[jpzk]

I didn't know how to word my title but here is the "question":

I am making some experimenting with the Pentax AF 540 FGZ as a slave flash while the built-in flash becomes the "controller".
Camera is the K7

Is it normal to have an overexposure even when:

- the external (remote/slave) flash is on "Manual" 1/64th power,
- the built-in flash power has been reduced to -2.0
- using a fairly wide aperture - - f1.4 to f2.8
- at a (probably too close) close range - - 4 to 7 feet.

- lenses tried: Pentax FA 50/1.4
Pentax FA 31 Ltd
Pentax FA 43 Ltd
Zeiss 85/1.4

Things seem to become much better (i.e. no overexposure) as I get farther away from the target and stop down a bit more.

I realize that there has been a lot of fuss regarding the overexposure from the K7 but I am just wondering if the above setting might be way beyond expecting any decent results.
Bear with me folks, I am still trying to make this flash thing work ... not easy!

I will gladly accept proper critisizing but no rudeness please.

Thanks.

JP

[philbaum]

jpzk,
I wouldn't criticize anyone using flash, one of the most complex subjects out there

The best discussion i've read about pttl flash is from Twitch in this post - it helped me a lot:

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/153865-flash-ov...ml#post1599117

So if you use Twitch's technique of using the Manual eposure mode, how many ev stops are you under a "perfect" exposure", twitch recommended 1 to 3 stops under?

Also, are you sure you have the onboard flash in controller mode - check the custom menu to make sure i think. Otherwise the onboard flash may be trying to make up the difference.

For the onboard flash, what flash ev setting is set?

What is your iso setting for this shot?

What exposure mode setting did you use for this shot?

1/64 is not a lot of power, but perhaps if you had a high iso setting, the preflash from the controller gave you more exposure than you intended. Also, if the onboard flash controller setting wasn't properly made, than the onboard flash may be trying to contribute more lighting than you intended, an a "master" flash.

best wishes,

[Digitalis]

The problem is that with using the built in flash at wider apertures with close-up subjects is that the built in flash will be far too powerful and it will visibly contribute* to the exposure - which is most likely causing the over-exposure, because the built in flash can't - or won't throttle the power level down far enough. I would recommend you use the longest lens you have to eliminate this effect( the Zeiss 85 should fit the bill).

* when the built in flash is set to controller theoretically it isn't supposed to have any effect on exposure but because you are close to your subject not much light is going to be seen by the slave flash - so the controller uses a higher power level to make sure the slave flash can synch reliably.

[SOldBear]

In wireless mode, even with the built-in flash set as "control," it may still be powerful enough to cause overexposure at close distance and at larger aperture.

Note that this problem is not unique to Pentax. Other camera brands have the same problem. I've read that Nikon SG-3IR also works with Pentax to reduce the effect of the built-in flash.

Also, "- the built-in flash power has been reduced to -2.0" does not apply in wireless mode.

---

Last edited by SOldBear; 10-02-2011 at 11:29 PM.

[jpzk]

jpzk,
I wouldn't criticize anyone using flash, one of the most complex subjects out there

The best discussion i've read about pttl flash is from Twitch in this post - it helped me a lot:

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/153865-flash-ov...ml#post1599117

So if you use Twitch's technique of using the Manual eposure mode, how many ev stops are you under a "perfect" exposure", twitch recommended 1 to 3 stops under?
Thanks Phil; Yeah ... sort of get the idea but as usual, not quite. I'll have to read this about twenty times before I understand.
Also, are you sure you have the onboard flash in controller mode - check the custom menu to make sure i think. Otherwise the onboard flash may be trying to make up the difference.
o doubt the built-in flash was the controller and the remore flash was the slave.
For the onboard flash, what flash ev setting is set?
I thought that this didn't matter because as SOldBear reported below: it doesn't apply in wireless mode.

What is your iso setting for this shot?
I've tried a few dufferent ISO settings but of course now I realize that the higher ISO's, at close range, will produce an overexposure.
What exposure mode setting did you use for this shot?
Mostly manual.
1/64 is not a lot of power, but perhaps if you had a high iso setting, the preflash from the controller gave you more exposure than you intended. Also, if the onboard flash controller setting wasn't properly made, than the onboard flash may be trying to contribute more lighting than you intended, an a "master" flash.

best wishes,

As you mention, this is very complex and this whole business of flash photography is always a big pain the the %*! for me. I used the 1/64 power at the slave flash as a baseline to see what results I would get by slowly increasing the power, step by step.
It is not working too well anyway.
I'll keep at it for a bit and try to figure out a way to take at least ONE good shot with flash.

Thanks for the reply.

