Saturday, January 05, 2008

P-TTL Reliability

Since the first Pentax DSLR was created, there have been numerous unfavourable user reports floating around on the Net for the poor accuracy and inconsistency with the Pentax P-TTL flash system, particularly there are more adverse reports associated with the latest model AF-540FGZ flash unit then the older 360 one, which is something really worrisome. Well, below are a few of the recent reports amongst all those:-

P-TTL the P stands for Pathetic

P-TTL and Pentax Flashes - Pure Frustrations


540 let me down Christmas Day


A little disapointed...

Well, in fact I was one of the first Pentax DSLR users who posted about my unpleasant experience of the P-TTL years ago, with my fist *ist D (on which traditional Pentax TTL is almost perfect, in contrast). In fact, at that time, I had already found that the results with P-TTL were with poor accuracy and consistency and in fact it was really hard to predict for the results, too. At that time, after all these unfavourable results obtained during my practical shooting, I decided to carry out some measurbation tests to check for the case, finally:-

P-TTL Vs TTL: Is Newer Better?

With no surprise, my measurbation test yielded the same results and conclusion which are mostly agreed with my practical experiences, i.e., the P-TTL tends to underexpose but exposure results are inconsistent and unpredictable.

Nevertheless, the most funny thing which I can see (but have been happened repeatedly) is that some P-TTL fans always told others to "learn" how to use the P-TTL system. And, according to what they said and say, those who have found and/or reported problems *should* "try" to compensate (how?) and to adapt to (how? I just wish to ask again!) to the system, as it is designed! (But HOW? How it is designed?? Please tell me and all of us here! .. if you really know!) Well, these particular people could even know when the P-TTL will be fooled (but they pointed out many cases that the system will be fooled! Really funny!!) and actually I just wish to know afterall: Anyone except Pentax knows the logics of the "intelligent" (supposed to be) P-TTL system? If not, how could they know how to compensate for such an Artificial Intelligent advanced flash system but which is inaccurate.

Well, all in all, if the P-TTL system is fairly accurate, there would not have been so many complaint cases and more importantly, there will be no need to compensate randomly by chance by so many Pentax users just because irregularities do happen from time to time.

In fact, as you can see from the above and other posts, those people who have used those similar intelligent advanced flash systems of Nikon and/or Canon would mostly comment that the Pentax's P-TTL really sucked.

In fact, there have been different Pentax DSLR users found that (and verified again and again that) the Auto mode (which was using the 60s electronics and technology) of the Pentax P-TTL flash guns would put back things mostly right on track. But then this Auto mode has two annoying problems/limitations which could cause much inconvenience, for what it is designed:-

1. Everytime when the flash unit is turned on, the Auto mode needed to be re-selected;

2. With the Auto mode activated, the zoom head of the flash unit is fixed at widest (I believe that the Auto mode circuitry does not cater for the change in GN for its calculations when the lens (and thus the zoom head) is zoomed, nor there is any feedback/input of such data in the control logic as such).

Furthermore, for Auto mode for flash metering and exposure control, it is still not Thro-The-Lens (aka TTL) afterall and hence all the disadvantages of the Auto flash can be applied here.

Last but not least, in the Pentax land, the case has been made even worse just because there are so little choices and limited availability of P-TTL compatible flash units, no matter for original or 3rd party ones - and up till now, there is still NO Macro Ring Flash. Furthermore, for 3rd party P-TTL flash guns, compatibility cannot be well ensured as it is very proprietary, for example, there were just older P-TTL "compatible" Sigma units which are not compatible with the latest Pentax K DSLRs.

So, now that many people and I do believe that Pentax's P-TTL is the poorest flash system on Earth for DSLRs, what Pentax can do and should do to change the situation? There is actually always fast and direct solution, get the TTL mode back and re-include it in at least some Pentax DSLR models and let the user to choose and store in memory for what mode they prefer when the flash unit is started up, namely, P-TTL, TTL, A mode or even M mode.

To do it even better, Pentax should upgrade the Auto mode control logic so that it can communicate and receive feedback data from the camera for what focal length is currently selected.

Nevertheless, the ultimate solution to the problem is to debug and improve the P-TTL system, of which the poor intelligence and logics used is the primitive problem, frankly speaking. If Pentax is still to be insistent in supporting the P-TTL system alone as the only TTL flash mode in the foreseeable future (just like Nikon and Canon have done, anyway), they should put more R&D efforts so that to make the P-TTL to be an usable one, with acceptable reliability, my humble words..

6 Comments:

Anonymous said...

no disagreement here. when itg doesn't want to expose right, I can't even figure for sure how you are 'suppose' to compensate, let alone how to do it.

P-ttl has an exposure compensation button on it, but can see the results change in the photo.

selecting different 'modes' P, AV, X, etc seems to change the results of what happens.

I can't figure if changing the exposure bias as you would for natural lighting does anything or not. It's been pretty exasperating.

I"ve been wondering if I could safely use my OLD pentax flashes that predated the TTL mode.

