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Forum: Pentax K-5 & K-5 II
03-07-2013, 08:54 AM
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In the beginning my K10D suffered bad underexposure with AF540FGZ but then I discovered a fix on this forum, a very serviceable fix indeed. There is a trimpot (trimmer potentiometer) hidden beneath the FIX label just above the hotshoe of the AF540FGZ. By adjusting this trimpot, the sensitivity towards underexposure can be much reduced to almost non-existent. The presence of the trimpot on the flash is an indicator that Pentax is struggling with matching the flash to the camera. For some unknown reason, perhaps Pentax engineers thought they got smart with a new PTTL algorithm, they decided to ditch the function of the trimpot from K7 forward. I have since confirmed the trimpot has absolutely zero effect on the flash exposure for the K7. This is a bad move for me because the last hope of taming this overexposure problem is lost.
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Forum: Pentax K-5 & K-5 II
03-05-2013, 11:23 PM
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I understand not everyone experience this problem in the field but anecdotal evidence clearly points to a sizable user population that has this problem which affects four to five different models. If I were Pentax management, that is enough evidence for concern. In fact I believe the problem was not noticed by an even bigger population of users because Pentaxians have got used to the poor PTTL performance in the earlier generations of models, e.g. istDS, K10D, K20D that they have workaround the problem using various means or they just don't use external flash any more.
If Pentax were aware of the problem (they must be) even though it may affect only a certain percentage of the products, they are still deliberating selling defective products to consumers without any intention of fixing it. The fact that the problem has spread from K7 in the beginning to now five models in a period of four years is testament to this. This is very shady business practice.
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Forum: Pentax K-5 & K-5 II
03-04-2013, 10:12 PM
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I started this discussion back in 2011 writing about my experience and findings with K7 overexposure with bounce PTTL flash. See K5 bounce flash overexposure - mystery solved! MUST READ!: Pentax SLR Talk Forum: Digital Photography Review and similar threads. I have since disappeared from all Pentax forums for over a year and I am both surprised and also felt relief to discover more people who own the latest models are also experiencing this issue. This shows the resolute of Ricoh-Pentax to bury its head in the sand to the protest of its customers and a long-suffering Pentax populace. I do not think we as consumers have stood up to our rights and demand Ricoh-Pentax takes firm and prompt actions to resolve this issue and vote with our feet if Pentax fails to bow to pressure. Instead we as a community have chosen to use our ingenuity to develop workarounds and band-aid fixes to solve a problem that rightly belongs to the manufacturer. I cannot imagine Canonians or Nikonians would be so kind and patient if a problem of similar nature or magnitude happen to their equipment.
David
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Forum: Pentax K-5 & K-5 II
06-23-2011, 03:14 AM
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wizofoz, I am convinced the different behaviour is the result of subtle difference in the camera hardware even though the firmware may be the same.
Can you tell me the serial no. of your K7 and K5 and the firmware version of the K7?
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Forum: Pentax K-5 & K-5 II
05-26-2011, 03:31 AM
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"trimpot" is the shorthand for trimmer potentiometer.
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Forum: Pentax K-5 & K-5 II
05-25-2011, 10:20 PM
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I am wondering whether the OP can confirm that with his setup, whether the flash heads are actually in the zero degree position. My experience with the K7 and AF540 in an on-camera bounce setup, it is only when the flash head deviates from zero degree that PTTL starts to misbehave. Exposure is fine with the flash head at zero degree.
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Forum: Pentax K-5 & K-5 II
05-25-2011, 05:25 AM
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Forum: Pentax K-5 & K-5 II
05-23-2011, 11:04 PM
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Entropy, I can also confirm that the trimpot is effective for adjusting exposure on the K10D but it has no effect whatsoever on the K7. Can you confirm whether the trimpot affects exposure on your K5? This suggests the PTTL algorithm has changed between two camera generations, K10D/K20D and K7/K5.
I, however, have a very different experience with off-camera wireless PTTL with the K7, instead of underexposure, it overexposes severely (>2 stops).
Can wait to see your test results.
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Forum: Pentax K-5 & K-5 II
05-22-2011, 11:37 PM
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I can't resist chiming in...can anyone please do a quick test to confirm the following on your K5/K7 + AF540/AF360:
Fix a focal length on your lens, set aperture to f/4 or f/5.6
Set camera to M mode, ISO between 200-400
Point flash to ceiling, pull out the reflector card but not the diffuser panel
Change the zoom setting on your flash (by pressing the ZOOM button) and observe whether exposure varies in accordance with the zoom setting.
