Originally posted by Mike Cash
What the auto circuitry does is to cut off the flash output when it senses enough light reflected back from the subject to give a correct exposure.
So if I had a manually controlled flash it would be forced to flash no matter what, right.
Originally posted by Mike Cash
With the manual stuff you can't help but be aware of what the settings are on everything and hence having at least a starting point for knowing what to move around or adjust. You see what effect those changes had and learn from them.
I think that's where I'd like to get, where I can do the quick calculation in my noggin. Otherwise I'd tend to become totally dependent on just checking the little slidebar calculator on the back of the flashes.
Originally posted by jolepp
As for a cheap, decent all manual flash with straightforward output control I'd vouch for the YN-560 (got one from ebay for ~$65, shipping included, saw a similar price with an Amazon seller the other day).
Jolepp, how much (or what increments of) direct control do you have over the power output on this flash?
Originally posted by Mike Cash
Getting your exposure in the ballpark when setting up manually is not hard at all. All it takes is a very little bit of in-your-head math and the ability to roughly estimate distances.
The output of flashes is usually expressed in terms of "GN" (Guide Number), which is really nothing more than a shorthand way of removing all the hard math from figuring out exposure. The important thing for figuring out exposure is flash-subject distance (camera-subject distance is irrelevant). The strength of the light varies tremendously depending how far the subject is away from the light source and with the same output level we need to use different apertures depending on the flash-subject distance. This is where our dear friend the GN comes in and rescues us from hard math....
GN divided by distance equals aperture. So easy to do that it is hard not to feel like a fraud when you use it.
What you need to know about GN is that it is a number that is sometimes expressed in feet and sometimes in meters....depends on what is common where you live. All that is important is that you know whether you're using feet or meters for the GN and to guesstimate your distances the same way so the math doesn't get all funky. GN is also usually expressed as being for ISO100 on your camera. Some off-brand flash manufacturers list their GN for ISO200 to make their flash look more powerful than it really is (the GN would appear to be twice as big), so check specifications carefully if you buy a new one.
Excellent info, Mike! I didn't find any mention of GN in the manual for my AF280T flash, but I Googled it and found both GN28 and GN91 @ ISO100. So GN28 must be in metres and GN91 in feet. My K-X only goes down to ISO200, which would double the GN? So a subject 5 metres from the flash would require an aperture in the neighbourhood of (56/5) 11.
Originally posted by Mike Cash
One very important point to keep in mind is that shutter speed plays no role whatsoever as far as the flash portion of your lighting is concerned. For mechanical reasons having to do with the camera you have to stay at or below sync speed (1/180 for us), but that has nothing to do with whether the flash portion of the light is correct or not and no amount of monkeying with the shutter speed will help you adjust the flash exposure up or down. You do that solely with the aperture.
So if I were to set the camera for a slower shutter speed it would make no difference at all to the exposure of the subject being illuminated by the flash, but would increase the exposure of the background?
Originally posted by hoanpham
Hi Yukoner777,
I always plan the shoot, ie. by looking for background, distances, ambient, gels and other light modifiers. Setup for portrait indoor will take from a minute to 10-15 min. Setups for parties and weddings require several flash units and planning. Private parties 10-15min. For weddings I need an hour to go through and setup all flashes to cover every spot, all use the same radio channel - a bit waste of battery, but since I shoot alone and this saves me the time to move light stands.
?
Hi hoanpham.
So assuming you have your locations picked out, and your gear is set up in the location(s), do you take a few test shots before the event to check the exposure? If so, are you taking shots of objects, volunteer test subjects, or what? Is it important/necessary to do test shots with
people before the event or will any objects work?
Thank you all for taking the time to share what you've learned.