Please help: ND filters and outdoor portraits

[aussiearef]

Hi guys,

It's a while that I've been practising portrait photography. I take some friends and random people (!) out and take their portraits. now this is the problem that I need help with:

1- I have a canon camera and a zoom lens
2- I have a canon speedlight that supports ETT.
3- I have a speedlight that works in Manual and Slave modes only.
4- I have a wireless flash trigger

Having these gears I am taking a girl out at the middle of the coming sunny Saturday. So I am thinking to use ND filters to overpower the sun.
I do not have a light meter so I have to rely I the camera's light metering. I understand that I want to drop background's light but I want to properly expose the subject. So if I use evaluate metering I guess the subject will be over exposed. What kind of technique should I use to keep the background a bit darker but properly expose the subject? Shall I use spot metering? or should I use manual flash until I get a good shot?

p.s I don't want to use high speed sync technique. I want to practice with ND filters so this is the only option

please help

 

[vandervalk]

ND filters won't help you. You'll be letting less light in equally. You might also have a hard time over powering the sun with just speedlites, but it will also depend on how close they are to your subject.

Just remember this. Shutter speed has no effect on how much flash gets let in. Use shutter speed to set your ambience light (sun, sky etc). Find that exposure and then use you aperture to expose your subject with the flashes. Stop down, less light. Open up, more light.

 

[aussiearef]

Thanks Vandervalk
so do you mean these two guys have used powerful strobes!? the second one is saying he has used flash.

Overview of the Graduated Neutral Density Filter | Photographer & Web Designer Ray Alamo

using a neutral density (ND) filter with flash « Neil vN – tangents

I assume the subject can be lighten up by two manual flash (or one ETTL and one manual) because the subject will reflect the light but there is nothing in the background (e.g. when the subject is at the beach) to reflect the light. am I wrong?

Shutter speed won't go faster than 1/200 unless I use the flash with in high speed sync mode which means way less light.

 

[480sparky]

An ND will not help you. Not only will it reduce the light from the sun, it will reduce the light from your lighting.

What you will need to do in increase your lighting output.

 

[rtex42]

In your two examples, the first is using a graduated ND filter to darken just the sky.
The second example is using ND to reduce DoF by requiring a larger F-stop (number) like 2.8.
Neither was attempting to overpower the sun.
Rick

 

[MK3Brent]

You need more light output.

You will meter for the background, take test shots to get the exposure you want, then work with your light.

Depending on how bright out it is, your shutter will be > 1/250. You're in auto FP / high speed sync at this point. (most cameras.)

What some do, is piggy back multiple flash units together and trigger iTTL with another strobe. (such as your built in flash unit, or hot shoe mounted speedlight for example.)

 

[Majeed Badizadegan]

ND filters won't help you. You'll be letting less light in equally. You might also have a hard time over powering the sun with just speedlites, but it will also depend on how close they are to your subject.

Just remember this. Shutter speed has no effect on how much flash gets let in. Use shutter speed to set your ambience light (sun, sky etc). Find that exposure and then use you aperture to expose your subject with the flashes. Stop down, less light. Open up, more light.

An ND will not help you. Not only will it reduce the light from the sun, it will reduce the light from your lighting.

What you will need to do in increase your lighting output.

Depending on your purpose and application of the ND filter, I have to disagree with both Sparky and Vandervalk. Less light let in will allow you to use a wider aperture and decrease your DOF in some situations. If you can take a couple stops off the natural light and increase the output of your flash/off camera flash while controlling direction of the light, you can decrease DOF, contain the dynamic range of the photo, and have more control over the exposure.

There's more than one way to skin a fish. Some advanced portrait shooters I know of keep ND's in their toolkit for situations that call for reduction of light when shooting at wide apertures.

 

[480sparky]

Depending on your purpose and application of the ND filter, I have to disagree with both Sparky and Vandervalk. Less light let in will allow you to use a wider aperture and decrease your DOF in some situations. If you can take a couple stops off the natural light and increase the output of your flash/off camera flash while controlling direction of the light, you can decrease DOF, contain the dynamic range of the photo, and have more control over the exposure.

There's more than one way to skin a fish. Some advanced portrait shooters I know of keep ND's in their toolkit for situations that call for reduction of light when shooting at wide apertures.

But it will do nothing in terms of "overpowering the sun".

