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03-23-2014, 04:45 PM   #1
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K3 aggressively underexposes with flash?

I've tried hunting for info, but some of the existing threads were hijacked and went off the rails... I hate to re-hijack.

Anyway, I have a K-3 and am comparing it to my K-5. Works great in most cases.
Where it is a HUGE FAIL, is when using flash.



I take what you might call "product shots' on the side. Nothing pro, just products for a local thrift store raising funds for a animal shelter. But I have been doing this for several years with my K5 and have a setup that gives predictable results 99% of the time using the flash in PTTL mode. Naturally, I get the stray excessive specular highlight (P-TTL's Kryptonite) and have to adjust things once in a while.

But with the K3 (firmware updated to 1.03), I have a success rate of about 10% or less!!
I see similar behavior with and without specular highlights.
I have to jack up the exposure compensation 3-4 full stops to get a decent image. Its just crazy!

I have a af540fgz attached. I've used full power as well as -1.5 stops of power (P-TTL mode).
The camera is in AV mode at ISO 100 and f/3.5.

I can't figure out what is going on.
I can see and hear that the flash output is greatly diminished with the K3 so that is the obvious reason for the underexposure, but I can't figure out what the camera thinks it is seeing.

One thing I noticed is that with the K5, the EXIF data shows data values in the 9 - 12 range for "Flash Metering Segments".
The K3 on the other hand is showing all 0's!! WTF?

Is my new K3 broken?

You can see the DNG files here;
test_K3.DNG
test_K5.DNG

---------- Post added 03-23-14 at 07:54 PM ----------

Oh, important info.... the flash head is pinter straight up with a large reflector -- somewhat like the Rouge Flashbender.
I have not shot with the head straight forward yet (I almost never shoot that way but I guess I'll give it a go for testing).


Last edited by amoringello; 03-23-2014 at 05:07 PM.
03-23-2014, 05:33 PM   #2
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It might be stupid but is your K3 flash mode set to Wireless? In this mode, the flash will barely fire... Should be set to flash ON.
03-23-2014, 06:10 PM   #3
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QuoteOriginally posted by amoringello Quote
Is my new K3 broken?
It is hard to say. I have had the occasional underexposed P-TTL flash image from my K10D, but usually it was a situation where one or more elements in the scene were white or had potential for specular highlights or when I did the exposure before the flash was ready.

I might suggest a manual flash setup for product shots.


Steve
03-23-2014, 06:27 PM   #4
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It should work fine. I suspect some settings or hardware problem. Can you set the AF540 to slave mode, the body to wireless controller, and see what happens?

I have a metz af50 and it works fine bounce, slave, direct, whatever.

Another thing to check is if you have the body set to spot metering. It is literally spot, quite dramatic and can throw exposure way off.

03-23-2014, 06:56 PM   #5
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QuoteOriginally posted by derekkite Quote
It should work fine. I suspect some settings or hardware problem. Can you set the AF540 to slave mode, the body to wireless controller, and see what happens?
I have a metz af50 and it works fine bounce, slave, direct, whatever.
Another thing to check is if you have the body set to spot metering. It is literally spot, quite dramatic and can throw exposure way off.
Prior models used the entire sensor for flash metering regardless of the setting on the camera.
Does the K3 change that behavior?
Regardless, I have Center Weighted metering set on the camera.


FYI, K3 is not in wireless. Oddly, some photos turn out perfectly fine.
Prior the the K5, specular highlights caused a horrible time trying to predict of the flash would work properly or not. The K5 seemed to fix this, but my K3 seems to have reverted to prior behavior with a vengeance and the problems is orders magnitudes greater than before.
I wonder if the white background is being "seen" as a large specular highlight? Not sure how to fix that since it is not over exposed at all, i.e. not a super large specular highlight.

Additionally, aiming the flash head straight forward "fixes" the problem... of course that gives an absolutely abysmal result with harsh straight on lighting and shadows.
Sort of leads me to a hardware problem but the flash works on the K5, so it must be a K3 software problem???????????

---------- Post added 03-23-14 at 10:00 PM ----------

HA! Found the answer! The K3 sucks!

Well, removing the white background resolves the problem.
Of course I am left with whatever is behind the white board.

So apparently the K3 sees the white background as a huge specular highlight.
What BullS--t!


