Lighting a background.

donkeymusic

donkeymusic

Suspended / Banned
Messages
2,524
Name
Carlo
Edit My Images
Yes
Hello,

I purchased two printed backgrounds, one is a wooden floor and one is a worn paper look, with the hope of achieving something like this >>http://sarahwilkesphotography.co.uk/w/newark-newborn-baby-child-photographer/ scroll down to the little girl photos.

I set my stand up and new backdrops and metered them at f8, with just one light off right and with a 50cm square softbox.

Now my first test gave me this, which is too bright any you can see the location of the softbox

http://www.flickr.com/photos/carlomullenphotography/9447780166/

The second one is metered at f5.6 and gave me this which look s a litte too dark.

http://www.flickr.com/photos/carlomullenphotography/9447773664/in/photostream/

Im sorry about the links as im not sure how to share with the new flickr, think the share button wasnt working on my machine for some reason. when i get home i will try an update the links.

So basically im asking what Th.e best method is too light the setup, was thinking of a much larger softbox direct behind me?? the photos on the original link look so much better lit and natural, how would i go about this??

Thank you for any help offered.
 
Sorry I am also learning OCF so not an expert, but when having a play last night I was getting that blown out bit when the flash was on full power.

Are you using you flash as manual or ttl?
 
The photos in your link are just blitzed with light from all directions. A lot of people do this, to get really even lighting, which presumably they think is good, and if that's what you want then just have large light sources (softboxes or umbrellas) all over the place.

Your own photos are suffering from the effect of the inverse square law, i.e. the light reaching the nearest part of the subject to the light is receiving far more light than the part furthest away from the light.
 
Inverse square law - double the distance equals one quarter the brightness, a two stops drop. In other words, light falls off rapidly with distance, and at close range like say the light is 1m from the near side of the background and maybe 3m from the far side, the difference in exposure levels is going to be massive.

The answer is a) move the light back as far as possible to minimise ISL fall off, and b) use a second light to balance from the other side. In the link, there is a third flash head, a large octa, from the front left as key subject light to give a little modelling and that is also brightening the left side nicely. Sounds easy, but it's not and the photographer there knows what they're doing and has balanced and gridded/screened everything very skilfully.

I know Garry doesn't like super-soft and almost shadowless lighting much, and each to their own, but punters do ;)
 
Last edited:
This is why you learn 'the inverse square law'.

I had to write it, even though I've seen those 2 have posted, and I know that's what they said. :shrug:
 
Garry Edwards said:
The photos in your link are just blitzed with light from all directions. A lot of people do this, to get really even lighting, which presumably they think is good, and if that's what you want then just have large light sources (softboxes or umbrellas) all over the place.

Your own photos are suffering from the effect of the inverse square law, i.e. the light reaching the nearest part of the subject to the light is receiving far more light than the part furthest away from the light.
Click to expand...

Are you referring the first link from Sarah wilkes? That are blitzed, does that lighting not look natural? I know there are not many shadows.
 
HoppyUK said:
Inverse square law - double the distance equals one quarter the brightness, a two stops drop. In other words, light falls off rapidly with distance, and at close range like say the light is 1m from the near side of the background and maybe 3m from the far side, the difference in exposure levels is going to be massive.

The answer is a) move the light back as far as possible to minimise ISL fall off, and b) use a second light to balance from the other side. In the link, there is a third flash head, a large octa, from the front left as key subject light to give a little modelling and that is also brightening the left side nicely. Sounds easy, but it's not and the photographer there knows what they're doing and has balanced and gridded/screened everything very skilfully.

I know Garry doesn't like super-soft and almost shadowless lighting much, and each to their own, but punters do ;)
Click to expand...

I do, to a degree understand the inverse square law.

But I think what I was trying to find out, on a background that is only five foot wide and will be used for baby shots, do I need to be having my light at 45 degrees with a small software or should I use a large soft box centrally behind me, given an even lighting much like the first sample link i posted?

Thanks
 
donkeymusic said:
I do, to a degree understand the inverse square law.

But I think what I was trying to find out, on a background that is only five foot wide and will be used for baby shots, do I need to be having my light at 45 degrees with a small software or should I use a large soft box centrally behind me, given an even lighting much like the first sample link i posted?

Thanks
Click to expand...

No. If you want an evenly lit background, the best way is with two lights - as described above. This also allows you to light the main subject separately.
 
HoppyUK said:
No. If you want an evenly lit background, the best way is with two lights - as described above. This also allows you to light the main subject separately.
Click to expand...

Just watching the video posted above and that cleared things up but also created more questions.

With the ISL, if I was to set the large soft box further away from the subject and background, the the amount of fall off would minimal so both subject and background would be evenly lit?

Also is the ISL always rated on the distance in feet? When I do my portrait sittings, my soft box is approx five foot from subject metered at f8. Which means I'm only getting 1/25 power or 4% so do I need to get my light in closer to the subject?
 
donkeymusic said:
Just watching the video posted above and that cleared things up but also created more questions.

With the ISL, if I was to set the large soft box further away from the subject and background, the the amount of fall off would minimal so both subject and background would be evenly lit?
Click to expand...

If you can get the softbox far enough away, in theory there should be very little difference in brightness between the main subject and background. Like sunlight, because the sun is a long way off, so in that sense you're right. However, the subject would cast a strong shadow on the background, you'd have no option to shape or adjust the light on the main subject, and you'd need to crank the power up.

Also is the ISL always rated on the distance in feet? When I do my portrait sittings, my soft box is approx five foot from subject metered at f8. Which means I'm only getting 1/25 power or 4% so do I need to get my light in closer to the subject?
Click to expand...

I'm not clear what you mean here, it appears contradictory.
 
HoppyUK said:
If you can get the softbox far enough away, in theory there should be very little difference in brightness between the main subject and background. Like sunlight, because the sun is a long way off, so in that sense you're right. However, the subject would cast a strong shadow on the background, you'd have no option to shape or adjust the light on the main subject, and you'd need to crank the power up.



I'm not clear what you mean here, it appears contradictory.
Click to expand...

Does it mean that for when I do all shoots I should have my light one foot from subject to get full power at f8?
 
donkeymusic said:
Does it mean that for when I do all shoots I should have my light one foot from subject to get full power at f8?
Click to expand...

I'm sure the answer is no, but the question still doesn't make sense!
 
I'm sure we've been here before with you, with the same questions and the same answers...

The distance from your key light to your front subject (person) and from your front subject to your rear subject (background) will affect the amount of light falloff on your rear subject, because of the inverse square law. For example, if your softbox is positioned 5' from the subject and results in an aperture of f/8, and the light then travels a further 5' to reach the background, then 4x as much light will reach the front subject as the rear subject and the background will be underexposed by 2 stops. Double the distance from key light to front subject and your rear subject will "only" be underexposed by 1 stop - but the relative size of the light will be much smaller, so the light will be harder, which may or may not be what you want.

I refer to "front subject" and "rear subject" because they are in fact two separate and distinct subjects that need to be lit separately, unless you front subject is right up against your rear subject, which would cause different problems.

As explained before, you will NOT get even illumination of the background with just one light. That video explains the reasons perfectly, it's actually an excellent video.
Also is the ISL always rated on the distance in feet?
Click to expand...
The Americans use feet because that's their unit of measurement, they haven't caught up with the rest of the world yet:)
 
You must log in or register to reply here.
Back
Top