Photoforum Photography Challenge 2012-1 - Shooting in Mixed Light

[TCampbell]

Here's a "moderately" advanced challenge, but I wanted to provide this because it's a good tip to know and work on.

This being winter-time where I live, I find I'm taking more indoor photos than outdoor, and that means shooting near windows... and that means I have a mixed lighting problem. Shooting in mixed light can be frustrating. I'm going to use an example of shooting someone in front of a window, but this same challenge applies in many other situations (more on that later). This is a situation that happens to all of us. Either you've already learned it control it, or you want to learn to control it.

Cameras don't automatically know how to deal with this. The problem seems complicated... but it's a bit like a magic trick in that it only seems complicated when you don't know how the trick is done. Once you learn the trick, you kick yourself for not thinking of it.

Time to see some examples of the "problem":


Exposure: ISO 100, f/4, 1/6th second.

I shot the above example to show what a camera does by default. This shot was taken simply using exposure settings as recommended by the camera's "evaluative" metering of the shot. In comparison to what might have happened, this exposure (while poor) is actually better than I expected.

To find a better exposure for the background, I'm going to switch from "evaluative" metering to "spot" metering, point the camera at the background (and just the background), and take a meter reading (we just want to know what the suggested meter reading is for the background.) If you don't know what that means, read this:

Cameras measure the amount of light that reflects off the target and into the camera. This is called "reflective" metering. A dedicated light meter works by placing the meter in the same light with the subject so that it can read the amount of light landing on that location. This is called "incident" metering. Incident metering is extremely accurate. Reflective metering has a margin of error because not all subjects "reflect" the same amount of light. Some subjects are highly reflective (for example, white snow is extremely reflective) where as other subjects don't reflect much light (for example, black fabrics are usually not very reflective). Since the camera doesn't "know" what the subject material is, it just has to make assumptions based on the average percentage of light that the average subject reflects.

To compensate for the fact that the camera doesn't specifically know how reflective a subject is, instead of taking a general average reading of light, it uses a matrix to meter many many specific locations within the frame. This improves on the camera's estimate, but you'll find that there are still scenarios that throw off the cameras accuracy.

Since mixed lighting compositions provide some "extremes" for the camera to deal with, it's best not to leave it up to the camera. Turn off the "evaluative" or "matrix" metering mode, and switch to a "spot" metering mode. In this mode, the camera only meters the light at one specific location in the frame (typically a spot in the very center) and it completely ignores all other areas of the shot. This allows us to ask the question: How much light is being reflected from this specific point? If it's critically important that we get the exposure "right" for that point, the spot metering will still let us do that.

There are some additional nuances I'll leave out w.r.t. the various levels of reflectivity of certain subjects... just know that the information metered even from spot metering is nothing more than a good start... but not necessarily the "right" exposure. You'll often need to tweak the exposure rather than accept the advice of your built-in meter.

Knowing this, you can switch your camera to "spot" metering (which may be called something else on your camera) and fix the over-exposed background by reading the correct exposure for the background.

And if you use this "spot meter the background" technique, you'll see that it does indeed fix the problem of the over-exposed background:


ISO 100, f/4, now 1/100th second

See? I didn't lie. The background is MUCH better. Problem solved! Unfortunately solving that problem seems to have created a new problem... my subject is now a silhouette.

And this is the problem of shooting in "mixed" lighting. How to get an exposure that's correct for both?

Answer: Break it down and think of this as two exposures (Don't worry - I'm not sneaking in a challenge on HDR photography. We plan to fix this by taking just one single exposure.) HDR and Photoshop will not be necessary. You can get this shot right, straight out of the camera.

We have to think about this as two exposures. First is the "outdoor" exposure. While we'd love to be able to control the lighting outside, we simply cannot. It is what it is. We have to accept it. The second is the "indoor" exposure. Hopefully my hint about controlling the outdoor lighting sparked a thought... yes, we can do something about the lighting inside.

