Discussion in 'Pentax' started by don_myers|1, Apr 1, 2013.

  1. I'm having a bit of trouble understanding how to control the light output on my 540 external flash. When I set it up in wireless mode it fires everytime with no problems at all; however, the flash is firing at full strength and casting heavy shadows. I ran a bunch of tests this weekend using my built in flash (K5) as both primary and control, noticing no difference in the intensity of the shadows.
    When I tried varying the output of the flash using the output ratio of 1/1, 2/3, 1,2, 1/3 there was still no difference. After going back through 35 individual pictures, (the point at which I gave up,) there was little or no difference: the only changes occured when I either adjusted the aperature, shutterspeed, or EV compensation, and then the shadows were not less intense, just less exposed.
    It should be noted that when I connect the 540 directly to the camera (either by cord or mounting on the hot shoe) no such problems occur; it is only in wireless mode. (It is odd that though the flash is in P-TTL mode, no changes can be made to the flash by the camera: all changes must be made to the flash itself.) The following are the camera and flash settings I used as a basis, varing the aperture, shutter and EV on the camera, and changing the output ration on the flash.
    X-Sync Mode, 50mm lens, Av 5.6, Tv 180, ISO 100, EV 0.0, WB flash, flash wireless mode.
    P-TTL mode, 1/1 ratio, EV 0.0, leading curtain sync, 48mm zoom.
    The only changes that occured were when I adjusted the amount of light (shutterspeed, aperture, etc.) hitting the sensor; no changes occured in the intensity of the flash.
    One thing of note: It seems to me that if I can connect the flash dirrectly or indirrectly to the camera and have complete control, them should not that same control be present when the flash is remote? It would seem the technology is there.
  2. Without actually seeing the results of your experiment, I'm trying to piece this togeather in my head, but I'm getting hung-up on the fact that we are discussing quality of shadows, not accuracy of metering.
  3. I guess my basic question is,"how do I decrease the intensity of the flash output, or does it fire full strength no matter what?" Is it an all or nothing deal?
  4. Couple of things. Tv of 180 is too fast. What 50mm lens are you using? And does the flash need to push more light to get a proper exposure at the x-sync speed, hence, no way to turn the flash down?
  5. I have been able to control wireless P-TTL flash output with both AF-360FGZ and AF-540FGZ with all wireless-capable bodies I've tried it with (K10D, K20D, and K-7), I doubt K-5 is any different.
    Output ratio (1/1, 2/3, 1/2, 1/3, etc.) is not really controlling output level -- that's what Pentax calls 'contrast control', when balancing multiple flashes. Unfortunately, Pentax's documentation for contrast control flash really stinks, so the best I've been able to do is experiment and watch the results.
    I think this feature is really meant for use with multiple contrast-control-capable flashes, and I think they should work similarly whether connected wired or wirelessly. When I use an AF-540FGZ and AF-360FGZ triggered by my K-7's built-in flash, I can see the effects of changing this -- if I have the flash on the left set to 1/3 and the flash on the right set to 2/3, the shadows on the left will be darker as the output on the right was stronger. If I switch to 2/3 and 1/3, I predictably see the opposite effect. In both cases, I get essentially 'correct' exposure, but the balance among the flashes is varied.
    When using a single wireless flash, attempting to change flash balance using this setting isn't as smooth -- I think this is because the built-in flash isn't really adjustable for contrast-control, it probably behaves as if it's always set to 1/1. I think what you may be seeing is that when you reduce the setting on the off-camera flash to 1/3, the built-in flash power increases to compensate.
    When using P-TTL (wireless or wired, even with just single built-in flash) you can adjust flash output via flash exposure compensation; hit the flash button on your camera body, and below the flash modes you can dial down flash with the camera's e-dial.
