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05-23-2011, 08:34 PM   #256
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Thanks Entropy. Can't wait to see the samples.

05-23-2011, 11:04 PM   #257
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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.
05-24-2011, 06:43 AM   #258
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QuoteOriginally posted by dtsui Quote
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.
I believe the trimpot seems to be working for on-camera, but not off-camera. Unfortunately, due to the significant deltas between bounce and non-bounce exposure, it's impossible to adjust the trimpot properly for the 5.
05-25-2011, 01:52 AM   #259
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Excuse me, but what the hell do you mean by "trimpot"?

05-25-2011, 05:25 AM   #260
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QuoteOriginally posted by simico Quote
Excuse me, but what the hell do you mean by "trimpot"?
See this post in dpreview AF540FGZ hidden adjustment trimpot: Pentax SLR Talk Forum: Digital Photography Review.
05-25-2011, 09:02 AM   #261
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QuoteOriginally posted by dtsui Quote
Which is also discussed here - https://www.pentaxforums.com/forums/pentax-flashes-lighting-technique/103779-...x-flashes.html (I linked to that thread in my post on the previous page of this one...)
05-25-2011, 10:20 PM   #262
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QuoteOriginally posted by AussieTrev Quote
Well I set up a bit of studio in the lounge room. Blue back drop with a little back light coming through. My K with both my 540 and 360 reflected with umbrellas. then I went nuts and was shooting just my wife, then both of us. All shots have no significant exposure problems. I used Av first then full M. Still no exposure problems. Well the battery went flat on the K5, I haven't got a spare yet. Switched to my K20D same lens 16-50 f2.8 again very similar results with exposure. Afterwards I realised that I had the K20D set at 1600 ISO with the K5 at 400. Results were very similar, except with the 600 ISO they had a bit of grain. I even then had the wife shoot with her K20D at 200 ISO. We swapped to the 105 Sigma macro again consistent results.

We did drop the flash compensation and raise it from time to time, but then we were getting creative. Again very consistent results. We switched to shoot through umbrellas again consistent results. As I posted previously I have even shot with the 540 and a diffuser on and off camera, again consistent results.

In short I am way happy so far, except I should have ordered a second battery.

I will try and post some of the results as soon as I get time.

Hope this helps.
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.
05-26-2011, 02:47 AM   #263
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QuoteOriginally posted by dtsui Quote
Ah, ok. I know that, just didn't know it's called "trimpot" (never heard this word before and my dictionary also doesn't know it). Thanks!

05-26-2011, 03:31 AM - 1 Like   #264
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"trimpot" is the shorthand for trimmer potentiometer.
05-29-2011, 08:16 AM   #265
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I previously owned a K10 and Metz 58 AF-1 and the exposure was spot on in PTTL or Auto mode. With The K5 in PTTL i always get overexposed pictures even at ISO 80. In Auto mode all pictures are good. Definitely a problem with K5 IMO.....
05-31-2011, 08:29 AM   #266
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Unfortunately I wasn't able to get around to my samples run this past week/weekend - Half of my county lost power due to severe storms Thursday evening, I didn't get power back until Saturday and Internet back until Sunday, others in the county still don't have power.
06-22-2011, 06:04 PM   #267
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QuoteOriginally posted by dtsui Quote
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.
G'day Dtsui

I may be a little late to the party here, but I just did exactly what you asked.

K-5 rather than K-7, but when progressing the zoom through the range (on camera, pointed straight up, reflector card out, but not diffuser) I get almost exactly the same exposure for each frame. The histogram has a peak on the right at approximately the 2/3 mark. It seems my 540g/k-5 is working as it should, adjusting the flash output with change in flash angle with relation to the subject.

I'll try the same with my k-7 and see if there is any difference.

Cheers
06-22-2011, 06:10 PM   #268
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ok, I just did the same thing with the K-7 and got similar results. The peak is further to the left (at exactly the same lens, shutter, speed and ISO settings) but the exposure is almost identical throughout the flash zoom range.

Interesting
06-22-2011, 06:25 PM   #269
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I just did exactly the same procedure with my K-5/540, and got consistent exposures throughout the flash zoom range.
06-22-2011, 10:43 PM   #270
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i did check it as well, the overexpoure without built in diffuser of the flashgun is just a little bit less pronounced than with it... for about 0.7 EV. However im getting consistent results with and without diffuser, the only difference is i set -1.0EV flash compensation without diffuser and -1.07EV with diffuser. To get exact exposure i need to change compensation depending on iso applied, the higher iso the more compensation i need.
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