Need help with K20D and wireless flash

kthung · 10-30-2009, 09:57 AM

I can't seem to get my K20D to work with my 530 Super in controller mode. Whenever I try and do so, the onboard flash shows up in the picture. I am using the pop-up flash as an onboard controller (which should work, right?).
Here is an example:

The flash is off camera left and the bright reflection you see in the phone is on board flash.

What am I doing wrong?

*mtroute* · 10-30-2009, 10:45 AM

Originally Posted by kthung

I can't seem to get my K20D to work with my 530 Super in controller mode. Whenever I try and do so, the onboard flash shows up in the picture. I am using the pop-up flash as an onboard controller (which should work, right?).
Here is an example:

The flash is off camera left and the bright reflection you see in the phone is on board flash.

What am I doing wrong?

Not sure on the K20 but my K200 has a setting in the custom menu (item 16: "flash in wireless mode")to switch the built in flash to controller mode so it doesn't act as the main flash. This should fix the problem.

*Ash* · 10-30-2009, 11:00 AM

That's right. It's the same on the K20D. Once flash in wireless mode is switched off, then it won't fire during exposure (only to control the wireless slave).

amoringello · 10-30-2009, 11:03 AM

Note that the pop-up flash MUST fire during exposure to tell the remote flashes to fire. (how else would they know when to go off?) BUT, as the controller the pop-up flashes very with very low power.

In most instances the pop-up flash will not be seen and will not affect the image (unless you're very close), but it can still be noticed on reflective surfaces.

*Ash* · 10-30-2009, 11:56 AM

That's news to me. Thanks. But in any case, light intensity from the controller should be negligible.

amoringello · 10-30-2009, 04:40 PM

By the way... it looks like you may be pretty close and the pop-up might still affect the image as well is being visible in the reflection.

What I have done in the past is take a piece of white cardboard and bounce the flash towards the remote flash, keeping any light from hitting the scene. This should greatly reduce or even eliminate influence from the pop-up.

You can also up the aperture and the remote flash power to make the pop-up flash even more negligible. Helpful if you do need to be very close to the subject.

*Ash* · 10-30-2009, 06:02 PM

Guess there is a virtue for having an external flash unit as a controller - you can control the direction of the trigger flash.

kthung · 10-30-2009, 08:08 PM

I have set the setting in the custom menu to have the flash off (ie. controller mode) it was my understanding that the onboard flash should only preflash before the shutter is released to tell the wireless flash to fire. In either case, it is certainly not negligible and I can tell that the onboard flash fired even without a reflective surface since I can see a shadow from my lens partially obstructing the flash.

amoringello · 10-30-2009, 09:03 PM

Yes PTTL flash communicates various info prior to shutter opening, but the actual full power flash needs to be triggered by a final minor flash from the pop-up... and that needs to be while the shutter is open.

Still, without more information it is difficult to tell if what you're seeing is expected or not.
What aperture is being used? And how far are you from the subject?
Both of these will have an affect on how much the pop-up will be visible.

Although it sounds like the pop-up is contributing more than would be expected... just difficult to tell without more info. Silly question... do you have the flash on the camera set to wireless-mode?

I would do a test with the camera about ten feet form the subject.
Put the remote flash about one or two feet from the subject.
Set the aperture on the camera to f8.
Take a photo with the remote flash on, and another with the remote flash off.

If you do not get an extreme difference in exposure and you still have significant exposure from the pop-up, then things are not working properly. At ten feet with the remote flash off, you should get a near black image (assuming little or no ambient light).

One more thing... I am not familiar with the 530 Super. I am assuming that it has a PTTL compatible mode and will properly respond to the pre-flash communications. If it did not, I would suspect an near black image for both of the above tests.

If that fails, I think I'm out of suggestions.

kthung · 10-30-2009, 10:06 PM

Thanks for the suggestions Amoringello. I'll try some of those suggestions tomorrow. In this particular example it was:
1/125
f/2.8
65mm (~2 ft from the subject)
iso 100

I double checked several times, making sure that the flash was in wireless mode (the off camera flash won't fire otherwise) and that the onboard was wireless mode. I'm willing to accept that some of the pop-up flash will contribute to the final picture, but I can't accept that there is no discernible difference between master and controller modes for wireless flash.

*Sew-Classic* · 10-31-2009, 06:49 AM

Originally Posted by kthung

Thanks for the suggestions Amoringello. I'll try some of those suggestions tomorrow. In this particular example it was:
1/125
f/2.8
65mm (~2 ft from the subject)
iso 100

I double checked several times, making sure that the flash was in wireless mode (the off camera flash won't fire otherwise) and that the onboard was wireless mode. I'm willing to accept that some of the pop-up flash will contribute to the final picture, but I can't accept that there is no discernible difference between master and controller modes for wireless flash.

