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Comparing current PTTL-compatible flash options
Posted By: mattdm, 03-19-2008, 08:05 AM

UPDATE: Further updates to this article will be done on a web site dedicated to this purpose.

The Definitive Guide to Pentax and Third-Party P-TTL Flash Options

This is available for collaborative editing and released under the Creative Commons Attribution-Share Alike 3.0 License. Please follow the link above for the latest version. Thanks.


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There are currently three flashes made by Pentax which work with the P-TTL flash metering system, plus two from Metz, one from Sigma, and three from Promaster.

There's also a "generic make" flash sold as the Soligor DG-420 Z, Sakar / Digital Concepts 952AF/PEN, Dörr D-AF42, and perhaps other names (Praktica / Exacta DPZ 38AF?). This apparently also has P-TTL support. It doesn't have high-speed sync or work as an optical wireless slave.

The Sigma flash comes in two models, with the "Super" version including the ability to work as a wireless slave and in high-speed sync mode. The most basic Pentax flash (AF200FG) can't work as a wireless slave either. Both Metz models can, although only the more expensive one can act as an on-camera controller. (All slaves can be controlled by the built-in flash of the K10D or K20D, making that at least good for something.) The Promaster models don't have the ability to work as wireless slaves or in high-speed sync mode.

The relative power of these flashes is quite hard to compare because the manufacturers don't deign to list their flash power specs by luminosity, only via guide numbers. And to make things worse, they all provide a random sampling of different focal lengths at which they've measured the GN, so correlation is difficult. And there's not an industry of rigorous third-party testing for flashes, so we have to take them at their word. With some scouring, though, I put together this list manufacturer-claimed guide numbers for ISO 100 @ 50mm:
  • Pentax AF540FGZ = 148'
  • Metz 58 AF-1 = 137'
  • Sigma EF-530 DG = 132'
  • Sakar 952AF/PEN, et al115' *
  • Metz 48 AF-1 = 114'
  • Promaster 7500EDF = 112'
  • Promaster 7400EDF = 100'
  • Pentax AF360FGZ = 94'

* For the Sakar/generic flash, there's no published spec for 50mm, so I'm interpolating. I trust this number least of all.

Also, the following flashes can't zoom to 50mm, so presumably this data is roughly the same as the coverage for 28mm on the zoom flashes. However, that would make the Promaster 7200 more powerful than the 7400 or 7500, which seems dubious. So, I'm not quite sure exactly what to make of either of these numbers.
  • Promaster 7200EDF = 100'
  • Pentax AF200FG = 66'

The guide number gives the (nominal) number of feet away a subject can be to be lit at that focal length and ISO, at f/1. Divide by aperture to get effective distance stopped down to the realm of real lenses — that is, the Metz 48 AF-1 is listed as providing full lighting at about 14 feet away at f/8.

If we assume they're all lying equally then that makes a somewhat useful list. The power in terms of light output is proportional to the square of the GN, so the Metz 48 AF-1 is (again, going on claimed numbers) about 1.5× more powerful than the Pentax AF360FGZ.

Here's the whole list in terms normalized to AF360FGZ as 2.0 (I had the AF200FG as 1.0, but since that really can't zoom to 50mm, the AF360FGZ makes a better base. But it still makes the other numbers come out nicer if we make it 2.0 instead of 1.0)
  • Pentax AF540FGZ = 5.0×
  • Metz 58 AF-1 = 4.3×
  • Sigma EF-530 DG = 4.0×
  • Metz 48 AF-1 = 3.0×
  • Promaster 7500EDF = 2.9×
  • Promaster 7400EDF = 2.3×
  • Pentax AF360FGZ = 2.0× (Of course.)

Which comes out nice and satisfyingly close to whole numbers, eh? That's probably not coincidence. The K10D's built in flash, by the way, comes out at ¼×.

Probably an even more honest answer would show the power at the widest setting, not with the reflector zoomed to 50mm. (Although, hard to argue with the practicality.) And I wouldn't be terribly surprised if there's a discrepancy here in some manufacturer using 1.5× crop-factor converted focal lengths (that is, claiming the 50mm numbers for the field of view of a 75mm full-frame lens). So this really ought to be tested somehow to give a perfect answer, but this is what I can do with the publicly-stated data.

Also, the Metz, Sigma, and Promaster flashes have a reflector which can focus the beam more tightly than the Pentax and Sakar/Digital Concepts flashes — they go to 105mm (35mm full-frame), whereas the Pentax and Sakar models have zoom reflectors which stop at 85mm. The listed guide numbers for the most narrow setting are:
  • Metz 58 AF-1 = 190'
  • Pentax AF540FGZ = 177'
  • Sigma EF-530 DG = 174'
  • Metz 48 AF-1 = 157'
  • Promaster 7500EDF = 138'
  • Sakar 952AF/PEN, et al = 138'
  • Promaster 7400EDF = 120'
  • Pentax AF360FGZ = 118'

So, on a current 1.5× crop Pentax dSLR, the relative power if you're at a focal length of 70mm or above (with the difference between the numbers in the first comparison starting to kick in at around 56mm) is as follows (again normalized to AF360FGZ as 2.0).
  • Metz 58 AF-1 = 5.2×
  • Pentax AF540FGZ = 4.5×
  • Sigma EF-530 DG = 4.3×
  • Metz 48 AF-1 = 3.5×
  • Promaster 7500EDF = 2.7×
  • Sakar 952AF/PEN, et al = 2.7×
  • Promaster 7400EDF = 2.1×
  • Pentax AF360FGZ = 2.0× (Of course.)