The solution is to set an exposure that will not overexpose the outside shot, and then supplement the indoor lighting to illuminate our subject until the exposures are a match. They don't have to be an exact match, but we're looking to get it close.

If we do that, we end up with something a bit more like this:


ISO 100, f/4, 1/125th, but using flash

For the above shot, I set the camera for the same exposure as the previous shot, but I turned on the flash (ok, I put a 2nd flash off to one side and shot it through a diffuser to soften the light, but I could have used a pop-up flash on a point & shoot camera just as easily.) You can see that while this isn't perfect, it's a huge improvement.

There's one more thing to consider before we're done: Not only is the amount of light different on the inside vs. the outside, the type of lighting is also different. The outside is using "continuous" lighting. The inside is using "flash". There's a world of difference.

Continuous lighting is weaker, but it provides a steady stream of light photons. As long as the camera shutter is open, it continues to collect light from a "continuous" lighting source (such as the sun)

Flash lighting is stronger, but it provides all of it's light in one big momentary burst. Leaving the shutter open longer will not collect any additional light from the flash. But it will collect additional light from ambient and "continuous lighting" sources.

Knowing this fact, means it's trivial to control the balance of outdoor light to indoor light.

Camera's have a shutter speed known as the "flash sync speed". This is the fast shutter speed the camera can use and still get an even flash exposure. On older cameras it was usually 1/50th or 1/60th. On newer cameras it's usually 1/200th or 1/250th. It's important to make sure that you don't use a shutter speed which is faster than your camera's maximum flash-sync speed.

1. Spot meter the outdoor light and set the camera with a manual exposure that captures a correct "outdoor" exposure.
2. Turn on the flash to boost the "indoor" light (really the local light that we're directing onto our subject.)
3. If you need to adjust the "local" lighting, alter the "aperture" (Not the shutter speed. If you don't believe me, just try adjusting the shutter speed and you'll see that it doesn't work.) Changing the aperture will alter the amount of light the camera can collect from the flash. It'll also alter the amount of light that the camera can collect from the outside but that's easily remedied in the next step.
4. Re-comensate for the change of light collected from outside by changing the shutter speed to collect more or less light as needed (remember, the sun is a "continuous" light source.

If you do that, you can end up with an exposure with good lighting on your subject and good lighting on the scene out the window.


ISO 100, f/10, 1/200th sec. With flash.

And there we have it. I did not do any adjustments to this shot via Photoshop (or anything else) and this is not a merged HDR result. This is what we get straight out of the camera with just a single exposure and a flash. Notice the light on the model's face is good, while the lighting out the window is extremely well-controlled. I did this by adjusting "aperture" until I was happy with the exposure on the model, THEN I adjusted the "shutter speed" until I was happy with the lighting out the window. Also notice that I'm just focusing on the balance between the model's face and the exposure out the window. If this were commercial photography, we'd be using more lights and controlling the balance of the scene even better.

Although I happened to pick a subject in front of a window for this particular challenge, you'll notice the same problem pattern in other mixed lighting scenarios. For example... say you're trying to photograph someone outside in a park, and to eliminate the harsh shadows from the sun, you move your subject into the shade of a large tree. You get the subject exposed right, but the background (the rest of the park) is over-exposed. Use the same technique to balance the light.

Your challenge:

Find a mixed light situation (You don't have to use a window just because I did.)

Balance the lighting in the exposure. If you want, post the shot that the camera wants to take by default (without you taking charge to fix it), then post the shot showing the balanced exposure. And since this is a learning challenge for everyone's benefit, bonus point to you if you include your exposure info and any comments on what sort of lighting you used to fix the problem.

And now for the rules:

1. Only photos taken during the challenge period should be posted.
2. Limit of 2 pictures per post for this topic.
3. Discussion of technique and/or inspiration is encouraged!
4. Remember - this is NOT a contest - no voting, no prizes - other than better photos!