    This is additive to the flash's built-in compensation dial, that is -- if you set flash to -1 and body to -2, that's effectively -2. I believe if you're using two flashes, you could set each separately with different FEC settings and/or contrast-control settings, and then control all of them from the body. For example, Flash 1 is set with 0.0 FEC, Flash 2 with -1 FEC. On the camera body you dial FEC to -1, so effectively F1 is now -1, and F2 is now -2. What exactly you get when you do this and set contrast-control as well, I don't know exactly, though I think there will be an effect. I have typically not used contrast control as much as just either using manual mode or FEC on the off-camera flashes to control output.
    When I'm doing this kind of multi-flash setup P-TTL (including contrast-control) sort of works but if I'm shooting something where I have the freedom of a little trial and error, manual flash tends to be more consistent & repeatable if flashes-to-subject distance is constant.
    I think the reason Jemal is asking about which 50mm lens is that with old manual-focus lenses, flashes may always fire full-power.
    Sample pics might help us understand what kind of lighting conditions you're shooting in and whether we think what flash & camera are doing is reasonable/predictable or not.
  6. I replicated the situation (with a K-5) and the output adjustment seemed to work correctly. It worked correctly doing the adjustment on the camera, too.
    But your problem may arise from the environment where you are doing this. Is it indoors or in open air? Indoors the flash is more certain to get the adjustment signals (small flashes) from the camera, in open air or a large room they may get lost and it just gets the one telling it to fire up.
    The 540 GFz should be a little bit in front of the camera, preferably with the sensor (under the dark red window) turned towards the camera. I mostly use a homemade extra diffusor on the camera flash to make sure it carries the signal sideways.
    In theory at least you could be too close to your subject, too, and then the flash simply doesn't have any lower output level to offer. But with ISO 100 and f 5.6 that doesn't seem likely.
    And you have set Custom function Nr 21 to Off, as you should have? Otherwise what you see may be mostly the light from the built-in flash. Being able to use it only as controller is a nice feature.
  7. Jemal;
    180 is the flash sync speed. I'm using a 16-50 f2.8 DA*. I can turn the flash up to high-speed sync mode, lessening the amount of light reaching the sensor by using higher shutterspeeds, but short of manipilating the amount of exposure, there is no decreasing the flash intensity, and that is what I am interested in doing.
    I'll spend some time this next week and reshoot, seeing if there is something I missed.
  8. I've been shooting K10s with 540 flashes for over 5 years, and I never use X...
    1/180 is the FASTEST shutter speed you can use, not the ONLY shutter speed you can use. I almost never run that fast indoors. Slowing the shutter speed down (a.k.a. dragging the shutter) will let more ambient light come up in the shadows.
    Shutter speed only controls ambient light, not flash exposure.
  9. Agree with Matt, if anything you can often get away with even slower than normal speeds, relying on the short flash duration to freeze the action. That said, while experimenting with flash output levels, locking shutter, aperture, and ISO is probably a good idea.
    Also, note that the custom setting to make the built-in flash a controller will not completely eliminate its contribution to the image, but will reduce it significantly. I have sometimes used a white card to 'bounce' its output away from the subject even though it's configured as controller. This is probably more of a concern for relatively close subjects without much ambient light.
  10. Well, this was shot in a confined space controlling the output of the wireless flash. No ambient light to speak of. Flash output +1, 0, -1 and -2 stops, PTT-L, the built-in as controller. Lens FA 1,4/50.
    Output ratio on the 540 at 1/1 in all shots.

    The shutter speed is not the problem, and assume Don uses 1/180 because that's what he wants to do.
  11. I initially misread the problem/question. Sorry. I do have a question. Does your K-5 have the shadow adjustment/highlight protection settings turned on? It could be that those settings are throwing off the flash when used wirelessly. I ask because you said that " the shadows were not less intense, just less exposed." Just curious. My 540 flash is broken (I need the hot shoe replaced - I broke it), and I don't have it with me currently anyway.
  12. Jemal;
    I checked and both highlight and shadow correction are turned off; should they be on? There are so many different settings and senarios that figuring out all this camera can do will take a very long time!

Share This Page