Properly exposed black... is black!

[Michel Hardy-Vallée]

Here's my lesson learned for today. I was taking portraits last night of people in front of a black backdrop. Same setup as I used before, but last time I used a grey backdrop.

I have a main softbox, a reflector, a hair light, and a backdrop light for the "halo" behind the subject. All strobes.

There I go with the incident flash meter balancing my lights. OK, main light is at f/8, reflector gives about f/5.6, so I'll put the hair light at f/8 as well.

So I set the lens at f/5.6. I am shooting Portra 160NC, so I don't worry about the highlights. I just want to make sure I don't lose shadow details.

Background light? Well, I'll give it f/8 in the brightest part, and f/5.6 in the darkest, creating thereby a pleasant gradation behind my subject.

Except that I was ... WRONG! My backdrop is black. Properly exposed black is black. That's the beauty of measuring incident light. When you don't compensate, you will usually get a tone that's pretty much correct.

To turn my black into grey-ish, I think I should have measured the brightest part of my halo somewhere around f/11 or f/16. I'll make sure to test it next time.

That makes me think: is there such a thing as a reflected light flash meter? It could come in handy...

 

[MattKing]

Gossen Digiflash?

That makes me think: is there such a thing as a reflected light flash meter? It could come in handy...

Michel:

I've recently acquired a Gossen Digiflash, which features flash metering, but the manual is frustratingly silent about whether the flash meter function should be used with or without the incident light diffuser, or whether it may work both ways.

So far I haven't really experimented with the flash meter function on the meter. Maybe someone else here has it, and can chime in.

Matt

 

[climbabout]

Here's my lesson learned for today. I was taking portraits last night of people in front of a black backdrop. Same setup as I used before, but last time I used a grey backdrop.

I have a main softbox, a reflector, a hair light, and a backdrop light for the "halo" behind the subject. All strobes.

There I go with the incident flash meter balancing my lights. OK, main light is at f/8, reflector gives about f/5.6, so I'll put the hair light at f/8 as well.

So I set the lens at f/5.6. I am shooting Portra 160NC, so I don't worry about the highlights. I just want to make sure I don't lose shadow details.

Background light? Well, I'll give it f/8 in the brightest part, and f/5.6 in the darkest, creating thereby a pleasant gradation behind my subject.

Except that I was ... WRONG! My backdrop is black. Properly exposed black is black. That's the beauty of measuring incident light. When you don't compensate, you will usually get a tone that's pretty much correct.

To turn my black into grey-ish, I think I should have measured the brightest part of my halo somewhere around f/11 or f/16. I'll make sure to test it next time.

That makes me think: is there such a thing as a reflected light flash meter? It could come in handy...

You got exactly what you should have with a black backdrop. Your main measures f8 and you say your backdrop measured f8(incident) so your backdrop received the same amount of light as your subject, - so it will be rendered as it's correct tone. You're on the right track - you need a flash meter that measures reflected light to accurately predict your backdrop tone. Years ago when I had a studio, I used a Minolta IV digital, that had an incident dome and a spot accessory attachment to take reflected readings off the backdrop. First take an incident reading of your main to establish your exposure, then take a reflected reading off the backdrop. Assuming you are using a neutral color backdrop, A REFLECTIVE reading that is equal to the main incident reading will give you a middle grey tone(zone 5), a reading 2-1/2 stops greater will give you pure white and a reading 2-1/2 stops lower will give you black. You can make a black backdrop pure white or a white backdrop pure black, if you control the light hitting it. The late Dean Collins taught me this over 25 years ago and it was the most valuable photography lesson I ever had.
Tim

 

[Michel Hardy-Vallée]

Tim, how would you do that with flash? With continuous lighting, I know how the tone placement works, but with flash, it would require a meter that measures reflected flash light.

 

[climbabout]

The Minolta IV measures both continuous and flash in both incident and reflective modes.
Tim

 

[Michel Hardy-Vallée]

The Minolta IV measures both continuous and flash in both incident and reflective modes.
Tim

Sweet! I'll see if my rental place has one.

 

[phaedrus]

That makes me think: is there such a thing as a reflected light flash meter? It could come in handy...

My Sekonic L508 does that, even adds them up as you pop the flashes one by one. Gives a ratio ambient light / flash light as well. Here's a link to the manual.

 

[David A. Goldfarb]

For what you want to do, you might look into renting a Minolta Spotmeter F, which is a spotmeter for reading flash.

I can also do it with my Minolta Flashmeter III, and I think all the Flashmeters can, one way or another. I'd probably use the 5-degree finder, but if you just remove the dome, I think the open cell will read reflective at a 40-degree angle. I also have a Booster II for making spot readings off the groundglass, which is another option for cameras that have an accessible groundglass.

 

[DKT]

i learned this long ago as "threshold" exposure. a reflected meter reading of the shadows 2.5-3 stops under gives the correct tone. "white placement" was the opposite--meter reading off a white tone, plus 2-3 stops. of course you had to establish the film speed first for this to work, but the point was to meter correctly--incident meters were taught as the lazy man's way around this more accurate tone placement--but all the same, it's what I use most of the time....

 

[Michel Hardy-Vallée]

My rental place has the L-508 and the Minolta Spotmeter F, both of which can do reflected spot readings, so I'll rent either next time.

 

[climbabout]

Dean Collin's on lighting,backdrop tone, metering

Here's a link I found for the complete DVD set explaining lighting and metering. I learned these principles firsthand in the 80's from his studio workshops and old "Finelight" monthly publications. While I have not seen these DVD's, I'm sure the production is first rate and the information is as relevant today as it was 25 years ago. These principles took the guesswork out of lighting, whether it was in the studio or on location, whether shooting people or products.
http://www.software-cinema.com/prod...f-dean-collins-on-lighting/product_details/78
Tim

 

[Christopher Walrath]

"My rental place . . ."

Man, that sucks! I don't have one of those.

 

[haris]

That makes me think: is there such a thing as a reflected light flash meter? It could come in handy...

Minolta Spotmeter F has reflected flash metering and in flash metering mode it is also spot meter.