View Full Version : How do I prepare and expose correctly for externally mounted flash?

8th April 2008, 12:52 PM
Hi All

Here's an interesting one I'd like some advice on if I may please. I have the Olympus FL-50, and have recently acquired a lead that allows me to use this excellent flash unit off-camera. Now - what I would like to try, is to mount the FL-50 close to my bird table on a tripod stand, say about 4' away from where the birds would land, and then with it (obviously) connected to the E-3, use this to take some 'action' type shots when birds come to the table and feeders.

I often capture some birds arriving at the feeders, or leaving them, but because the light isn't perfect, and the lens combination I use isn't the fastest, these shots don't freeze the flight motion. Using flash in P mode would.

How though, do I ensure that I get the correct exposure as the flash won't be positioned on the E-3 and will be much closer to the birds than the camera will be.

Can someone advise as to the process for ensuring correct exposure please...? Thanks.

art frames
8th April 2008, 01:15 PM

I am very interested to see the answer to this and also to ensure I get the right cable to use the FL50 off camera (for butterflies rather than birds).

Hope someone knows.


B.P.S Studios
8th April 2008, 01:22 PM
Hi Music man,

This is a tricky one. There is a strong risk that you will over expose if the flash is going to be closer to the subject than the camera based on what the camera sees from its own position. You may need a light meter here to set the Aperture/GN number for the flash. The first thing to do is to frame and focus your subject with the camera in Manual mode ( use auto focus) Set a shutter speed of about 1/500sec and take a reading with the light meter from the subject for your aperture based on the shutter speed. 3. Then go to your FL50 and put in the aperture reading two stops below the meter reading and the focal length of the lens. 4. Set the meter to flash mode and do a test burst from the fl50 to make sure the aperture is at least 2 stops below the camera Aperture.

You may need to experiment with this to get it right. You can use P mode on the camera but the meter will be more accurate.

Best of luck.

8th April 2008, 02:11 PM
Not got a clue on this one John, but watching / subscribing to the thread looking for answers :D

8th April 2008, 08:04 PM
IMHO It's not that complicated.

The flash puts light onto your subject which is reflected into the lens. How much depends on the flash/subject distance rather than the flash camera distance so in the Old days we had to think about this in terms of the flash output with careful calculations (oh how I remember the pain !) , but these days it's just a quick decision on where the calculations resulting in a "shut off" are being done. so...

If you were using an "automatic" flash with the sensor/calculations in the flash then you would need to set the "flash distance" into the flash so it could do the calculations. As the guns used to get overloaded with too much light too close that was why they used to have those little switches.


Now you're talking about a dedicated gun with the camera sensor control coming from the camera to the gun so you just plug it in and let the camera do the thinking for you. You just need to make sure that the camera is metering at the right spot. So I suggest spot metering for a small subject like a bird

There are a couple of exceptions/small wrinkles in that A) you may want to over or under fire the flash for a specific reason (make the shot more atmospheric) or B) the newer guns also understand what zoom you are on and use that as part of their calculations. This can need to be overridden when the.

If you want to get really clever then you will need to as Ian (BPS) says You may need to experiment with this to get it right

If you want to get really really clever then look out for a copy of Images Below by Chris Howes. Ref a related old quote from an Old Oly Mag posting. He's one of the acknowledged masters of flash photography.

I have to declare that he's a mate of mine in posting an unashamed plug.

Ian Aston, Olympuser magazine (53), Winter 1997/98

THE name Chris Howes, FRPS, will be familiar to many readers through the medium of his excellent cave photographs which we have published on these pages in past years. As a very experienced caving photographer he is the ideal person to write the definitive manual on the subject, which is what this is.

He is an OM user and the book very much reflects this, but it is a superb book of reference on all branches of photography. The chapters on flash are masterly, covering every aspect of this essential subject (in his situation!). Close-up and macro photography are fully covered, there is nature photography, composition and a useful section on assessing work for publication. All this aside it is an interesting book to read, describing as it does a world most of us will never enter yet find fascinating.

The book contains well over 450 photographs and diagrams. We warmly recommend this super book.


8th April 2008, 08:08 PM
Can you use a TTL Cord..It may too short though.

1) I think it might be like a studio reading...with a flash meter aimed at the "Place" were the subject is, pop the flash from the camera placement spot. ..Adjust the flash power to give you a good histogram..From Camera Position...

Although It sounds like good advice. It may be flawed. Since I have no way to try it myself.

I use this method in the studio. (home)

2) Experiment in Manual all the way...Start with the flash at 1/4 power and adjust the f/stop for a good exposure...When you get it.,..Jot down the Flash:Subject distance and Camera:Subject distance..With the Flash and Camera settings -including ISO.
----This is how I adjust my camera for Studio Shots of Models. It works OK.

Let us know how it goes..with an example...

8th April 2008, 08:18 PM
On reading this again I noticed that you didn't say it was a dedicated lead e.g. a CB-05 or similar (there were some posts relating to cheaper versions and alternatives a while ago).

If that's the case then my comments stand it not then some of the other ideas will need to be tried


8th April 2008, 10:05 PM
Hey Nick - It's actually a Canon lead, but it's a dedicated flash one!! It works 100% as though the FL-50 is attached to the E-3.

This (http://cgi.ebay.co.uk/Canon-Off-Camera-Shoe-Cord-3-OCE3-OC-E3-2-NEW-3F_W0QQitemZ380014572905QQihZ025QQcategoryZ29982QQ ssPageNameZWDVWQQrdZ1QQcmdZViewItem) is not the buyer I purchased from, but it is the same lead.

9th April 2008, 06:31 AM
Hi John,
The problem is really simple. Just follow my links. The first is about the Canon flash cord and the second is how I modified it for the purpose you want. Well, not for birds, but it can be used for that as well.



Full TTL works, so you don't have to worry about overexposing, the camera will correct according to the light it receives in the image area, not according to the distance from the subject. Of course, you can't place the flash closer than the specs allows, but I assume you don't want to fry the birds but to photograph them. One thing you have to test out, that is the angle of coverage. If you take an image which also includes an area outside the area lit up by the flash that area will be underexposed. In fact, it is important that you don't zoom out that much because the image will look strange and bad. You have to test that out. I have used a 5 meters long PS2 cable, but I am sure longer cable is not a problem.

Good luck.