AF-540FGZ inconsistent results

stantheman · 10-12-2010, 08:54 PM

I do weddings on a very part-time basis. Since I got the AF-540FGZ, I have thought that the results were inconsistent. Shooting a wedding last weekend, it seemed worse. I would change the aperture or the exposure compensation trying to get a good exposure, and finally get a good picture. This would happen when the background of successive shots did not change, but the exposure would. It got a little embarrassing as I was constantly have to fool with my camera, taking 4 or 5 shots or more, where I would normally have done 2. I haven't looked yet, but I just hope the exposure on unique action shots was within a range that I can correct it.

I use it mounted off-camera, connected to a K20D. I set the camera exposure on manual.

wlachan · 10-12-2010, 08:55 PM

Set the flash to A instead of P-TTL which is a Pentax embarrassment.

stantheman · 10-13-2010, 07:59 PM

Thanks for the advice. Is this a problem that is acknowledged by Pentax, or one that users have discovered?

skyoftexas · 10-13-2010, 08:43 PM

Originally posted by wlachan

Set the flash to A instead of P-TTL which is a Pentax embarrassment.

I'm in the same boat as the OP except that I use a Metz 58 AF 1 dedicated to Pentax. I'm starting to get really exasperated with the inconsistent flash exposures. Is the pTTL problem with the camera or the flash?

**Ash** · 10-13-2010, 08:49 PM

This has been discussed a lot on the forum. P-TTL is far from perfect, it's not even consistent, but it is useable *once* your settings are put right.

I've just come off a wedding myself and realied how much fiddling it does take to get it working as expected, but once I got the result I wanted (after about 3 or 4 test shots) with a wireless setup, then I was set to go from then on. P-TTL managed to give *reasonably* consistent results thereafter. I'm not trying to defend P-TTL, just noting how it's worked for me in the past. Do a search on P-TTL and its inconsistency and you'll be surprised how many threads exist on it.

jboyde · 10-14-2010, 07:35 AM

Weird, mine have been pretty consistent. The only times I've had trouble is shooting with a mirror in front of me, then the flash underexposes like crazy. Another time is when I use multi-light setups in studio with my PTTL flashes. If I don't gobo them just right then flare messes up the exposure and doesn't fire some of the flashes.
I wonder if the exposure settings are what's making the inconsistency problems. I keep mine center-weighted while others might do full evaluative. I figure with evaluative that any change of lighting on the outside fringes of the viewfinder can affect what PTTL does. Just a theory.
I guess I'm trying to "debunk" the whole PTTL thing (knowing full well its not CLS by any means) because I keep thinking of an offshoot of Murphy's Law that says "if everything is working well, watch out...you have obviously overlooked something."

arm_jstp · 10-14-2010, 09:16 AM

I did many test and found that AF-200FG has very consistence results than the AF-540FGZ and AF-360FGZ. The worst result is from the 540, the 360 is better and 200 is the best.

Perhaps because the 200 is the newest model with some improvement in flash algorithm.

Entropy · 10-14-2010, 10:44 AM

What I have seen:

Certain aspects of a picture can drive any P-TTL flash to underexpose. Namely, any reflective surface that catches the flash.

Also, many AF-540s come from the factory calibrated improperly so that they *consistently* underexpose even with +1 FEC. The discovery of the trimpot under the "FIX->" label at least lets users fix this one. I'm a LOT happier with my 540 since that trimpot was discovered and I tweaked it. Prior to that, it would even underexpose when shooting a frame that was dominated by a matte black object (my shoulder bag from work) and set to +1 FEC.

There's a thread regarding the trimpot somewhere here, don't have the link on hand at the moment.

NeverSatisfied · 10-19-2010, 04:52 PM

+ 1, Entropy. I think quite a few of the complaints about the 540 underexposing may be related to the trimpot issue. Both my 540's trimpot adjustments were far from optimum.
https://www.pentaxforums.com/forums/pentax-camera-field-accessories/103779-in...x-flashes.html

SOldBear · 10-20-2010, 11:53 AM

The problem with p-TTL is not underexposure. It is the inconsistency. This problem is very pronounced with K10D and K20D. With my K10D bodies, I use p-TTL only when it's absolutely necessary.

The K7 (and subsequent models) is much improved. The exposure is more consistent.

p-TTL has the annoying preflash strobe. In general I try to avoid p-TTL when taking photos of people, especially of a group of people.

