How do I underexpose the background and meter for my flash?

<p>I watched a video that Chase Jarvis did and he was shooting in a skate park</p>

<p>He said to get skys more dramatic that you should underexpose the background by 2 stops and fill the rider with flash</p>

<p>I understand half of what he is saying and I guess I know how to meter the sky. Just point, meter and your done but how do I then get proper flash exposure?<br>

<br />What value am I changing to under expose the background? I know aperture controls flash and shutter speed controls ambient light but it sounds too simple in my head..</p>

<p>Can someone explain a little more without confusing me further lol?</p>

<p>Shooting with a 5D + Sunpak 120j battery packed so I wont have any power issues. I could get out and shoot it but it will annoy me if I dont get it right..</p>

<p>Any help would be great! Thanks! </p>

<p>First, this involves <em>manual exposure</em>. Meter for the sky, and then go dark by a couple of stops. That means either lowering the ISO by two stops, closing up the lens by two stops, or raising the shutter speed by two stops. Any of those (or some combination) will cause you to underexpose as desired. This is harder to do if you're in an automated or semi-automated epxosure mode. So, set the ISO, aperture, and shutter speed <em>manually</em> once you see what your meter thinks is correct.<br /><br />Note that you have to have your shutter speed at or below the synch speed you have to use in order to get your flash to work correctly. This might be 1/250th, etc., unless your rig supports a high speed synch mode.<br /><br />Then, <em>manually</em> set your flash power to get the final results you're looking for. If you don't have a flash meter, you have to chimp. Simple as that. It should take momemts to meter and then under-expose the ambient light, and then it should take only a couple of test shots to dial in the flash power. Just remember that the flash's power falls off at the square of the distance. If you change the distance between the flash and your subject, you'll have to revisit the power level you've chosen.</p>

<p>Couldn't you just use exposure compensation to adjust the background? I am guessing that the flash exposure would be unaffected as this has it's own separate Flash Exposure Compensation. Does that sound right to you guys?</p>

<p>Exposure compensation impacts the entire exposure. If you're letting the camera and flash unit decide how to handle the exposure (including how much flash power to add to the exposure), then modifying that program by entering an exposure compensation value will impact the <em>whole</em> exposure. <br /><br />I don't know off the top of my head whether/how that Sunpak unit integrates with the metering and exposure brains on the camera, or how Benjamin setting up the flash (an auto limiting mode, etc?). Taking control of both is how you take control of a scene like that.</p>

<p>Lots of variables to play with. Shutter speed, ISO setting & f stop affect ambient. Only f stop & ISO affect flash, except sync speed of your camera.<br /> I run my cameras & flashes manually; flashes off camera with pocket wizards. <br /> With the work I do I have to analyize a situation and get set up fairly quickly.<br /> My recommendation, write down the variables I mention above. Put your camera on a tripod and go out and work on these items, under various lighting conditions, until you get it down. You may need to take notes as to what you change and the corresponding results.<br>

I see many photographs where flash is so obvious. That's not my style as I consider using a flash like garlic in cooking, a little bit goes a long way and too much can ruin a good thing.<br /> Practice, practice, practice. <br /> Good luck!</p>

<p> </p>

<blockquote>

<p>Exposure compensation impacts the entire exposure. If you're letting the camera and flash unit decide how to handle the exposure (including how much flash power to add to the exposure), then modifying that program by entering an exposure compensation value will impact the <em>whole</em> exposure. </p>

</blockquote>

<p>Maybe this is true for Nikon, but he's using a Canon. I do know that with Canon's, exposure compensation and flash exposure compensation are completely different. He can dial down exposure compensation and that will adjust the background. The flash will go with no exposure compensation unless he changes the flash exposure compensation.</p>

<p>There are two ways. </p>

<p>One is to set the camera manually so that the sky is exposed as desired(two stops under). Than, manually set the flash power to properly expose the rider. Its that simple. You may have to trade off between your aperture and shutter cause as you know aperture affects flash while the shutter will not. You can also adjust ISO to give more flexability.</p>

