Lighting 101 issues

[darkman]

Not wanting to spend a huge amount of money on alien bees or similar, I bought a pair of large soft boxes with 1000 watt bulbs. 2000 watts sounds like quite a bit of light after all, and when they're on, things get pretty bright.

Another problem is my low-budget backdrop that consists of a canvas drop cloth dyed with a double dose of Ritt dye. It's gray, and doesn't absorb shadow at all.


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A large light source, like a large SB, is relative to the subject. For a light to be soft, you need a light source that's large relative to the subject AND placed close to the subject. I see many large SB's on ebay that are really medium sized. A rule of thumb is the distance from the SB to the subject should be 1/2 the diagonal. I hate rules of thumbs because you understand how to get the result you want, not use a rule. However, following this rule of thumb as an example, your shadows on the backdrop will be negligable even with the subject close to the backdrop. As you move the source farther away the light becomes harder and the shadows become more prominent. Consder the sun, it's huge relative to me and you, but it's also so far away its become a point source that casts hard edged shadows. The unfortunate side of this is large light sources eat up lot of light, thus needing a more powerful source.

[JCPhoto1]

Actually the rule for the optimal distance the softbox is to the subject is the diagonal of the box face measured along the longest distance not 1/2. For a light to be soft, you need a diffused light source that's large relative to the subject and placed close to the subject.

[AC_Photo]

Yes, they are tungston, and they really are large boxes. 32x44 to be exact (although advertised as 36x48). I know about that distance rule too I was just asking too much of the lights given my need for a short shutter speed and a small aperture and was venting my frustration at having to go back to my little flashes. They did a great job though. I did say I was a total noob at portrait stuff!

My Alien Bees should arrive today! Luckily, I saved so much on the boxes and the heavy duty stands for them on ebay, that I'm still ahead on price compared to buying one of AB's packages. I can't wait to try them out!

[darkman]

Actually the rule for the optimal distance the softbox is to the subject is the diagonal of the box face measured along the longest distance not 1/2. For a light to be soft, you need a diffused light source that's large relative to the subject and placed close to the subject.

You're right as far as the way often preached "rule" goes. I do, however, disagree that this is "optimal." This version of the "rule" is a guideline to the effect that a softbox doesn't really give soft light if its distance from the subject is more than about the diagonal measurement. In reality, if you want soft, wraparound lighting then you need to be much closer than that.

The best advice is to avoid any kind of lighting formulas and jargon and place your lights to suit your subject and the effect you want to achieve. Try and imagine the light emanating from the SB and the angles the rays will hit the subject. From this you can get a rough idea of where to place the SB for your version of optimal.

BTW, AC, I consider those boxes to be medium.

[Sebastian]

The best advice is to avoid any kind of lighting formulas and jargon and place your lights to suit your subject and the effect you want to achieve. Try and imagine the light emanating from the SB and the angles the rays will hit the subject. From this you can get a rough idea of where to place the SB for your version of optimal.

Stuff like that is why I wish you would post more.

[Asylum Steve]

The best advice is to avoid any kind of lighting formulas and jargon and place your lights to suit your subject and the effect you want to achieve...

Well, like I said, a starting point. Guys, let's not waste energy discussing precise distances as a factor of the size of a piece of lighting equipment, and whether one is more correct than another.

Not once in all the years I've done studio work did I EVER measure the distance of a light from my subject, based on a softbox diagonal or anything else.

You move your light close you get an effect, you move it further away you get a different effect. And up and down and all around...

[Photo-John]

And up and down and all around...

And you do the hokie pokie and you turn yourself around.

Boogie oogie oogie, get down.

[Asylum Steve]

Consder the sun, it's huge relative to me and you, but it's also so far away its become a point source that casts hard edged shadows...

So, are you saying that natural photographic light would be a much softer and better if we were A LOT CLOSER to the sun?!?!?!

Ah, just kidding you, Mike. Hey, it's Friday, and I'm feelin' frisky...

You're absolutely right, and you make a good point that may not be obvious to everyone. I think rules of thumb, much like lighting formulas, can be very useful, but (IMO) only as starting points.

One will always need to play around with light positioning and see the results to really learn anything...

BTW, if rules of thumb are valuable tools, I need to add that much of the really creative style of studio photography comes from straying from or even breaking those rules. Using a medium to large softbox a father distance away from your subject does indeed create more of a point source illumination, but it is still much softer than a pure specular light.

This can create a very wonderful light: soft, but directional. If used the right way (for example overhead gives a skylight effect), it is one of the best fashion and portrait lighting techniques to try...