**Ash** · 10-20-2010, 12:24 PM - **1 Like**

Pre-flash exists with almost all new flash systems. It's perhaps the best way of automatically calculating flash intensity required for all types of scenes.

The inconsistency with Pentax is unfortunate but is gradually getting better with each camera. It would be interesting to see how the K-5 fares with the 540 flash in different situations.

On my K20D and K10D, with wireless setup and center-weighted metering, I get decently exposed portraits with P-TTL with FEC at +0.7 on the camera and anywhere between 0 and +1 on the flash. Fill flash, I just keep at FEC 0 on body and 0 on flash for best results most of the time.

Bob photo 4 life · 11-02-2010, 11:30 AM

I am also trying to learn my AF360 with KX combination. The thing I have noticed about PTTL is that it seems to try and preserve the natural look of the scene, in other words not creating the "bright subject, dark background".

When I first tried this unit, the pre-flash was obvious, but now I don't see it at all. Any suggestions on a good starting point for settings on camera and flash would be appreciated.

SOldBear · 11-02-2010, 11:39 AM

Originally posted by Bob photo 4 life

When I first tried this unit, the pre-flash was obvious, but now I don't see it at all.

In p-TTL, the pre-flash strobe is there. Most people can't tell that there are 2 strobes because they happen very close to each other (about 1/20 sec is my guess) and thus appear as one strobe.

To see the strobes apart, in p-TTL mode, set your camera to 2 sec timer delay. When you hit the shutter release, you will see the pre-flash strobe, then the mirror raising, then 2 second delay, then the shutter release and the main strobe.

**Ash** · 11-02-2010, 11:46 AM

Bob, the post right before yours describes the P-TTL settings that have been working for me for years.

Eruditass · 11-02-2010, 12:54 PM

Odd, on my K-x, I either get fine exposures or random super overexposed shots.

10-12-2010, 08:54 PM	#1
stantheman New Member Join Date: Oct 2010 Location: Louisiana Posts: 5	AF-540FGZ inconsistent results I do weddings on a very part-time basis. Since I got the AF-540FGZ, I have thought that the results were inconsistent. Shooting a wedding last weekend, it seemed worse. I would change the aperture or the exposure compensation trying to get a good exposure, and finally get a good picture. This would happen when the background of successive shots did not change, but the exposure would. It got a little embarrassing as I was constantly have to fool with my camera, taking 4 or 5 shots or more, where I would normally have done 2. I haven't looked yet, but I just hope the exposure on unique action shots was within a range that I can correct it. I use it mounted off-camera, connected to a K20D. I set the camera exposure on manual.

10-13-2010, 08:43 PM	#4
skyoftexas Senior Member Join Date: Dec 2009 Location: United States Posts: 156	Same for Metz 58 AF 1? Originally posted by wlachan Set the flash to A instead of P-TTL which is a Pentax embarrassment. I'm in the same boat as the OP except that I use a Metz 58 AF 1 dedicated to Pentax. I'm starting to get really exasperated with the inconsistent flash exposures. Is the pTTL problem with the camera or the flash?

10-19-2010, 04:52 PM	#9
NeverSatisfied Veteran Member Join Date: Dec 2007 Location: S.E. Michigan Photos: Albums Posts: 688	Related Thread + 1, Entropy. I think quite a few of the complaints about the 540 underexposing may be related to the trimpot issue. Both my 540's trimpot adjustments were far from optimum. https://www.pentaxforums.com/forums/pentax-camera-field-accessories/103779-in...x-flashes.html

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10-12-2010, 08:55 PM	#2
wlachan Veteran Member Join Date: Sep 2006 Location: Canada Photos: Albums Posts: 2,625	Set the flash to A instead of P-TTL which is a Pentax embarrassment.

10-13-2010, 07:59 PM	#3
stantheman New Member Join Date: Oct 2010 Location: Louisiana Posts: 5 Original Poster	Thanks for the advice. Is this a problem that is acknowledged by Pentax, or one that users have discovered?

10-13-2010, 08:49 PM	#5
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	This has been discussed a lot on the forum. P-TTL is far from perfect, it's not even consistent, but it is useable once your settings are put right. I've just come off a wedding myself and realied how much fiddling it does take to get it working as expected, but once I got the result I wanted (after about 3 or 4 test shots) with a wireless setup, then I was set to go from then on. P-TTL managed to give reasonably consistent results thereafter. I'm not trying to defend P-TTL, just noting how it's worked for me in the past. Do a search on P-TTL and its inconsistency and you'll be surprised how many threads exist on it.

