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06-10-2008, 02:15 PM   #1
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Pentax Flash Question

I am confused as to which flash I should get between Pentax AF540FGZ or Metz 58 AF1 or Promaster 7500.

Meanwhile, before I buy any, I have a question about Pentax 540.
Someone mentioned that with Pentax 540, we have to set the f and ISO everytime manually. Is that correct?

Does it mean if I use a lens for ex: Sigma 17-70mm 2.8-4.5 + K100D + 540FGZ and set the ISO in the camera to auto then the flash won't be able to follow the camera's ISO setting?
How about if I zoom in / out with the lens that has variable aperture like this Sigma?
Do I need to adjust the f on the flash everytime I change the focal length so it will match the lens aperture?

If money is not a problem, which would be the best to get for me among those 2 flashes above? I'm using K100D but planning to upgrade and keep my K100D I love my K100D.

06-10-2008, 03:06 PM   #2
Ash
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QuoteOriginally posted by HermanLee Quote
I am confused as to which flash I should get between Pentax AF540FGZ or Metz 58 AF1 or Promaster 7500.

Someone mentioned that with Pentax 540, we have to set the f and ISO everytime manually. Is that correct?

Does it mean if I use a lens for ex: Sigma 17-70mm 2.8-4.5 + K100D + 540FGZ and set the ISO in the camera to auto then the flash won't be able to follow the camera's ISO setting?
Who said this?

In P-TTL mode, you don't have to do anything on the flash. Everything is communicated between the camera and flash. All I've had to do is turn up FEC to +0.3 to 0.7 and I get very reasonably exposed direct or bounce flash shots almost every time.

As it is with the other P-TTL flashes, they're designed to calculate the flash intensity required with the settings you've got on the camera. So it doesn't matter what mode you're in (except M/B mode), P-TTL theoretically takes the thinking out of working out the flash settings needed to make it totally automated.

As you might hear though, even from me, P-TTL doesn't always give you the results you want, so you put it in M mode to get a consistent flash intensity... All depends on what you need it for. I did quite well with a totally manual flash for a while, which costed me a whole $30, but I wasn't astute enough to get the right settings at the beginning without a little trial and error.

But rest your mind, P-TTL means everything is automated, no need to set anything (if you want that).
06-10-2008, 08:41 PM   #3
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Hi Ash,

Here is the thread that I meant:
https://www.pentaxforums.com/forums/pentax-camera-accessories/29322-metz-58-vs-af540.html

The comment from Mattjazz said that in auto mode w/ 540 we need to adjust the f and ISO, not like Metz58.

So which one is correct? is Auto mode different than P-TTL?

Sorry for the confusion. I never played with any of these flash.

Explanation will be appreciated.
06-10-2008, 11:18 PM   #4
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Herman, flashes operated in Auto mode use a metering system in the flash to read the overall exposure (ambient+flash) and cut short the flash duration to get an exposure that is "right" for the ISO and aperture being used (at the camera's flash sync shutter speed).

Since these Auto systems (often called "auto thyristor") are built for use with a very wide range of camera bodies, including early film bodies without electronic communications with the flash other than the triggering contact, you have to do a little manual setting of exposure parameters. Just like in the old days!

If you don't want to set ISO and aperture according to the flash's guidelines, then you would need to use the AF540FGZ in P-TTL mode with a body capable of P-TTL communications with its flash(es).

06-11-2008, 09:07 AM   #5
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Thanks, Christine.

So, if I understand it correctly, Auto Mode is different that P-TTL.

Is it true that with Metz 58 we don't need to adjust the f or ISO even when we are in AUTO mode? (not P-TTL mode)
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