[feiron]

I use the AF360FGZ with both of my K10D and K100D.

I put it in P-TTL mode all the time. The results weren't consistent at all, lots of the shots were underexposed. I tried slower shutter speed but it didn't make any difference.

Last night, I tried using the auto mode but my trick was to dial the flash iso lower than actual iso, and make the flash think that I close the aperture 1 step slower than the actualy f-stop.

bottom line is, it worked very well in auto mode. although the auto zoom didn't work at auto mode?

the questions:

1. what did I do wrong?
2. how do you use your flash?

ps: I linked AF to AE

[Ash]

I'm also interested in this problem as I'd been looking for a P-TTL flash for some time, thinking it would end all the exposure problems with bounce flash. Theoretically, the pre-flash should automatically calculate how much flash is needed to expose the shot correctly, no matter how the head is tilted, ensuring perfect exposure every time. I'm surprised I'm hearing of these exposure problems from quite a few users - I considered the Pentax P-TTL flashes the gold standard in flashes for Pentax dSLRs. Any comment from other frum members?

PS: I don't have one of these P-TTL flashes, just an auto one which has worked well.

[egordon99]

Shutter speed will only affect your ambient exposure. Opening up the aperture can let more flash light in though.

I have an *ist DS and a Sigma EF-500 DG Super and I don't have any problems with P-TTL exposure. I switch to Manual mode (on the camera dial), ISO400, 1/180s, and set the aperture according to how much DOF I want (keeping in mind that higher/slower f-stops limit my flash power) Sometimes if there is alot of white in the subject (ie person wearing a white sweater) it might underexpose a bit so I dial in +1 FEC. I shoot RAW so I can push a decent amount during post-processing if I messed it up.

Also keep in mind that if you are bouncing, you can lose a fair amount of flash power depending on the color of the ceiling and how high it is. I find Joe Demb's Flip-It diffuser helpful in situations like this as it can direct some flash forward to compensate for these situations.

[HGMonaro]

I'm not happy with my 540. Thought it would provide faultless flash photos but I usually have to take a few test shots to dial it in to something acceptable. Anything bounced needs +1 comp on the flash (wish it went higher!). For a flash with a guide number of 54 or something it doesn't seem to have the grunt my old Agfa with a guide number of 35 does. Need to play with it more to decide that it is truely sub-standard! I find the on board flash is a lot more accurate exposure wise.

[mysterick]

I'm not happy with my 540. Thought it would provide faultless flash photos but I usually have to take a few test shots to dial it in to something acceptable. Anything bounced needs +1 comp on the flash (wish it went higher! DITTO!!!). For a flash with a guide number of 54 or something it doesn't seem to have the grunt my old Agfa with a guide number of 35 does. Need to play with it more to decide ...

Yes, this is driving me up the wall as well...:ugh:

[nosnoop]

I am very happy with my 540 and 360. They gave spot on exposure when bouncing with StoFen Omnibounce.

The wireless flash works great. Sometimes I have to dial in some EV on wireless flash, but once adjusted, the flash exposure is very consistent.

P-TTL works very well for my application.

[Ash]

When you experienced users have 'figured' out these flash units, what have you found makes them work on P-TTL? What are the newbies missing? Is it wrong to assume perfect exposure (within the limits of the flash) anywhere, everytime on P-TTL mode?

As for me, I'm happy to stick with my cheap auto flash and camera on M mode with some chimping for the moment. It's good for me to sharpen my skills anyway....

[feiron]

I am very happy with my 540 and 360. They gave spot on exposure when bouncing with StoFen Omnibounce.

The wireless flash works great. Sometimes I have to dial in some EV on wireless flash, but once adjusted, the flash exposure is very consistent.

P-TTL works very well for my application.

could you please elaborate on the settings you use? I use the Omnibounce too, but the exposures weren't consistent at all. I tried taking some pictures of my gf doing some hand craft, and some of the shots were underexposed in P-TTL.

Auto mode solved my problems. I dialed less sensitive ISO and 1 f-stop slower on the flash.

ie: actual = ISO 100 at f5.6
on the flash = ISO 50 at f8

this setting lit the whole frame nicely, I'll get some sample picture tomorrow

[Entropy]

+1 to +2 exposure compensation.

