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12-29-2010, 10:05 AM   #1
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Metz 48 underexposing on Pentax k-x

Hi folks,

I recently bought Metz 48 AF-1 for my Pentax K-x. While doing tests shots (this is the reason why I have not sent my k-x to the service center yet because of dis-located focus points) I have found that it is underexposing by quite a bit when in P-TTL mode, which is supposed to work best.

If I take the picture using the Pentax K-x little on-board flash the exposure looks acceptable, just maybe a small bit darker than the same picture from my Nikon D70s (taken using its on board flash as well), but still close enough.
The story changes when I put Metz 48 AF-1 on my Pentax K-x. Direct flash (just for experiment sake) underexposes a lot, while bounced flash (from the white ceiling in the living room) is a bit better, but still underexposed.

I wonder is my copy of Metz 48 AF-1 defective and I should return it, or it is the usual for the external P-TTL flashes?

What confuses me is the fact that the K-x on-board flash consistently gives me acceptable exposure, while much bigger, a lot more powerful and much more flexible Metz flash gun does not deliver the same expected results.
Both of them are working in P-TTL after all. If the P-TTL exposure determination is impaired because of some blown-out highlights in the scene (what pre-flash determines), then why on-board flash gives me better exposed pictures?

Any experiences with Metz 48 and Pentax K-x? Did you have similar issues? If so, how these were resolved (if they were resolved at all)?

I found that setting Metz 48 exposure compensation to +1 gives me better exposure, but this does not work as consistently as I would like to (at times this can overexpose a bit).

Metz 48 has the latest firmware installed (which is 1.1 for its Pentax version), the same applies to my Pentax K-x.

I will post example pictures later today.

thanks,
elg (Erika)

12-29-2010, 11:05 AM   #2
elg
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Picture samples to illustrate the issue.

1. Pentax K-x with on board flash (the first one in the set, and the lightest one from all three K-x pictures);
2. Pentax K-x with Metz 48 AF-1 direct flash (the darkest one from all three K-x pictures);
3. Pentax K-x with Metz 48 AF-1 bounced flash;
4. Nikon D70s picture with on-board flash (the last one - for comparison with K-x. Its color balance is a bit different than all three K-x pictures).

Other settings were the same for all three shots:
Kit lens, manual exposure (mode M), f/5.6, focal length 55mm, ISO200 (fixed), shutter speed 1/40s.

No post-processing were done on the pictures except resizing and saving for web in Photoshop Elements application.
Attached Images
       

Last edited by elg; 12-30-2010 at 10:29 AM. Reason: added additional attachment picture
12-29-2010, 12:03 PM   #3
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I use a Metz 48 also and find the exposure varies greatly depending on how it is configured but typically I can get exactly what I need. Try flipping the diffuser the opposite of how you used it for your samples and see if that makes a big difference. Also, I always use iso400 for flash shots at normal indoor ranges. I don't know why except that always seems to work best and maybe I picked it up from using iso400 film for indoor shots.

I agree, the direct shot is quite different than my results but I use K20D/K5 and do not know our metering settings match (center? matrix?).

Does pushing the Metz by 0.3-1.0 strength make it better or does the camera adjust the shutter and remain under exposed?
12-29-2010, 01:54 PM   #4
elg
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QuoteOriginally posted by imtheguy Quote
I always use iso400 for flash shots at normal indoor ranges. I don't know why except that always seems to work best and maybe I picked it up from using iso400 film for indoor shots.
Thanks, I will check how things are with 400 ISO, but I doubt that this will make big difference (though who knows, it may work for some peculiar reason).

QuoteOriginally posted by imtheguy Quote
I agree, the direct shot is quite different than my results but I use K20D/K5 and do not know our metering settings match (center? matrix?).
For all three samples the metering was set to matrix. Btw. I tried to use center-weighted metering, but it made no difference for the flash exposure. I also tried to bind exposure to the focus point (The focus point was set to the central one). This made no significant difference either.