On my K7+AF540+Sigma 17-70mm, the exposure will steadily decrease from 16mm to 58mm (on the flash), normal exposure is usually achieved at 34mm.
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Forum: Pentax K-5 & K-5 II
05-19-2011, 08:19 PM
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Sigma 17-70 f2.8-4.5 at f/4 to f/5.6. ISO200-400 in A or M. Bounce to ceiling about 2.7m high, at 75 deg.
I think this is quite typical of most bounce shots.
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Forum: Pentax K-5 & K-5 II
05-18-2011, 03:38 PM
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I was told by CR Kennedy that no other person has sent in a camera with a similar problem before. I cannot imagine I am the only one on the planet that has this problem. I think a significant number of users just work around the issue, using either manual control or Auto A or just accept this is the way it is or they just do not shoot flash at all. This lets Pentax gets off the hook too easily. Had the same problem happened in either Canon or Nikon camp, their users may be filing law suits already.
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Forum: Pentax K-5 & K-5 II
05-18-2011, 01:30 AM
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I don't have a K5 but my K7 with AF540 behaves in very similar manner to what people described here with their K5 and that is overexposure in bounce flash particularly at wide angle shots and close distance. I noticed one thing that no one else seemed to have mentioned before, that the exposure is dependent on the zoom angle on the flash unit. If I manually changed the zoom angle on the flash I could vary the exposure from overexposure at the wider angles 16,19 to underexposure with 48,58, etc. all on the same scene, at the same lens angle and the same f/stop. This should not have happened with PTTL at all. I tested this with my K10D and it certainly did not behave in this manner.
I also experienced massive overexposure with the K7, >2 stops, with wireless off-camera PTTL flash which corresponds with the experience of some K5 users.
In mid-Feb, I managed to persuade the Pentax agent in Australia (CR Kennedy) to send the camera and flash back to the factory in Japan to get them examined. It was to my utmost disappointment that after 3 months of delay, the factory handed down the verdict: there is nothing wrong either with the camera or the flash!!!
What more or else could I do? I can sympathise with those K5 owners who are in a similar situation. To me it looks like a issue that can be easily rectified by a firmware upgrade. Yet after months this problem went public Pentax has yet to come up with a solution or even denied the problem exists. I am deeply disappointed by their attitude to say the least.
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Forum: Pentax K-5 & K-5 II
12-09-2010, 06:33 AM
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Try turning on Highlight Correction, it helps on my K7 and AF540. I think PTTL metering is either too primitive or flawed, it should not rely on tricks to achieve correct exposure. Interestingly, the K10D/K20D is just the opposite, underexposure is the norm with bounce flash. I do not understand why Pentax has so far failed to come up with a solution for this issue given other manufacturers have mastered it for such a long time.
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Forum: Pentax K-5 & K-5 II
12-08-2010, 11:51 PM
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I have a similar problem with my K7 and AF540, the overexposure is dependent on the zoom setting on the flash. Manually set the zoom and avoid the widest setting and see if it helps.
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Forum: Flashes, Lighting, and Studio
09-24-2010, 06:28 PM
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The camera was on M and the flash head was tilted 75 deg up with the white reflector drawn out during bounce.
Auto mode is set on the flash, press the mode button on the flash once and it will change to A. Before TTL flash was invented, it was called Thyristor Auto. In this mode, PTTL metering in the camera body is disabled the exposure is determined by the flash using its internal metering.
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Forum: Flashes, Lighting, and Studio
09-24-2010, 07:53 AM
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Just to show some examples what I am talking about. Shot with K7 and AF540FGZ f/4 1/50 ISO 200 M-mode multi segment metering.
Set 1 PTTL direct
Set 1 PTTL bounce
Set 1 Auto bounce
Set 2 PTTL direct
Set 2 PTTL bounce
Set 2 Auto bounce
Set 1 PTTL bounce is clearly overexposed (wall at top is blown out) while PTTL direct is ok while Set 2 both PTTL direct and bounce came out spot on. I suspect with a K10D, set 2 would come out underexposed. The A mode photos serve as comparison.