Go to the custom settings menu.

Go to setting number 29 (Flash Discharge in Wireless Mode)

You can select either

1. On - Discharges the built-in flash

or

2. Off- Discharges the built-in flash as a test flash

You want option number two. Have you selected that?

I kinow that with the K2000 and the K-7 the discharge of the onboard flash can be controlled and there is a marked difference in th results between the two settings.

amoringello · 10-31-2009, 07:03 AM

I forgot one important issue...
Be sure to run these tests with NON-refective subjects. Make sure things are working correctly first!!
I was running some tests and wanted to post examples, but then quickly remembered how much trouble specular highlights give Pentax's PTTL flash metering system!!!!!!!!!!

Any specular highlight from the flash will be metered into non-hilights.. i.e. Pentax seems to want to set the flash such that i ensured that NO part of the subject is over-exposed.
Well, the definition of a specular highlight is that it is a spot of super bright light, usually pure white or higher!!!

Thus, the entire scene is BLACK with a spot of flash. In most cases this results in ugly underexposed images... such as when you photograph a lady with a shiny necklace or someone holding a glass of champagne. ARGH!!!! ARGH!!! ARGH!!!

With a reflective surface, the exposure was nearly identical with and without the flash being in controller mode.
The exposure was also nearly identical with the remote flash at +1 brightness... the specular highlight forced the remote flash into its lowest power setting and nearly matches the pop-up flash power so again NO significant difference in exposure.

This will also happen if about 10% or more of the image contains a white wall behind the subject!
Note also, that when metering, Pentax uses the FULL sensor regardless of the metering mode you have it set to. There is no such thing as SPOT metering with regards to metering required flash strength. (I believe other brands behave the same way... I'm sort of guessing that the camera needs to determine ambient v.s. subject lighting). I did not get an explanation why from Pentax, but they did confirm that the entire sensor is used with determine flash metering.

Pentax's PTTL is a royal pain in the ass and sucks very hard!
I have not heard of such difficult issue with other brands.
Don't get me wrong, PTL is nice for most situations but if there highlights that should be white, FORGET IT!.

I have since gone to pure manual for any sorts of portrait work.
Even for dogs portraits, if they still have a collar on, the slight reflective point from the leash-link will cause the exposure to suck. Remove the collar and the image is just fine!

Sorry, I have not used PTTL in so long that I forgot the main reason I don't use it any more. I guess I was more interested in answering your questions than trying to convince your to drop PTTL. If you get PTTL to work well and consistently, it works well. It is just very difficult to look at every scene when it is dark, and pre-determine if the camera is going to have issues.

*Sew-Classic* · 10-31-2009, 08:05 AM

I shoot alot of old, shiny, black sewing machines, and reflections are my nemisis. I've had both my face and camera show up in knobs and levers, really weird looking!

Anyhow, if, in wireless flash mode, the built-in flash is set to Off (Discharges the built-in flash as a test flash), and if it's showing up in your photo, then chances are that you need to recompose things. Even without any flash, your camera would likely show up in that situation.

Below is a shot I took using the AF360 as a slave (wirelessly -the flash was about three feet off to the side) in full PTTL mode, controlled by the buit-in flash which set to discharge as a test flash only. You'll see that there is a white box, a mirror a dark table, light gray brick and a black fireplace in the scene. I set the K-7 to M mode, f/5.0, 1/80s, iso 200. Ugly and dirty, but quick.

I find that with any scene that has really dark and reallly light subject matter (like black and white) it pretty tough to get both exposed properly using any auto exposure or PTTL systems. I'm sure that some equipment handles it better than others, but to a certain extent, it's the nature of the beast. Thsi is where going full manual and using a grey card can be helpful. Using the +/- compensatin settings on the flash helps too. Most of the time, when I use my flash wirelessly, I use it in manual mode (1/8, 1/16, etc.. power). I don't know if the Sigma flash will allow that.

"What's with the weird sign??", you ask. I've been playing with using it to illustrate the shininess of the machines.

kthung · 10-31-2009, 03:30 PM

Thanks for the help everyone, I guess the problem was the working distance. Moving back to about 4-5 ft made all the difference. And yeah its a huge PITA to try and get consistent results from P-TTL. I guess I'll eventually just get some radio triggers and go manual

amoringello · 10-31-2009, 04:50 PM

Fantastic! Glad that helped.