Narrow depth of field in photography can be both frustrating and useful! It’s something you have to deal with a lot in macro photography but you probably wouldn’t need to think about it so much in landscape photography. As most of what I do is photographing small things, I encounter it a lot.
The technical bit
In order to get a good photo of a tiny, busy creature, you need to keep your shutter speed reasonably high, but this can often mean you then have to have a wide-open aperture to let enough light in.
Confusingly with aperture, the wider it is, the lower the number. With my 100mm macro lens I can go down to 2.8 in order to get enough light for my close-up shots with the shutter speed at 200 or more. I could use a higher ISO, but then the shot will be more grainy and I lose the crispness of the image.
If it was a flower I was photographing, I could use a tripod which would let me use a slower shutter speed, but that’s not going to work if I’m trying to photograph a moving insect. Also I don’t really like carrying a tripod around with me when out on a walk.
When your aperture is 2.8, your focus is very fine. A millimetre is huge when your image is close-up and your aperture number is small. So you can have just one tiny part of the image in crisp focus and the rest of the image is blurred. So the depth of field is narrow – the depth into the image that is in focus is small.
I’m often trying to get the eyes of an insect in perfect focus, and it’s quite difficult, especially if they’re moving. There’s a narrow window to get the focus right, and it often doesn’t work out. For every photo I post on here or Flickr, there are a lot I discard!
Having said that, sometimes you might want to deliberately make your focus narrow. You can get lovely bokeh effects when the background of your image turns to sparkles or a lovely soft glow. It can enable you to make busy backgrounds less distracting. And it can help with focusing on creatures that are behind a fence, like the ones I was photographing at the zoo recently. Fences can become almost invisible if you’re lucky.
What does it look like?
I took this picture of some frost on my garden chair in January. You can see that there is a narrow line of focus, and the frost at the back of the picture is completely blurred out. The frost at the front is also blurry. There just that narrow line across the photo where the crystals of ice are focused.
In this photo of one of our succulents (I’ve posted this image before), you can see the detail of the fuzzy leaf just off centre at the front of the plant, but the one to the right isn’t quite focused, and the rest of the plant is quite blurred.
Another of our houseplants, a cactus this time. This one has a number of ‘fingers’ and I’ve focused on the spikes on the ones at the front of this picture. The rest of the fingers, outside of that narrow depth of field are all gently blurring into the background.
How about this little guy? He’s a really tiny tree-like succulent and I discovered when photographing him that his leaves are very textured. You can’t really see that very well with the naked eye. But because the depth of field was so narrow, you can see that although the leaf to the right of centre is in focus, the smaller ones in the middle aren’t, and the ones further down the stem are blurred. You might need to look closer to see what I mean – just click on the photo to see a bigger version.
Using it to your advantage
I love a bit of bokeh on my images, and this is something that you can achieve by using that narrow depth of field to your advantage.
And finally here’s another from years ago when I was deliberately creating rainbow bokeh using a pile of sequins!
Inspired by the Lens-Artist Photo Challenge #84: Narrow.