[pathdoc]

I've been looking at what Santa brings me if I'm a good enough boy this year, and reflecting on quite a few pictures I didn't take at my son's scout meetings - because there was not enough ambient light for my K-5/18-135 combination to lock focus on (outdoors, late twilight heading into night under tree cover outdoors).

Looking at either the AF360 or 540 FGZII flashes, it appears they may be the answer to my prayers - weather sealed, powerful enough to reach out as far as I think I need to, and with that lovely white LED assist/supplementary light that should solve 99% of my focus lock issues. The only hesitation I have is about the whole P-TTL thing. I understand how it works - fire a pre-flash, assess the power requirements, fire the main charge and expose - but what's the time delay associated with all this? Precious moments can be fleeting, and I don't want to miss one because the camera/flash system was decicing what to do!

Use would (at least for now) be directly from the camera hotshoe.

The other question of course is, should I just go straight to the 540 in order to have more light than I could ever possibly need? I can always crank up the ISO to boost the guide number for any particular distance - not afraid to sacrifice a bit of quality - but for outdoor use I really think I should grab the most powerful option. This is especially the case with the newer 540 being so relatively small..

There was a part of me that wanted the TTL/auto functions that went with the older models, but it looks like their AF assist modes may not be quite as helpful as the newer ones.

Is there anyone who's shot either of the new flashes in similar circumstances and can advise?

[Ole]

P-TTL introduces a delay. If it is too long of a delay for your use is hard to say.

A sure fire way to avoid a delay is to go with an older flash that supports "Auto Flash". It doesn't have to be older than the previous generations like the AF360FGZ or AF500 FTZ, which both have AF assist. If you could forgo AF assist (use manual focus) you could go further back in time to flashes which can be had for a song. The AF280T would be an example of an older powerful flash which is still reasonably compact. If you go for a cheap second hand flash, perhaps Santa would bring you something else for night use like a fast 50mm or 77mm F1.8 prime?

In Auto Flash mode there is no delay. The exposure is cut off by the flash when it detects that sufficient light has been reflected from the scene. Exposure accuracy is surprisingly good.

[RGlasel]

but what's the time delay associated with all this?

There has never been an official fix and the total delay can be less than a quarter of a second, so the horror stories you read are probably the result of an unlucky combination of camera settings. Film era TTL or thyristor flashes were better than using a guide number calculator, but were a crapshoot when it came to fill-in lighting. If you have the opportunity to get your subjects to remain fixed in one spot while you experiment with manual settings, you will get better results than P-TTL. Otherwise, take advantage of the electronics to make all the calculations for you. The time delay involved in retaking pictures is far longer than anything the P-TTL system produces.

should I just go straight to the 540 in order to have more light than I could ever possibly need

Yes.

As soon as you bounce flash off of anything, you increase the distance flash light travels, reducing power by a power of 2 and light dispersion robs you of at least a full stop of exposure. More power means a better experience with HSS as well. Until the size of the flash becomes an obstacle, there is no such thing as having too much available flash power.

[clackers]

Looking at either the AF360 or 540 FGZII flashes, it appears they may be the answer to my prayers - weather sealed, powerful enough to reach out as far as I think I need to, and with that lovely white LED assist/supplementary light that should solve 99% of my focus lock issues.

The best you can buy.

A combination of P mode and P-TTL is very quick and gives good results with people as subjects - parties and so on. Ride the FEC to suit.

Moving subjects such as a sport you would flick over into Manual mode. Once you chimped enough and were happy with the settings, leave them there for the rest of the shots at your vantage point.

If you determine 1/4 power, 1/500s, ISO 400, f8 is to taste, then tell the camera to use that over and over again, not spend any time estimating it.

[pathdoc]

I cannot forego AF assist, as I am shooting in near darkness at times. WR is essential as I may have to operate in drizzle or near spray. If the TTL delay is in the order of a half second or so, I can cope with that; more than a second would be more of a problem. Manual focus is NOT an option as the ambient light is too low, particularly with a lens as slow as this one is at the long end.

As for my subjects, they are far from being able to stay fixed. A fast prime (which I have, BTW; an FA50/1.4) is also not an option as I sometimes do not have the flexibility to zoom with my feet - these are kids in constant motion, absorbed in their activities and being photographed as such, not posed static subjects.

Let me put it another way; what is the time delay inherent in P-TTL?

Clackers, you posted while I was still composing this. Your points are noted. Can you clarify what the FEC is, please?

[UncleVanya]

With the k5 p-ttl is a minimal delay. The K3 adds slightly to the delay but it is not a problem for me using the series 1 af540fgz.

The 360 is smaller. That may or may be a factor you need to take into account.

[stevebrot]

I have is about the whole P-TTL thing. I understand how it works - fire a pre-flash, assess the power requirements, fire the main charge and expose - but what's the time delay associated with all this?

The time delay depends on the body. For most models, the time for P-TTL preflash and calculation delay is about 0.02s. The K-3 adds an additional 0.19s lag before the preflash.

Edit: I misinterpreted the oscilloscope data in the link below. For the K-3, the base shutter latency to mirror up is 0.012s. With P-TTL, this increases to 0.188s plus an additional 0.023s (for preflash) before mirror up. Total latency for P-TTL is 0.211s (1/5s).

