Digigraphica

Picking the Right Viewfinder Camera

Shutter Speeds, Flash, and Autofocus

Dan Knight - September 2002

Shutter Speeds

Many of today's SLR cameras offer action-stopping shutter speeds of 1/2000 sec. or faster. None of the point-and-shoot models come close, although some do offer speeds fast enough to stop most action.

Looking through the list of zoom models in Popular Photography, the top shutter speed ranges from 1/250 to 1/770 sec. 1/250 is enough to stop for most human action, but even 1/770 isn't enough to stop an Indy car. That said, if you plan on shooting car races - or even bicycle races - look for a model with 1/500 or faster. You'll also tend to get better action stopping shots of soccer and football at 1/500.

Shutter speed interplays with focal length due to camera shake. As a general rule, you can handhold a picture at 1/F (where F is the focal length of your lens) and not worry about camera shake. The longer your lens, the higher the shutter speed you need to use to avoid camera shake - this can become a big factor when shooting something as long as the Pentax IQ Zoom 200 at the long (200mm) end.

Film Speed, Part 1

The third part of the equation is film speed. To get a higher shutter speed, shoot faster film.

A ancient rule of thumb is that on a sunny day, correct exposure will be f/16 at 1/S, where S is the ISO rating of your film. That really comes into play with today's point-and-shoot zooms, especially at the long end.

Again, let's look at the Pentax IQ Zoom 200 at the long end, which is f/13. With ISO 100 film on a clear day, we're looking at a top shutter speed of about 1/150 sec - low enough that camera shake may well be a problem, as well as subject movement in sports like soccer and football. If we switch to ISO 200 film, we move the shutter speed to a much safer 1/300 sec. Moving to ISO 400, we'll be shooting at the camera's highest shutter speed of 1/400 and an f/16 aperture. This makes ISO 400 film ideal for shooting sports on a sunny day with this camera.

But on a hazy or overcast day, we can easily lose two stops or more of light, which means the ISO 400 film is now shooting 1/150, and the problem of camera shake returns. Moving to ISO 800 bumps us to an action stopping, shake reducing 1/300 - which helps explain why many camera shops now recommend 800 speed as the best all around film for point-and-shoot cameras with longer lenses. (Fujifilm's 800 speed film is excellent.)

Flash

You really don't want to know the sad realities of flash on zoom lens point-and-shoot cameras, but you need to.

First, the built in flash is pathetically small and underpowered. Why? To keep the size, weight, cost, and battery drain down. A bigger, more powerful flash would increase cost and size, which makes it harder to market the camera.

As helpful as Popular Photography's annual point-and-shoot roundup is, even they don't publish flash range information in their summary, although they do a great job of mentioning it when they review individual cameras.

For instance, the May 2002 issue reviewed the Fujifilm Zoom Date 1000 and Yashica Zoomate 110W. At the 28mm setting, the Fuji is rated to 9.5' with ISO 100 film and the Yashica to 10'. Multiplying distance by aperture, the Zoom Date 1000 has a guide number (GN) of 55 (9.5 x 5.8) and the Zoomate a GN of 60. That's actually a full stop more power than the built-in flash of most 35mm SLRs, but the SLRs tend to have higher speed lenses and thus don't need as much power.

All things being equal, we would expect that as the Fuji zooms for 100mm and f/10.5, the maximum flash range would drop to 5.2' with 100 speed film. Likewise, the Yashica at 110mm f/13.1 would only reach 4.6' at ISO 100.

Fortunately, all things are not equal. To help offset the reduced light transmission as the lens zooms, the flash also zooms. In the case of the Fuji, the flash is rated to 6.5' at the long end, giving us a guide number of 68 (6.5 x 10.5) - a small but helpful boost from 55 at the short end. Likewise, the Yashica flash is good to 6' at 110mm, which gives us an impressive GN of 79. Of course, if you're using the lens zoomed to the long end, you're probably shooting something more than 7' away....

Zooming flash helps, but only so far. I every case, a zoom point-and-shoot has a much greater flash range when the lens is as the short end. As you zoom in to capture the kids in their school play, you actually reduce the likelihood of having an acceptable exposure. You are far better off moving closer to the stage to take your flash photos.

Film Speed, Part 2

Faster film comes to the rescue again. Because light falls of with the square of the distance (the same kind of ratio we saw with f-stops), doubling your film speed increases your flash range by 40%. Here's how that works out with the two cameras mentioned above:

ISO 100 ISO 200 ISO 400 ISO 800 1600
Fuji 28/5.8 9.5' 13.4' 19' 26.8' 38'
Fuji 100/10.5 6.5' 9.2' 13' 18.4' 26'
Yashica 28/6 10' 14' 20' 28' 40'
Yashica 110/13.1 6' 8.5' 12' 17' 24'

It's very easy to be 10' or more from your subject when shooting indoors, so you want to avoid ISO 100 film for flash photography with this type of camera. In fact, I'd suggest nothing slower than 400 speed so you can zoom in on your subject from 12-13' away (and no further).

And just as we saw with the Pentax IQ Zoom 200 outdoors, moving to 800 speed film gives you that extra edge with flash as well - but you still want to be less than 20' away from the stage when shooting that school program.

This is just one more reason camera store employees generally recommend ISO 400 or 800 film for zoom point-and-shoot cameras. (And a lot of us shoot the same thing in our SLRs for exactly the same reasons.)

Autofocus

Underexposed flash pictures are probably the most common problem with this type of camera, and using a fast enough film can really help there. But the second biggest problem has nothing to do with film - it's a matter of focus.

Until about 2002, autofocus point-and-shoots were consistent in always and only focusing on the center of the picture. That was great if that was where your subject was, but what happened when you were shooting two people with some space between them? That's right, the camera focused on the background, which would be tack sharp with two out-of-focus people in the foreground.

Unless you're using one a camera that actually analyzes your composition and makes an educated guess where you want to focus (not that common in film point-and-shoot cameras), you need to remember that these cameras focus in the center of the frame. If your subject is going to be off center, you need to make sure the camera you buy lets you focus on your subject, lock focus, recompose, and then take the shot - and learn how to use this feature as soon as you get the camera.

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