Aperture Priority Mode

Aperture Priority Mode

This was the first automatic exposure mode I encountered and is my preferred way of working by far.

It's generally accepted that aperture has the largest influence on the resulting look of an image. By and large it's true because it has a huge impact on depth of field. Before I continue, that does break down at extremes such as when using a long lens – there's not going to be a big difference between f/4 and f/8 when using a 500 mm lens. Add in some action and the resulting shutter speeds will be far more important. But I'll save that for another day.

My second SLR, the Pentax ME Super, had Manual and Aperture Priority modes. However, most of the time as I recall was used in Aperture Priority. Automatic exposure meant that exposure errors were much less of an issue especially in changing light conditions, even if that only meant moving from sunlight to shade. It was easy to just to turn the aperture ring to achieve a desired shutter speed, often to stop action or avoid camera shake. It was as my photography progressed that I regularly started to use aperture as the powerful control of image appearance that it is, particularly for landscapes and close-up work. Remember, in those days, the most popular film speed was ISO 100 (and not much above 400) which you had to stick with for the whole film, so the need to get a picture often influenced settings.

Nowadays, I give aperture much higher, er, priority for much more of my photography.

For most photography I'd suggest you do to. At least pay more attention to it. So here are some areas where choice of aperture should be the prime consideration (even if you choose to work in other modes).




Close-up and macro work, including still life. Careful choice of aperture is necessary in order to achioeve sufficient depth of field to cover the subject. Usually this means smaller apertures to get as much sahrp as possible, but don't dismiss wider apertures to throw a background soft or to concentrate attention on one component (the differential focus I mentioned above). Aperture choice is also important for focus stacking.

Landscape. Very similar to close-up as regards requiring small apertures, but wide apertures creating a narrow zone of sharpness can work well with some scenes.




Portraiture. Wide apertures help separate a subject from the background. However, just because you can use f/1.8 doesn't mean you should (it can create wonderful effects but focus technique needs to be perfect). Though f/4 is often better than f/8.

Flash. Aperture is crucial in controlling the influence of flash coverage. The downside is where the camera tries to cater for ambient light too which can result in a very slow shutter speed and unintended results.

It's this control over appearance that aperture has which means those 'in the know' like to use wide aperture lenses if possible, not just for very shallow depth of field but for differential focus effects. With the superb low noise high ISOs available today a wide aperture isn't as necessary as it once was. Just keep upping the ISO. With electronic viewfinders you won't notice the darkening I,agenwhen you're using the long end of your zoom at a maximum aperture of f/6.3. However, when you're up against it trying to squeeze something out of dark conditions wider aperture lenses will deliver results when your standard zoom has run out of puff.




Later I'll look at Shutter Priority mode, but next up will be something about lighting.


All text and images © Keith Rowley 2021