Digital photography: Area behind subject is really dark

Factual Questions
1

Can someone help me out here and tell me what I’m doing wrong? When using the flash taking pictures of my daughter or anything else for that matter, anything in the background is almost completely dark in comparison. Here’s what I’m talking about…
First a shot of a room without any subject in the foreground. The flash seems to light everything up pretty well.

http://www.slackercentral.com/images/photography/flash-issue1.jpg
And here’s what it looks like when I have a subject in the foreground.

http://www.slackercentral.com/images/photography/flash-issue2.jpg

Any thoughts? This is using a Canon Powershot SD900. Thanks for any advice!

2

It’s because so much of the light on your subject is coming from the flash, and the things behind your subject are so much further from the flash.

If you can slow your shutter speed down, you’ll provide more illumination in the background in comparison to what the flash does. That would help.

If you can put the flash farther away from the scene that would help too.

If you could aim your flash at a white ceiling, so your subject and background are about the same distance, that would be much better.

If you could slave other flashes to the one aimed at your subject, and aim them at the ceiling or background, that’d be way better.

If you could back way down on the flash so it’s more of a fill flash, that would help.

These are all photographic flash issues that don’t depend on things being digital.

And if you can’t change any of those things, you can also manipulate your greyscale curve while looking at a histogram in a digital imaging program on a PC. You want to create a flat spot in the curve to bridge the two peaks of the histogram together. It won’t help much, though - much better to do it with the flashes.

3

Light follows the inverse square rule; the amount of light hitting an object decreases as the square of the distance from the source of the light. So, if the person is two feet away and the walls of the room are 8 feet away, then the walls receive 1/16 the amount of light as the person. Ther previous poster gave several good suggestions for addressing the problem

4

I just wouldn’t use the flash. Generally you don’t particularly need it while shooting indoors or during the daytime.
If anyone else is having trouble seeing the pics - copy the link and paste it into a new window.

5

[QUOTE=Gentle Robot]
I just wouldn’t use the flash. Generally you don’t particularly need it while shooting indoors or during the daytime.
[/QUOTE]
Not true. Shooting indoors, even during the day, will generally require flash unless you have a room that gets a lot of natural light (i.e., skylights, or very large windows), or you have a decent digital SLR that will take good pictures at very high ISO settings (1600 or above). Even then, it will help to have a fast lens (f 2.8 or faster).

If you only have a point-and-shoot digital, with only a camera-mounted flash, the best thing you can do to get more background detail is to slow the shutter speed. Of course, if you slow it too much, then camera shake becomes an issue, and the background might end up well-lit but blurry due to motion.

If the background is reasonably light, this shouldn’t be a problem. Set a shutter speed of about 1/20 or 1/15 of a second, and your pictures will have a more even lighting. Experiment a bit with different shutter speeds. Your on-camera LCD should give you an idea of how successful you are.

Even if you do get background blur from slower shutter speeds, it needn’t ruin the picture; in fact, it can often make the picture better.

Here are a couple of shots i took in a very dark club with my digital camera. The first one is just using the flash on automatic mode, while the second uses a very slow shutter speed to add background detail.

Flash only

Flash plus slow shutter speed (~1 sec.)

Not only is the background visible and more interesting in the second on, but i think the foreground looks better as well.

6

[QUOTE=mhendo]
Not true. Shooting indoors, even during the day, will generally require flash unless you have a room that gets a lot of natural light (i.e., skylights, or very large windows), or you have a decent digital SLR that will take good pictures at very high ISO settings (1600 or above). Even then, it will help to have a fast lens (f 2.8 or faster).
[/QUOTE]

Actually, I’ve gotten pretty good no-flash indoor pictures with various P&S digicams. Generally, the lens needs to be fast, and higher ISO settings and image-stabilization help a lot. Lately I’ve been using a Panasonic Lumix digicam that goes up to ISO 800, but I got pretty good pictures with a Nikon Coolpix P2 which only went up to ISO 400.

ETA: I can’t recall seeing a P&S digicam lately that didn’t have a lens that was at least f/2.8. When the lenses are as small as those in digicams to begin with, it doesn’t seem like it’s that hard to make them fast (usually, the longer a camera lens gets, the slower it gets due to the limited amount of light that can get through the lens, the higher the f-stop number, the slower the lens)

But yeah, try turning off the flash on the camera, and holding it as steady as you can when you take the picture. Also see if the camera has a “High Sensitivity” or “Low Light” mode which will make this even easier for you. If you DO use the built-in flash, I’ve noticed that some cameras have a setting where the flash strobes for a longer period of time, giving time for the light to hit the back wall before the picture takes, while still lighting the subject properly. I think on the Panasonic I use, this is in a special mode called “Party”.

