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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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03-21-2008, 01:02 AM   #2
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There's also the flash from digital concepts. I have it and IT IS a p-ttl flash and can be controlled wirelessly by the onboard flash. Has tilt and swivel, front and rear curtain.
03-21-2008, 07:11 AM   #3
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QuoteOriginally posted by Deni Quote
There's also the flash from digital concepts. I have it and IT IS a p-ttl flash and can be controlled wirelessly by the onboard flash. Has tilt and swivel, front and rear curtain.
Is that the "Sakar Digital Concepts 952AF TTL Power Zoom Bounce & Swivel Flash for Pentax & Samsung"? Sakar

Can you look up some things in the manual? What guide numbers do they claim? I found a listing at BuyDig which says 42m at 85mm. Do they happen to also give a 50mm rating? And what are the minimum and maximum zoom settings?

Thanks!!
03-21-2008, 10:00 AM   #4
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Not to mention some users of the Promaster flash say it's p-ttl as well but nothing in the literature saying it is- it just works for some reason.

03-21-2008, 10:14 AM   #5
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QuoteOriginally posted by mattdm Quote
Is that the "Sakar Digital Concepts 952AF TTL Power Zoom Bounce & Swivel Flash for Pentax & Samsung"? Sakar

Can you look up some things in the manual? What guide numbers do they claim? I found a listing at BuyDig which says 42m at 85mm. Do they happen to also give a 50mm rating? And what are the minimum and maximum zoom settings?

Thanks!!
The compatibility listing indicates that the Sakar flash is TTL rather than P-TTL, putting it into the same situation as my AF500FTZ - it don't work any more.

Guide numbers for the Sakar of 42 in meters at 85mm compare to the Pentax by simply taking the last zero off the flash model number. The AF540FGZ has a guide number of 54 in meters at 85mm, the AF360FGZ has a guide number of 36 in meters at 85mm at 100 ISO, my AF500FTZ has a guide number of 50 in meters at 85mm at 100 ISO.
03-21-2008, 10:19 AM   #6
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I just did a little looking into that Promaster flash and here's what I come up with..

Promaster 7500 EDF 7273

Complete compatability with theK10D, K100D, etc http://www.promaster.com/books/7000series.pdf

For some reason, I think Promaster is saying 'digital ttl' instead of p-ttl-because they do the same for each manufacturer.

Have a look here too Promaster

Can anyone tell me where to buy one in the states?
03-21-2008, 10:19 AM   #7
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QuoteOriginally posted by mattdm Quote
There are currently three flashes made by Pentax which work with the P-TTL flash metering system, plus two from Metz and one from Sigma.
you need to add 7500EDF, 7500DX, 7400EDF, 7200EDF from Promaster ...
03-21-2008, 10:20 AM   #8
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QuoteOriginally posted by Tom M Quote
I just did a little looking
beat me by a second

03-21-2008, 12:44 PM   #9
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Those companies just increase my annoyance with the lack of power information provided — they only tell numbers for the most narrowly-focused beam, which of course gives the biggest most impressive number. Fairly or not, that makes me extra suspicious of their data overall. But if it can be trusted as well as anyone else's, looks like the Sakar Digital Concepts 952AF fits between the Metz 48 AF-1 and Pentax AF360FGZ in power, and the most powerful Promaster (7500EDF) at about the level of the AF360FGZ (but with a zoom head that goes to 105 instead of just 85).

I wouldn't be surprised if the non-zoom Promaster 7200EDF is just the same as the 7400EDF without the zoom, which then makes me wonder how they're measuring the GN given for that — the listed "100" at the coverage angle of 28mm for 35mm would make it about 10% more powerful than the number Sigma gives for the EF-530 DG at 28mm, and I'm skeptical of that, given that the 7400EDF is less than half as powerful at 105mm.
03-21-2008, 01:08 PM   #10
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I'd be weary calling the Digital Concepts 952AF flash P-TTL.
Deni, if you believe it is, do tell us the specs and your experience using it.
Modes on the flash (ie P-TTL? A? M?),
Reliability exposing in direct and bounce flash in "P-TTL" mode,
Wireless performance,
Manual power settings.

I had the next model down once, for a few days, and was totally disappointed. Wasn't worth the packaging it came in for a K10D/K100D. TTL? Maybe. P-TTL? No way.
03-21-2008, 01:30 PM   #11
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QuoteOriginally posted by mattdm Quote
Those companies just increase my annoyance with the lack of power information provided — they only tell numbers for the most narrowly-focused beam, which of course gives the biggest most impressive number. Fairly or not, that makes me extra suspicious of their data overall.
Promaster has all tables in manual = http://www.promaster.com/books/Instructionmanuals/7500EDF_Digital_Flash.pdf
03-21-2008, 06:57 PM   #12
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QuoteOriginally posted by deejjjaaaa Quote
Huh, good for them. That's actually pretty much the best manual (in English, at least) of any of these brands.

That puts the 7500EDF at about 2.4× on the scale for 50mm guide numbers above.
03-22-2008, 07:11 PM   #13
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The Promaster is definitely P-TTL - Spoke to a Pentax dealer who sells them and he highly recommended it. He had the 7500ED but wanted $279. It's a nice flash! Now I just need to find it online for cheap!
03-23-2008, 05:46 AM   #14
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QuoteOriginally posted by Tom M Quote
The Promaster is definitely P-TTL - Spoke to a Pentax dealer who sells them and he highly recommended it. He had the 7500ED but wanted $279. It's a nice flash! Now I just need to find it online for cheap!
I'd like to carry on with this discussion in the Camera Accessories forum — can anyone interested join me over there? Thanks. Meanwhile, I'll add 'em to the chart above.
03-23-2008, 11:11 PM   #15
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I have a promaster 5750dx with the 5050dxr. I love it! Got it for less than $150 on flebay.
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