To the best of my knowledge, the K-3 is the only model that has that behavior. That additional delay is perceptible by many users. Since you have your K-5 in hand, you should be able to use the built-in flash to get a feel for the time involved for the P-TTL pre-flash/calculate/flash sequence. It should be essentially the same for other flash units.

Here is a link to a comment on the much longer thread regarding P-TTL on the K-3 showing measurements done with an oscilloscope.

https://www.pentaxforums.com/forums/172-pentax-k-3/242556-k-3-delay-when-usin...ml#post2972999


Steve

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Last edited by stevebrot; 11-07-2015 at 08:17 PM.

[mcgregni]

The newest Pentax AF-540FGZII makes perfect sense for many situations, and certainly for the sort of on-camera dynamic type of flash photography that you refer to. You'll always find a need for that extra power especially when you need to bounce off surfaces like ceilings that are higher than average.

I'm not aware of any specific test comparisons between the older type 'red cross bars' AF assist beam and the new LED spotbeam technology. I rarely need it myself but I've tried it and it works quickly ... there are two strength settings depending on the amount of ambient light and your particular requirements (such as trying to not to disturb a subject).

There is an entirely new section comparing the older and newer Pentax flash models, plus a run-down on all the LED and function menu features, in my Pentax Flash Guide which you can download from the link below my post here .....

[Alex645]

I cannot forego AF assist, as I am shooting in near darkness at times. WR is essential as I may have to operate in drizzle or near spray. If the TTL delay is in the order of a half second or so, I can cope with that; more than a second would be more of a problem. Manual focus is NOT an option as the ambient light is too low, particularly with a lens as slow as this one is at the long end.

As for my subjects, they are far from being able to stay fixed. A fast prime (which I have, BTW; an FA50/1.4) is also not an option as I sometimes do not have the flexibility to zoom with my feet - these are kids in constant motion, absorbed in their activities and being photographed as such, not posed static subjects.

Let me put it another way; what is the time delay inherent in P-TTL?

Clackers, you posted while I was still composing this. Your points are noted. Can you clarify what the FEC is, please?

Shooting flash in a light drizzle or spray is problematic. All those water particles will appear frozen throughout your shot from the flash. Sometimes the technology just can't handle the situation as well as telling the coach or the team that they need to gather in an area out of the elements or when and where there is more ambient light.

[WPRESTO]

Do not overlook the newest Metz flash units. The 52 AF-2 is especially good: pTTl, manual, slave, wireless pTT, first or second curtain, reduced pTTL output, all the bells-and-whistles plus powerful and reasonably priced. The touch screen is user-friendly & very intuitive, you almost don't need the instruction manual, which looks intimidatingly thick only because it duplicates all warnings and directions in at least five languages.

[pathdoc]

Shooting flash in a light drizzle or spray is problematic. All those water particles will appear frozen throughout your shot from the flash. Sometimes the technology just can't handle the situation as well as telling the coach or the team that they need to gather in an area out of the elements or when and where there is more ambient light.

Coach? Team? I don't mean to offend, but have you actually been paying attention to what I've been saying? These are scouts (i.e. boy scouts plus girls, because the Canadians - and Aussies too - play the game that way) doing their routine outdoor activities, often in fading light and inclement conditions. I have NO control over their movements, NO control over their location... it's see, shoot, respond, and the gear has to stand up to whatever weather is fit for the kids to go out in.

[UncleVanya]

With variable outdoor conditions the af540fgz version 1 or 2 should be your first choice.

The combo of power plus weather resistance are best with that unit.

[pathdoc]

Uncle Vanya, Stevebrot (especially Stevebrot), you've told me what I need to know. 0.02 second is trifling - negligible for my purposes. Even 0.19s probably wouldn't be a problem, as it's probably shorter than my own reaction time anyway (irrelevant as I am using the K5). WPRESTO, shall think about it.

ETA Uncle Vanya, with regard to size I'm told the new 540 is possibly smaller than the old 360. What that means for the new 360 I do not know, but under the circumstances I would rather have the power and not need it than the other way around.

[clackers]

Clackers, you posted while I was still composing this. Your points are noted. Can you clarify what the FEC is, please?

Pop up your K-5's inbuilt flash, look at the flash mode settings, and you'll see you can vary the Flash Exposure Compensation several stops (+1 to -2) by turning a dial.

This will also apply to anything you put on the hotshoe that supports P-TTL.

I'll probably use it a great deal today at a local Zombie Shuffle, even though the event is happening in the middle of the day.

It'll be fill, to ensure the subject is brighter than the background.

[derekkite]

Weather resistance. Weather resistance. If you don't need that, a Metz or Sigma would be fine. Or manual, then you can get inexpensive Yongnuo's.

The Pttl delay is annoying for any moving subjects. But it probably will get fixed in the next bodies. My theory, hmmm, hmmm, is that the AF tracking is ineffective for the same reason there is a delay in the Pttl flash; the metering sensor communication bus is slow.

The AF54FGZII handling is very nice. I have three modes that I set up, and it is quick to reset by power switch, then press a button three times.