QuoteOriginally posted by imtheguy Quote
Does pushing the Metz by 0.3-1.0 strength make it better or does the camera adjust the shutter and remain under exposed?
For all three shots I used the same settings. Mode was set to manual, so I was setting shutter speed, aperture and ISO (which were the same for all three shots), leaving for the camera to adjust the flash intensity. As you can see it did quite well with the on-board flash, and not so well with the external Metz 48 AF-1 flash.
The ISO was deliberately set to 200, in order to match my Nikon D70s (which I used for testing as well, and on which ISO200 is the lowest ISO). That said, Nikon D70s exposure of the same scene with on board flash was very similar to the Pentax K-x exposure with on board flash (colors being better on Pentax).

If I set exposure compensation to +0.7 or +1 on the Metz 48, then I can get similar result like from K-x on board flash for this particular scene, i.e. the exposure looks better. It is not consistent however and I cannot leave EV set to +1 on the flash permanently, as for some other shots then I can get slight over-exposure.

12-30-2010, 10:31 AM   #5
elg
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I edited my post with sample pictures and added Nikon D70s sample for comparison with K-x.
12-31-2010, 02:11 AM   #6
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If possible, try another Metz 48 flash and take shots with it and with yours. There were very few cases where the flash needed some calibration. If other flash gives good result under exactly the same conditions then yours may need servicing. Otherwise the exposure depends entirely on the camera in P-TTL, the flash is just a dumb slave following the orders of the camera.
12-31-2010, 12:30 PM   #7
elg
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Thanks, simico, for your input.

Today I went back to the store where I bought Metz 48 AF-1 flash. We shot a few pictures (both direct flash and bounced flash) in the store with one of the sales people, and the flash performed ok-ish. I.e. It did not underexposed as much as in my living room. The lighting in the store was different, of course. I decided to test the flash for a couple days more, and then decide what to do with it. So far I'm quite disappointed. The Metz 48 P-TTL performance is inconsistent.

The guy in the store mentioned that I can exchange it to another flash if I want, but they do not have any other Metz 48 AF-1 for Pentax at the moment, as not many people buy Pentax accessories anyway. He mentioned that he doubts that exposure with original Petax flashes will be much different from Metz, and that Pentax flash system is behind Nikon and Canon flashes in both - consistency and accuracy.

After coming back home I checked Metz 48 AF-1 in my living room again, and it is back to its old self - underexposing a lot. I will try to experiment with it using different flash and camera settings for a couple more days, and if I will not find things that work for me, I guess I will give Pentax and Pentax compatible P-TTL flashes a miss for the time being, and maybe go with Nikon/Nikon iTTL compatible flash (as I have Nikon DSLR as well).

I wanted to make K-x work for all things including external flash, but it looks like it is not gonna happen. Sadly enough.

Last edited by elg; 01-01-2011 at 09:21 AM. Reason: better phrasing
01-01-2011, 04:35 AM - 1 Like   #8
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I have Metz 48, used it with my previous K-m camera, now with the K-5. In my opinion P-TTL is quite reliable, you just have to understand how the camera works. Cameras before K-7 & K-5 use a more conservative metering, i.e. photos may look underexposed compared to Canon and Nikon cameras. This is the same with flash in P-TTL. You have to evaluate the scene and make + or - exposure compensation as appropriate because the camera's meter have no idea why it reads high light level: is it because the subject is white or because too much light? Unlike the camera, you know this and thus have to guide the camera.

In the above posted photos the background is a white reflective wall and pretty much the entire scene has bright colors. In this situation you have to apply + exposure compensation because the camera wants to expose everything to 18% gray, so if you're shooting without flash you set + exposure compensation with the +-EV button, if you're shooting with flash you set + flash exposure compensation on the flash (or in the camera after pressing the flash button on the 4 way control buttons). Similarly, if your scene contains mainly black (dark) subjects and background then you have to set - (flash) exposure compensation to avoid brightening the photo (because the camera wants to make blacks 18% gray).

Now you may ask why the on-board flash gave brighter result. This is probably due to the difference in the power of the on-board and the external flash, i.e. the Metz may have a stronger pre-flash and hence stronger direct reflection from the white wall, therefore the cam calculates a lower exposure and main flash power value. The bounced flash photo is better because less strong direct light was reflected back from the walls.


Last edited by simico; 01-01-2011 at 04:41 AM.
01-01-2011, 07:37 AM   #9
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Testing with a dark background (too) might be worth trying or at least interesting especially in comparision to the Nikon you have. I understand flash operation is Nikon's particular strength.

