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Does auto mode of flash metering have any advantage over TTL?

One advantage that I can think of is the absence of a pre-flash in the auto metering, which can make some people blink. (But I rarely use direct flash anyway, so a TTL pre-flash doesn't seem to make people blink if it's bounced. Alternatively, I can get a meter with a pre-flash, lock the flash value, and shoot without preflash.)

So is there any advantage of flash's auto mode at all over TTL, when the camera body is capable of TTL?

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Different manufacturers and systems may define 'auto' differently. Could you be a little more specific about the system within which you wish to compare 'Auto' and TTL? –  Michael Clark Nov 11 '13 at 2:52
    
It depends on system, but note that the same thing you mentioned with pre-flash and metering can be done on many cameras with TTL if it supports an FE lock. On my 5D Mark iii I frequently will do a pre-flash/FE lock before taking the actual image and it seems that this avoids the pre-flash (though my preflash is often so fast it's hard to notice). –  AJ Henderson Nov 11 '13 at 14:52
    
Basically by "auto" I mean exposure by a thyristor sensor on the flashgun itself, as opposed to the through-the-lens metering taking place in the camera body. –  Anon Dec 1 '13 at 5:13
    
The more I think about it, I only see things to add to the "cons" column of the auto flash compared to TTL: it doesn't know the presence of any filter put on the lens, and it's not as good at metering for an off-center subject (you can but you have to carefully aim the thyristor sensor at the subject, which will be hard with on-camera-flash). –  Anon Dec 1 '13 at 5:16

2 Answers 2

One big advantage is that the flash doesn't need to communicate with the camera, so you can mix'n'match flashes and camera brands. Even though my Canon 580EXII speaks eTTL-ii, and my Panasonic GX-7 does TTL, they're not the same TTL. :)

But an autothyristor doesn't require camera/flash communication to automatically limit the flash's power output. With E mode (external sensor) I can use my Canon 580EXII on my Panasonic GX-7 with automated flash power, without resorting to TTL or having to spend another $300 on a micro four-thirds TTL flash.

And I can also do this with the 580EXII off-camera, using manual radio triggers between my GX-7 and my 580EXII. Similarly, I can use my Nikon SB-26 with automated power setting with my Canon dSLRS.

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TTL is a more recent technology, so it's supposed to be more accurate because it computes the light that actually comes into the lens. Anyway like other photo parameters, you need to know what you espect, what light you want on your photograph. Then you can choose the way you will compute the exact light you want. (TTL, Flash-auto, lightmeter, manual (try and see what you get)... )

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