When use your camera’s built in flash (flash basics 2)

The first post in the flash basics series was when not to use flash, as I said in that post I love flash photography (and loving it more every day) but the camera’s built in tiny flash is very limited and we have to work within it’s limitations.

Basically there are only 4 good reasons to use your camera’s built in flash (that I know of):

Fill Flash

Surprisingly the best time to use on-camera flash is when there’s plenty of light, to demonstrate this I’ve convinced a garden gnome to pose for me in the bright mid-day  summer (well, spring) sun, to help with this bright eye-hurting sum I’ve let the gnome use a hat.

As you can see the gnome’s face is in the shadow (in real life the gnome is quite bright) especially you can see dark shadows below the eyes – sometimes those are lovingly referred to “raccoon eyes” – but if we add a little flash:

The shadows on the face aren’t gone (we don’t want them gone) but they are much lighter and not nearly as bad.

To use fill flash on a Canon DSLR just use the Av mode and pop open the flash.

On a Nikon DSLRs it’s a bit more complicated – half press the shutter in your favorite shooting mode and look at the settings the camera selected (aperture, shutter speed and ISO), now switch to manual mode and set the same values, pop up the flash and you’re ready.

On some compacts you have to switch to a special fill flash mode or enable fill flash in the menu, sometimes you will also want to lower the flash power when used as fill, the setting for flash power is usually called “flash exposure compensation”.

When it’s the only way to get the shot

Basically sometimes its better to take a bad picture than no picture at all – but this is not an excuse to use flash when it’s ineffective, only use flash when:

  • The subject is close – your flash maximum range 3-5 meters (approximately 10-15 feet) depending on your camera, and this is for cameras with “real” flashes, if you are using a cell phone with a LED flash the range is even shorter, anything farther than that is just not lit by the flash.

    If you are at a show or a sporting event the action is way too far away the light from you small flash does not reach the stage at all.

  • Long exposure is out of the question – if the subject isn’t moving and you have a few seconds to set up you can still use the ambient light – just switch your camera to “no flash” mode and put it on something steady (or at least lean against something steady) so it doesn’t move.

    This won’t work if it’s completely dark (extremely rare those days) or if the ambient light has a really bad color cast (unfortunately a lot of street lights are like that)

Triggering off camera flash(s)

This is a good reason to use on-camera flash – but a bit too advanced for the second post in the flash basics series, maybe we’ll talk about it in a much later post.

Getting creative

Photography is an art – and there are techniques that use the built in flash to get a specific effect (and not every effect has to make people look good) – if you have a creative technique to use the camera’s built in flash please share in the comments.

Controlling Light Falloff

In this post we will see how to control “light falloff” – the difference in light intensity between the areas of the photo who are closer to the light source and the area who are a bit farther away – this will let you create dramatic lighting (for example, cause one side of the face of fall into darkness) or more even lighting that is very flattering in portraits and essential for product photography.

Basically, this is very simple, the intensity of light drops has the subjects gets farther from the light source (no surprises there) but the drop is not even – the light drops off very quickly near the light source but very slowly farther away.

This is because the light falls off according to something called “the inverse square law” – here’s a picture of a wall lit by a flash to demonstrate the effect:

If you look at the area between the rightmost blue line and the center blue line you can clearly see that on the right is much brighter than the center – actually it’s about 4 times brighter (or 2 stops), now look at the area between the center and leftmost blue lines, this area overs approximately the same distance but the lighting difference is much harder to see – I’ve measured it and the center is twice as bright as the left (1 stop).

If we also look at the red ranges around the blue line we can see that in that tiny distance around the rightmost blue line we lost 20% of the light intensity, at the same distance around the center line we lost only 10% of the light and at the leftmost line the light is the same for the entire range.

So what does it mean in practice? let’s take a “one of a kind” toy from Ikea and photograph it with the flash to camera right just out of frame:

We see the left side of the face is completely dark and so is the background, let’s take the exact same picture but move the flash about 2 meters (6 feet) back (and raise the flash power to compensate for the change in distance):

Now the face is well lit because the relative distance between the parts of the face is now small compered to the distance from the flash, also, the background is no longer black (because the distance between light and  to background is no longer much longer than distance from light to subject).

If you remember in previous posts we used this effect to make the background black by placing the flash very close to the subject and to make the background white by placing the flash near the background.

Now, there’s just one more thing, while the light drops in intensity between light source and subject it does not lose power between subject and camera, to show this I’ve taken two more pictures of the same toy, both pictures are taken with the same camera settings (f/8, 1/200 sec, ISO 400, 135mm) and the flash at the same position with the same power settings, the first picture is from the closest distance that fits the subject in frame:

The second picture is from another room, the farthest I could get inside my home:

And here is the first picture and a crop of the same area from the second picture, the colors are a bit different because I forgot to turn auto light balance off but the brightness is absolutely the same:

Hope you enjoyed this post, and that this will help you better control the lighting in your photos.

Using light to show or hide texture

Sometimes you want to show the texture of what you are photographing, for example, you may want to exaggerate the texture of wooden or paper items to make them look more authentic, other times you want to hide texture (and make skin look smother).

Today we’ll see how you can control just how much texture we will see in the images.

Our first test subject is a printout of the dinosaur from the white background post a while back printed on cheap office paper.

For this experiment I’ve set the camera in manual mode, ISO 100, f/8, 1/200, at those settings all the light we see is coming from the flash (without flash the picture is completely black), the camera is on a tripod looking almost strait down at the printed paper that is on a small table.

In the first picture the flash is on the camera pointed directly at the paper and in minimum power (because the white paper reflects a lot of light back at the camera) and we get this:

In the second picture, with the same camera settings and the same flash at the same distance from the subject and still pointed directly at the paper – but this time located to camera left at the same height as the paper and in maximum power (because this time most of the light crosses from left to right without hitting the paper) and we get this:

The picture is too dark so we open the aperture and raise the ISO and get this:

We can clearly see the difference in the paper’s texture between the first and third picture (the second picture is here to prove that the difference was caused by moving the light and not by changing the camera settings).

Now, I’ve chosen those two extreme positions To make the difference obvious in real life, you rarely light your subject directly from the side and, unless you don’t have a choice, you also rarely want the light to come from the camera, in most cases you should choose something in the middle.

Why does this happen? when the light source is close to the camera and the light hits a textured surface all the surface is more or less evenly lit – making the surface look flat.

On the other hand, when the light is coming from the side it only lights one side of each little ridge that makes up the texture – transforming the surface into a series of lighter and darker patches and bringing out the texture.

This is why people say the light from on-camera flash is “flat” it makes 3D object seem flatter and reduces the feeling of depth is the image.

That’s it for today, see you next week.