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melcat
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Re: Starter flash


The main specification you're looking for is guide number. This is usually expressed in metres, and flash model numbers often hint at it, e.g. Canon's 580EX II has a guide number of 58. Guide number is defined by the formula GN = distance × f-number, so a flash with GN of 56 will light up a subject 10m away at f/5.6 (at ISO 100, which is assumed by convention).

Obviously that's more powerful than you'll usually need. The reason many keen photographers have such flashes is that when you want to use a faster shutter speed than the sync speed (usually around 1/200s on more expensive cameras) the flash has to fire in many very short bursts so a lot of its power is wasted, so-called "high speed sync". You usually do this when you want to shoot outdoors to fill in the shadows in bright sun, but that is specifically not your use case. In other words, you don't need high speed sync for that and you don't need a high-end flash.

Going back to the GN formula, if your family is sitting across the table from you, you have an f/4 zoom lens, and you're bouncing the flash off a white ceiliing 1.5m above you, you need a GN 16 flash.

You also want a bounce and swivel head and preferably a zoom head. Without the zoom head, you need a higher GN because some of the light is wasted whenever you use a focal length longer than the widest one the flash covers.

E-TTL is nice to have. The older type that had the sensor on the flash itself meant you had to adjust for bounce.

Although there will be used flashes out there for $20 that will do the job for you, I don't recommend you buy one for three reasons:

1. If it isn't a Canon EOS flash, it may have a high trigger voltage. If you know how to use a multimeter to check it's below 5V, this doesn't apply to you.

2. If it's a Canon EOS flash, some of them used an earlier E-TTL system that doesn't work with the digital cameras.

3. Flashes contain an electronic part called an electrolytic capacitor that degrades with time. After 20 years they are suspect.

So we're left with Canon's E-TTL flashes from the last 10 years, and third party equivalents. I don't know details of the models, but I really don't think you need anything as expensive as a 580 EX II or 480 EX.



Dec 20, 2016 at 05:31 AM





  Previous versions of melcat's message #13846819 « Starter flash »

 




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