I make a pilgrimage twice per year to Daytona International Speedway, for the Turkey Rod Run Thanksgiving weekend and for the Spring Turkey Rod Run. These car shows typically attract about 4,000 cars (!) which translates to lots of photo opportunities for a car guy like me. Those opportunities also present some challenges.
Being a morning person, I like to get out to the car shows before the crowds. This makes taking photos easier, and sometimes provides opportunities that get lost as the day wears on (golden hour light, morning dew on cars, etc.). I also like to use a polarizing filter to minimize surface reflections. If you're not familiar with a polarizing filter, think of it as the equivalent of sunglasses. Here's where the ISO thoughts come to mind. Sometimes, if you have an overcast sky and your camera lens is wearing sunglasses, you need to compensate for the reduced light you have to work with. This can be accomplished in a few ways:
- Slower shutter speed
- Higher ISO speed
Each solution has tradeoffs, and each may be be more/less desirable at times. Let's look at the pros and cons of each:
Slower shutter speed - This is a great solution for objects that are not in motion, particularly if you are using a tripod. However, if you are shooting moving objects slowing down your shutter speed too much will give you a blurry image. Likewise, if you are shooting without a tripod, handheld shooting can get blurry if you shoot too slow.
Flash - Using a flash is a good way to light up subjects close to you, and a flash can help to fill in some of the darker areas that a harsh midday sun can create. However, flashes don't help for landscape photography or distant subjects, and they can create artificial bright spots, harsh shadows, and red eye. Some of those can be fixed post-production, but not always.
Higher ISO speed - Higher ISO speed allows you to shoot with a faster shutter speed, which is particularly useful when you have so-so light and subjects in motion. The downside - noise. Higher ISO speeds translate into a noisier (or grainier) image. Most newer cameras can shoot at fairly high ISO speeds before noise becomes a problem though.
So, I was thinking about what ISO to use on the overcast morning that I was shooting photos of show cars at the speedway. Remember, the camera has all sorts of adjustments and settings available to you. Use them, and you can get superior results to the 'auto' mode, even when shooting autos :-) And remember, if you're not having fun when you're out shooting, you're probably doing something wrong.