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7 Factors I Consider When Choosing the Right ISO For My Digital Photos

Setting the correct ISO on a camera can make a big difference in a photo. Digital cameras are getting smarter and smarter but a good photograph still may require a bit of camera work.

By Navid Jafari  |   Jun 2019  | 0
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Setting ISO on a camera determines how sensitive that camera sensor or film is to light.  Furthermore, sensitivity to light determines the darkness or lightness of your photo’s exposure.  The higher the ISO, the more sensitive the camera’s sensor or film is to light coming into the camera and conversely, the lower an ISO setting, the less sensitive the end result will be to light.  That’s the basics idea anyway.

It goes without saying but determining the correct ISO setting can make a significant difference in a photo.  In the old SLR days, films were sold based on their sensitivity to light and therefore, it was rather inconvenient (to say the least) to have to carry so many different films.  Today, with digital photography, one can adjust the ISO on shot-by-shot-basis – with ease.  The only challenge that remains is knowing what the right ISO is for a planned shot.

Typically, ISO settings tend to make the biggest difference in low light settings since such settings require a higher sensitivity to light.  Of course, one does not have to worry about ISO at all if one plans to shoot in automatic mode – since the camera tends to figure out the right numbers for the most part – automagically.  Although, typically camera does a good job with this automatic setting, at times, however, we need to intervene and adjust the ISO manually to get the most optimal shot.

Here are 7 factors that I consider when choosing the right or right-ish ISO setting (right-ish since each scenario demands individual fine-tuning):

Indoor photography and ISO

Indoor photography naturally needs a bump in lighting for an optimal image.  It is always a good idea to (all other variables the same) increase the ISO to increase the sensor’s sensitivity to light, in this situation.  This will ensure better lighting for the photo’s subject(s) while keeping in mind that too much of a good thing is never really a good thing.  Increasing ISO too much will lead to unintended overexposure of the photos and cause blurring and grains to appear in the final product.

Depth of field

Another important factor in determining what ISO settings to use for the photo’s depth of field.  Simply put, a large depth of field allows the camera to essentially have the entire photograph in focus.  To create this effect, f-stop needs to be increased in order to allow more light into the camera. This by itself eliminates the need to increase the ISO and therefore, when shooting a photo with a high depth of field, you would need to reduce your ISO settings (or simply not increase it from normal).


Using a tripod

If I am using a tripod, then I am reducing the possibility of unintended movements.  The use of tripods is, in fact, crucial at times where the shutter speed is slower – allowing the camera’s sensor to be exposed to the field longer.  Naturally, having the shutter speed increased leads to more light coming into the camera’s sensor – and much like the previous side effect of widening the aperture, the ISO would need to be reduced.

Overexposure as an art form

Of course, there are cases where the intended artistic expression of a photo comes from its overexposure to light.  For example, this increases the graininess of the photo and if that’s the intended artistic approach then it makes sense to go against common wisdom.  Film Noir is a great example of an art form that goes against the proper ways of adjusting ISO.

Moving subject(s)

If the subject I intend to photograph is standing still, then I don’t need to reduce my shutter speed significantly.  However, if I am photographing a moving subject (say, a race car), and I want to “freeze it” (meaning taking a snapshot of time as though the subjects were standing still), then I would need to increase the shutter speed significantly (BTW, this assumes that the subject(s) are moving side-to-side relevant to where I am standing).  Increasing the shutter speed will limit the amount of light coming into the camera and therefore, it is wise to increase your ISO to allow ample light on your photo.

Avoiding Grains

If I plan on making my photos as grain-free as possible in (very) large sizes, then it is important to note that increasing the ISO too much will cause grains and noise in the photos and therefore, needs to be avoided.  Determining the right ISO to avoid grains is best done by trial and error.  I usually start with a low ISO and work my way up to determine the right amount of light without artifacts or graininess.

Using Flash

If I am planning on using flash then I would probably need to reduce my ISO (or at least not increase it than normal).  Flash will inherently add additional light to the shot and therefore if ISO is also increased, then the combination of the two will create too much light in my photo.

How do you determine your ISO?

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