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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 15 Jul 2011 (Friday) 15:54
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how? what? why? when?

 
TheBurningCrown
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Jul 15, 2011 22:50 as a reply to  @ post 12765884 |  #16

ekinnyc wrote in post #12765556 (external link)
im one of those people that just needs to understand everything, or at least try to, i guess. even if i may not use it, id like to understand the idea behind using flash, so that i can round out my knowledge i guess.

Oh, so you're like me :lol:. On the first day of one of my film classes I asked the professor how exactly the chemical processing worked. Not because it was relevant to the image, but because I was curious ;).

Google and Wikipedia aren't bad starting places. I assume you understand the exposure triangle? If so, see if you can follow this:

A flash pulse is an incredibly short amount of time, much shorter than the sync speed of the camera. Therefore, power of the flash only has to do with aperture and ISO (because your shutter speed on a Canon DSLR, aka a camera with a focal plane shutter, can't go fast enough to NOT encompass the whole flash duration). Does that make sense?

If it does, look up the inverse square law. It will help you understand how flash power diminishes at range. When you're done with that I can suggest some more ideas :p.


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egordon99
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Jul 16, 2011 11:01 |  #17

thestone11 wrote in post #12765446 (external link)
Spend some money on a Gary Fong Lightsphere....I love using it outdoor as a fill light. Very soft lighting even aiming the flash head directly to the object.

I fail to see how using the lightsphere can make your light source any bigger outside....And making your light source bigger is the ONLY way to make the light softer.




  
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Jim ­ M
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Jul 16, 2011 11:42 |  #18

Here is how to do anything in photography, flash included. Start simple. Attach the flash to the camera on the settings you usually use for everything. The flash will probably be on ETTL. Take pictures for a while with that combination. Look at the pictures. Do they satisfy you? If so, you are done. If not, ask yourself what you would like to change. Then look for a way to change that. Try to ignore people that tell you that you have to do this or that unless you have found something dissatisfying and are looking for advice on how to change it.

The other approach is to play around. Making digital images is fairly cheap once you have the equipment. Make plenty of them while trying various things. See what you like and don't like. Figure out how to reproduce those things you like and how to avoid those things you don't like.

Ignore any advice to get a piece of equipment (such as a Gary Fong modifier) unless you decide you need the effect it produces.

I've been into photography for about 50 years. I figured out how to do something last night that would improve certain pictures. I'm going to go out right now and stand by a hot race track in the 100ยบ+ heat for about twelve hours and in some of the 500-1,000 images I expect to generate today, I'll be doing something new. It never ends. My point is, don't expect to figure out how to do everything right away. Let your images help teach you.




  
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ekinnyc
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Jul 18, 2011 10:16 |  #19

TheBurningCrown wrote in post #12766505 (external link)
I assume you understand the exposure triangle? If so, see if you can follow this:

A flash pulse is an incredibly short amount of time, much shorter than the sync speed of the camera. Therefore, power of the flash only has to do with aperture and ISO (because your shutter speed on a Canon DSLR, aka a camera with a focal plane shutter, can't go fast enough to NOT encompass the whole flash duration). Does that make sense?

If it does, look up the inverse square law. It will help you understand how flash power diminishes at range. When you're done with that I can suggest some more ideas :p.

yup, i got the triangle part down - iso, F, s/s.
so ok, a camera has an sync speed, 1/200 right? thats how fast the shutter physically moves? so how does it tie in to the flash?

as for ISL... logically, i understand, the farther the object is from the light source, the less light hits the object. give me more

Jim M wrote in post #12768717 (external link)
Here is how to do anything in photography, flash included. Start simple. Attach the flash to the camera on the settings you usually use for everything. The flash will probably be on ETTL. Take pictures for a while with that combination. Look at the pictures. Do they satisfy you? If so, you are done. If not, ask yourself what you would like to change. Then look for a way to change that. Try to ignore people that tell you that you have to do this or that unless you have found something dissatisfying and are looking for advice on how to change it.

ettl works. but my curiosity leads me to want to understand how flash works, and how to use it manually, WHY to use it manually (that is, how would i know when i want full power, or 1/2 power, etc)... ad infinitum


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windpig
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Jul 18, 2011 10:37 |  #20

ekinnyc wrote in post #12778633 (external link)
so ok, a camera has an sync speed, 1/200 right? thats how fast the shutter physically moves? so how does it tie in to the flash?