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Forum: Flashes, Lighting, and Studio
09-24-2010, 12:08 AM
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I have two problems with my K7 and AF540FGZ and I am wondering whether anyone has such experience:
1. The combo has a tendency to overexpose with PTTL bounce flash especailly with a darker/middle grey subject in the middle against a light color wall. The wall will come out overexpose. A lighter subject is okay. This is quite the opposite to my K10D. No such problem with direct flash, both external and built-in. I tested this in P/Av/Tv modes. I have tried turning 'Linked AE to AF' on/off but with no effect. Metering patterns also has no effect.
2. When the ambient light is very low or in complete darkness, bounce flash comes out heavily overexposed (aporox +2 stops). Direct flash is fine, both external and built-in.
Lenses do not make any difference. I am trying to figure out whether it is a camera or flash problem.
David
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Forum: Pentax DSLR Discussion
08-01-2010, 08:25 PM
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I had similar experience on my K7. I used to adjust the AF under tungsten light using a focus chart. However on field tests of far away objects focus is always off by a margin. I found that a better way is to adjust AF using far away subjects (just tune AF until subject is the sharpest, I usually focus on number plates), it is then good under tungsten light as well (haven't recheck whether it is exactly spot on with a focus chart) but at least it is sharp under field conditions.
David
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Forum: Pentax DSLR Discussion
02-14-2010, 08:12 PM
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I am tempted to go for K-x because of its great value for money.
In Australia K7 is almost double the price of K-x so it's hard to justify for a K7 given K-x featurewise is so close to K7, not to mention its great high ISO performance. Whether a rugged body, weather seals, quieter shutter, more buttons and dials, AF adjustment, top LCD, pentaprism viewfinder, AF points overlay and rechargeable Li-ion battery are worth double the price depends a lot on the individual.
The other consideration is the cost of ownership over the relatively short lifespan of digital SLRs because of the rapid pace of technological improvement. Unless one absolutely need those advanced features and cannot live without them the K-x represents much better value for money.
David
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Forum: Pentax DSLR Discussion
05-07-2008, 06:50 PM
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Great! I learned something new as well:) SL2 can also be used if you have a non-Pentax flash attached to an optical slave sensor. I have a Nikon SB-26 with a integrated optical slave sensor and a AF540. In a dual flash setup, the SB-26 won't fire properly if the AF540 is on SL1.
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Forum: Pentax DSLR Discussion
05-07-2008, 12:19 AM
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HTML Code:
You can not use the onboard flash in wireless mode if you do not have a modern lens attached to the body. This is a huge annoyance for me. I like to have my AF540 off of the camera body when I shoot, so I use the onboard flash as the optical trigger. BUT you cannot be in wireless mode if the camera can't use P-TTL, which is fine for some purposes, but what about us folks who like to put their off-body flash units in manual mode and don't need any metering? I don't have a vintage Asahi lens so I can't verify whether this will work or not but it is worth trying. It is possible to put the AF540 in optical slave mode which is one of two wireless modes supported by the flash. To do that you push the LIGHT button on the flash for at least 2 secs until SL1 appears on the LCD. Push the S button on the flash to change to SL2, confirm the setting by pressing LIGHT again (refer to p52 on the flash manual)
Take the flash off the camera and put it in wireless mode as usual making sure it is in Slave mode. If you want to you can select M mode on the flash and vary the output level as desired.
Raise the flash on the K10D, knock down flash compensation to -2 and fire away. The idea of -2compensation is to turn it into a trigger by significantly weakening the output compare to the off-camera flash. You may want to experiment with different compensation. You should be able to use whatever exposure mode on the camera as well.
Let me know if this works.
David
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Forum: Pentax DSLR Discussion
05-01-2008, 12:55 AM
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Can someone who owns a K10D with any Sigma lens (17-70mm is desirable) and a Pentax AF360/540FGZ flash run a test for me tonight in the dark and tell me what your experience is?
I am keen to eliminate the possibility that my K10D body or flash is screwing up the focusing.
David
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Forum: Pentax DSLR Discussion
04-30-2008, 11:19 PM
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I used AF-S mode and select the centre AF point.
And btw I live in Australia so I can't send the lens to Sigma US.
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Forum: Pentax DSLR Discussion
04-30-2008, 10:00 PM
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The OOF is immediately apparent on the LCD when magnified to 4x. It is grossly OOF, not just a tiny bit. I actually ran a test to examine the change in focus on the distance scale, the focus consistenly falls behind the subject by about 0.5m whenever the AF beam fires. In terms of AF speed, I would say it is roughly the same as if it was focusing in a dim environment without AF beam firing, in other words, slooo...w.
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