wonky flash power?

I'm new to small flash so bear with me.

I was playing with my new 430ex today and I noticed that manually setting 1/64 flash power results in much brighter exposures than -3 flash compensation in TTL mode, all other things being equal.

Why is this the case? I would think it would be possible to manually set the flash at it's lowest power output?

LostArk wrote in post #15368071
I'm new to small flash so bear with me.

I was playing with my new 430ex today and I noticed that manually setting 1/64 flash power results in much brighter exposures than -3 flash compensation in TTL mode, all other things being equal.

Why is this the case? I would think it would be possible to manually set the flash at it's lowest power output?

Because 1/64 is probably putting out more power then the ttl with -3 FEC.

Just because the lowest flash setting in manual is 1/64 does not mean the flash can not put out less power in ttl mode.

A work around would be to put some diffusion material or mesh on your flash if you didn't want to stop down and reduce shutter speed.

LostArk wrote in post #15368071
I would think it would be possible to manually set the flash at it's lowest power output?

Also, when used as a wireless slave, the flash can be set to 1/128 power from the master. And as you've noticed, using E-TTL and negative FEC, output can be reduced even more.

gremlin75 wrote in post #15368772
Because 1/64 is probably putting out more power then the ttl with -3 FEC.

Just because the lowest flash setting in manual is 1/64 does not mean the flash can not put out less power in ttl mode.

This is what I figured but wanted to confirm. Thanks!

I just wish there was a way to have manual access to lower power. Why should TTL be able to do things manual mode can't?

-3EV compensation should be equivalent to 1/8 power...1/1 (0EV), 1/2 (-1EV), 1/4 (-2EV), 1/8 (-3EV)...RELATIVE to the assumption that full power is 0EV starting point (which might well NOT be the starting point for a given shot!)
The problem is that with ETTL, when you use 0EV compensation, the flash is still likely NOT to be having to output true full power but is outputting at a lower level...it might be starting with 1/8 power because that is all that the ETTL is commanding of the flash, so that when we dial in -3EV compensation that is 1/64 power...1/8 (0EV), 1/16 (-1EV), 1/32 (-2EV), 1/64 (-3EV)

Flash compensation merely tells the flash metering what to output relative to what it considers to the 'proper exposure' for a given aperture and ISO.

[QUOTE=Wilt;15370060]-3EV compensation should be equivalent to 1/8 power...1/1 (0EV), 1/2 (-1EV), 1/4 (-2EV), 1/8 (-3EV)

quote]

Doesn't it depend on the apeture and ISO? 1/8 power is the same output regardless of the apeture and ISO settings, but -3EV in ETTL corresponds to a different output for each apeture and ISO combination.

[QUOTE=doidinho;153701​94]

Wilt wrote in post #15370060
-3EV compensation should be equivalent to 1/8 power...1/1 (0EV), 1/2 (-1EV), 1/4 (-2EV), 1/8 (-3EV)

quote]

Doesn't it depend on the apeture and ISO? 1/8 power is the same output regardless of the apeture and ISO settings, but -3EV in ETTL corresponds to a different output for each apeture and ISO combination.

'Proper exposure' matters...based upon ISO and Aperture and lens coverage angle and the flash-to-subject distance

'proper exposure' might ...

• require full power, if the ISO was 100 and the lens were 50mm and the aperture f/8 and the distance were more...GN130 at full power 50mm coverage angle and f/8 provides enough light when subject is 16' away.
  
• require 1/8 power, if the ISO was 100 and the lens were 50mm and the aperture f/8 and the distance were less...GN130 (at full power) 50mm coverage angle and f/8 provides enough light when subject is 2' away

[QUOTE=Wilt;15370333]

doidinho wrote in post #15370194
bride in white wedding gown in a white room reflects back a lot more light than 18% average, so one needs to dial in -1.5EV or so of Flash Exposure Compensation or the meter is fooled.

Hmm.............I would think it would be +1.5 in FEC

[QUOTE=windpig;1537036​1]

Wilt wrote in post #15370333
Hmm.............I would think it would be +1.5 in FEC

You're right, I had a brain fart...I modified the earlier post

Wilt wrote in post #15370333
[The flash meter thinks the scene averages to 18% gray, but a Scandanavian bride in white wedding gown in a white room reflects back a lot more light than 18% average, so one needs to dial in +1.5EV or so of Flash Exposure Compensation or the meter is fooled.
A flash meter at the bride would read the identical reading, whether she was a) black skinned in dark dress against a dark background or

This is weird. When reading the post the EC suggested showed as a minus. Which is in the wrong direction. When I clicked on the Quote button to make this post, the text shows a plus, which as Wilt knows is the proper compensation.

Also, in this example as well as other situations when using Av for ambient exposure remember that Exposure Comp and Flash Exposure Comp have to be introduced independently. Just as if shooting manual one has to make the appropriate adjustment to the ambient exposure by changing the shutter speed and then make a FEC input as well.

[QUOTE=Wilt;15370373]

windpig wrote in post #15370361
You're right, I had a brain fart...I modified the earlier post

That explains the anomaly.

[QUOTE=Wilt;15370333]

doidinho wrote in post #15370194
'Proper exposure' matters...based upon ISO and Aperture and lens coverage angle and the flash-to-subject distance

'proper exposure' might ...

• require full power, if the ISO was 100 and the lens were 50mm and the aperture f/8 and the distance were more...GN130 at full power 50mm coverage angle and f/8 provides enough light when subject is 16' away.
  
• require 1/8 power, if the ISO was 100 and the lens were 50mm and the aperture f/8 and the distance were less...GN130 (at full power) 50mm coverage angle and f/8 provides enough light when subject is 2' away

...and the subject/scene were 'average' (18% tonality) in brightness

Exposure compensation and Flash Exposure Compensation is a modification of METERING, which happens to translate into increase/decrease of flash output. It is NOT a increase of power or decrease of power, per se.
The flash meter thinks the scene averages to 18% gray, but a Scandanavian bride in white wedding gown in a white room reflects back a lot more light than 18% average, so one needs to dial in +1.5EV or so of Flash Exposure Compensation or the meter is fooled.
A flash meter at the bride would read the identical reading, whether she was a) black skinned in dark dress against a dark background or
b) white skinned in white dres against white background

...the ETTL meter would be fooled (and therefore need appropiate amounts of FEC).

Even without FEC, the ETTL meter would alter its output amount of light for both A and B in spite of the fact that the actual required exposure to achieve 'proper exposure' is identical for both situations!

Nevermind, I re read your initial post after reading this and now see that when you said 1/8, 1/2, 1/1, etc that you meant that to be a fraction of the full ETTL output rather than a fraction of the flashes full output.

dmward wrote in post #15370400
This is weird. When reading the post the EC suggested showed as a minus. Which is in the wrong direction. When I clicked on the Quote button to make this post, the text shows a plus, which as Wilt knows is the proper compensation.

Also, in this example as well as other situations when using Av for ambient exposure remember that Exposure Comp and Flash Exposure Comp have to be introduced independently. Just as if shooting manual one has to make the appropriate adjustment to the ambient exposure by changing the shutter speed and then make a FEC input as well.

Not weird...the OP tried to lower power with the use of EC, and that does require MINUS value (less exposure); my example Scandanavian bride would need to tell the flash to give MORE exposure (else the white is underexposed to gray)