WHICH EXPOSURE MODE TO USE? Av, Tv, Program, or Manual?

I teach an on-line Fundamentals of Photography Made Easy course for Betterphoto.com, and I get a lot of questions about which exposure modes are best for various situations. Here is my answer to that important question. In reading this, you will find it especially interesting regarding my thoughts on Aperture priority (Av).
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Aperture priority (Av): This is an automatic exposure mode where you set the aperture on the lens and the camera varies the shutter speed according to the light and your ISO.

Use Av mode when the lens aperture is very important. Av is important when shooting subjects that require complete depth of field (or when you specifically want shallow dof). Small apertures like f/22 or f/32 give you maximum depth of field where the foreground and the background are both sharp. You only use Av when SHUTTER SPEED ISN'T IMPORTANT. Assuming you want a tack sharp picture, this last phrase is crucial. This means that you are using a tripod and your subject isn't moving -- such as a landscape, cityscape, architecture, a macro subject where there is no wind, etc. The reason I make this point is because it is very, very easy to use a small lens aperture thinking, 'Oh, now I have lots of depth of field and everything will be sharp', and you forget what's happening to the shutter. If the shutter speed inadvertently gets too slow, your picture will be blurred and you will end up getting the opposite of what you want.

What good is maximum depth of field if the picture isn't sharp?

Therefore, keep in mind that Av can be ‘dangerous’ unless you are on a tripod and your subject is perfectly still. If you want to purposely blur your pictures, such as when shooting moving water, that’s a different story. If you want a completely tack sharp picture and you use Av hand-held, you must always pay attention to what’s happening with the shutter speed. If it gets slower than 1/60th, chances are your images will not be sharp. If you are using a telephoto lens in the 300mm or 400m range, you need a shutter speed at least 1/250th of a second, although 1/500th is better.

The other situation in which you can use Av is when you want the fastest shutter speed possible, given the light and given the ISO. If you set the lens to the largest aperture, such as f/4, then the shutter speed will be as fast as possible. This is what I do when I photograph wildlife with my 500mm f/4 lens. I use Av and set the lens to f/4. I know that this will give me the fastest shutter speed possible to freeze any movements of an animal.

Shutter priority (Tv): This is an automatic exposure mode where you set the shutter speed and the camera automatically varies the lens aperture.

You use Tv when you specifically want a particular shutter speed, such as when you want to blur a dancer or a running horse. You could choose 1/8th of a second, for example. If you are shooting something that moves very fast, like a kid playing soccer, you can select a fast shutter such as 1/500th of a second.

Program mode (P): Program mode automatically varies both the aperture and shutter speed according to the light and the ISO you’ve chosen.

When I am hand-holding the camera, I use Program mode most of the time because it is designed to select the fastest shutter speed possible, minus about 1/3 f/stop. It assumes you are hand-holding the camera and it tries to give you the sharpest picture possible. I take the camera off Program mode when I want a specific depth of field or a specific shutter speed. If, for example, Program is dictating 1/250 at f/5.6 and I want more depth of field, I will switch to Av.

Manual mode (M): Manual mode means that you physically turn the shutter speed and aperture dials to set the camera according to what the in-camera meter tells you is the correct exposure. Many amateur photographers (and some pros) think that this gives you the greatest creativity. Not true. All you are doing is relying on the in-camera meter and doing what it says. What is the difference between manually turning the dials or having the camera do it for you? The answer is … there is no difference. Manual exposure mode slows you down. For fast moving subjects like children, sports, and wildlife, shooting on manual means that you will miss a lot of pictures because you’ll be fiddling with the controls on your camera instead of concentrating on the subject and shooting.

Exposure Compensation: This feature that all digital cameras have allows you to over- or underexpose your pictures in 1/3 f/stop increments. If you are using any of the automatic exposure modes (Tv, Av, or P), this gives you all the creativity you need in varying the exposure according to what you want.