Last edited by jolepp; 01-01-2011 at 09:56 AM.
01-01-2011, 09:54 AM   #10
elg
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Thanks, simico, for your answer. It explained some flash things to me.

QuoteOriginally posted by simico Quote
I have Metz 48, used it with my previous K-m camera, now with the K-5. In my opinion P-TTL is quite reliable, you just have to understand how the camera works. Cameras before K-7 & K-5 use a more conservative metering, i.e. photos may look underexposed compared to Canon and Nikon cameras.
My older Nikon D70s likes to underexpose, therefore I regularly keep +0.3 exposure compensation on it (except for testing when I want fully controlled things, or for specific situations where picture may benefit from dialing the exposure compensation down).
That said I did not notice that Pentax K-x underexposes much. Maybe because it was released after K-7 where Pentax has already corrected underexposure.

QuoteOriginally posted by simico Quote
This is the same with flash in P-TTL. ...
Now you may ask why the on-board flash gave brighter result.
This is the exact question I was wondering about. I thought if both flashes (K-x on-board and Metz 48) work in P-TTL, they must expose similarly. Metz, although being more flexible, bigger and more powerful, operates in the same P-TTL, so if it underexposes, so should the on-board flash, and vice-versa. I did not think that pre-flashes from them may be different, and because of this I decided, that Metz does not work properly. After reading more reports (both here and on dpreview) about the P-TTL underexposure with original Pentax flashes I thought that Pentax has general flash communication issue.

Do not get me wrong. I like Metz flash (apart its fragile plastic leg and slightly cryptic user interface). It seems powerful enough (GN48), can tilt and twist. It looks like nice alternative to the original Pentax flashes (both of them are very expensive where I live), apart from the fact that it underexposes in comparison to on-board flash on K-x.
01-02-2011, 05:13 AM   #11
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It'd just like to add that direct on-board flash always gave me more brighter results than any hot-shoe mounted flash, although I've used the on-board flash only in "emergency" cases (when I didn't have any external flash with me, but needed flash light).

I had also used Nikon D70 with SB800 flash and after purchasing K-m and Metz 48 flash I could compare the two. In my experience the Nikon combo wasn't really better or more reliable than the Pentax combo. Of course, the D70 is quite old camera now, I'm sure the recent Nikon bodies have advanced I-TTL now.

I'd say forget the on-board flash, use it only as a wireless commander to your external flash if you'd like to use off-camera flash. Otherwise just use the Metz (or whatever external flash) and after some time and a few hundred photos you'll get the hang of it. This is like car driving, the more you do it, the better you become
01-13-2011, 03:30 AM   #12
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Yesterday I shot a bunch of photos of that particular 'tricky' stuffed toy scene using K-x and Metz 48 AF-1 with various settings, and compared these shots with the photos taken using K-x on board flash.

The general underexposure (i.e. for the most of the photos) of Metz 48 when compared to on board flash was by 0.7-1 fstop (I tried direct flash, 90 degree bounced and 45 degree bounced).

I sent a query to Metz about general underexposure of Metz 48 AF-1 flash. So far I did not get any answer from them.

Cheers,
Erika
01-23-2011, 09:24 AM   #13
elg
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I got the answer from Metz:

"...we could analyse the pictures and we also could reproduce this with our samples. We also could realise the differences between the built-in flash unit and the flash unit mecablitz 48 AF-1 digital. However, we also checked the Pentax flash unit AF-540 FGZ in the same way. With this flash unit we also could realise the differences. This Pentax flash unit works comparable to the mecablitz 48 AF-1 digital in this case."

Then I posted another question to them:

"If I understood this correctly in your test environment Metz 48 AF-1 flashes with Pentax K-x cameras performed similarly to what I have described (i.e. they underexposed similarly to Pentax external flash unit), therefore my flash may be ok (maybe the problem is overall Pentax P-TTL metering on K-x)?"

To which their answer was:

"You are right! We also could realise the mentioned underexposures with external flash units and the Pentax digital-camera. Therefore your flash unit surely is OK. We also could make the experience that this occurs with all Pentax digital-cameras which are equipped with the P-TTL-flash-control."

They also suggested to check my flash unit with their representatives.
So, it is a P-TTL issue.

Cheers,
Erika
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