[BruceBanner]

During my own experiments, I found that both K-5 II and K-1 are extremely hesitant to engage the AF-assist light.

Even when the camera is noticeably struggling to obtain focus, it will activate the AF-assist light as a very last resort only.

I'm not sure why that is, potentially Pentax engineers are trying to avoid bothering people (subjects) with the AF-assist light and if it doesn't make a lot of difference in many situations anyhow that could explain why the cameras are so hesitant to use it at all.


I'm not sure that is the case.

Every AF system becomes a lot slower in low light.
Pentax AF is better in many aspects than people think.

It's main weakness is predictive AF for subjects moving towards or away from the camera. Test sites pick on that and Pentax AF develops a bad reputation in general. Just to clarify, I'm not saying at all that you are unduly criticising Pentax. I'm just pointing out that I have my doubts as to whether Pentax AF is really "under par" when it comes to low light AF. We all know that it could be better with "action" shots in general.

I think this is a fair point, however the 540II still I think is not wholly complete. Why does AF Assist not come on in AF.C mode? Why then when the camera is in LV mode does illumination button on the 540II not work, it blinks and refuses to stay on (for the 10secs or so it's supposed to)... :/
Maybe my unit is slightly faulty?

I just feel it would be nice to have some kind of adjustment threshold of where AF Assist comes to the rescue, maybe it's too hard... or is it a simple R&D fail? Did no one take a Pentax camera out with a flash and test in a variety of environments and then realise it's gonna be problematic in x,y and z shooting scenarios? I have little flash experience but already I'm seeing that as being it's major fault (and as you pointed out most likely on lots of brand and flashes).

Another thing to keep in mind is how fast you have the shutter speed. Even though the flash duration is in thousandths of seconds the ambient lighta still affect the sharpness of the photos when there is motion. I use the K3II and it has a sink speed of only 1/180. I do a lot of bowling (tin pin) shots of bowlers throwing the ball. If I use 1/180 I get motion blur because of the ambient light in the bowling centers. I use HSS to overpower the lighting in the bowling centers and shoot at speeds of 1/500 to 1/800 even at speeds of 1/350 the bowlers arm has motion blur. The flash can freeze motion if you can controls ALL the light sources. But being in a venue like you were in you don't have that control.
Attached photo shot at f:3.2 1/320 (notice the arms motion blur) no processing two Cactus RF60X'S triggered by a V6 II
I also like the technique of pre focusing on were you think the next shot will be☺

Excellent shot. I'm yet to get the wireless triggers but will eventually, they're on the very next purchase list.

Honestly I think I am just bad with flashes and not controlling everything around me properly, for example if I push for HSS sometimes the flash bumps me back off it, prolly because I have Auto ISO and Av mode enabled and am not fully Manual and controlling all the camera controls fully. I'm sure there exists a plethora of different kinda flash assisted shots that make interesting interpretations of a single potential shot.

[Photobill]

I was very reluctant to use flash a few years ago myself. I am slowly learning some of the ins & outs (very slowly). I was using them just like you would with a point and shoot camera and always using TTL. My first digital camera *ist D my flash from the film days still worked fully auto. Then last year I moved up to a K3 II and it no longer had TTL 😟 so I started looking into a new flash system. I decided to go with the Cactus system because they were about 1/2 the price of the Pentax's flashes at the time. They also offers cross platform firmware & and at the time I was not sure I was going to stick it out with Pentax (discussed in another feed). I also added a "Yongnuo YN585EX wireless flash Speedlite" for less than $90.00 new on Amazon. It offers full TTL and will work with other Pentax flashes. I also loved it and the focus assist worked very well. But it saved my camera in a fall but didn't survive itself. I will be replacing it!
But all this forced me to get out of the auto setting. Now I am starting to get the shots that I see in my head😀
What really stinks for Pentax users is there is never anyone around that you can try there stuff to see if your stuff is working the way it should 😨😨😨😨😨

[Class A]

Why does AF Assist not come on in AF.C mode?

Presumably because the camera has no way of knowing when to turn off the AF-assist light again.
In AF-S mode, the camera can turn off the AF-assist light as soon as focus has been achieved. In AF-C mode, the premise is that AF may have to resume at any point in time again.

[mcgregni]

Yes, Flash based AF Assist is not compatible with AF.C. mode, switch to AF.S . As Class A says, the technical solution that is AF assist is not suited to a continuously focussing scenario.

[BruceBanner]

Presumably because the camera has no way of knowing when to turn off the AF-assist light again.
In AF-S mode, the camera can turn off the AF-assist light as soon as focus has been achieved. In AF-C mode, the premise is that AF may have to resume at any point in time again.

Couldn't it toggle off if no more focus changes for half a second or so? I mean in AF.S mode I have had the AF Assist from the flash blink rapidly fast almost acting like AF.C was selected as the camera struggled with getting focus (or I spammed the shutter focus button and switched to another object nearby, basically copying a kinda manual AF.C effect)?