Syn on the 40D, 50/D and 7D is 1/250
Sync on the 5DII is 1/200
The reason for the difference is that the shutter has to travel further on a full frame sensor.

at 1/250th and higher (crop) 1/200th (FF), the second part of the shutter is closing (coming into the frame). In other words, at the sync speed or slower, the sensor is totally exposed at the time the flash goes off. At higher speeds a portion of the shutter will be in the frame because the exposure window becomes a moving slit rather than a complete opening. That slit gets smaller the faster the shutter speed. (smaller slit, less light). That rear part of the shutter will be seen as a black band on non synched shots. High speed syn flash is not a single pop of light, but is when the speed light emits a quick pulse.

try this link
http://dptnt.com/2007/​10/flash-sync-speed/ (external link)


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TheBurningCrown
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Jul 18, 2011 12:02 |  #21

ekinnyc wrote in post #12778633 (external link)
as for ISL... logically, i understand, the farther the object is from the light source, the less light hits the object. give me more

Read up on size differences in light sources. That is, the difference between a large light source and a small one. This will key you into the concepts of "hard light" and "soft light." It will also help you to understand how to get light to "wrap" around your subject.

ekinnyc wrote in post #12778633 (external link)
ettl works. but my curiosity leads me to want to understand how flash works, and how to use it manually, WHY to use it manually (that is, how would i know when i want full power, or 1/2 power, etc)... ad infinitum

Use it manually when the light isn't changing, you want an absolutely consistent result after every shot, and you don't want the automatic tools to screw it up. Same reason you use manual mode on the camera.

You would know how much power to give it based on a few things:
1.) The guide number.
2.) A flash meter reading
3.) Chimping!

1.) The guide number of the flash is a basic estimate that, in rough terms, says that you will get a correct exposure at X distance with Y settings. The 580EXII has a scale at the bottom in meters (I believe you can change it to feet) that will tell you this. Unfortunately, it only works for direct flash and only without any modifiers. If you want to use it for anything other than, you still can, but you have to compensate for the change. For bouncing: you have to estimate how high of a ceiling you have, double that (the light has to come back!), and calculate the amount of light you'll lose reflecting off of the ceiling itself. Same thing for modifiers. However: once you know that difference between the calculated guide number and the guide number you need, you can use the guide number system for an entire event.

2.) If you're in manual mode, you can easily see how much light your flash is putting out (regardless of position or modifier) by using a flash meter. A simple handheld device that can take an exposure reading off of your flash output. Problem: somewhat expensive and bulky to carry around.

3.) Chimping is by far the simplest way to judge flash exposure (even if it isn't the most accurate). Simply put: after taking a shot with flash, look at the histogram of the shot you've just taken. If it's underexposed, boost the flash power. If it's overexposed, lessen the flash power. Wash, rinse, repeat. Quick and dirty, but it can get the job done in a pinch.

Once you start to "know" your flash a bit more, you can start predicting what sort of flash power you need based on your prior experiences. Hope that helps.


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ekinnyc
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Jul 18, 2011 12:14 |  #22

ok, ill digest the above.

what about FEC? where does that come in


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windpig
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Jul 18, 2011 12:21 |  #23

ekinnyc wrote in post #12779307 (external link)
ok, ill digest the above.

what about FEC? where does that come in

When you're using flash in ETTL mode it allows you to over ride the output the camera would use.


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pilsburypie
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Jul 18, 2011 14:02 |  #24

Purplecow wrote in post #12765397 (external link)
If you look in the 580ex manual, they call the card "catch-light card." .........The card should be used when outdoors or if you don't have a wall to bounce the light off of.

Should this not read "The card should not be used when outdoors"?


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TheBurningCrown
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Jul 18, 2011 18:01 |  #25

pilsburypie wrote in post #12779950 (external link)
Should this not read "The card should not be used when outdoors"?

I believe the statement is incorrect all-together. It isn't used as a bounce source, it's used to add fill/a catchlight.


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thestone11
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Jul 18, 2011 18:16 |  #26

egordon99 wrote in post #12768510 (external link)
I fail to see how using the lightsphere can make your light source any bigger outside....And making your light source bigger is the ONLY way to make the light softer.

You will never know until you try it...using the light sphere outdoor shooting portraits is great. It gives that natural look to the skin. YouTube some videos on light sphere, and you will see the difference. I know the price tag is high but IMO well worth the money.


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FORUMS General Gear Talk Flash and Studio Lighting 
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