[andy888]

Nonsense.

It is true that the master emits some light even in control mode and that can create unwanted reflections in glasses, for instance, but the amount is way too small to make an image look "flat".

I am talking about the accuracy of TTL metering. That is Not "non-sense".


You seems know little about it. That is not only glass. any surface reflective would take account. because the TTL is made by the light meter inside the camera. which is a refective light meter.


Control light is not always small. depends on the setting of the camera. but always contribute light.


That is why Pentax has "exteranl cable" when has optical wireless TTL.

[clackers]

The optical wireless TTL is cheap, but TTL metering is not as good as wire connected.

You sure come up with some eccentric stuff, Andy.

Please explain why the metering would be different with or without a wire.

BTW, indoors, you wouldn't need a cable or trigger, the optical wireless is fine.

[Class A]

I am talking about the accuracy of TTL metering. That is Not "non-sense".

I only referenced the part of your post in which you claim that the contribution by the master flash, even in control mode, makes a photo look "flat".

1. That has nothing to do with TTL accuracy, and
2. Your claim is indeed nonsense.

I'm not 100% sure whether you mean what you write but there is no denying that what you wrote about optical triggering resulting in a "flat" photo is nonsense.

You seems know little about it.

Please, if you don't understand what someone else is writing about, don't accuse them of not knowing enough about the subject.

My correction stands as it is and anyone having used optical triggering will support it. I know more than enough about TTL accuracy as well, but that wasn't the topic.

[andy888]

You sure come up with some eccentric stuff, Andy.

Please explain why the metering would be different with or without a wire.

BTW, indoors, you wouldn't need a cable or trigger, the optical wireless is fine.

I think explaination is already very clear.


You have your preference. That is OK for you only. not me. I want excat TTL metering and no front lit.

[clackers]

I think explaination is already very clear.


You have your preference. That is OK for you only. not me. I want excat TTL metering and no front lit.

No, it's not clear, since TTL metering is done from the camera, not from the flash, what you've written you really puzzles me.

[andy888]

No, it's not clear, since TTL metering is done from the camera, not from the flash, what you've written you really puzzles me.

It is not dificult to understand what I said. only need some knowleage of TTL.


For preflash, the optical control also makes its contribution. what the camera meters is actually the mixture of the control leakage light and the slave flash light. it is not that "pure".


For the "main flash", it is caculated by a confused preflash, and mixed with the conrol leakage light.


That is the nature of optical trigger.


To make more accurate, need to use an exteranal cable or infrare trigger(like the SU800 for Nikon or ST-E2 for Canon)which contributes not visiable light.


Or the acon R930 radio trigger.

[clackers]

It is not dificult to understand what I said. only need some knowleage of TTL.


For preflash, the optical control also makes its contribution. what the camera meters is actually the mixture of the control leakage light and the slave flash light. it is not that "pure".


For the "main flash", it is caculated by a confused preflash, and mixed with the conrol leakage light.


That is the nature of optical trigger.


To make more accurate, need to use an exteranal cable or infrare trigger(like the SU800 for Nikon or ST-E2 for Canon)which contributes not visiable light.


Or the acon R930 radio trigger.

Well, if that's what you mean, I do half agree with you.

There is a hotspot that can appear even in the final image if you don't take precaution, because the commander flash hasn't fully decayed before the shutter opens.

But your master should be pointing at the slave flash, not the subject. You can flag it (some call it the 'black foamy thing') to make sure there is no direct contribution.

A pop up flash is a little harder but you could also reflect it off a wall or ceiling with something homemade - silver foil on the back, black cloth in the front - if you really wanted to.

[andy888]

Well, if that's what you mean, I do half agree with you.

There is a hotspot that can appear even in the final image if you don't take precaution, because the commander flash hasn't fully decayed before the shutter opens.

But your master should be pointing at the slave flash, not the subject. You can flag it (some call it the 'black foamy thing') to make sure there is no direct contribution.

A pop up flash is a little harder but you could also reflect it off a wall or ceiling with something homemade - silver foil on the back, black cloth in the front - if you really wanted to.

I want it but I don't need to, because I use triggers 930.


You can try these hard things to struggle from unwanted light. but never you can make it as easy and simple as these triggers
For example, you have many flashes at both side, which one would you point the comander to?
You can use the ugly reflect sheet. but weaken the control light, it is double edge sword.
You caon try to avoid the lit using manual mode of flash, because no metering is needed.
but hard to avoid metering confused. because this is more sensitive to weak light.

[mcgregni]

There is a series of pre-flashes. The initial control pre-flash sends instructions to the slave BEFORE the metering pre-flash ....the actual metering pre-flash comes from the slave, not the control unit, which is already at the decay stage of illumination when the metering starts. So the idea that controller pre-flashes mess with TTL metering is hard to buy into really.

[clackers]

There is a series of pre-flashes. The initial control pre-flash sends instructions to the slave BEFORE the metering pre-flash ....the actual metering pre-flash comes from the slave, not the control unit, which is already at the decay stage of illumination when the metering starts. So the idea that controller pre-flashes mess with TTL metering is hard to buy into really.

There will be some contribution from the master during the metering and during the shot.

Manual doesn't have this problem. For portraits, you don't get anyone blinking at the pre-flash, either.

[mcgregni]

But we need to define 'contribution' ..... Surely it is never more than a decaying remnant of stray weak light, not coinciding with the actual metering pre-flash. Could we seriously expect the effect of this to have any significant impact on the actual flash exposure that is calculated?

[andy888]

But we need to define 'contribution' ..... Surely it is never more than a decaying remnant of stray weak light, not coinciding with the actual metering pre-flash. Could we seriously expect the effect of this to have any significant impact on the actual flash exposure that is calculated?

By experiment, it does. some times the leakage flash make error exposure.


with the 930 triggers. it gets perfect exposure!

[mcgregni]

1/3rd of a stop? 1/2 a stop? Seriously? Or is it less than 1/3 stop ..... Really, even that sort of significant difference doesn't matter much as it falls within the range of normal variation for TTL metering and user creative decisions. As clackers said also, ideally our control flash won't even be pointing at the subject, but rather at the slave flash.

[andy888]

1/3rd of a stop? 1/2 a stop? Seriously? Or is it less than 1/3 stop ..... Really, even that sort of significant difference doesn't matter much as it falls within the range of normal variation for TTL metering and user creative decisions. As clackers said also, ideally our control flash won't even be pointing at the subject, but rather at the slave flash.

It depends. with relationship to the reflectiveness of the sceen.


Some times they are the same. some times not. 1/2 to 2/3 stop. you can see this still OK. in some cases 1 stop, error.


Some times, using the optical wireless giving different feel than radio or wire. It gets "flat". these are different pictures to compare there stops.

[Class A]

with the 930 triggers. it gets perfect exposure!

As if P-TTL computed the exposure perfectly down to a 1/3 stop or so.

P-TTL gives you a defined exposure for 18% gray but that hardly ever is the desired exposure for a shot. P-TTL can be useful in certain situations to give one a usable exposure but the artistically correct exposure will almost always be different to the technically correct exposure. For starters, the camera is either taking a spot reading of something that isn't of interest to you or doing some evaluative scene metering that sometimes hits the spot but often does not. The camera never has an idea of the mood one is after and if you start fiddling with flash exposure compensation you might as well go manual and have full precise and repeatable control.