Choosing the Best F-stop

Well I thought another blog with Hal Quanbeck’s photos was in order, especially since he said such nice things about my book. Let’s face it; Hal must be a very astute, smart guy to use my book to improve his animal photography.

Ok, enough with the commercial. In the blog last week, Hal wrote that there are some things we can do to take better photos with our cell phones even though cell phones don’t have an f-stop option.

F-stop?  I got quite a few questions about that, so thought I’d better explain.

F-stops (also referred to as the aperture number),  are a system of metal leaves in the lens that open up and close down to control the volume of light passing through the lens. It is the lens’s equivalent of the iris of our eye.

With photography, we refer to “opening up the F-stop,” which means making the aperture size larger to allow more light through the lens and “stopping down the F-stop,” which means making the aperture size or F-stop smaller to allow less light through the lens. It’s confusing because larger aperture sizes are represented with smaller numbers so f2.8 is a larger f-stop than f5.6.

There’s lots more technical mumbo jumbo about F-stops, but you know I’m not going to go there. We have to walk before we run, so the first concept is to learn that the f-stop you choose affects the depth of field in your photograph. Large f-stops (F-2.8, F-4) will produce shallow depth in your images and small F-stops (F-8, F-11) will give you more depth in your images. The rule is that the chosen depth of field will render your subject sharp from the point of focus 1/3 in front of that point, and 2/3 behind it.

Ok. We get it. So when Hal was photographing this wonderful image of his  mother and her dog, he was using a real camera with real F-stops.

It’s a wonderful image isn’t it? Hal has done everything technically that he needed to do, plus he’s captured the personality of his subjects. I love it!

But making great images doesn’t come easy. Let’s study a few more he took during the same shoot which illustrate the importance of choosing the correct F-stop.

In this photograph, the dog is rendered tack sharp, but Hal’s mother is beyond the chosen depth of field so sh’e much too soft. To correct this, Hal chose a smaller F-stop (F5.6) when he took the perfect shot.

Here is the same problem, but this time, it’s the dog who is rendered too soft in the final image. Can you see that in both these photographs the chosen depth was too shallow regardless of where Hal focused his camera?

If you have a depth of field preview button (read your mannual to find out), you can use that button to check your depth before you shoot. A depth of field preview button will stop down the lens to the chosen F-stop so you can view the results before you shoot.

However, with an image like this, where Hal has set it up so there is nothing behind the subjects, just choose a mid F- stop range and go to work.

Well done Hal.

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