<p>The other way is to, as before, set the camera manually to get desired exposure for the sky. Then allow the camera to use TTL to set flash exposure for you. You can then use Flash Exposure Comp to adjust your flash output.</p>

<p>Jason</p>

<p>There's a third way, which Chris Nielsen pointed out. You can easily set the camera to aperture priority and set exposure compensation to -2 (or whatever) and leave the flash or use flash exposure compensation. I don't get why people are trying to make this so complicated.</p>

<p>Thanks for all the responces. I dont know where to start. I guess I'll start with saying I always shoot manual!</p>

<p>I have a light meter too, sekonic L358 which I use with my Pocketwizards and Sunpak 120j and I always shoot it manual</p>

<p>Is it any easier to meter the sky using my light meter then my camera? Ill have my shutter speed set at 1/250th, ISO 100 and probably about f8, if I meter f8 as good exposure then 2 stops will be f16? I might not even start at f8 but its good for the sake of an example.</p>

<p>How do I sort my flash out? Will it be a case of starting at its lowest power setting and then just adjusting it as I go? Normally I'd use my aperture to control it but seeing as though I'm "using my aperture to underexpose the background" I cant really touch it can I..</p>

<p>I guess I could always bump my ISO up 3rd stops if I needed that little bit extra light and didnt want to go a full stop on my flash</p>

<p>Am I heading in the right direction with this??</p>

<p>The camera's light meter doesn't know about flash in manual mode, so use the meter to set your exposure for background. If your flash is TTL it will try to expose the foreground properly so you can use flash exposure compensation to dial down/up the flash as you feel necessary. Set minus one on the flash and it will reduce the output by one stop. Job done...</p>

<p>The shutter speed controls the Ambient light, the aperture controls both available light and flash available. If you change the shutter speed it only impacts the portioon of the image illuminated by available light. if you change the flash power setting it only impacts the portion of the image illuminated by the flash. If you change the aperture it impacts both portions of the scene available flash and available(ambient) light. Changing the ISO can also affects available light, I usually lower or increase the ISO to "subtly" lighten or darken my backgrounds while shooting digital. If you are shooting film, changing the ISO on a fly can cause more problems than benefits.</p>

<blockquote>

<p>There's a third way, which Chris Nielsen pointed out. You can easily set the camera to aperture priority and set exposure compensation to -2 (or whatever) and leave the flash or use flash exposure compensation. I don't get why people are trying to make this so complicated.</p>

</blockquote>

<p>Exactly...me either.</p>

<p>We're talking about a 5D and Sunpak 120J so there are some limitations to be aware of. The 5D can't sync past 1/200s unless using E-TTL + HSS so your max shutter speed is 1/200s. You can use Av mode with -2 comp but you must be careful and and ensure the shutter does not go past 1/200s (it most likely will if shooting during the day and using large apertures). Set your camera to manual mode, ISO 100, 1/200s. Take an incident reading with your meter at ISO 400, 1/200s ... this will be your aperture at -2 EV from "normal". For the flash exposure, adjust the flash output until you get a normal exposure on the subject (either chimp or use a meter).</p>

 

<p>You have a DSLR so experimenting is free,it would it easier to go out and take pictures. Just remember you can't go above the sync speed which is 1/200th sec so in bright sunlight you will be at very small apertures.</p>

<p>We use a similar technique when shooting portraits outdoors. Think of it this way- the shutter speed controls the ambient light, the f/stop controls the flash. For instance, if I want an underexposed sky when it is bright out, I first set my camera to the highest sync speed- 250, and then meter, either with a hand-held or in camera meter- to give me the f/stop that will make the sky underexposed. Lets say f/5.6 makes the background 1.5 stops underexposed. I now want to use my flash to light up my subject. I set the flash to manual mode, meter it, and adjust it to give me an f/5.6 on my subject. For a quick fix on the light on the subject, you could open up to a f/4. This would add more light (at the same flash power) to the subject, but it would also brighten the background a bit as well. Once you get the basic technique down, you'll see how far you can push it either way to get the desired results. </p>

