One or two lights?

Janice

Janice

Suspended / Banned
Messages
11,626
Name
Janice
Edit My Images
Yes
Can someone explain something to me please?

I have been using a portable light studio this afternoon with a studio flash at the side of it, going through the white side of the studio box.
I have the camera on manual so the settings stay the same.

Now what I cant understand is this: when i take a shot with just the strobe at the side the shot is pretty overexposed (not a problem as I would then just alter aperture) BUT if I then pop up the onboard flash and take the same shot again.... the shot is perfectly exposed.

How can it be darker when using 2 lights and brighter when using one??
 
Check the exif and see if they are really at the same settings first.
 
Yes the camera settings are the same...same aperture, same shutter speed...only difference is that one says flash fired and one says flash didnt fire (which was the bright one where only the studio flash fired)
 
Dont really know much about all this, but its possible the Studio Flash isnt talking to the camera, as it isnt TTL, this will then be pumping out light at whatever power it is set to, without telling the camera to adjust anything, the onboard will talk to the camera and adjust its power allowing the shot to be better exposed ?

Someone will come along shortly and ridicule my thoughts im sure ! ;)
 
I think the answer Janice is that the pop up flash will always attempt to get you the correct exposure within it's range limits, and it's obvious limits with regard to aperture size. The onboard flash will operate in TTL mode regardless of what mode you have set on the camera... even manual.

Once you fire the onboard flash the returning light from the subject passes through the lens and hits a flash sensor inside the camera which deems when exposure is sufficent and kills the flash.
 
CT said:
Once you fire the onboard flash the returning light from the subject passes through the lens and hits a flash sensor inside the camera which deems when exposure is sufficent and kills the flash.
Click to expand...

Sorry.... and closes the shutter. :) So it's highly probable that the exposure is all over as far as your camera is concerned long before your studio light has output enough flash to over-expose the shot.

All in all it sounds like a happy but accidental state of affairs, and very dependent on the distance and power settings of your studio flash.
 
CT said:
Once you fire the onboard flash the returning light from the subject passes through the lens and hits a flash sensor inside the camera which deems when exposure is sufficent and kills the flash.
Click to expand...

That's why I asked but if the exif says the same then the same it will be - surely!:thinking: :shrug:

My next place to look will be at the light unit itself to see what might change there.

A real head scratcher Janice. :thinking:
 
Here are the shots....exif included: ah just noticed change of shutter speed............although original exif said both at 1/125 odd.

1st with the studio flash with a synch chord to the camera:

baublewithstrobe.jpg


and here with the flash popped up:

baublewithstrobeandflash1.jpg
 
I far prefer the first shot out of those two. :shrug:
 
Yes i havent done anything exept resize i just wondered why it was happening :|
 
Oh well who cares WHY its happening....just alter things till they turn out like I want them!! No problem!! :D
 
LOL. I've got to give it to you Janice, you ask some corker questions! :lol:

Seriously, I don't see any compelling reason to use the pop up flash at all in a studio setup. Remember, the pop up flash is a puny little effort with a tidgey widgey guide number compared to your studio flash.

It looks as though the pop up flash has taken complete control here which is what I'd really expect to happen with a built-in flash?
 
Yes of course you can.......................dont blame me for your idle ways!!!

So if I use a Sigma 500 DG Super off -amera as well as the strobe....i would need the onboard flash to trigger the sigma..........would the same thing be happening?
 
Lightweights!!!! :D :lol: :D
 
LOL @ HUN. :lol:

My gut feeling Janice is you'd be far better off using the Sigma via an extension cord from the hotshoe, which will retain all it's TTL capabilties and still fire the studio flash.

The main thing to understand is that your studio flash is purely manual and you can only obtain a correct exposure from it by setting it at the right flash to subject distance and at the correct power ouput. You can work most of this out from the unit guide number, but most people seem to prefer trial and error.

My approach would be get the Sigma producing a good result on it's own, then add the studio light into the setup adjusting it's distance from the subject and/or it's power output until you get a nice combined result from the two units. :)
 
What a clever boy! Even I understood that!! :D
 
Not easy stuff Janice and props to you for tackling it. I know it's a huge turn off, but an understanding of guide nos is crucial really with manual flash - we're all ruined by TTL systems and not having to think about it these days. ;)
 
CT said:
Not easy stuff Janice and props to you for tackling it. I know it's a huge turn off, but an understanding of guide nos is crucial really with manual flash - we're all ruined by TTL systems and not having to think about it these days. ;)
Click to expand...

Oh god Youve started me off again now!! If I know the guide no. of my strobe then i have to position it for distance and adjust the aperture of the camera accordingly. so does that mean i cant have the aperture I want on the camera for dof ?
 
Or move the light further away/nearer. No in fact switch it off....walk away from the camera! :p
 
HIMUPNORTH said:
No in fact switch it off....walk away from the camera! :p
Click to expand...

Now dont be like that!!! ;) Im afraid I just have to know how and why things work if Im going to use them. I cant just do it because someone says so!! So thank you all for your help, it's very much appreciated. :razz:
 
Now why does no-one ever believe me when I say that flash should always be kept under 100% manual control? This is typical of the confusion and head scrating that occurs when you let the computers do the thinking.

TTL, ETTL or whatever we have on cameras now is just for the lazy and braindead who have no interest in knowing how or why their cameras do what they do. That pretty much excludes everyone who might want to spend time on a forum like this one.