Meh... curious to know if this is a Pentax flashgun thing or if all brands of cameras and their flashguns are too also restricted to AF.S for their LED Flash Assist feature. No hating on Pentax here, just curious. In my couple of years owning Pentax gear it has more often than not beaten my expectations. The two areas I have ran into (that made me question if this is a poorly implemented aspect or just general technology current limitations) has been the buffering issue and overall Flashgun experience (especially AF Assist as I pointed out earlier in this thread).
Reading a little more these days about other Pentaxians who broaded their equipment range with other brands to solve certain issues that Pentax have not been particularly strong in (such as quicker and faster/more accurate AF).

[mcgregni]

A quick search found the Manual for the Nikon SB-910, a flagship unit. Here is a quote from the notes in the AF Assist Section .....


"AF-assist illumination can be used if an AF lens is mounted and the camera’s focus mode is set to S (single-servo AF with focus priority), AF-A, or AF. "

Anyone know what AF-A or AF means in Nikon Lingo?


Bear in mind also Bruce, that not all flashes use an LED light for their AF Assist. This is a fairly recent technology for that. It used to be mainly a red-beam, crosshair type of light, which some users report they found better. The older Pentax AF-540FGZ used this, with the crosshair light passing through a red plastic cover on the front of the flash.


However, certainly not with Pentax, this different technology for the light beam doesn't affect the compatibility with focus modes ..... both types need to be used in AF.S mode.

[Class A]

Meh... curious to know if this is a Pentax flashgun thing or if all brands of cameras and their flashguns are too also restricted to AF.S for their LED Flash Assist feature. No hating on Pentax here, just curious.

The culprit is the camera so all flashguns suffer.

The only workaround I see is to use devices that support manual engaging an AF-assist light, such as the Cactus V6II. The V6II has a manual AF-assist mode in which you can initiate the AF-assist light of the V6II (which has no structure but is very bright at its highest setting); the light turns itself off, when you take the shot.

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Last edited by Class A; 03-06-2018 at 06:03 PM.

[BruceBanner]

A quick search found the Manual for the Nikon SB-910, a flagship unit. Here is a quote from the notes in the AF Assist Section .....


"AF-assist illumination can be used if an AF lens is mounted and the camera’s focus mode is set to S (single-servo AF with focus priority), AF-A, or AF. "

Anyone know what AF-A or AF means in Nikon Lingo?


Bear in mind also Bruce, that not all flashes use an LED light for their AF Assist. This is a fairly recent technology for that. It used to be mainly a red-beam, crosshair type of light, which some users report they found better. The older Pentax AF-540FGZ used this, with the crosshair light passing through a red plastic cover on the front of the flash.


However, certainly not with Pentax, this different technology for the light beam doesn't affect the compatibility with focus modes ..... both types need to be used in AF.S mode.

I think AF.A means a mode where it's Auto and toggles between a AF.S and AF.C type scenario, but then the rest of the bumpf suggests AF.S, perhaps it works in AF.A mode but only when that mode is deeming AF.S is the correct scenario...

The culprit is the camera so all flashguns suffer.

The only workaround I see is to use devices that support manual engaging an AF-assist light, such as the Cactus V6II. The V6II has a manual AF-assist mode in which you can initiate the AF-assist light of the V6II (which has no structure but is very bright at its highest setting); the light turns itself off, after you have taken the shot.

Hey that's really interesting to hear. I've yet to go down the road of wireless triggers but intend to. What you're suggesting here mimics something I said earlier in the thread about how it might be handy to force the AF Assist beam to be constantly on (not flickering with the sync of the lens trying to gain focus) but then when it comes to the actual shot the LED AF Assist light is removed from the shot. I thought that might not be possible due to to AF Assist lighting actually affecting the exposure calculations for ambient light and flash power etc. I must read more about this feature...

[Photobill]

I was doing a shoot this weekend and thought about your thread. I was working with my Cactus flashes. You can set the focus assist to full time as well as control it's power output.
I know this does not help with your flash but other manufacturer's have this available.

[BruceBanner]

I was doing a shoot this weekend and thought about your thread. I was working with my Cactus flashes. You can set the focus assist to full time as well as control it's power output.
I know this does not help with your flash but other manufacturer's have this available.

With those cactus flashes does the focus assist toggle off for the shot then (when in 'full time mode'). Like my 540II can have the LED focus assist beam on all the time, but the shot taken actually also keeps the beam on as well :S

I think I'll be heading down the Cactus V6II route eventually and i think the radio trigger has a good focus assist feature on it (need to read more about it tho).

[Photobill]

Off hand I want to say yes the focal assist does go out when the you shoot.
I have been very happy with the Cactus line. Do your research and see if it does all that you need. ☺