I would love to hear if anyone else does not have similar issues.
03-23-2014, 07:14 PM   #6
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Try dialing some +EV comp in before the shot. I would start with +2EV. Remember exposure meters try to turn everything into middle gray.
03-23-2014, 07:36 PM   #7
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I get that underexposure problem with P-TTL and bouncing off wall or ceiling if I'm real close to the subject. If I move back at least 2 feet from subject I get near perfect exposures every time. So if I need to get real close, now I just put the flash on manual. P-TTL does seem to behave differently between K-5 and K-3. I notice a strange delay between pressing the shutter release and when the first pre-flash fires. (K-3 with AF540FGZII)
03-23-2014, 08:25 PM   #8
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Remember that there was some acknowledgement from Pentax of the inconsistent exposure of P-TTL flash on all Pentax DSLRs.

Pentax implied that they had tracked the inconsistent exposures to flash circuitary which is hard wired into the cameras. This is why a firmware patch will not fix the problem.

Pentax used different circuitary in the K-3 that now lets P-TTL get correct exposure more often. there may be other changes to flash metering and flash in general in the K-3 as well.

I guess for you it means re-learning P-TTL flash from what you had been using on your K-r.

Regards

Chris

03-23-2014, 10:05 PM   #9
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Look at the EXIF for your K-3 images.
What does it say of the flash metering?
03-24-2014, 02:27 AM   #10
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QuoteQuote:
Look at the EXIF for your K-3 images.
What does it say of the flash metering?
EXIF for Flash Metering Segments is ALL 0's for the K3.
For the K5, all metering is in the range of 9-12.

When the flash head is pointing straight ahead, metering data on the K3 matches the range 9-12.
So I guess that's my answer. The K3 is broken and does not properly handle PTTL !!

NOT HAPPY AT ALL!!!


QuoteQuote:
Try dialing some +EV comp in before the shot. I would start with +2EV. Remember exposure meters try to turn everything into middle gray.
Yeah, I realize what metering does (or supposed to do), but one can hardly call what I am getting in the example above, "middle gray"! :-)
I have to put in an EV+4 to get anything near useable. Of course that means either this shutter speed, aperture or ISO is going to be all messed up to compensate.

Last edited by amoringello; 03-24-2014 at 02:34 AM.
03-24-2014, 02:33 AM   #11
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Firstly, a couple of questions:
- What exposure mode are you using in the camera (eg Av, M, Tv ...) ?
- What is your lighting source (other than the flash) ?
- I am not sure what you mean by -1.5 power. Do you mean -1.5EV ?
- What is the range from camera to item item ?
- What focal length are you using ?

I tried to simulate a similar setup as you have shown above with my K3, a SIgma 18-250 f3.5-6.3 and my Metz 58AF-2 flash. For M mode, 1/60th, f3.5, flash in PTTL mode at -1.5 EV, it under-exposed (not as badly as you show above), but I expected it to underexpose because the lighting on the subject wasn't too good and the flash had been derated by the -1.5EV setting. I could not simulate a result that I didn't expect. If the flash was left at left at 0EV, I got perfect exposures every time.

I use my Metz flash most of the time - usually it is mounted off camera with a Better Beamer over the 500mm f4.5 lens. I am really happy with the results I get and am yet to find any behaviour that I did not expect for the conditions. If anything, the K3 has better flash control than some of the earlier cameras.
03-24-2014, 03:00 AM   #12
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OK, very odd. I had about five minutes to check something (It bring up more questions than answers and I will have to look into this further later tonight)

If the center "spot" circle has the white background within it, the K3 underexposes by about 4 to 4 stops.
If I angle down just slightly to keep non-white in the center focus (metering range), the scene exposes within reasonable expectations.

Behavior does not mater whether I have metering set to Spot, Center-weighted, or Matrix mode.
So it is unexpected that the center "SPOT" matters that greatly and only when the flash head is in a bounce position.

So I would still have to say something is definitely "wrong".
Maybe there is some setting I changed that affects this???
Does pairing and/or locking AE-L with AF segment actually make a difference now?
Time to reset to factory defaults and see if behavior changes and work from there. :-(

Too many questions remain and no time this morning to answer them.
I'll keep up with what I find later tonight.