Dialing it in with the front dial in Program mode (surprised that worked as that's normal EC, not FEC) works for me.

I am disappointed that my new AF540 consistently underexposes by a minimum of one stop in all situations (bounce or no bounce, wireless or not). It would not be such a big issue if not for the fact that the 540's onboard FEC tops out at +1, meaning that you must change settings on the camera.

[wlachan]

I bought the 540FGZ new some months ago but eventually sold it for this exact reason. It's not about 1 or 2 EV underexposure, it's simply not consistent in P-TTL mode. For 2 shots which were 95%+ identical, the actual exposure could be way different. That means each shot must be treated individually, and often not quite practical, and certainly not what P-TTL flash was designed to be. Ironically, A flash worked great but all auto settings would be disable (but why?). Eventually I moved back to my Metz 40MZ-2/3i flashes in A mode. If not for the HSS or wireless, I see no reason for Pentax made P-TTL flashes, not to my limited mind anyway. But some claimed linking the camera's AF point to AE would solve the problem, I didn't keep my flash long enough to find out. You might give it a try and report back.

[Entropy]

I bought the 540FGZ new some months ago but eventually sold it for this exact reason. It's not about 1 or 2 EV underexposure, it's simply not consistent in P-TTL mode. For 2 shots which were 95%+ identical, the actual exposure could be way different. That means each shot must be treated individually, and often not quite practical, and certainly not what P-TTL flash was designed to be. Ironically, A flash worked great but all auto settings would be disable (but why?). Eventually I moved back to my Metz 40MZ-2/3i flashes in A mode. If not for the HSS or wireless, I see no reason for Pentax made P-TTL flashes, not to my limited mind anyway. But some claimed linking the camera's AF point to AE would solve the problem, I didn't keep my flash long enough to find out. You might give it a try and report back.

I tried that trick.

I'm extremely tempted to return it to B&H. It seems like underexposure is an extremely common problem, and I'm better off finding a "manual" (in reality, same as "auto" non-TTL mode on TTL-capable flashes) Pentax module for my Quantaray QTB-9500 - other than the lack of TTL/P-TTL for Pentax it's a damn nice flash, I especially like the built-in secondary fill flash. (It appears to be identical to the highest-end Promaster flash, and likely is just a rebadged Promaster.)

Edit: I've found that putting it in X mode with the aperture set to 5.6 or so gives far better results, on par with "auto" mode.

Auto mode works extremely well without any exposure compensation tricks. (i.e. camera set to f5.6/ISO 100 and flash set to same) I haven't tried seeing what happens with the flash set to 4.0 or 2.8 (the latter only possible with my manual primes). Auto mode does work incredibly well with my manual primes - in fact shooting with K/M lenses (i.e. pre-A) is far easier with the AF-540 in "auto" mode than those same lenses in daylight - don't need to hit the green button for metering.

So far, I have yet to see a single situation where P-TTL works and Auto doesn't, if I could be sure the old Quantaray still worked I'd return the 540 in a heartbeat, but unfortunately the QR is in New Jersey and had issues last time I worked with it, but that could have been a problem with my hacked up "digital slave" module that was made by adding a slave trigger circuit to one of their "manual" modules. Since I have no way of testing the old Quantaray any time soon I will probably wind up keeping the 540 and hoping P-TTL gets fixed somewhere down the line with a firmware update.

One more edit: Some people claim that the underexposures are occurring in "difficult" scenes with reflective objects or lots of white. My 540 underexposes even when spot metering on a matte black object. Such a situation SHOULD result in massive overexposure but it actually still results in underexposure!

Another edit: I've had a bit more time to fool with it. Today the flash in P-TTL mode was only slightly underxposed (so slightly that I would be worried about blown highlights if it were any more aggressive) in most situations with the camera in X mode with multisegment metering at most aperture settings. Spot metering on a dark object would actually cause significant underexposure, the exact opposite of what one would expect from spot metering on a dark object. If the camera was in P mode, it would underexpose significantly at the same aperture settings as in X mode.