes, another 7 months has passed without a single post... I am not going to even try to bore you with excuses, so just accept my apologies, and let's just jump straight in.

First, a brief potted history of the last few months... I've been to Malolo Island (Fiji) again earlier this year - it is such a great place to relax that it is turning into an annual pilgrimage for us - I'd love to take my camera scuba diving with me - but that's a whole bunch of expense that I think I'll pass on.  This year, we flew in a seaplane from the main island out to Malolo itself, giving me a brief chance to do some aerial photography.  Then we traveled to the UK for a couple of weeks, via Paris for a couple of days on the way there, and Abu Dhabi for a couple of days on the way back.  Paris was a great place to stop and I got some nice photos there (Eiffel Tower, Eiffel Tower, Arc de Triomphe, and uhm... Eiffel Tower), but the UK was all about visiting the rellies, and opportunities for photography did not really abound.  There were some stunning buildings in Abu Dhabi, but it was so hot, most of my pictures were taken from within the air conditioned comfort of a dust covered Land Cruiser!

Our zoo membership expired, and when we didn't renew it straight away, the zoo offered us an extra 3 months for free - BONUS!!  So we've just renewed it again, and I'm looking forward to many more visits (he he - watch out for loads more Meerkat pictures :-] )  We never managed to get out to the Western Plains Zoo (that's the other zoo that is covered by our membership, but it's a good 8 hour drive away) during our last membership period, but maybe we can get there this time.

I've discovered a nice little area of bush/woodland near where I work, that has opened up more lunchtime opportunities for wildlife photography, especially birds, though it has also enlightened me as to some of the hazards of wildlife photography - even in a seemingly innocuous area of woodland just 200m from my office - like being dive-bombed by angry nesting magpies, bitten by giant mosquitoes, being on constant watch for deadly snakes and spiders, and finally, taking home a blood-sucking passenger or two...  It's all in a day's work ;-)

I've tried my hand at photographing the rugby out in the park near me during the winter months, and also tried to get some shots of my niece doing her gymnastics and physie competitions (in poorly lit sports halls, with no flash allowed...)  Neither of these attempts were particularly successful, but I'll maybe post some of the pictures and discuss the difficulties later.

I feel like I've reached a decision point in photography - I do enjoy photographing anything and everything, but feel like I'm just drifting and not really advancing my skills in any particular direction.  I'm a 'Jack of all trades, but master of none...', so it's time to choose a 'specialist subject' as they used to say on Mastermind ("I've started, so I'll finish.").  While I'd really love to do sports photography, I recognise that the pre-requisite of spending $1000+ on a nice bit of glass is somewhat prohibitive, and I have decided instead to learn more about lighting, and using it for product and portrait photography, which I can do on a small scale far more cost-effectively with a 'budget' DIY home studio setup.  Developing the lighting skills on inanimate objects (while hard enough) will be the easy part - developing the skills to direct people is the bit I dread but really want to be able to do...

I already have my daughter's SB-800 on long-term loan (thank you for never asking - but I'll give it back one day, I promise) and a Cactus V5 Duo radio trigger set, and I've purchased a cheap set of 2x500W workshop lights for some constant lighting.  I'm hoping to supplement this with another (cheaper) speedlight, some proper light stands, etc., as well as building myself a backdrop holder, and makeshift supports for reflectors and so on ("Stick-in-a-can" type, a la Jim Talkington).  Eventually, I can invest in one or two actual studio strobes perhaps, after I build up a selection of stands and modifiers (and learn how to use the speedlights effectively)...  I bought myself some white and black material for backdrops, and some white and black sheets of card for making reflectors this weekend, and am waiting to lay my hands on some empty paint cans - lucky one of my sons is a painter.

OK - enough for now, and lunchtime is over so I'd better get on with some work.   I'll be back with some actual photos in the next couple of days (or 7 months...)

Happy Snappin'
Grum