I've got a 280 made for the super Program that has nice sliders on the back of it for calculating the exposure, and I used my pentax ring lite for some years with a K2 where I manually calculated the exposure.

I saw somewhere warning about flashes with bad voltages in the firing circuits, but have assumed those were NON pentax flashes, but I could go full circle and use the flash units I had for the K2--in the K2 automation mode.

kittykat46 said...

In the last 6 months I've taken nearly a five hundred flash photographs on my K100D, a mixture of AF360FGZ and on-board flash, always with P-TTL, usually in Program Mode or Portrait scene, using the Kit lens. I'm no Pentax loyalist, nor a pro, just that I've been toying with cameras and flashes since I was a kid 20 years ago.

Frankly, my Canon IXUS 850IS Point and Shoot has more consistent flash performance than the K100D.

But most (80%+) of my K100D flash shots have come out fine, though I realise that's a bit subjective. Many of the photos would be, strictly speaking, slightly underexposed 1/3 to 1/2 stop, but it fits my personal preference, as technically "correct" flash exposures (filling the whole histogram end to end) look overbright and harsh to me.

Some input from my experience.
- Any significant bright reflective surface near to the line of sight of the focus point would cause underexposure.
- I always switch on the histogram and overexposure warning.
- Most times when the shots are underexposed, sure, there's a clearly visible burned out bright spot somewhere near the subject.

Solutions
- I try to recompose the photo away from the bright spot.
- If that's unavoidable, only way is to crank up the Exposure compensation and re-take . You can actually estimate the amount of E/V needed from the histogram.
- My two toddlers won't stay still long enough to re-take the photo, so I sometimes have to do some Post processing. Fortunately, most times, the amount of underexposure is slight - no real loss of IQ in brightening up the photo on the PC.

- Try to stay away from the rated minimum and maximum flash range - and also maximum and minimum zoom for a zoom lense - the accuracy gets bad at these extremes.

Yes, I agree Canon and Nikon have a better handle on flash, even though other dSLRs I've tried out have some underexposure response when faced with the exposure challenge I've given above.

If I were a photographer who needs to take flash photos for a living, I probably wouldn't go for a Pentax K10D or K100D. But me, I just take photos for fun.

There are slightly inconvenient ways around the P-TTL problem (most of the time)and the K100D's great performance in available light and in daylight is more than worth it.

Haleemur said...

I'm considering getting the K200D, with the AF-360 flash. Have there been any update in the P-TTL algorithm to tackle the underexposure that everyone here noticed in the K100D and K10D.

How does the Pentax flash system compare with Sony and Olympus. I already knew that Nikon and Canon offer superior flash performance, but it seems to me that Sony and Oly are more direct competition for Pentax. It would be more meaningful to compare Pentax flash with those brands'.

I'm also considering using the flashes off camera. AF-360 can be triggered without any wires. But what are the pros and cons of this method? What gear should I be looking into.

Anonymous said...

I have had a Pentax K200D for 2 months, and a newly purchased AF-360 flash, and I have problems getting them to work together. Though the K200D manual clearly states how to use the 360 flash, pictures are usually underexposed, and though I am able to sometimes fix it using manual mode, or by changing the exposure controls of either the camera or the flash, it's simply not what I expect from a relative high-end camera. My point and shoot Canon, aged 5 years, offers far better flash performance. If I had read these forums before buying, I would never have chosen a Pentax. I have been to pentax.com, and there seems to be no fixes (or references) to the problem, even though everyone seems to struggle with it.

Matthew Miller said...

So, I've had a K10D with a Metz 48 AF-1 flash for about a year now. I've used it pretty heavily, especially in the darker months here in Boston. I had a Sigma EF-530 DG Super earlier, but returned to for reasons having nothing to do with exposure — because with both flashes, exposure generally either worked perfectly well or else I was doing something wrong which I could figure out and solve.

If you're still having problems (or, if you have stumbled across this page in a web search), check out OK1000's introductory guide to P-TTL and (particularly if you are having exposure problems) the P-TTL flash guide from Pentax User UK. That should help get you back on track.

Haleemur, you mention the off-camera wireless optical P-TTL mode. This is what I use most of the time, actually, and I find the automatic flash exposure to work so well that I rarely have to think of that aspect of composition. One particularly cool feature Pentax has is that the on-camera flash can be used as a controller for the wireless system (with or without contributing to exposure). You just need to buy a single P-TTL flash (either from Pentax, Metz, or Sigma) and you've got a very flexible lighting solution. You won't get that from Canon, and not from Nikon on entry-level or mid-entry cameras either — but Pentax even includes it on the new K2000/K-m.

Glanglois said...

I'm using a Metz 54MZ-4 with the original foot upgraded to M2 software by Bogen at no charge.

When set to auto mode, it boots back up in auto mode. It readily sees and follows my ISO setting and my focal length. So it works fine in Av or manual as it is still communicating with my K10D.

I've tried the P-TTL mode and, as others, found it wanting. But it works fine in auto and I'm happy to have the flash.

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