Manual flash is really soooooo simple, once you've got past the silly terms and the long standing misconception that it's something to fear.
:) :)
 
Janice said:
Oh god Youve started me off again now!! If I know the guide no. of my strobe then i have to position it for distance and adjust the aperture of the camera accordingly. so does that mean i cant have the aperture I want on the camera for dof ?
Click to expand...

No! Get the exposure right at your chosen aperture with the Sigma then adjust the studio flash distance and power output unil it blends nicely with the results from the Sigma. That's what I'd do.

If you were using the studio flash as the sole power soursce then the aperture would be an issue. Ditto if you were doing things the other way round with the strobe set up first and flash providing the fill.

It's a bit of a nightmare with guide nos. Don't forget you need to decide whether you use the guide no in feet or meters, and it varies with ISO setting. If you intend to use guide nos a lot, I'd work out the guide nos at all the ISOs you're likely to use then stick them on a note somewhere handy (on the strobe) saves a lot of brain fade. ;)
 
You can have the aperture you want by recalculating the distance for your flash unit e.g. GN / Aperture = Distance

As in this extract ...

"To find the aperture (f stop number) required to take a photo of a subject you divide the flash unit’s guide number by the distance to the subject. To find the maximum distance that can be reasonably illuminated using the current aperture setting you divide the guide number by the f stop number. In each case it’s the distance from the flash to the subject that’s important, not the distance from the camera to the subject. These two distances may be the same with on-camera flash, but not with off-camera flash or when using bounce flash.

f-stop number = GN / distance
distance = GN / f-stop number"

From this useful little dialogue ...

article on eos-flash

Dunno if that is any use ... but at least it is easy reading ... :D



:p
 
CT said:
If you were using the studio flash as the sole power soursce then the aperture would be an issue. Ditto if you were doing things the other way round with the strobe set up first and flash providing the fill.
Click to expand...

I am! The strobe is the main one... and the sigma is wireless as the fill. Perhaps thats not the best set up, or maybe id be better off with another strobe the same as the first.
 
Janice said:
Now dont be like that!!! ;)
Click to expand...

Like what. :shrug: I answered the question didn't I :D


Like CT says once you have practiced it you will find it all makes sense and eventually you will know what you want it to look like and dial in accordingly.

Not to say it isn't frustrating. When shooting manual / off camera / outdoors in changing light you can get michty flustered!


I see the household objects in your other thread.....whats next? :naughty:
 
Stop right there Janice! A light source is a light source. I still use my old EZ flashes for fill lights - always set to manual.

I have given this link before but for some great off camera lighting tips visit here.


HTH :wave:
 
You can calculate your settings for flash work with the guide numbers and a tape measure.Taking into account film speed and exposure compensation for any colour corection filters etc.

Much easier than that is to stick a flash meter in front of the subject and set your aperture accordingly.

Easier though even than a flash meter, is to work off the histogram. Set up the camera and lights and take a punt on the aperture you'll need. If the shot is a little too bright, close the aperture down or reduce the light. Too dark, do the oposit.

There really is no more to it than that. Working off the preview/histogram is the most reliable and quickest way there is to use flash.
 
Thank you. :notworthy: Its just practice, practice, practice then.
If people stand up then sit down etc etc during a portrait shoot....I would have to up and down the lights on their stands accordingly would I , to keep them athe same angles to their faces ?
 
Daz is right of course, people only think manual flash is difficult because we rarely have to do it any more until we're confronted with a manual flash setup as Janice is here.

It's basically very simple, you either...

1. Divide the aperture into the guide no to give you the correct distance.

2. Divide the distance you want to work at into the guide no to give you the correct aperture for that distance.

Where things get a bit trickier is when we want to balance flash with daylight (fill flash) when you have a focal plane shutter - which all our DSLRs have. You use the guide no and aperture from your ambient reading to calculate your working distance which is completely fixed by that calculation. I suspect that along with hordes of other wedding togs Daz, I'll plead 'Guilty' to being a bone idle sod and happily relying on TTL flash on those occasions. ;)
 
I suspect that along with hordes of other wedding togs Daz, I'll plead 'Guilty' to being a bone idle sod and happily relying on TTL flash on those occasions.
Click to expand...
The main reason I never ever use TTL is that I don't trust it. Since I don't know exaclty what those algorthyms or whatever else is at the centre of the software is actually doing, I have a deep mistrust of it.

Whenever I've had a play with it on the Canon, I always end up having to dial in some comp to get what I want anyway. It takes less time to fire a frame and tweak the aperture.

So who's the lazy one really? :lol:
 
If people stand up then sit down etc etc during a portrait shoot....I would have to up and down the lights on their stands accordingly would I , to keep them athe same angles to their faces ?
Click to expand...

In short, most likely yes.

It all depends on the angle of the flash to the subect and distance. If you have your lights far enough away from the subject, a change in height of a few feet might not make much difference at all as the angle wont change a lot and the coverage gets wider as you move the lights back anyway.

If you're short on space and/or using lowish powered lights so you cant move back then a small change in position will greatly alter the relationship between the lights and subject and all your setup will float out the window.

It's at times like this that those bloody expensive powerful heads start to show their value. :)
 
You must log in or register to reply here.
Back
Top