If you had to pick the most important parameter to adjust when taking culinary photography, it’s the choice of aperture (example f/2.5 or f/22).
Depending on your choice, the size of the zone of sharpness in your photo will vary. You can also make the background really crisp or plunge it into a nice blur in order to single out the subject of the shot. It’s what we call depth of field.
So when should you use a large or small aperture in your pictures?
– Quick reminder: What does the number after f/ mean?
I’ll just say a few words about this subject for beginning photographers.
In every lens there’s a circular diaphragm that manages the amount of light to let through. Aperture corresponds to the diameter of this diaphragm, and it’s indicated with a small f, followed by a slash and a number, like this: f/10.
To break the idea down: it’s like the pupil of your eye which dilates in order to let light in. When the diaphragm is wide open, there will be an abundance of light. On the other hand, if the aperture is practically closed, only a fine shaft of light will penetrate to the sensor.
Just to complicate things a bit more, the size of the number does not correspond to the size of the aperture. The smaller the value (f/4, f/1.8…) the larger the aperture, and vice versa.
The diaphragm is composed of blades that open and close differently according to the aperture selected.
– Manage the depth of field
The choice of aperture will let you control the distribution of the picture’s areas in focus and out of focus.
When the diaphragm is completely closed (f/22, f/18…), the area that is out of focus is much smaller, if not non-existent. The image will seem sharp in both the foreground and the background.
When the diaphragm is wide open (f/1.4, f/2…), areas out of focus become much more prominent, leaving only a slim area of sharp focus The more the diaphragm is open, the more lack of focus becomes visible and pronounced.
Here is the same photo taken twice. The only difference is the aperture. On the left, I took the shot in f/1.8 and on the right in f/22.
So in some respects, but not in every respect, depth is managed by aperture. You should also remember that the distance between the lens and the subject, the distance between the background and the subject, as well as distance between the lens and the camera are all factors to take into consideration when adjusting the depth of field.
Distance to the subject: with a fixed aperture, the distance between you and your subject will determine the depth of field. In fact, the closer you bring the lens to the subject, the less depth you will have. The farther away you get, the more extensive the area of clarity in the shot.
The same is true with the background. According to the distance between the subject and the background, the background will appear more or less out of focus, regardless of the aperture.
Now, we should also talk about your equipment, because it will have a direct impact on the depth of field. And it’s the size of your camera’s sensor that will play a role on this point. Because compacts have a smaller sensor than a reflex, depth will be greater at the same aperture. So with this type of camera it’s more difficult to get that really nice blurring effect in the background. I recommend using the macro setting so you can get more pronounced blurring.
As for reflex cameras, every lens is different. The shorter the focal length (24mm, for example), the greater the depth of field. But if the focal length is greater (100 mm, for example), the blurring effect will be heightened.
Depth of field is first and foremost a personal judgment call. In what proportion do you want to apportion areas in focus and areas out of focus? That’s the question you should ask yourself before taking each shot.
– When and why should you use a large aperture?
Personally, I always shoot with a large aperture, between f/1.8 and f/2.8 with my 50mm and between f/2.8 and f/4.5 with my 100mm, because that’s how I like to take culinary photos.
Less pronounced depth of field is useful for highlighting the subject of your photo and setting it apart from the surrounding decor by creating a blurring effect both in front and in back of it.
It’s a way to give the shot more relief, while at the same time making it less descriptive and setting the subject apart to draw the viewer’s eye to the sharpest zone in the picture.
That’s how you can eliminate superfluous information and present what is the real essence of the photograph.
So the background will become a mass of color and your picture’s readability will be simplified. This is all the more important if you’re taking a frontal shot.
Here are two photos taken with an f/1.8 aperture. On the left, you can see that only the toast is really clear, while the foreground and the background are brought out of focus.
On the right, the view is a bit higher up than what I usually want to shoot. This type of combined view with a large aperture achieves a more dreamy type of photo.
– When and why should you choose a small aperture?
When you take a shot with a smaller aperture, you can achieve more descriptive, less “artistic” photos, if you will. They are a little trickier to achieve because you’ll need to pay more attention to the background in order not to take a shot that is so busy you lose yourself in it. You’ll want to stay pretty sober in terms of your composition, and hold on to a little bit of blur in the background.
A small aperture is also recommended when taking a shot from above if your scene will include items placed at different heights. That way, everything will appear sharper.
The choice of aperture is really one of personal taste. I do use smaller apertures, going as small as f/10, but I rarely go beyond that. Usually photos taken with these apertures are for clients, so I can highlight their products. For my blog, I always go with large apertures.
Here are two photos for the blog. They are taken from above using relatively large apertures with respect to the lens and the distance from the subject. They were taken with f/6.3 using a 50mm.
Bokeh refers to the artistic blur in the background from which the subject is clearly distinguished, thanks to a small depth of field. What determines the blur and its quality is the shape of the lens diaphragm and the number of blades.
When sources of light appear in the background, these points will take on a softer form that is more or less geometrical. That’s how you get bubbles of light to create a magical background. Candles, glitter, and bright garland are among the items that can create these sparkling bubbles. With glitter, situate yourself so that the light reflects above to succeed in creating the bokeh effect.
Also, for really great bokeh effect, make sure the points of light are set off against a dark background!
In the photo on the left, I used little silvery stars which sparkle and turn into these bubbles of brightness when the light reflects on them.
In the photo on the right, I used sugar sprinkles I scattered on the scene. With a small depth of field (f/1.8 with a 50mm), they turn into little gold circles.
You can also get a great bokeh effect using granulated sugar like in the photo on the left or with aluminum foil, like in the photo on the right.
Under the pseudonym chefNini, Virginie has written a culinary blog by the same name since February, 2008. She shares her recipes, technical articles, purchasing guides and test products.
Since 2011, she has offered photography, styling, and culinary creativity services.
She has written a book on culinary photography published by Pearson, as well as a Cooking Almanac published by Editions 365.