The inverse square law :)

3 squared is 9 to make it the inverse 1/9 :) not really very useful if you know your f-stops that is more useful

1.0, 1.4, 2.0, 2.8, 4.0, 5.6, 8.0, 11.0, 16.0, 22.0.
1,2,3,4,5,6,7,8,9,10

The units don't matter a deal work in inches, feet, meters if your flash is 2 meters from the subject if you move the flash back to 2.8 meters without changing the power the subject receives 1 stop less light if you move it closer to 1.4 meters your subject gets twice as much light.

What is interesting is the fall off if the flash is 2 meters from the subject then anything 4 meters from the flash will receive 2 stops less light whats there will be pretty much lit by the ambient light. if you move the flash to 2.8 meters from the subject up the power by a stop to keep the exposure of the subject the same then the background at 5.6 meters back is 2 stops down the fall off takes longer.

If you bring the flash close to the subject then the range of the flash can be much shorter. e.g if you were to take a photo of a flower with the flash 4 inches from the flower at 8 inches the flash would have no effect isolating your subject. All the background would be in the shadows. You can kill the ambient light using a small aperture (so without the flash everything would be under exposed) or maybe use an nd filter to reduce the effect of ambient light. Fun isn't it :)

Hi again, blackest:
I scored 3/10. Totally missed question #3. Should have gone with my first hunch on "Land" and "ISO". At 1 in the morning, I knew light and square went together but went with cubed instead. Oh well. DA attack.

Bought a flash with my AE-1 but never got the hang of it. Always seemed like I over or underexposed most everything. In a few short sentences you have made some things click in my head. I think I may be starting to understand this whole flash concept. Even if I am somewhat confused by the info in your last paragraph, I think I can piece together what I will read in the future. I may even feel confident in the near future in posting a question, which I had NO idea how to even formulate before.

Thank you sir for training my brain.

Your welcome,

That last paragraph maybe think of a torch pointing at the ground it lights up a circle underneath it if you lower the torch the circle gets smaller and the light becomes stronger and if you raise it higher the circle gets bigger but the light is weaker. So if your subject is in the middle of the circle you can vary the light just by moving the torch nearer or further away. If it was a flash you could alter the power too so at different distances your subject can be equally bright. The other thing you see is that as the flash light gets further away a larger area is illuminated by the flash and as it gets closer a smaller area gets illuminated. So you can see that you need less power to illuminate your subject as the flash gets nearer and also the fall off gets steeper too. So outside the light being supplied by the flash the only illumination is ambient light.

Wow! Do you teach? That's a powerful example. For a retired shop teacher that's easy to visualize and understand.

You can control the ambient light primarily through aperture. e.g if f2 1/180th iso 100 gives the correct exposure for mid gray then f2.8 1/1/180th iso 100 would under expose by a stop. f2 -f2.8 f4, f5.6, f8. f11 at f11 you are under exposing 5 stops and even bright high lights are now in shadow. but with your flash you can be brighter than the sun (if it is near enough) and correctly exposure your subject while leaving nearby objects in darkness.

In other words, by using a flash, I can put the other contest models on a crowded table in the dark so that the one I am photographing will hopefully "stand out". If the room is not well lit.


You might use an nd filter to darken the ambient light rather than just using aperture. That way you can control depth of field too.

Ok, aperture does control the dept of field. When you're shooting within inches, the DoF is kind of narrow. Not as shallow as Macro photography, which I did considered until I looked closely at posted Macro shots. That 1/4" DoF would be useless for me.

I guess that's the difference between a snapshot and a photograph with a photograph you are taking some degree of control and getting the photo you want rather than what you are given. They can be very good snapshots, but luck and timing play a part too. A commercial photographer pretty much knows what they want and how to get it.

Your welcome,

That last paragraph maybe think of a torch pointing at the ground it lights up a circle underneath it if you lower the torch the circle gets smaller and the light becomes stronger and if you raise it higher the circle gets bigger but the light is weaker. So if your subject is in the middle of the circle you can vary the light just by moving the torch nearer or further away. If it was a flash you could alter the power too so at different distances your subject can be equally bright. The other thing you see is that as the flash light gets further away a larger area is illuminated by the flash and as it gets closer a smaller area gets illuminated. So you can see that you need less power to illuminate your subject as the flash gets nearer and also the fall off gets steeper too. So outside the light being supplied by the flash the only illumination is ambient light.