 

[MLeeK]

Wait... I missed a beat somewhere here (nothing new... Sometimes I am pretty limited like that.)
A ND would be perfectly correct in this situation if I read things correctly.
Let me try to recap what you are doing:
You want to use an ND filter to reduce the power of the sun so that you can use a wide aperture such as maybe 2.8
Then you want to use your flash(es) to light your subject properly.
I think your using the terms "overpowering the sun" is where everyone is hung up... right? You aren't trying to OVERPOWER the sun, you are trying to bring it down so that you can use a wide aperture. Right?

 

[TCampbell]

Generally you'd go outside and find some light to medium shade -- just keep in mind that the exposure in the shade will be at least a full stop darker than the exposure in the sun... possibly nearer to 2 stops. This means the background will appear over-exposed when the subject is correctly exposed or if the background is correctly exposed the subject will appear under-exposed.

To remedy this you need to add flash to the subject, but you want an uncontrolled level of flash. The goal is to add just enough that it brings up the subject exposure to balance the shot between foreground and background.

A light meter capable of measuring "flash contribution" would be perfect, but you said you don't own any light meter (much less a meter that can meter flash contribution.)

I just posted a response a few days ago with a link to Sekonic's free videos. Here's another (different lesson but the same topic is being covered):

Blending Flash & Ambient Light for Beautiful Outdoor Portraits

Sekonic makes light meters, so the point of the video isn't *just* to teach you how to balance the shot... they'd also love to sell you a light meter. Just pay attention to the concept of balancing the exposure. The meter really just makes it very easy. Without the meter you can do this buy guide number.

e.g. suppose you have a Canon Speedlight 430EX II. It has a "guide number" of 43 meters (at ISO 100 and f/1.0). You wont be using f/1 of course, but it makes the math easy.

Suppose your subject is 10' away. If you switch the meter to 1/4 power (2 stops down... which cuts the distance by HALF (each full stop cuts the power by the square root of 2 (1.4) but since 2 X the square root of 2 is actually just "2" you can simply divide the distance by 2. So now the guide number of the flash is 21.5 meters instead of 43 meters -- again, at f/1.0 and ISO 100. 21.5 meters is about 70'. Divide that by the f-stop you plan to use and it results in the distance. BUT... since you already have a distance in mind (10 feet) you can divide it by the feet and it'll tell you the f-stop you should use. In this case, f/7. There is no f/7, but there is an f/7.1 (1/3rd stop down from f/8).

You can meter the outdoor exposure using the camera. If the exposures are equal, then you'd be doing a 50% flash contribution. Photos usually look more flattering if the flash contribution is a bit less than 50% (I like the "look" of about a 30% contribution). You can move the flash slightly closer or farther to increase or decrease the power.

I did that calculation manually. A light meter that can meter incident light in ambient, flash, and also report flash contribution just makes it a whole lot easier.

So much of photography is about controlling light. With that in mind, why wouldn't every photographer own a light meter?

Joe Brady (the photographer in that video) made a comment in the video. He said "Whenever I hear a photographer say 'I prefer the look of natural light', what I really hear is 'I have no idea how to control my flash.'" I laughed because that's EXACTLY what I think whenever I hear someone say that.

 

[Majeed Badizadegan]

Wait... I missed a beat somewhere here (nothing new... Sometimes I am pretty limited like that.)
A ND would be perfectly correct in this situation if I read things correctly.
Let me try to recap what you are doing:
You want to use an ND filter to reduce the power of the sun so that you can use a wide aperture such as maybe 2.8
Then you want to use your flash(es) to light your subject properly.
I think your using the terms "overpowering the sun" is where everyone is hung up... right? You aren't trying to OVERPOWER the sun, you are trying to bring it down so that you can use a wide aperture. Right?

Yep, I think that's what OP meant.

 

[Majeed Badizadegan]

Also, for those advanced flash shooters out there, correct me if I'm wrong: Since most cameras have a 1/250 max flash sync speed, there are many situations, especially in mid-day sunlight, where there's no way you could get a shallow DOF and keep SS 1/250 or under. In this specific situation, you'd be forced to use ND if you want to use on camera/off camera flash. Is this correct thinking?

 

[TCampbell]

Also, for those advanced flash shooters out there, correct me if I'm wrong: Since most cameras have a 1/250 max flash sync speed, there are many situations, especially in mid-day sunlight, where there's no way you could get a shallow DOF and keep SS 1/250 or under. In this specific situation, you'd be forced to use ND if you want to use on camera/off camera flash. Is this correct thinking?

