Question - Over exposed backdrop...

[SUNR15E]

I was playing with the January assignment....

And I hit a mental block...well not so much block...I know the theory...but.....it's not working....so I changed a million settings and moved the flash and moved me and changed some more settings.....

and on it went...

Well I have had to stop because my batteries went flat...So I will ask you Ladies and Gents....Please help...ALL OF YOU.... The more theories I get for this one the more I can try..

So here goes please be patient.


Part1 by SUNR15E, on Flickr

I'm pushed for space so 10ft is all I have...But I know that is not the problem...

Looking at the above setup...I get a great silhouette of the subject in the center of the room with little to no bleed of light breaking the silhouette....this is great....the backdrop is almost perfectly white (I will work on those settings I know I can fix that).

BUT


Part2 by SUNR15E, on Flickr

Can you tell me what SHOULD happen when the flash on the camera fires. I have read loads and I think I have the idea set up correctly in my own head....BUT...in practice something is not right...

The camera is set up to allow the flash behind the subject to overexpose the backdrop.

I will add more about what I think should happen and also what is happening Once I have a few theories and answers here first if you don't mind.

So in summary.

In the above setup

What should happen?
What should the final picture look like if the camera flash fires?

Many thanks for your input...And yes I will be adding pics to show my fails....!!

SUNR15E

[Citruspers]

Your subject should be properly (though harsh) illuminated from the front?

[SUNR15E]

OK yep that's one theory...

And yes that is what I was expecting to see....

But

What would/should happen to the backdrop??

SUNR15E

[Trevor Harris]

The background in each photo would look the same... provided the camera is in manual mode, which it should be if using the scientific method of "all things being equal apart from one variable".

[SUNR15E]

Thanks for that....Again I was assuming the backdrop would be over exposed in each pic...

As you say Camera set to manual so that nothing changes.

The only difference as stated was the flash fired on the camera..

Tomorrow I will add two pics showing my dilemma..(sorry it's late and I have had a long day)

Goodnight...but please if others have anything else to add please comment.

SUNR15E

[SUNR15E]

Ok before we go to much further....I was not in a studio and I was not expecting to put these on display... I was simply playing with Light.

I was simply confused with the results..

So here is the picture I was happy with....All I was looking at was to explode white all over the backdrop....simply to see if I could white it out completely...


SUNR15E_20120110_17-56-30 by SUNR15E, on Flickr

Then I thought maybe I would like to see the something in the center of the room. I assumed that adding more light would add to the whiteout on the backdrop....PLUS add exposure to the item in the center of the room....with the possibility that it may be over exposed but...I was confused with this.


SUNR15E_20120110_17-56-46 by SUNR15E, on Flickr

I have no idea what I have done to make it all CLEAR..??

Both Flashes fired...no setting changed...yet rather than whiting out the backdrop...I can see the backdrop...What?? How??

At first I thought the rear flash had not fired...?? Which I will assume I will be told..But I tried a few times...and got the same results. Different ISO different aperture different just about everything.

I will go away and do all of this again....but before I do....

Please tell me what image number two should look like with the flash firing on the camera..?? Should the backdrop remain overexposed and whited out as I assume it should..??

The more I write here the more I am convinced that the rear flash completely missed but I have no idea how this can happen..??

Please note I was not attempting to produce a quality image...I was simply playing with Light.

Thanks for your help if you can offer something which points me in the right direction.

SUNR15E

[SUNR15E]

So I am right then...it is all to do the the lunar alignment??

Thats what I thought...

SUNR15E

[ianganderton]

What setting did you have the camera on and what setting did you have the flashes on, I.e. What metering were you using? I'm assuming it wasn't manual across the board (camera and flashes)

Where were the flashes in relation to the wall and the 'object' in the first and second shots

While the camera settings (ISO, appature and shutter) might have remained the same (I can't see the exif data) the power of the flashes must have changed

Based on an assumption you had some form of metering going on If you only lit the background in the first one the camera would have also tried to expose the foreground correctly. Because you lit the foreground in the second one the camera could adjust the power of the 2 flashes to expose the 'scene' correctly.

As an exercise turn everything to manual including the flashes and see what effects you can reproduce

[SUNR15E]

Everything was exactly the same in both shots....nothing changed.

The only difference is the camera flash fired in the second picture...

The flash was mounted behind the subject in the center of the room.

The backdrop was 5ft behind the subject which was 5ft in front of me.

The flash was set up at maximum everything to over expose the backdrop and completely white it out. Which it was close to doing. But everything staying the same and the only addition being the flash on the camera being allowed to fire has confused me. It should not have done what it appears to have done. The efix match for both pics down to the smallest details.

I guess I will have to go away and do something similar and see if it happens again..??

Sorry it makes no sense to me...both pics should have the backdrop whited out....I will go try again..

Cheers anyway.

SUNR15E

[Citruspers]

Well, the theory is solid, that's been proven many times.
Practice CAN'T be wrong, so I guess the error lies in the execution somewhere.

Maybe you missed a small setting somewhere. Are you shooting completely manual? (both flashes and camera?)

I'll reproduce your experiment tomorrow, just for the hell of it

[SUNR15E]

Your madder than me if you are going to do it yourself...lol

I want to prove to myself that the info I am giving is wrong..??

It should not happen like this and I want to prove it should work the way I expected it to come out.

I look forward to seeing how you do it. And I expect the results will be what I expected to find myself.

Cheers

SUNR15E

[Plymer]

Okay, a few pieces of info are missing here.

What is your background light (as in, what kind of flash unit)?

Is it on any kind of automatic setting? Or was it in Manual and set to a certain ratio (1:1, 1:2, etc)?

How are you triggering your background light?

And is it the pop-up flash that you're using as your on-camera light?

The result in the 2nd photo looks as if somehow the background flash has not fired at all, either not being synched properly or it is knocking the power down somehow. I think this has something to do with your you're triggering the background light though...

[Citruspers]

Here's my attempt. Everything is on manual (both flashes, shutter, aperture, ISO).


Single flash behind the subject


Flash behind the subject + flash front left

All settings were consistent between these shots, and as you can see the background exposure is roughly the same (it might be a bit brighter due to the second flash).

[SUNR15E]

Yep...

Exactly what I would have expected to see..

So I will assume it was the flash which fired incorrectly...

I will look into that and see what I need to do differently to make it fire when I need it to.

Thanks.

I will go away and play for a while.

Cheers for the input everyone. It has all helped me with the thought process involved in this one.

SUNR15E