7

[QUOTE=Raguleader]
Actually, I’ve gotten pretty good no-flash indoor pictures with various P&S digicams. Generally, the lens needs to be fast, and higher ISO settings and image-stabilization help a lot. Lately I’ve been using a Panasonic Lumix digicam that goes up to ISO 800, but I got pretty good pictures with a Nikon Coolpix P2 which only went up to ISO 400.
[/quote]
Perhaps my point of view simply reflects the age of my camera. My Minolta Dimage 7Hi is over three years old, and sensor technology has improved a lot in that time. While my camera’s ISO settings go up to 800, the noise is so great at 400 and 800 that it’s effectively useless at those settings.

I have taken a few good indoor pics without flash, but they were taken at ISO 200, and were carefully planned to make maximum use of window light. The Minolta GT lens on my camera is a 2.8, and is a great little lens, but when your maximum effective ISO is 200, you really don’t get much chance to work in low light conditions.

8

Point and shoot digital cameras compromise quite a bit on flash power and lens size for battery power and portability, respectively. Napier’s comments are spot on, but perhaps not very practical for a digital point and shoot in certain shooting situations.

Most cameras have a number of additional presets that may be more effective than the auto setting indoors under low light conditions. In my experience, it is extremely crucial to stabilize the camera on a tripod or table, etc. when shooting with these settings.

Or, on preview, what Raguleader said

9

[QUOTE=Stan Doubt]
Most cameras have a number of additional presets that may be more effective than the auto setting indoors under low light conditions. In my experience, it is extremely crucial to stabilize the camera on a tripod or table, etc. when shooting with these settings.

Or, on preview, what Raguleader said
[/QUOTE]
Right. For example, my Canon has a “night portrait” auto setting to take care of those situations: it adjusts the various speeds so that it gets enough light from the background while the flash “freezes” the foreground subject.

10

Thanks very much everyone for the advice. I’ll try out the suggestions tonight and post the results.

PS sorry about the links not working - I forgot about the hotlinking protection. I changed the settings on my server so it won’t happen now.

11

Having looked at the specs for your camera, it may also be down to the shooting mode you are using. Unless your camera can produce RAW images (which the SD900 doesn’t seem to) there is a certain amount of image processing that occurs internally in your camera when a shot is taken.

In the samples you’ve shown the darkening may be down to the camera trying hard to make sure the central subject is not overexposed. Unfortunately this is leaving the backgrounds underexposed.

I also note that the SD900 uses a form of processing called “Face Detection AF/AE” apparently designed to automatically determine what is the subject of a portrait shot and adjust exposures correctly.

A few things to try:

If you have not done so already try making sure that you are set to “portrait” or “indoor” modes.

Try setting the ISO a little higher as suggested above.

Try not to have a large distance between your subject and whatever’s behind them as Napier and Dan Blather said.

Adjust the exposure compensation by a couple of ev levels. I can’t recall off the top of my head whether you need to increase or decrease it, but a little experimentation will soon tell you.

Finally try different types of light metering. Your camera is capable of “spot” which measures the light levels of whatever is central in your viewfinder, “center-wighted” which measures everything but gives bias towards the central subject and “evaluative” which takes the whole picture into consideration.

12

[QUOTE=mhendo]
Not true. Shooting indoors, even during the day, will generally require flash unless you have a room that gets a lot of natural light (i.e., skylights, or very large windows), or you have a decent digital SLR that will take good pictures at very high ISO settings (1600 or above). Even then, it will help to have a fast lens (f 2.8 or faster).

If you only have a point-and-shoot digital, with only a camera-mounted flash, the best thing you can do to get more background detail is to slow the shutter speed. Of course, if you slow it too much, then camera shake becomes an issue, and the background might end up well-lit but blurry due to motion.
[/QUOTE]

I forgot to add a YMMV. No flash works fine for me, I have a P&S and I have no clue how to alter the shutter speed if I even can. If there’s any doubt, I take one with and one without flash. That’s one great thing about digital.

