1/8 power. -1 2/3rds and f8s....help me

[RoryOD]

Ok.. this is probably a really simple thing, and i feel stupid asking, because i feel everyone else knows this but me, but im lost?

I have and use a 580 Ex mkII and mk I

on the dial it goes from +3..+2 2/3..+2 1/3.........0......-2 1/3..-2 2/3..-3

I understand that is is changing the output power of the flash. + stronger and - weaker.

I see photos where people say they used full power, half power or 1/8power and so on.
How can i translate that into +'s and -'s on the back of my flash?

In other shots where studio flashes are used the light is rated in f-stops eg light at f8 and the other at f11. again how does this work in relation to what i have on my flash.

Is it as simple as a table saying:
+3 on flash gun = full power = f11 on studio
0 on flash = 1/2 power = f5 etc.

I really want to understand lighting, but i feel that not understanding this in relation to my flash means that ill be lucky if ill ever crawl, never mind get to walking and running.


Could someone put me out of my misery!

[bauerman]

I believe that the +1, +2, -1, -3 settings are actually flash exposure compensation when you have your flash in ETTL or "auto" mode - to make tweaks to what the flash thinks should be the proper amount of flash light in your scene. To get to the power settings - you would need to put your flash in manual mode, then you will see the setting you describe of 1/2 power, 1/8 power and so forth.

[Curtis N]

Baurman is correct. In E-TTL mode you adjust FEC in 1/3 stop increments. In manual mode you adjust the power in absolute terms, also in 1/3 stop increments.In other shots where studio flashes are used the light is rated in f-stops eg light at f8 and the other at f11. again how does this work in relation to what i have on my flash.A handheld flash meter will give you a reading in f/ stops, essentially telling you how to set your aperture for proper exposure. You can use a flash meter in conjunction with your 580EX II in manual mode.

[PacAce]

Ok.. this is probably a really simple thing, and i feel stupid asking, because i feel everyone else knows this but me, but im lost?

I have and use a 580 Ex mkII and mk I

on the dial it goes from +3..+2 2/3..+2 1/3.........0......-2 1/3..-2 2/3..-3

I understand that is is changing the output power of the flash. + stronger and - weaker.

The values mentioned above refer to the amount of flash exposure compensation that will be applied to the power output value determined by the camera with the flash in ETTL mode. In other words, when the flash is in ETTL mode, the camera will automatically determine what it thinks is the correct flash output to correctly exposure the shot. You can, if you deem it necessary, then override the flash output determined by the camera and increase or decrease the flash output by up to 3 stops via the flash or 2 stops via the camera. With an FEC of 0, no flash exposure compensation is applied.


I see photos where people say they used full power, half power or 1/8power and so on.
How can i translate that into +'s and -'s on the back of my flash?

When the flash is in manual mode, as opposed to it being in ETTL mode, you have to set the output of the flash yourself since the camera won't do it for you. You need to determine how much output you need based on the aperture and ISO set on the camera as well as the flash-to-subject distance and the zoom position set for the flash head. Bouncing the flash instead of pointing it head on will also affect the flash output level required.

This manual power settings have nothing to do with the flash exposure compensation setting discussed at the top of this post.


In other shots where studio flashes are used the light is rated in f-stops eg light at f8 and the other at f11. again how does this work in relation to what i have on my flash.

Is it as simple as a table saying:
+3 on flash gun = full power = f11 on studio
0 on flash = 1/2 power = f5 etc.

I really want to understand lighting, but i feel that not understanding this in relation to my flash means that ill be lucky if ill ever crawl, never mind get to walking and running.


Could someone put me out of my misery!

When a flash meter is used to read the output of the strobe, the value is given in terms of aperture values. There is no absolute relationship between the power level a strobe or flash is set to and the resulting aperture after metering. It's all relative because a lot of factors determine the metered reading, such as flash-to-subject distance, ISO, whether modifiers are used, the actual full-power output of the strobe or flash, etc.

So, when one flash or strobe reads, for example, f/8 and another reads f/11, all that means is that the first light is one stop dimmer than the 2nd light.

[RoryOD]

thanks a million guys. just gone into manual and seen it goes from 1/1 - 1/128.
Im used to shooting in e-ttl with an st-e2 and then i use ratios and ex. comp and flash distance to subject to change the output levels. Ill have to get into manual flash, kinda sounds scary!

As far as i understand- in manual in order to find out the correct output, the following factors have to be taking into account: iso, Apeture and flash distance to subject?

I have seen some fantastic shots that are taken with just 1 or 2 580's and i cant get close to it on ettl.

does anyone recommend and sites to set me straight on the road to manual flash
i know strobist is mentioned alot.

Thank you all again for the info. I appreciate it.

[Curtis N]

As far as i understand- in manual in order to find out the correct output, the following factors have to be taking into account: iso, Apeture and flash distance to subject?Those things, plus the flash zoom setting. And this is assuming you're using direct flash (no bouncing, no modifiers).

Now the beautiful thing is, the flash has a distance scale on its LCD that automatically accounts for all of those factors. Adjust the aperture, ISO and/or zoom setting until the scale indicates the correct distance and it should work pretty good.