Using flash in manual mode can be tricky, especially if you want to avoid common problems like red-eye, harsh shadows, or color casts. In this article, you'll learn some tips and techniques to overcome these flash challenges and get better results with your digital photography.
Flash challenges are usually caused by the interaction between the flash light and the ambient light, the subject, or the camera settings. For example, red-eye occurs when the flash reflects off the blood vessels in the eyes, creating a red glow. Harsh shadows are formed when the flash is too strong or too direct, creating a contrast between the lit and the dark areas. Color casts are the result of the flash having a different color temperature than the ambient light, creating a mismatch in the white balance.
For many photographers, learning to use flash is one of the more difficult and technical photography skills. I recommend taking lighting classes well as reading multiple books, online learning and most importantly, practicing. There are far too many variables to properly illuminate (garden the pun) in a few paragraphs here. If your desire is to be versatile in photographing in various conditions, learning lighting is a must.
Since the world is already filled with mixed colors and temperatures, I prefer to just go with what is introduced..... because that is the natural use of the technology...... Yes, I do also play with filters and balance but I find it more artistic to mix it up and not to over complicate the moments. Keep it simple in most situations and shoot for the luminance and the contrast. It is much more fun to drag the shutter and mix it than to calculate and miss shots.
One of the easiest ways to prevent red-eye is to avoid using the built-in flash on your camera, as it is too close to the lens and more likely to cause reflection. Instead, use an external flash that you can angle or bounce off a ceiling or a wall, or use a diffuser to soften the light. You can also ask your subject to look slightly away from the camera, or use the red-eye reduction mode on your camera, which emits a pre-flash to shrink the pupils before the main flash.
Sometimes, the use of flash is unavoidable. Bright LED lighting is very conspicuous in social settings, much more so than the blink of a flash. Red-eye reduction pre-flashes work, but they also cause a lot of people to blink, or, assume the picture is taken and start to walk off. Taking the flash as far away from the lens (off axis) is a great option, as is bouncing it off a white wall or ceiling. Both of these avoid the light going into the eye and reflecting straight back to the camera.
Don't use flash! For my DSLR students, I tell them not to use flash. Check what the camera says about exposure then manually adjust to achieve the exposure that they want. For old time photographers, this is just bracketing adjustments, but the new kids don't have the same experience, so they have to learn. How does aperture affect exposure, how does shutter speed affect exposure, how does ISO affect exposure. Kids now a days are all about the automatic, PLEASE teach them about the variables.
There is a mathematical formula for red eye which involves the distance of the lens to subject and lens to flash. Moving the flash 12-16" above the lens (slightly higher than if it's shoe-mounted) will eliminate harsh side shadows.
This is so easy to overcome. Use a small white card taped to the flash head. It's called "bounce flash" and there is no red eye. If you do not have an independent strobe and you use the one that open from the top of your camera, become a pro and use a speedlight... with a white card taped to it. Use a gold card for warmer color.
To reduce harsh shadows, you need to modify the quality and direction of the flash light. You can use a softbox, an umbrella, or a reflector to diffuse the light and make it more even and natural. You can also move the flash away from the camera, either by using a flash bracket or a wireless trigger, and position it at an angle that creates a more flattering shadow. Alternatively, you can use a fill flash, which is a low-power flash that fills in the shadows without overpowering the ambient light.
Softness comes from size, a larger light source will cover the subject in light from lots of different angles, avoiding the creation of those harsh shadows. It's also important to realise that it's the relative size that matters. There's no point having a big softbox and putting it 5 meters away from the subject. The sun is a HUGE light source, but, it's a long way away, so it subtends a very narrow angle, therefore casing the harshest of shadows. A small softbox, placed very close, just out of shot, can be very effective.
To correct color casts, you need to adjust the white balance of your camera and your flash. You can use the white balance presets on your camera, such as tungsten, fluorescent, or daylight, or you can set a custom white balance using a gray card or a white piece of paper. You can also use color gels or filters on your flash to match the color temperature of the ambient light. For example, if you are shooting in a room with warm incandescent lights, you can use an orange gel on your flash to balance the colors.
To level up flash photography for indoor uses and events, use 1/4 or 1/2 CTO gels on the flashes when photographing indoors with tungsten light (most indoor lighting is tungsten temperature). This will help balance the blue-ness from the flash and the orange-ness of the tungsten indoor lights. Skin tones and color balance will be much easier to edit! An easy way to practice recognizing tungsten lights is to test a flash indoors with the lights on. Test on a subject with a CTO gel and without, and balance for the skin tones. You’ll see the background go from very warm orange to a much more balanced look depending on the use to the CTO gel.
Regarding Tungsten indoors. Yes, it's true that the source may not be a red hot tungsten wire, but, LEDs are widely available in a range of colour temperatures, including right down around 3000K, commonly just referred to as 'tungsten'. Now, balancing colour casts. Its advantageous to carry a collection of both CTO (colour temperature orange) and CTB (colour temperature blue) filters as well as +-magenta and green ones. This will allow you to match warm interior light with cool window light, Cool LEDs to warm evening window light, and, attempt to match the vast array of various coloured white fluorescent lights you still find in offices.
Indoor light tungsten!! This can no longer be taken for granted. Most venues use leds as they arecheaper to run My own home has leds too. Sadly this tungsten advice is a little out of date
To control flash exposure, you need to understand how the flash works in manual mode. Unlike in automatic mode, where the camera determines the flash output based on the metering, in manual mode, you have to set the flash output yourself. The flash output depends on four factors: the flash power, the flash distance, the aperture, and the ISO. You can use the guide number formula to calculate the flash output: GN = f-stop x distance x ISO factor. For example, if your flash has a guide number of 32 at ISO 100, and you want to use an aperture of f/8 and a distance of 4 meters, you need to set your flash power to 1/1 (full power).
If you want to balance flash and ambient light, you need to adjust both the flash exposure and the ambient exposure. The flash exposure is determined by the flash output, aperture, and ISO, while the ambient exposure is controlled by the shutter speed, aperture, and ISO. To achieve this balance in manual mode, set your camera and flash to manual mode, choose an ISO that is suitable for the lighting conditions and desired noise level, set the shutter speed to the maximum sync speed of your camera (usually 1/200 or 1/250 of a second), set the aperture to your desired depth of field and creative effect, and use the guide number formula or trial and error to set the flash output. After taking a test shot, check the histogram and LCD screen. If the flash is too bright or dark, adjust its output; if the ambient light is too bright or dark, adjust the shutter speed.
The most important thing is to practice in non paid activities. Avoid on camera flash, use great triggers and reflectors/modifiers. Definitely check the image on your camera between shots so you can make adjustments while the opportunity is still available.