You can use "high speed sync" mode on the flash, but there are caveats.

For those not familiar with how a rolling "curtain" shutter system works (I realize most of you know this, but many new photographers wont.):

In a rolling curtain shutter one curtain opens to expose the sensor, then a second curtain later closes after the shutter has been exposed for the desired amount of time. Since the curtain does have to slide open and shut, the camera accounts for the fact that part of the sensor will be exposed longer than other parts. So the "clock" on the shutter speed really does start ticking as soon as the shutter starts to open and doesn't wait for it to be completely open.

If the camera has a shutter sync speed of 1/250th that means that at that speed, the first curtain would be capable of opening completely before the second curtain has to start closing. But at faster speeds (say 1/500th), the first curtain only makes it half-way open before the second curtain begins to close. You can think of this as a "slit" which sweeps across the sensor rather than the shutter actually ever being totally open.

The consequences of the "slit" occur with flash. When the flash fires, where the "slit" happens to be will be nicely exposed, and everyplace else will be under-exposed (those areas of the image would only have received ambient light.)

Back to the topic now...

Dedicated speedlights will often have a mode known as "high speed sync" (HSS) (and the camera also has to support this... hence the requirement that it be a "dedicated" flash.) HSS causes the flash to pulse _very_ rapidly. It does this as the curtains sweep across the sensor exposing the "slit". It results in a fairly even exposure of "flash" across the sensor even when the camera is shooting at speeds that exceed the flash sync speed.

The "catch" is that the guide-number of the flash is based on a full-power discharge. After a discharge the flash needs time to recharge the capacitors before it can fire again. If it shoots at full-power, that'll take a while. High-speed sync fires at a fraction of the flash's full-power.

How much less than full-power? That depends on the shutter speed. At higher speeds, the flash will require more pulses. To have enough power for each pulse of light means that each single pulse has to fire at a fraction of the flash's total capacity (otherwise it would run out of power before the shot is exposed.) If, for example, it will need to flash 8 times then the each single pulse cannot be more than 1/8th of the flash's total power.

That reduction in total power will cut into the subject-to-flash distance at which you could normally use the flash.

As for the use of the ND filter...

An ND filter reduces all light... not just the sun, but the flash as well. The difference is the sun is continuous light source and the flash is momentary. This means you can fiddle with the ratio of flash to ambient by fiddling with the shutter speed (within limits). It's not really easier to have a flash "over-power" the sun because when you use the ND to reduce the light from the sun it's also reducing light from the flash by the same ratio.

The only thing the ND filter will really do for the outdoor shot is allow a wider aperture to collect the same amount of light when using flash without having to resort to HSS. If there's no flash involved then you can still shoot at a wide aperture by using a very fast shutter speed. From Sunny-16 the speed is 100th (we'll round off to 125th since that's a neat "full" stop) you bring the aperture down 5 stops to get to f/2.8 (from f-16) so you take the shutter speed up 5 stops to 1/4000th (from 1/125th) and you're there. If you had 5-stops worth of ND then you could return the shutter back to it's original speed but still leave the aperture at f/2.8.

 

[aussiearef]

Hi guys,
Thanks for all your helpful tips.

Sorry to use a wrong term. As you pointed out I want to bring the sun down not to overpower it. I did some test as below:

1- I did not use an ND filter. I used f8 and metered the environment light (at the beach) then in M mode I underexposed it by one stop. Then I used two flashes (one on camera and one as slave) with their full power. The result was quite nice because the background was darker than the subject and also I could create effect with the flash light.

2- I used ND filter so I could use a wider aperture. As you said ND filter does not do a magic as the camera adapts itself to it (e.g. uses a lower shutter speed). An ND filter helps in this situation because it does not affect the colors (which underexposing does) and it makes the background more blurry. It also helps with eliminating over expose spots such as reflection of light on the water or the sun.

This was what I learned by doing that test. I have to go through all your tips and trying them too

 

[Vautrin]

if you use a strong enough nd filter, bright sunlit areas will look dark, like its night

add enough flash light and you can then take a shot with a properly exposed person with a dark underexposed background -- kind of like what youd see at night

but itll look a little spookier as its not really a night shot

tricky but it can be done