550ex & portraits

[mick johnson]

I want to photograph my grandaughter using a 550ex & Eos3. I have a

white/silver umbrella, suitable background, white reflector, & Portra

160. I am baisically copying what I used at a studio a week or so ago

but that was pro equipment.

 

What I need to know is will I get a decent result & do I need to

compensate as I've been told I need about 1 stop overexposure when

firing into a umbrella. I know the film latitude will cover this but

I want to use slide film as well later.

 

I do actually have 2 550's, ste2, & off camera cord so if I could do

it better tell me please.

 

Mick.........

[chuck_dowling]

I am a big fan of environmental portraits, but I have been reading and practicing with studio lights. Someone please correct me if this setup is wrong. How about keeping it simple. Place one 550EX fired into the umbrella 45 degrees right of the camera (as you look at your subject) and above the subject, 7-8 feet high, angled toward your model. Trigger the 550 with the STE2. Use the reflector to kick some light back to the models right side. As far as exposure or flash compensation, the stytem could be used in ETTL or manual mode. Try both, but for manual mode, a flash meter would be handy. You want your model 5-6 feet away from the backdrop to throw it out of focus. I'm not sure what lens you will be using, but 80-100 or so mm works well.

[chuck_dowling]

One more thing. Perhaps the remaining 550EX could be used to light the BG. You can set ratios for the two flashes.

[mick johnson]

Thanks for the info Chuck.

 

That was more or less what I intended to do. I shall use my 105mm macro lens although I used a 28-135 at the studio at about 100mm.

 

I don't have a flash meter so do you think 1 stop over would be a good starting point for slides. I shall have to experiment with exposure I know.

 

At the studio I used manual mode and set the max sync speed 1/200 on the camera. What would be the ideal shutter speed for this type of work, 1/125?

 

Mick........

[peter_langfelder]

With Eos 3 and 550 Ex's you can use FE lock - point the camera's spot meter at the face, lock flash exposure (with +1 to +1.5 stops flash exposure compensation for white/caucasian skin), then recompose and take the shot. FE lock works corretly whichever way the flash is pointing (umbrella, ceiling, straight on...). BTW, the flash exposure compensation is needed not because of the umbrella (TTL flash meter will take care of that), but because you don't want your model's skin to come out as 18% grey - that would be too dark.

[jimstrutz]

If you are using E-TTL or TTL metering, you should not need to compensate unless shooting subjects that are unusually dark or light.

 

If you are using the flash in manual mode and are adjusting flash exposure by way of Guide Numbers, you will need to add the distance from the flash to the umbrella surface plus the distance from the umbrella surface to the subject. This adds about 4 feet to your flash to subject distance.

 

Then you will need to consider that once the flash has bounced off the umbrella it no longer acts like a point light source and GN calculations get increasingly inaccurate. So whereas from a point light source the light decreases with the square of the distance, from a broad light source the light decreases less rapidly. However, the light is now scattered and light loss is actually increased greatly. Making an accurate determination is difficult and once you do find an accurate exposure for one flash to subject distance, it seems to have little bearing on what the best exposure is from a slightly diffent distance.

 

I find that most umbrellas lose more than on stop of light. 1.5 stops might be more accurate, but it's difficult to determine because of the above problems.

 

Using 400 ISO print film I set my 550EX on a light stand that is about 6-8 feet from the subject and use f/5.6-8 with the flash set to 1/2 power. I would never try this with slide film without a light meter.