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Food Photography Basics # 7: ISO

Posted Dec 01 2011 12:00am

T
his post has been due for a while, and here it is finally. We have already looked at Aperture and Shutterspeed and now it is time for ISO, the third part of the Exposure Triangle. This is probably something that a lot of budding photographers don’t think much about when playing with exposure but ISO has an important part to play.

What is ISO?
ISO, formerly known as ASA/ film speed from the days of film cameras, stands for International Organization for Standardization and is a world-wide accepted standard indicating how sensitive a particular film was to light. Today, in the world of digital cameras, ISO indicates how sensitive the camera sensor is t light. ISO is measured in stops/numbers starting at 100, 200, 400, 800, 1600, 3200, 6400, etc. depending on the camera.
There are some cameras with and ISO of 80 and the higher end digital cameras also have fractions of ISO stops. My present camera (a Canon 60D) for example has 2 fractional stops between every 2 full stops so I can go from ISO 100 to 125 to 160 before I reach 200.
The lower the ISO on the camera, the less sensitive the camera sensor is to light and vice versa.  This means that the ISO settings can be used to control the light and exposure along with aperture and shutterspeed settings. So if you have adjusted your aperture and shutterspeed settings for a particular shot and you need more light (before you resort to using a flash or external source of light), then you can push up the ISO.  

(ISO 100 - 1/60s; ISO 400 – 1/250s; ISO 1600 – 1/1000s; ISo 6400 – 1/4000s; aperture constant at f/4.0)
This will enable you to use faster shutterspeeds to shoot in low light situations, and also minimise camera shake. Of course, you could avoid the camera shake bit by shooting with a tripod and a remote trigger if possible. A higher ISO is useful in situations where one is shooting in places that aren’t well lit and using a flash might not be an option (like inside buildings, parties, concerts, weddings, etc.) where the subject might not be well lit or may be moving. This is not usually the case with food photography. The flip-side of a higher ISO is that your photographs start becoming “noisy” or “grainy”. This might not be apparent immediately but if you zoom into your higher ISO shots, you can see a grainy effect which is also known as “noise” in photography. Also, you could lose sharpness at very high ISO settings. You can see this in the photographs of the pomegranates above. I have maintained the aperture settings at f/ 4.0 for all the shots. As the ISO setting increases, a grainy look or noise becomes apparent especially at the higher ISO numbers. This is not apparent at first glance in the photographs mostly because they have been resized to 500px for this blog.  You will also notice that as the ISO increases, the shutterspeed decreases to maintain the same exposure, since the aperture setting is constant. However,  if you see the cropped versions below you can see how the grain is very visible at ISO 6400. The blur in the cropped picture is because I have taken the shallow DoF areas from the original photographs to illustrate the noise.



So then comes the question, “What is the best ISO setting to use in food photography?” The “best” ISO would really depend on various factors. How much light is available (natural or artificial), what exposure and DoF (depth of field) you are aiming for, are you doing a regular food shot or a pouring shot, are some questions to answer first. In my opinion, in food photography, t is always best to use the lowest ISO setting possible for food photography, especially since the food is not going to be moving. So I would typically start with ISO 100 and then increase it to 200 if I must and I rarely go beyond and ISO of 400 while photographing food. It helps that I shoot my food photographs in natural light which I have plenty of since I live in the sunny tropics! There are occasions where one would need to use a higher ISO in food photography. If you need to freeze movement, as in pouring shots or splashes, you need to use a fast shutterspeed and a smaller aperture (big f-number) to freeze motion. This means light available in the camera comes down. So you would need a higher ISO and lot of ambient light to get a good photograph. Having said all this, I must stress that the higher end dSLR cameras available today handle higher ISO settings very well with very little noise/ grain at even 1600 and 3200. So don’t just stick to an ISO of 100 for every photograph. Experiment with your camera and different ISO settings and see if you’re happy with what you get.




(Aperture – f/5.0, Shutterspeed – 1/50s and ISO 100 shot at a focal length of 146.0mm) And if you are going to use your photograph on the web or print it in postcard size or something similar,  very small amount of noise will not be visible except if you’re viewing your photographs in full size. Some amount of noise can be treated with special software. Many free versions of editing software have this in some form (Smart Blur/ Noise Reduction) and Neat Image is supposed to be very good (I’ve never tried it as I’m a bit of a non-starter at editing!).




(Aperture – f/5.0, Shutterspeed – 1/4s at ISO 200 shot at 109.0mm focal length)
Noise or a grainy effect can also be used in photography very creatively. I have added a small amount of “noise” to the above  photographs of the spoons and the Bartlett Pears, in post-production. Grain tends to add “interestingness” especially to black and white or under-exposed photographs or where the subject doesn’t have much texture.
With a reasonable amount of practice with higher ISO settings, you would be able to get pretty creative with using grain in your photographs to advantage. To get a good "finish" to the grainy/ noisy effect in your photograph, you would still need to do some editing though. You can see the difference in the quality of the noise by comparing the pomegranate photograph where the noise was added in-camera with a higher ISO, and the noise added to the other ones using software.
Useful links:
What is ISO? How to choose the right ISO for your digital photography? How to take sharp photos in low light without  flash Use a high ISO to create grainy shots Tips on using grain/ noise in photographs

So Far  In This Series: 
Food Photography Basics #1 : Do I Need A DSLR To Get Good Photographs? Food Photography Basics #2 : Which Camera? What Lenses?? Food Photography Basics #3 : Getting Started Food Photography Basics #4 : It’s All About Light – Exposure Food Photography Basics #5 : Aperture And Depth Of Field (DoF) Food Photography Basics # 6 : Shutter Speed

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