And the most important rule: Have fun!

[Sponsors]

PhotoForum.com is a leading Photography Forum, Registered users do not see these ads. Register, it's free!

[Mirelon_D]

Such a wonderful Captured Photos.

[Fred Berg]

This photo was taken a few days ago from inside the entrance tunnel of the local castle. I went to the opening of the tunnel to get a measurement and set the camera accordingly, then I went to where I wanted to take the photo from and attached the flash so as to pick out a bit of detail inside the tunnel.





Agfa Precisa colour positive film, iso 100.

[Preeb]

I have some mixed light to show.... this image was taken at a Christmas Party in a bar. There was a random mix of incandescent, fluorescent, neon, even a lighted necklace on one subject - relatively dim overall. Taking with Canon T1i and EF-S 17-55 f2.8 lens. Settings: 1/13 sec at f2.8 and ISO 3200. 31mm on lens. No flash.

[Fred Berg]

Again, to avoid blowing out the arches, I measured the light through the arched window nearest the camera, set the camera accordingly and used the flash to pick out some detail of the inner wall:



Agfa Precisa CT diapositive film, iso 100.

[TCampbell]

Hi Fred,

You've got a great exposure out the end of the tunnel, but I think the problem inside the tunnel is that it's the area is too big for the flash.

If you look at the final photo of my model (the 3/4 body length shot) carefully, you'll notice that her face and upper body are exposed nicely, but the bottom of her legs and the table are under-exposed (I always shoot raw so I could have brought that up a bit, but I wanted to post un-retouched photos for the challenge... my goal was to show what you can do "in the camera"). My point is that even in the relatively small area of my living room, a single flash was only adequate to nicely expose one part of the image but I couldn't fix the whole thing with just one flash.

Due to the size of the tunnel, I think you'd need a MUCH stronger flash or you'd need several flashes. In this particular shot, I might strongly consider shooting HDR. Point the camera at the wall in side the tunnel and meter it (being careful not to allow the light from the opening influence the meter reading -- e.g. use spot metering, etc. or just point the camera so far away from the opening that it's not visible in the viewfinder). Then meter the outside exposure (as you've already done nicely). Put the camera on a tripod and take two shots (vary the shutter time, not the aperture... so the depth of field in both exposures will match). You can then merge the two photos into an HDR result.

I don't have Photomatix (what most people who regularly process HDR seem to prefer). Photoshop has a built-in HDR capability (probably not as good as Photomatix).

Last fall I shot a covered bridge and did this. I wanted the dark interior of the covered bridget to be noticeably darker than the outside (otherwise it wouldn't look natural) so I shot the bridge with just enough interior light to show off the detail of the old wood framing (but still dark). Here's a link to the photo. Without the processing, this bridge was pretty much black on the inside (no detail of the interior wood): "Ackley" Covered Bridge | Flickr - Photo Sharing!

[TCampbell]

Preeb - nice fun image! I see that you did not use flash, so it's not quite the challenge of augmenting the dark areas with some extra light to balance to the bright areas.

[TCampbell]

Much better Fred! I realize the distant left side didn't get the flash exposure that far away, but if you hold your hand over the left side and just evaluate the right side, it's a great result. The through-the-arched window exposure is nice & natural. The detail in stone walls is nicely visible, and yet it's dark enough to suggest that it's not as bright inside and preserves the mood.

This also brings up another style of shooting ... "Frames within Frames" (maybe that can be a future challenge topic.)

[Fred Berg]

Thanks Tim, your advice and guidance is very much appreciated - it's great to be able to tap in on your knowledge and experience a bit.

[ChicagoJohn]

december 3 in chicagoland our winter YOUR SPRING by ChicagoJohn, on Flickr

Is this what you are talking about, Tim? I took this in December when the light was not copacetic and use a flash to fill in the subjects' faces, as it were.... am I somewhat on track with what you are talking about?