I note in particular that even though they have the tighter zoom, the Promaster flashes don't actually have the boost in power one might expect from the more focused beam. Either the numbers are suspect or their reflector doesn't do as much good as that from Metz, which is the clear winner from this narrow (pardon the pun) point of view. (The Metz flashes "gain" about 90%, the Sigma flash 75%, but the Promasters only about 50%. 58% and 43% for the Pentax AF540FGZ and AF360FGZ, respectively. It's all very non-linear.) And again, I don't really trust the Sakar/Digital Concepts number very much — but at least this time it's based on a number they publish, not just a guess.


Last edited by mattdm; 12-06-2008 at 11:28 PM. Reason: point to google knol for latest version
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04-02-2008, 04:25 PM   #31
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Thank you so much for your time. Actually I meant Auto as in - "I don't know what I'm doing please help me" - so I think P-TTL is fine!
How come nobody mentions Sunpak?

04-02-2008, 04:53 PM   #32
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And why doesn't B&H have Promaster? Can't find them in this country and really don't want to spread my credit card number too widely! Grrr.
04-02-2008, 07:08 PM   #33
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not sure why b&h doesn't have promaster- maybe they don't want to commit to the requirements? They would have to offer full support as well as replacement - b&h does not strike me as that sort of company - Why don't we ask Henry?

OK - it's loaded...

Last edited by Tom M; 04-03-2008 at 07:11 AM.
04-03-2008, 07:17 AM   #34
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Testing the Promaster 7500EDF flash gun in "Multi" mode - Set to 10/25



04-03-2008, 07:57 AM   #35
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Thanks for all the great info Tom. Exellent research and work. Thanks to Matt as well.

I've been searching for an alternative to the 540 (worried about reliablity since I do paid work) and was considering the Metz 58. The Metz has the option of an external battery pack but it's $500! at B&H. So the Promaster seems like the way to go. I think I'll get one and a 540 (I have a TR power pack for this and it's a great add on for a day of shooting). So I'll have a backup flash incase the 540 lets me down when I need it most.

I wrote Promaster to try and find a dealer in Canada but if they have non I may send you a PM and see if I can get one shipped out of the states in the next month or so.
04-03-2008, 11:12 AM   #36
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FYI - The appeal to Promaster in my opinion is that it is indeed a quality product that the manufacturer stands behind. But, not every retailer wants to carry the product because repair or warranty work is handled on the spot, in the store.. Meaning, if my unit breaks, I return it to the store for a replacement and THEY have to deal with the manufacturer.

Go here.. Promaster Look at what they offer. And, look closely at the LENSES they offer For example - Does this look familiar????
04-03-2008, 11:17 AM   #37
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Yeah, so...

I do appreciate the research into the promaster flash, but I was hoping for this thread to be more high-level. Can we take the detailed investigation and back-and-forth to the Accessories forum? Thanks!

EDIT: I am actually interested, but I'd just rather keep this clean, is all. Not trying to be a jerk or anything.

Last edited by mattdm; 04-03-2008 at 01:42 PM.
05-07-2008, 08:03 PM   #38
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updated

I added a few more numbers for the maximum-zoom GNs. This is relevant when shooting with focal lengths of about 57mm and up.

06-02-2008, 05:06 AM   #39
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I managed to quick test the RIVA/Lexus/Tumax SB-880AF. I strongly believe it has P-TTL but no swirl, manual, wireless or EV adjustment. Here's the test of ISO100 1/180s direct flash with no diffuser.

f2.8


f8.0


f9.5


Product details;
TUMAX SB-880AF

Also other rebrand model of Sakar 952AF/PEN are Lexus/Riva SB-3000AFP & DPT386AFZ-P
06-04-2008, 05:20 AM   #40
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I believe the Sakar 952AF/PEN GN is not 38 but around 30-32. The Riva SB-3000AFP is another rebrand of 952AF/PEN

Here's a compare with AF-360FGZ (GN 36 at 85mm ISO100)



06-04-2008, 05:26 AM   #41
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QuoteOriginally posted by zeek10d Quote
I believe the Sakar 952AF/PEN GN is not 38 but around 30-32. The Riva SB-3000AFP is another rebrand of 952AF/PEN
Interesting, thanks. I suspected the numbers were overstated given the price (and everything else). Any chance of testing against the AF360FGZ at 50mm? (Which is to say, approximately 33mm on a dSLR, since the flash numbers are all done in full-frame terms...)
06-04-2008, 07:09 AM   #42
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QuoteOriginally posted by mattdm Quote
...since the flash numbers are all done in full-frame terms...)
GN is derived from aperture x distance. There should be no difference at all whether measured "in full frame terms" or otherwise.
06-04-2008, 07:20 AM   #43
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Here you go^^ BTW these are ceiling bounced.



06-04-2008, 08:35 AM   #44
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QuoteOriginally posted by creampuff Quote
GN is derived from aperture x distance. There should be no difference at all whether measured "in full frame terms" or otherwise.
It matters for flashes with zoom reflectors. Having the flash set to the 50mm position (which is expressed in 35mm full-frame terms) is a standard measuring point for most flash makers so it's what I chose to use as a base for comparison.
06-04-2008, 08:37 AM   #45
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QuoteOriginally posted by zeek10d Quote
Here you go^^ BTW these are ceiling bounced.
Hmmm. Don't they both go to the widest zoom at that point?

Not trying to make you jump through hoops. I just want to be comparing roughly the same sort of fruit that manufacturers use in their own listed numbers.
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