13

[QUOTE=mhendo]
Not true. Shooting indoors, even during the day, will generally require flash unless you have a room that gets a lot of natural light (i.e., skylights, or very large windows), or you have a decent digital SLR that will take good pictures at very high ISO settings (1600 or above). Even then, it will help to have a fast lens (f 2.8 or faster).
[/QUOTE]

Actually, usually 400-800 ISO is fine for indoor shots with natural light in most cases, if you’re shooting at f/2.8 or faster.

Here’s how the camera is thinking: basic flash modes usually default to a standard shutter speed, like 1/60 or 1/125 of a second. The camera sets the shutter speed and adds enough flash so that the foreground or plane of focus (depending on how advanced your metering system is) is illuminated to average 18% gray. (18% gray is what light meters expose for. A light meter has no idea what you’re taking a picture of. If you take a picture of a completely white wall and a completely black wall, they both will come out exactly the same shade of gray if you follow your camera’s light meter because it is assuming the scene it’s metering should average to 18% gray).

Anyhow, if you’re illuminating something three feet in front of you, of course you’re not going to illuminate the space 15 feet back equally. Light falls off and loses intensity in accordance with the inverse square law, as has been mentioned. If you illuminate the background correctly with the flash, you’re going to overexpose the foreground to holy hell.

There are many possible solutions to this problem. One would be to increase the ISO, so that 1/60th of a second exposure is more sensitive to the light in the background of your scene.

A second would be to slow down the shutter speed, down to about 1/15 of a second and use flash. This is usually most effective when the foreground is much darker than the background (as in mhendo’s examples). Otherwise, if the foreground and background are in equal or near-equal light, you may see “ghosting” or blurriness from the combination of the flash exposure and ambient light. When the foreground is dark, you don’t have to worry about the camera picking up much of the ambient light on your subject, and therefore the flash is acting as your only light source for the foreground, and completely freezes it. It doesn’t matter if you are particularly adept at handholding as a motion blurred background is usually not objectionable. However, if there is a significant amount of ambient light on your subject, what will happen is the camera will flash and freeze the subject, but as the shutter is open the ambient light will begin to bleed in. A little bit of ambient bleed doesn’t look too bad usually, and often it add quite a nice warmness to the image (when you photograph under tungsten lighting). However, too much and your picture is a blurry mess because of the exposures (flash + ambient) stacking up on each other.

In a case like this (where the foreground and background are equally lit), you might as well just try to take an exposure without flash, unless you are trying to fill in shadows from uneven or yucky lighting. In both cases, do your best to steady the camera–prop it against something, use a tripod, take many exposures, etc., as movement will be noticable.

A fourth, and more advanced possibility which is probably not doable with your setup, is to set up multiple lights to illuminate the foreground and background separately.

14

[QUOTE=pulykamell]
In a case like this (where the foreground and background are equally lit), you might as well just try to take an exposure without flash, unless you are trying to fill in shadows from uneven or yucky lighting. In both cases, do your best to steady the camera–prop it against something, use a tripod, take many exposures, etc., as movement will be noticable.
[/QUOTE]

This reminds me, when I used the Nikon P2, I ended up setting it to two-picture burst mode for the handheld no-flash shots. Oftentimes the first picture would be blurred from me pressing the shutter, and the second would be sharp as a tack.

15

[QUOTE=pulykamell]
Actually, usually 400-800 ISO is fine for indoor shots with natural light in most cases, if you’re shooting at f/2.8 or faster.
[/QUOTE]
Absolutely.

I was working on the assumption that the OP’s camera might not produce very good shots at 400 or 800. As i said, my older camera produces too much noise at those settings, especially in large areas with uniform color and tone. I can get a lot of the noise out using Photoshop and a special noise reduction plugin, but it’s a pain in the ass.

16

[QUOTE=mhendo]
Absolutely.

I was working on the assumption that the OP’s camera might not produce very good shots at 400 or 800. As i said, my older camera produces too much noise at those settings, especially in large areas with uniform color and tone. I can get a lot of the noise out using Photoshop and a special noise reduction plugin, but it’s a pain in the ass.
[/QUOTE]

True. The only P&S I’ve seen that is any good at 800 ISO or higher is the Fuji F30. In general, 400 ISO is the highest you want to crank these point and shoots up. I’ve got a Canon SD700, which is relatively new and I won’t shoot it above 400ISO unless there is absolutely no other choice. From what I’ve read about the SD900, it’s good through about 400ISO, and 800ISO can actually produce usable shots, but should only be treated as a last resort.