10-14-2010, 07:35 AM	#6
jboyde Veteran Member Join Date: Apr 2009 Location: New York Posts: 328	Weird, mine have been pretty consistent. The only times I've had trouble is shooting with a mirror in front of me, then the flash underexposes like crazy. Another time is when I use multi-light setups in studio with my PTTL flashes. If I don't gobo them just right then flare messes up the exposure and doesn't fire some of the flashes. I wonder if the exposure settings are what's making the inconsistency problems. I keep mine center-weighted while others might do full evaluative. I figure with evaluative that any change of lighting on the outside fringes of the viewfinder can affect what PTTL does. Just a theory. I guess I'm trying to "debunk" the whole PTTL thing (knowing full well its not CLS by any means) because I keep thinking of an offshoot of Murphy's Law that says "if everything is working well, watch out...you have obviously overlooked something."

10-14-2010, 09:16 AM	#7
arm_jstp Veteran Member Join Date: Apr 2009 Location: Blacksburg, VA Posts: 485	I did many test and found that AF-200FG has very consistence results than the AF-540FGZ and AF-360FGZ. The worst result is from the 540, the 360 is better and 200 is the best. Perhaps because the 200 is the newest model with some improvement in flash algorithm.

10-14-2010, 10:44 AM	#8
Entropy Veteran Member Join Date: Jun 2007 Location: Owego, NY Posts: 976	What I have seen: Certain aspects of a picture can drive any P-TTL flash to underexpose. Namely, any reflective surface that catches the flash. Also, many AF-540s come from the factory calibrated improperly so that they consistently underexpose even with +1 FEC. The discovery of the trimpot under the "FIX->" label at least lets users fix this one. I'm a LOT happier with my 540 since that trimpot was discovered and I tweaked it. Prior to that, it would even underexpose when shooting a frame that was dominated by a matte black object (my shoulder bag from work) and set to +1 FEC. There's a thread regarding the trimpot somewhere here, don't have the link on hand at the moment.

10-20-2010, 11:53 AM	#10
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	The problem with p-TTL is not underexposure. It is the inconsistency. This problem is very pronounced with K10D and K20D. With my K10D bodies, I use p-TTL only when it's absolutely necessary. The K7 (and subsequent models) is much improved. The exposure is more consistent. p-TTL has the annoying preflash strobe. In general I try to avoid p-TTL when taking photos of people, especially of a group of people.

10-20-2010, 12:24 PM - 1 Like	#11
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	Pre-flash exists with almost all new flash systems. It's perhaps the best way of automatically calculating flash intensity required for all types of scenes. The inconsistency with Pentax is unfortunate but is gradually getting better with each camera. It would be interesting to see how the K-5 fares with the 540 flash in different situations. On my K20D and K10D, with wireless setup and center-weighted metering, I get decently exposed portraits with P-TTL with FEC at +0.7 on the camera and anywhere between 0 and +1 on the flash. Fill flash, I just keep at FEC 0 on body and 0 on flash for best results most of the time.

11-02-2010, 11:30 AM	#12
Bob photo 4 life Forum Member Join Date: Jun 2010 Location: Oregon Posts: 81	I am also trying to learn my AF360 with KX combination. The thing I have noticed about PTTL is that it seems to try and preserve the natural look of the scene, in other words not creating the "bright subject, dark background". When I first tried this unit, the pre-flash was obvious, but now I don't see it at all. Any suggestions on a good starting point for settings on camera and flash would be appreciated.

11-02-2010, 11:39 AM	#13
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Originally posted by Bob photo 4 life When I first tried this unit, the pre-flash was obvious, but now I don't see it at all. In p-TTL, the pre-flash strobe is there. Most people can't tell that there are 2 strobes because they happen very close to each other (about 1/20 sec is my guess) and thus appear as one strobe. To see the strobes apart, in p-TTL mode, set your camera to 2 sec timer delay. When you hit the shutter release, you will see the pre-flash strobe, then the mirror raising, then 2 second delay, then the shutter release and the main strobe.

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11-02-2010, 11:46 AM	#14
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	Bob, the post right before yours describes the P-TTL settings that have been working for me for years.

11-02-2010, 12:54 PM	#15
Eruditass Veteran Member Join Date: Jul 2009 Photos: Gallery Posts: 2,207	Odd, on my K-x, I either get fine exposures or random super overexposed shots.