JP

[jpzk]

The problem is that with using the built in flash at wider apertures with close-up subjects is that the built in flash will be far too powerful and it will visibly contribute* to the exposure - which is most likely causing the over-exposure, because the built in flash can't - or won't throttle the power level down far enough. I would recommend you use the longest lens you have to eliminate this effect( the Zeiss 85 should fit the bill).

* when the built in flash is set to controller theoretically it isn't supposed to have any effect on exposure but because you are close to your subject not much light is going to be seen by the slave flash - so the controller uses a higher power level to make sure the slave flash can synch reliably.

Thanks, Digitalis ....

So, I would assume now that using getting too close is what I was doing wrong, causing overexposure.
I had no idea that the built-in flash, even when used as the "controller", would emit so much light as to cause O/E.

... because you are close to your subject not much light is going to be seen by the slave flash - so the controller uses a higher power level to make sure the slave flash can synch reliably ...
Is there a specific way to "place" (or a safe/optimal distance) the slave unit or is this simply a matter of "luck", hoping that the amount of light emitted by the controller will trigger the proper amount of light from the slave?

Using the 85mm lens will likely get me better results, as you mention .... I'll give it another go.

JP

[jpzk]

In wireless mode, even with the built-in flash set as "control," it may still be powerful enough to cause overexposure at close distance and at larger aperture.

Note that this problem is not unique to Pentax. Other camera brands have the same problem. I've read that Nikon SG-3IR also works with Pentax to reduce the effect of the built-in flash.

Also, "- the built-in flash power has been reduced to -2.0" does not apply in wireless mode.

I understand that issue with being too close AND using a large aperture ... will likely cause overexposure.

Digitalis and Phil reported that same issue in prior posts above, so that makes it three people telling me that I am too close to the subject AND using a large aperture ( my words: with a lens that allows me too get too close .... does that make sense?).

I'll get on with some more practice shots and hopefully post some here as samples.

Cheers to all and thanks!

JP

Forgot: ... about this IR panel ... how is this supposed to let the built in flash behave as the controller if this "panel" is mounted on the flash "shoe"?

[SOldBear]

... about this IR panel ... how is this supposed to let the built in flash behave as the controller if this "panel" is mounted on the flash "shoe"?

For the intended cameras (e.g. Nikon D200, D70 & D70s), the panel when attached to the hotshot probably does not prevent the built-in flash from raising.

The IR panel does not need to be mounted on the camera's hotshoe. The hotshoe is just a convenient anchor for it.

If the IR panel, when attached to the camera hotshoe, prevents the built-in flash from raising, you probably can find a way to mount the panel so it doesn't.

[SOldBear]

What if I tell you the IR panel costs you less than $12? In fact, it costs next to nothing.

Below are two photos taken consecutively with a K-7 and an FA 50. The settings were exactly the same: ISO 400, F/1.7, 1/100 sec, p-TTL wireless with the built-in flash as control, off-camera Pentax 540 as slave. The camera was about 3 ft. in front of Roo, the Pentax 540 (with a Sto-fen) was 4 ft. on the left of the camera.

The only difference: for the second photo, I covered the built-in flash with a leader of a roll of negative color film.

Yes, you can use a strip of fully-exposed negative film as an IR panel.

[jpzk]

I thought that covering the built-in flash would cut out the signal to the slave flash ??
Does that mean that your strip of film (exposed) still allows the IR light to reach the slave flash unit? That way, I would assume that this IR panel which was discussed earlier would allow for that too. I don't understand the principle here ... sorry.

JP

[snostorm]

I thought that covering the built-in flash would cut out the signal to the slave flash ??
Does that mean that your strip of film (exposed) still allows the IR light to reach the slave flash unit? That way, I would assume that this IR panel which was discussed earlier would allow for that too. I don't understand the principle here ... sorry.

Hi JP,

The exposed and developed color neg film effectively blocks visible light from the popup, but allows IR to pass, which is enough to trigger the slave. Ive been doing this for years, and it's a very useful tip.

Scott

[SOldBear]

I thought that covering the built-in flash would cut out the signal to the slave flash ??

Sure. But you use this trick only when the distance from the built-in flash to the object is short. There's a good chance the distance from the built-in flash to the slave flash is short too.

Otherwise the light emitted by the built-in flash as a controller won't have a noticeable effect on the exposure.

[jpzk]

Thanks a bunch, SOldBear and snowstorm: I get it now, sorry about my inexperience with those sorts of things. I'll give that a try and I also have a good supply of thouroughly exposed neg,s from "way back when".

One more thing: ... K5 + remote flash + HSS ... possible at all ? Works OK (HSS) when the flash is mounted on the hotshoe but not on remote mode. Any way to tweak this to work?

JP