In food photography, depth of field is one of the key tools that photographers use to make delicious looking images. Understanding depth of field, aperture, f-stops and their relationship is essential to mastering photography, particularly portrait and food photography – my bread and butter, so to speak.
I thought I’d skip my usual post for Monday Memories, the photography series in which I reflect on an image I took during the course of my work as a professional photographer, and instead look at the relationship between depth of field, aperture and f-stops, which is vital for photographers to understand, especially those focusing on food photography.
Depth of field refers to the amount of the image that is in focus either side of the focus point. It’s easier to explain in images rather than words or diagrams, so see the images above and the f-stop settings I used (bottom left corner of the images) to achieve the desired depth of field. But there are some important things to understand first…
The f-stop settings on the camera control the size or diametre of the aperture or opening which allows light to pass through to the sensor or film. When you adjust the f-stop you are therefore controlling the amount of light entering that opening.
One of the reasons you will see professional photographers using tripods and release cables to trigger the shutter, is that as the f-stop increases, the exposure time (i.e. the length of time that the aperture stays open) increases too. If the camera wasn’t on a tripod the images would most likely be blurry.
In the photos above, the exposure time at f/2.8 was 1/2 a second, while at f8, exposure time was three seconds – not something you could ever do handheld!
Depth of field increases with the f-stop, so an f-stop of f/2.8 has a small or shallow depth of field and f/22 has a large depth of field. If you look at the above images, you can see that by f/8 the burger in the background has more definition and that you can just make out the words ‘SLOW POT’ on the right in the background. (Yes, I pushed the burger down in that image to show the label.)
So, why is this important and why do photographers, and especially food photographers, shoot at all these different f-stops?
Well, the idea of using different depths of field for different food photos is so you can draw the viewers’ eyes to the most important part of the dish, generally the key ingredient.
In this case, the key ingredient is the pulled pork, which, by the way, spent eight hours in that slow cooker, filling the kitchen with the most mouthwatering aromas… but this is a photography post, so I won’t go on.
In the photos above, I’m actually not that happy with the depth of field as it looks like the coriander (cilantro to Northern American readers) is mostly in focus and not enough of the pork is in sharp focus. I should have placed that coriander further back in the bun, but the aromas of the pork were making me damn hungry.
In the photo shot at f/5.6 enough of the pork is in focus to make the burger look more tantalizing. By f/8 we can see more of the ‘SLOW POT’ and assume that it was probably involved in the making of the burger. If this shoot was for the maker of the slow cooker, I’m pretty sure the advertising execs would make me shoot it at f/22 so that the cookware was more in focus.
When shooting in close-up and with shallow focus, such as f/2.8, it’s very difficult to see exactly what is in focus and it can be challenging to judge the depth of the focus on the tiny screen on the back of the camera.
This is why you’ll see food photographers shooting ‘tethered’, which is when the camera is hooked up to a computer and the images are transferred directly from the camera to the computer and displayed on the screen.
This set-up makes it easier to judge whether you have the correct ingredient or section of the image in focus at the shallowest depth of field before shooting at increasingly bigger f-stops.
When shooting digital, it’s always a good idea to shoot up to f/16 from f/2.8 because with each different dish the ideal f-stop that best shows off the dish can really vary.
Food photography is a little like cooking. Even when you have a solid recipe, the seasoning still needs to be adjusted to produce that perfect dish that gets people salivating.
You’ll find more photography tips in my series Monday Memories, where I reflect on moments from my work as a professional photographer.
For a walk through of aperture & depth of field check out this YouTube video by photographer David Loftus.