The Inverse Square Law Use in Photography

[rolando]

Here's an article from one of my past books on photography.

The Inverse Square Law is one of those laws that can be your friend or foe, but understanding it always is a plus.

http://www.photographictherapy.com/2...se_square_law/

Thanks, rg sends!

[ThePhilosopher]

Quadratic attenuation makes for good problems in the classroom (I teach HS math). Good read Rolando.

[rolando]

Thanks for the nice comments. Wishing you the best, thanks, rg sends!

[CaptainTom]

It' one of those laws that seems to defy common sense until you truly understand it and then it becomes second nature.

I'm still working on using gels on the strobes to make the sunset change color.
I'm pretty sure what is going on, but I'm really sure it works very well.

Thanks for that lesson RG.

[studiocygnet]

Thanks for the lesson, Rolando. I knew about the law, but I didn't know that trick about using the aperture stops corresponding with the distance. Ya learn somthin' new every day.

[johnastovall]

the mouse is quicker than the mind

[Revision]

"Understanding this effect can help you produce the desired amount of contrast on your subject (moving the light away from the subject increases the contrast)."

Moving the light away from the subject decreases the contrast

Renato

[rolando]

Originally Posted by Revision

"Understanding this effect can help you produce the desired amount of contrast on your subject (moving the light away from the subject increases the contrast)."

Moving the light away from the subject decreases the contrast

Renato

No, the contrast increases. As the light becomes smaller, proportionately to your subject, it becomes specular and harsher, thus making shadows harder and increasing contrast. As your light modifier becomes larger, which can be done with a large light modifier or moving in your lights closer to your subject, the light becomes softer. The rule of thumb, "The closer the light, the larger the light modifier, the sweeter it is to your subject."

I hope that helps, thanks, rg sends!

[Revision]

Shadow edge transfer is different than contrast.
Shadow edge transfer: width of the transition between brightest area of diffuse reflection and deepest shadow.
Contrast: difference between values of brightest area of diffused reflection and deepest shadow.
Same light closer to subject (eg 0.7 feet) or farther from subject (eg 1.4 feet): diffuse reflection brightest area= 2 stops brighter at 0.7 feet; deepest shadow -area that gets no light from lightsource- = same at both distances=0, higher contrast at closer light range. Edge transfer: larger at 1.4 feet but no effect on max and min light values.
Best,
Renato

[rolando]

I stand by my statement and the Inverse Square Law. The further you move your light away from your subject, provided you're exposing for your subject, the harsher the shadows (light source becomes specular in relation to subject/light distance). Harsh shadows equals more contrast. To me, contrast is the difference between shadows and highlights, darks and lights, whatever you want to call it.

In layman's terms, when it's a bright sunny day, no clouds, the light source is the Sun, hence the harsh shadows, contrasty light. Throw in the clouds, now you have a diffused light source (think of clouds as the front of a soft box, the sun the studio flash head) and the light is now diffused, the front is closer and large (clouds), thus soft, low-contrast light, undefined shadows. Wishing you the best, rg sends!

[Revision]

We are just using two different definitions of contrast.
Our statements are all factually correct within the respective definitions of contrast.
You web site is wonderful.
Best,
Renato

[bondarnes]

Wow! Revision is our new four post genius.

[PIC]

Originally Posted by bondarnes

Wow! Revision is our new four post genius.

LMAO - In the land of Photo Forums anyone is a genius.
It used to be your photo college degree, education, what well heeled clients you have, how much you take in $$$ from clients, and other significant endowments.
I guess the same for those who write books and teach to the needy {aka those who can't make it the old fashion way}.

[Chief]

It reminds me too much of the old days doing Nuclear Physics. I'll just keep shooting the way I like and leave the Inverse Square Law to you Young Guys. hahaha

I'm getting a headache ( must be all the radiation )

Have fun

Gordon