You can control the ambient light primarily through aperture. e.g if f2 1/180th iso 100 gives the correct exposure for mid gray then f2.8 1/1/180th iso 100 would under expose by a stop. f2 -f2.8 f4, f5.6, f8. f11 at f11 you are under exposing 5 stops and even bright high lights are now in shadow. but with your flash you can be brighter than the sun (if it is near enough) and correctly exposure your subject while leaving nearby objects in darkness. You might use an nd filter to darken the ambient light rather than just using aperture. That way you can control depth of field too.

I guess thats the difference between a snapshot and a photograph with a photograph you are taking some degree of control and getting the photo you want rather than what you are given. They can be very good snapshots, but luck and timing play a part too. A commercial photographer pretty much knows what they want and how to get it.

I'm gonna say, speaking from experience, that luck is responsible for very good snapshots.

I see you are from Ireland. We hope to visit there soon. I was going to suggest that if you find your way to Pigeon Forge, Tennessee, you should drive down to Gatlinburg and back up Artist Road. There, visit Earlywine Pottery. They make beautiful ceramics. But look for the photos on the walls, taken by, I think, his daughter of Grandpa and Granddaughter. Her sense of timing is either miraculous, or she is using multi- exposure. But the photos are magic. Composition, timing, color, tint, mood, it's all magic.

Thanks for the additional lessons. I going to dig out my old flash.
Bill

ok flash photography is essentially a double exposure for my camera the sync speed is 1/180th of a second. So lets say we use f4 iso 100 for our normal proper exposure without flash, dropping a stop to f5.6 is one stop under exposed f8 2 stops f11 3 stops f16 4 stops hopefully at f16 the exposure just from ambient light results in a black frame.

Trouble is really on a crop sensor you don't want to really go past f8 , a full frame can be ok at f11. So lets screw an nd filter on that drops the incoming light 2 stops now the ambient light is as low at f8 as it was at f16.

Theres a thing called diffraction limiting basically as light passes through the back of the lens it starts to spread out and light which was meant for 1 pixel ends up going onto other pixels if the pixels are supposed to be different colors the colors get smeared and mush together and you lose detail the amount of spreading is related to f-stop smaller the f-stop the greater the spread smaller pixels get affected sooner than larger ones.

So now you have the depth of field you wanted (f8) and you have totally killed the ambient light. Now you can dial up the power on your flash get the proper exposure on your subject and have no input into the photo from the ambient light.

Your flash is a very powerful light but it's just a tiny pulse of maybe 1/10,000th of a second duration. So the shutter duration doesn't matter for the flash its effect is controlled by the aperture. There is a fella on here that photographs hummingbirds and with flash he can freeze the wings.

If you google strobist 101 you can find a whole lot more than i'm telling you.

Ok. I'm gonna start a notebook. Get a three ring binder, print this stuff out, and put it all in order so I can find it later.

I can follow what you are saying. And each time I read it, it makes more sense. But I don't think I can remember it all. Especially all the interactions. Am I interested? Yes! Will I remember it all till I get a chance to try it? No, it will be like the diffracted light, all mushed together.

Just out of couriosity, does using a full frame lens on a crop sensor body reduce the diffraction?

I don't think my old Vivitar flash is going to work with this camera, so I'm going to have to study up on flashes and buy something. I've been looking at ring flashes maybe for using at model contests. Canon's are pricey, so I may try a cheaper third party to try, just to see if I like one. But first I have to see about getting my camera and lenses focusing together. I figured out yesterday that is part of my problems of blurry images.

Again I thank you for training my brain. I don't know just exactly what or how you are wording things, but it is finally starting to make sense.

The inverse square law :)

3 squared is 9 to make it the inverse 1/9 :) not really very useful if you know your f-stops that is more useful

1.0, 1.4, 2.0, 2.8, 4.0, 5.6, 8.0, 11.0, 16.0, 22.0.
1,2,3,4,5,6,7,8,9,10

The units don't matter a deal work in inches, feet, meters if your flash is 2 meters from the subject if you move the flash back to 2.8 meters without changing the power the subject receives 1 stop less light if you move it closer to 1.4 meters your subject gets twice as much light.

What is interesting is the fall off if the flash is 2 meters from the subject then anything 4 meters from the flash will receive 2 stops less light whats there will be pretty much lit by the ambient light. if you move the flash to 2.8 meters from the subject up the power by a stop to keep the exposure of the subject the same then the background at 5.6 meters back is 2 stops down the fall off takes longer.

If you bring the flash close to the subject then the range of the flash can be much shorter. e.g if you were to take a photo of a flower with the flash 4 inches from the flower at 8 inches the flash would have no effect isolating your subject. All the background would be in the shadows. You can kill the ambient light using a small aperture (so without the flash everything would be under exposed) or maybe use an nd filter to reduce the effect of ambient light. Fun isn't it :)