Off-camera Flash

Using a portable flash like the Canon 580ex or the Nikon SB-800 off-camera is a great technique. It totally transforms an image. Side- or 3/4 lighting offers more texture, dimension, and depth than the flat, pasty look of on-camera flash. One of the mistakes that photographers make, though, when they move the flash off the camera is that they don't move it far enough away from the lens axis. For macro work, off-camera flash can be held at arm's length, but for shooting people who are more than three or feet away, the flash has to be several feet away from the camera. This requires the help of an assistant who can hold the portable flash per your direction.

The photo of the costumed carnival participant you see here was photographed against a huge door, and a friend of mine held the flash about six feet away from the camera. To trigger the flash wirelessly, I used the Canon ST-E2 mounted on the hot shoe of the camera. This works on line-of-sight, though, and if I wanted to backlight the model I couldn't use this particular wireless unit. In that case, I'd need to use the Pocket Wizard which works on an infra-red signal such that the flash can actually be placed behind the subject where the transceiver can't see it.

Make sure that you have fresh batteries loaded in your flash so the recycle time is held to a minimum. It's very frustrating waiting and waiting for the ready light to come because you risk losing the shot.

I demonstrate techniques like this on my photo tours and workshops. The next one to Venice for Carnival is Feb. 8-14, 2010 (http://www.jimzuckermanworkshops.com/carnival-in-venice-2010/)

Edge Lighting

One of the advantages of shooting when the sun is low on the horizon -- i.e. sunrise and sunset -- is that you have several different types of lighting to choose from depending on your angle to the subject. For example, you can take advantage of front light, side light, backlight, transillumination (where the sun comes through translucent objects like leaves and fabric), and rim light. The two photos I've attached here show the latter. Rim light (or edge lighting) helps to separate the subject from the background in a very artistic way, and it helps to give dimension to a picture. No matter what subject you might be shooting, lighting along the edge can dramatize an image and make it very appealing.

The photo of the two warriors was taken in a primitive area of India's northeast called Nagaland, and these young men are members of the Angami tribe. The red bellied woodpecker was taken through my office window as the bird came to feed. I used a 500mm telephoto plus a 1.4x teleconverter.

FLOWER ABSTRACTS

A non-digital technique that is fun to try is shooting flowers through textured glass. The
resulting images look like paintings. You can buy small pieces of texture glass at glass and mirror stores. Look through their remnants, and when you see a texture you like they will cut a small piece for you.

I carry an 8 x 10 inch piece into the field or the garden, and I tape the entire periphery to protect myself from getting cut. I simply hold the glass up to the flowers such that it is parallel with the back of the camera and shoot the abstract designs. Soft and diffused lighting produces the most beautiful pictures. The closer the glass is positioned to the flowers, the more defined they will be. If the glass is held even two or three inches in front of the flowers, they will be much more abstract.

Home PHOTOSHOP workshop a success

A wonderful group of people traveled to my home base in Tennessee to take an intensive two day workshop with me last weekend, and we explored the techniques I use to create many of my images. One of the favorite techniques I demonstrate is the replacement of a white sky. In the shot of the elephant I photographed in Amboseli National Park, Kenya, for example, the white sky is very distracting. The problem, though, is that it is impossible to cut around all that grass so another sky can be pasted into the background. Photoshop has awesome capabilities, but it can't do that.



The only solution is to use a layer mask. I pasted a dark, stormy cloud photo over the entire elephant image and then, after making a layer mask (Layer > layer mask > reveal all), I used the gradient tool (a significantly underrated tool) to blend the clouds in such a way that they disappeared from the bottom portion of the image but stayed in the sky. I then used the brush tool to brush away the clouds from the elephant. Layer masks are not available in Elements.

Note that it's crucial to make the lighting in the sky match the bottom portion of the photo. It would look silly to put a blue sky with puffy white clouds in the background. The lighting on the pachyderm was soft and diffused, exactly like you would see from a sky like this. I have a large folder of sky photographs in my photo library just for composites like this.

If you would like to participate in a Photoshop workshop in my home, the May 2, 3 workshop is sold out, but there is still space available for July 11, 12.