Manual flash power...how do you know?

I'll try to test that, tonight...

I've not had a chance to test anything - my roommate is on a mids shift, so I've gotta keep things quiet so as not to wake him.

I wanted to touch back on the part of the discussion about ISO settings, though.

Wilt - when you talk of the guide number change due to ISO settings, are you speaking of the camera or the flash? I would think that setting a higher ISO setting on the flash (in manual) would result in a LOWER output due to less flash power being needed for the higher sensitivity, would it not?

Mike,
My earlier comments about ISO and Guide Number were solely about the calculation of exposure (camera) and not a comment on the amount of light output by the flash. The assumption is that a full power output of light from the flash has a Guide Number which you can calculate the maximum effective range of the light, for a given f/stop on the lens. That is what you were trying to understand in the OP, right? The ISO - GN correlation was to show the effect to changing the GN if you chose to use a different ISO, such as to increase the max range of the light. All assuming flash on full power Manual or on Auto and outputting full power.

Ok - I *thought* that's what you meant, but wanted to make sure. Changing the ISO on the flash, in manual, DOES change the output of the flash, doesn't it? Unfortunately, the manual doesn't mention anything about that...

Nope. The flash output remains the same. The ISO change just gives you different parameters for calculating the exposure. If you want to change the output of the flash in manual, you change the the little gizmo that says "full, 1/2, 1/4..."

The way you use the ISO setting on the flash is to match it to the ISO setting on the camera when the flash is on automatic. Then you match the aperture setting of the flash with the aperture setting of the camera. The camera should be set to manual. The 383 flash does not communicate with the camera, so it doesn't know anything about what the camera is set on. You have to do that part manually to get automatic flash. If you want to set the flash on manual and use the full, 1/2, 1/4, etc. settings, that is where the guide numbers and distance scale come into play. (The exception to this is that the distance scale can tell you when you are out of range for proper automatic function.)

What should a properly exposed histogram look like? Can anyone provide this?

ALaS wrote in post #5266037
What should a properly exposed histogram look like? Can anyone provide this?

Can you take an "it depends" answer?

Here is a web page that has some info. The link takes you to the main page and you will have to click "Articles" then click the link to "Happy Histograms." A warning first – there is a picture of a lady without any clothes on the page about histograms.

http://www.ranum.com/f​un/lens_work/

The quick summary of what he says is a proper histogram will look different under different circumstances and you need to learn to recognize those circumstances.

I'll add that many flash exposure histograms don't look right when they are right. If there is a dark background, there will be a lot of dark tones represented in the histogram. Don't worry about it. Just make sure the light and medium tones are represented as well, although they probably won't be as tall as the dark tones.

Of course I can take that as an answer! Thanks for the link it's very informative and helpful!

Jim M wrote in post #5266663
Can you take an "it depends" answer?

Here is a web page that has some info. The link takes you to the main page and you will have to click "Articles" then click the link to "Happy Histograms." A warning first – there is a picture of a lady without any clothes on the page about histograms.

http://www.ranum.com/f​un/lens_work/

The quick summary of what he says is a proper histogram will look different under different circumstances and you need to learn to recognize those circumstances.

I'll add that many flash exposure histograms don't look right when they are right. If there is a dark background, there will be a lot of dark tones represented in the histogram. Don't worry about it. Just make sure the light and medium tones are represented as well, although they probably won't be as tall as the dark tones.

Best information on using flash is at the Strobist Blog at www.strobist.com.

Also the Strobist Group on Flicker.

Here is good information on Guide Numbers. http://en.wikipedia.or​g/wiki/Guide_number

It just so happens the Strobist Blog post for Friday is all about using manual flash settings. How is that for perfect timing?

Jim M wrote in post #5265979
Nope. The flash output remains the same. The ISO change just gives you different parameters for calculating the exposure. If you want to change the output of the flash in manual, you change the the little gizmo that says "full, 1/2, 1/4..."

OK, upon further perusal of the flash, it appears that the ISO scale merely changes the f-stop setting recommendation at the top of the distance scale. Changing power (even in Auto setting) changes the max/min distance scale.

Thanks, everyone, for helping set me straight on all this stuff. It's greatly appreciated!