Blowing a backdrop & Off camera flash

S

Slvrbck

Guest
Hi all 2 questions.

Blowing a backdrop
I saw in a thread (but now can't find it) that you can point a light at a studio backdrop in order t blow it and get a pure white background. I have had a quick look and found a few options but wondered what other people use, if anything at all.


Off camera flash
I have a 400D & a Sigma EF-500 DG ST Flash. I have done a couple of macro shots but they could be a million times better with some clever off camera flash. Do I need to look for anything in particular when looking for a sync cord or is this something you can only do with a "high end" flash unit?

Cheers for your help,
Gaz
 
You cant use a sync cord with a sigma flash as they dont have a socket... but you can use them wirelessly or buy an adapter which fits onto the hot shoe and gives you a pc socket that way.

as for blowing the bg two lights on the bg at 2 stops brighter than the subject will blow it.
 
Hi Janice,
Thanks very much for the great advice.

Would something like this work to provice off camera flash?

Don't want to blow loads off dosh on more lights untill I understand what I am doing with them :LOL: so will stick to touching the BG up in photoshop for now I think.
 
Slvrbck said:
Would something like this work to provice off camera flash?

Don't want to blow loads off dosh on more lights untill I understand what I am doing with them :LOL: so will stick to touching the BG up in photoshop for now I think.
Click to expand...


Yes it would. You can also daisy-chain them to provide a longer cable if needed.Though for the same money as one remote cord you could, as Janice says, get a wireless trigger set up wihich you can expand to work more flashguns as you get them. The only difference would be that the wireless triggers only work manually, so you would lose the ttl feature and have to set the flash output yourself, but as you gain more confidence you'll probably want to do this anyway.
 
How do you actually measure the background to two stops over? As when you meter for the BG the flashes are not alit and the meter will be showing the ambient light.
I need another two lights for this as at the minute i only have two which i use for the subject(s). Or could i use a couple of cheap nikon flashes to OE the BG?
 
You use a lightmeter, fire the flashes off while holding the meter and it registers the flash. The best ones at the moment are sekonic but if you don't want to spend a lot on a digital one them a good old fashioned Weston Master off ebay will do it. The only other option is to shoot and check the histogram on the camera but it is a lot less accurate.
 
Where can you pick up a reasonable decent light meter? Under £100.
 
ebay or a second hand camera shop. The seconics start at about £130.
 
£80 or so will buy you a new Sekonic 308s from URGalaxy on Ebay, a bit more if you want one of the higher-specced models
 
Flash In The Pan said:
£80 or so will buy you a new Sekonic 308s from URGalaxy on Ebay, a bit more if you want one of the higher-specced models
Click to expand...

Oh right, what would the higher spec'ed model ones give me that the 308 wouldnt?
 
Cheers for tthe advice all.
Looks like my next investment will be a light meter.
 
Janice said:
as for blowing the bg two lights on the bg at 2 stops brighter than the subject will blow it.
Click to expand...



2 stops is too much Janice, it should be 1 at most if it's white or there'll be so much light bouncing around it'll affect your subject

I shoot my subjects at f8 or f9 (depending on skin colour) and the background is set at f11

DD
 
Thanks O studio one! (y)
 
Yep, get too much light and it bounces back onto your subject.

I have to say though DD, most of the stuff I've read on studio lighting has said two stops.

I know that there are a lot of variables to take into account, not least what power are you putting on your subject, distance between subject and background (inverse square law will apply to the light reflected off the background too) and the reflective nature of the background in the first place.

I know you do a lot of studio work so I'm not about to question the wisdom you bring to the subject (I'm not that silly) but I have found a lot of stuff out there that does recommend two stops.

Down to trial and error at the end of the day I suppose. :)
 
Hi AliB

I think this simple point is easily the most confusing in studio work, by which we usually all mean the 'white' room effect, but (as GarryEdwards - big studio chap will attest too) all you need to do with a white sheet of paper/sheet is slightly overexpose it as white blows so easily

2 stops is fine if you haven't got the coverage from your background lights as a way of ensuring the whole thing blows to white... BUT

Most of us, and certainly with the queries we see on here, don't have a large enough space to allow those 2 stops to fizzle out before having an effect on our subject. If you blow a background to 2 stops and your subject is within 6 feet, possibly more, then the background is now lighting the subject - which can cause 'spill' light (often useful in small doses) but more often can almost rim-light your subject's hair

You light the background - then you light the subject

Small rooms have the background lighting the subject to some degree, so just slightly overexpose it to avoid too much effect

Make sense?

1/2 to 1 stop if your light spread is good enough will solve other problems; 2 stops is still okay IF your subject is far enough away from the background AND the side walls aren't close and white too - i.e. a converted garage

(y)

DD
 
Makes perfect sense, thanks DD.

Metering the background first is not something I've ever done to be honest, will have to give it a go. The f11/f8 combo is what I would normally be aiming for.

It's also one of the things I need to watch out for when using the lasolite hilite at home. If I'm not careful it can go from being a background to acting like a huge softbox!
 
This is all really useful folks, thanks.
I am using a small space and have another shoot this weekend so will have a play.

Cheers.
 
You could save a huge amount f money and buy a tape measure and manual flashes....it is only a matter of doing the maths. You do the maths ONCE, write down the answers in a table form - and then all you have to do is refer to the table. OR if you can't be bothered to refer to the table, then you can mark the floor with different coloured tape - you place your flashguns at the tape marks and set the flash for the distance to subject (1/16th, or 1/8th or whatever according to the aperture you want to use)
Mark the tape with the aperture and setting if you like - stuck down crib sheets if you like.
Automatic flashguns are just doing the maths for you.......and you pay for those sums to be worked out big time!
 
You must log in or register to reply here.
Back
Top