---------- Post added 03-24-14 at 06:06 AM ----------

QuoteQuote:
- I am not sure what you mean by -1.5 power. Do you mean -1.5EV ?
The flash doesn't really say what -1.5 is. In PTTL mode I assume it is 1.5 stops. Basically EV -1.5, but by affecting the flash output.

I am limited to about 2 to 4 feet from the subject. Nothing I can do about that.
I have found that sometimes when I step back the exposure loos fine... but I think it is because I have to change the composition and have less white background within the center spot.
I would love to hear if you have similar issues when the background is white and when it reaches into the center spot.

Lighting source has never mattered in the past, but I've been shooting under various lighting situations; incandescent, fluorescent as well as mercury vapor lighting (?? stadium/warehouse lighting).
03-24-2014, 03:15 AM   #13
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QuoteOriginally posted by amoringello Quote
I've tried hunting for info, but some of the existing threads were hijacked and went off the rails... I hate to re-hijack.

Anyway, I have a K-3 and am comparing it to my K-5. Works great in most cases.
Where it is a HUGE FAIL, is when using flash.



I take what you might call "product shots' on the side. Nothing pro, just products for a local thrift store raising funds for a animal shelter. But I have been doing this for several years with my K5 and have a setup that gives predictable results 99% of the time using the flash in PTTL mode. Naturally, I get the stray excessive specular highlight (P-TTL's Kryptonite) and have to adjust things once in a while.

But with the K3 (firmware updated to 1.03), I have a success rate of about 10% or less!!
I see similar behavior with and without specular highlights.
I have to jack up the exposure compensation 3-4 full stops to get a decent image. Its just crazy!

I have a af540fgz attached. I've used full power as well as -1.5 stops of power (P-TTL mode).
The camera is in AV mode at ISO 100 and f/3.5.

I can't figure out what is going on.
I can see and hear that the flash output is greatly diminished with the K3 so that is the obvious reason for the underexposure, but I can't figure out what the camera thinks it is seeing.

One thing I noticed is that with the K5, the EXIF data shows data values in the 9 - 12 range for "Flash Metering Segments".
The K3 on the other hand is showing all 0's!! WTF?

Is my new K3 broken?

You can see the DNG files here;
test_K3.DNG
test_K5.DNG

---------- Post added 03-23-14 at 07:54 PM ----------

Oh, important info.... the flash head is pinter straight up with a large reflector -- somewhat like the Rouge Flashbender.
I have not shot with the head straight forward yet (I almost never shoot that way but I guess I'll give it a go for testing).
There is only two things I can think of

1 the p-ttl pin is not connected (dirty unseated contact) so you getting center pin firing which will not sync with P-ttl shutter
2 Settings camera is not in P-ttl mode (but seems unlikely following your statements.)
03-24-2014, 07:54 AM   #14
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QuoteOriginally posted by awaldram Quote
There is only two things I can think of

1 the p-ttl pin is not connected (dirty unseated contact) so you getting center pin firing which will not sync with P-ttl shutter
2 Settings camera is not in P-ttl mode (but seems unlikely following your statements.)
Those would make perfect sense. So of course they do not apply to my screwed up little world.

I did some playing around with resetting camera default with regards to lining AE-L with AF, and (C.4 & C.5??)
It seemed to change behavior for the first three photos, where the K3 then took perfect photos in both cases; with white in the center focus spot and out of the center focus spot.
Sadly, as is true in my screwed up little world, that is where the behavior "fix" ended. The next ten test shots failed and were super-underexposed in both cases.

So, again I am at a total loss of explanation for what is going on. The K5 on the other hand is as close to flawless as one could expect from PTTL.
So ar it seems with the flash head pointing forward, the K3 is equally as reliable... but maybe it is just a matter of "luck" for the limited tests I've done.

My guess is if I work on this for a few hours that the K3 will exhibit even more unpredictable behavior than I've seen so far.
03-24-2014, 02:05 PM   #15
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By any chance are you using a 3rd party focusing screen? The ones with microprism and split prism focusing aid can mess up exposure considerably in some situations.

However even so I don't think it would cause as much error as you are experiencing. Has to be said though that I have not yet upgraded to 1.03 so I don;t know if that might be the difference.

I have myself only very rarely and intermittently got an underexposed shot and I put that down to some temporary issue such as dirty flash contacts.
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