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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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06-04-2008, 09:19 AM   #46
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QuoteOriginally posted by mattdm Quote
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.
No they dun, cos I set them to manual zoom.^^ So what u see are all 85mm and 50mm test. BTW for SB-3000 the manual stated GN36 at 85mm. My estimation is GN30-32 taken that AF-360FGZ is GN36

06-09-2008, 11:33 PM   #47
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I have the 952AF/PEN and if I go manual it's a pretty powerful flash but in pttl mode it underexposes and if you need a lot of power in pttl it cannot give it for some reason. I know that it can't give 100% because of how pttl works but it looks like it can't match even the 50% power. i.e. where 50% would expose perfectly, in pttl mode it will underexpose by some 2 stops.
06-10-2008, 02:08 AM   #48
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Deni, are you referring to the Digital Concepts flash in your signature? Are you sure it's really P-TTL? The flash can fire at full power. I'm assuming that it's the flash and compatablity with the camera. You may just have to use exposure comp or shoot in auto mode if the flash has a sensor.
06-10-2008, 07:38 AM   #49
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QuoteQuote:
Deni, are you referring to the Digital Concepts flash in your signature?
yes I am.

QuoteQuote:
Are you sure it's really P-TTL?
It has be. It does underexpose by about half a stop but it is consistent. If it wasn't pttl it wouldn't be consistent.

QuoteQuote:
You may just have to use exposure comp
I'm doing just that, but sometimes it'll underexpose massively even if I dial +2ev. I don't know if it's a problem with the flash or the batteries. I'm using eneloops.

QuoteQuote:
shoot in auto mode if the flash has a sensor
I haven't found an auto mode so I guess the flash doesn't have a thyristor sensor.

It can go manually to 1/16, 1/8, 1/4, 1/2 and full power manually though.

11-28-2008, 12:55 PM   #50
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Mixing Brands as Slaves

Has anyone fooled around with mixing flash models? I'm starting into some studio lighting/umbrellas using my AF-540 as slave (using onboard to trigger) and want to pick up a second strobe.

I seeking a AF-360, but would use an off brand if mixing brands/models will work.

Ideas?

Larry
11-28-2008, 02:12 PM   #51
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Mix them up as much as you like. Any brand and any type is fine. But if you are strictly firing the flashes with the camera's wireless system, You do have to stick with the Pentax 360 and 540. Some time ago I created the following thread and it helps to understand flash triggers https://www.pentaxforums.com/forums/pentax-camera-accessories/31950-those-con...-triggers.html
If you get serious about this you'll start to consider triggers for the range and reliability.
With triggers you can use any flash.

I use an AF540 and and AF360 as part of my portable studio setup with and AF400T as well. All are triggered with Flashwaves.

One word of caution though. There are a large number of older flash units that have very high trigger voltages and could damage the camera or the trigger because today's units are electronically switched and the old cameras were mechanical. The electronic switches are good up to 20 volts to a max of 30 volts. Some older flashes trigger at 200 to an extreme of 600 volts. The following web page has many user reports of tested flashes and their voltages. You should always test an old flash with a multi meter before use.

Photo Strobe Trigger Voltages
11-28-2008, 04:18 PM   #52
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QuoteOriginally posted by Peter Zack Quote
Mix them up as much as you like. Any brand and any type is fine. But if you are strictly firing the flashes with the camera's wireless system, You do have to stick with the Pentax 360 and 540.
Why's that?
11-28-2008, 04:33 PM   #53
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Actually I was in error. The Metz 48 and 58 will work and also the Sigma 530 as well correct? But do they work in PTTL when in wireless mode or just Auto or Manual? I don't own any of them so I'm not sure.

I'm pretty sure you are the resident expert Matt.

11-28-2008, 04:52 PM   #54
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QuoteOriginally posted by Peter Zack Quote
Actually I was in error. The Metz 48 and 58 will work and also the Sigma 530 as well correct? But do they work in PTTL when in wireless mode or just Auto or Manual? I don't own any of them so I'm not sure.

I'm pretty sure you are the resident expert Matt.
They work wireless. The Metz will work as a wireless slave and the 58 will work as the master or slave. They Metz 48 doesn't have an auto mode. I can't comment regarding the Sigma and Promaster models, but they also work p-ttl and certain ones work wireless.
11-28-2008, 04:58 PM   #55
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QuoteOriginally posted by Peter Zack Quote
Actually I was in error. The Metz 48 and 58 will work and also the Sigma 530 as well correct? But do they work in PTTL when in wireless mode or just Auto or Manual? I don't own any of them so I'm not sure.
They do P-TTL wireless. And actually, they don't do auto or manual wireless.

QuoteQuote:
I'm pretty sure you are the resident expert Matt.
Well, I'm trying. However, due to budget constraints I've never actually owned the Metz 58 AF-1 or Pentax AF540FGZ. And I returned the Sigma Super, and have only borrowed the AF360FGZ. And the Promaster flashes, only used in the camera store. That means most of my expertise is second-hand. But I have tried very hard to make sure it's all correct.
02-10-2009, 02:32 AM   #56
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Hi mattdm,

I am checking your GREAT pttl flash comparison page. I have the digital concepts flash and it can do wireless flash but only optical and it is fulled by the pre flash of pttl. I use it with an auto flash and it works fine that way.

I have a question about the 360 of pentax. Can it really do auto thyristor flash?
02-10-2009, 05:47 AM   #57
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QuoteOriginally posted by Deni Quote
I am checking your GREAT pttl flash comparison page. I have the digital concepts flash and it can do wireless flash but only optical and it is fulled by the pre flash of pttl. I use it with an auto flash and it works fine that way.
Do you mean it can work without being triggered prematurely by the preflash? Or that it is triggered every time? Or that it works and fires twice in succession, once for the preflash and once for the main flash?


QuoteOriginally posted by Deni Quote
I have a question about the 360 of pentax. Can it really do auto thyristor flash?
Yes, although it likes to revert to P-TTL mode whenever it goes to sleep.
02-18-2009, 06:45 PM   #58
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QuoteOriginally posted by Tom M Quote

Can anyone tell me where to buy one in the states?
Try OneCall . com. At this URL, (hope this isn't against the rules) ProMaster 7500EDF for Pentax Flash Unit - In Stock at OneCall.com
Promaster 7500EDF $229 plus about $8 shipping.

I bought the 7500DX from onecall.com about 2 years ago for Konica/Minolta and really like the flash. Can't comment on the Pentax version. I have the AF360FGZ for my K100D and I'm not as impreseed with it as I am with the 7500DX. Of course this isn't an apples to apples comparison.

BTW onecall.com is very good to deal with.
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