<p>As someone mentioned above, if you do this in bright sun, you'll be at the extreme ends of your aperture and sync speed. Go out on a cloudy day, or in the late afternoon (or in your living room with a lamp on) and practice this technique. Not learning in direct sun will give you more latitude in your exposure options and you'll be able to see changing the iso, shutter speed, and aperture effect the overall image and exposure. Once you get comfortable with the technique, you'll be able to adapt it to extreme conditions easily. </p>

<p>It was a lot harder for me to learn to use this in aperture priority mode than manual mode, but I think I'm one of those people who has to see exactly how what I'm changing changes the situation. I can see where it would be useful to get comfortable with this technique though. I shoot off-camera flash with no ttl-capability, so I use the method I described above. </p>

<p>You can use the camera in manual mode and once you have the flash amount you desire, by varying the fstop, then you can change the ambient using the shutter up to the sync speed.<br>

Nice thing about digital as you can check each change on the LCD of your camera.</p>

<p> </p>

<p>HI,<br>

That could be the best if you will First, this involves <em>manual exposure</em>.Then, <em>manually</em> set your flash power to get the final results you're looking for.This could help you to fixed your desired background light..</p>

 

<p>HI,<br>

That could be the best if you will First, this involves <em>manual exposure</em>.Then, <em>manually</em> set your flash power to get the final results you're looking for.This could help you to fixed your desired background light..</p>

 

<p>Benjamin, how'd your experimentation turn out? What did you learn?</p>

<p>When I first learned this approach, I also found it difficult to conceptualize, which I suspect is or was your main obstacle. You appear to be competent with your equipment and understanding of exposure, generally.</p>

<p>Here's one way of looking at it that helped me. Usually, the reason to underexpose the background is that the background (especially the sky) is bright, and would be over-exposed (and thus blown out) if you exposed the foreground subject properly. Think of all the images you take on sunny days where your eye sees a deep blue sky, but the photo shows a white sky or extremely light blue -- this happens because there's so much ambient light in the background and sky -- much more than what's reflecting off the face of your subject. When you expose the foreground subject properly, the sky just turns white.</p>

<p>So you want to get more detail in the background, and the first thing you do to get there is to drop the exposure. If you properly expose the sky so that it is nice and blue, and clouds have interesting detail, the foreground is dark. And an under-exposed sky is even more dramatic than a "properly" exposed sky -- simple clouds appear menacing, or day turns to dusk. </p>

<p>But if you underexpose the background, your subject will be underexposed, too -- maybe by four stops.</p>

<p>So, after dropping the exposure, you now want to use a flash to add light back into the foreground onto your subject, to get him or her back up to a proper exposure. The flash can't light the sky or far-away objects, so it only affects the foreground subject's exposure. If you're underexposing the subject by four stops in order to get the sky underexposed by two stops, then you need to add about four stops of light back into the foreground with your strobe.</p>

<p>When you do this, you don't need the strobe to talk to the camera -- in fact, you don't <em>want </em>the strobe talking to the camera and messing around with the exposure you've already set up for the background effect you want. You just want the strobe to refill the foreground so you can see what's going on there, because you've killed four stops of light from <em>the whole scene</em> in order to get the background the way you want it to look.</p>

<p>Maybe you understood this already, but the way you asked the question is exactly the way I asked it in my head when I first studied this approach, so I thought I'd walk through it this way.</p>

<p>One additional point: it's been said here that shutter speed controls ambient and aperture controls flash. For those just learning about strobes, it's useful to remember that <strong>both </strong>shutter speed <strong>and </strong>aperture control ambient. Flash exposure, by contrast, is affected <strong>only</strong> by aperture, because the flash bursts so quickly that all the light dumps into the scene nearly instantly. This is why shutter sync speed is important -- we don't want the shutter to be halfway open when the flash bursts, because the flash is so fast that it is finished adding light to the scene before the shutter has moved much, resulting in the missed-shutter-sync half-a-frame-exposed problem). </p>