Tech Tips for Better Pics: ISO

Posted by on Mar 6, 2013 in Blog | 0 comments

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So, you have trouble with blurry pictures and aren’t sure why.  Or maybe you get really nice pictures sometimes, but really grainy pictures other times.  Why is that?  Well, it is all based on how your camera chooses to handle different lighting conditions.

First, lets have a history lesson.  In the film days, once you selected a particular film (say Kodak ASA 100), you would only influence your exposure in two ways, Aperature and Shutter Speed.  We will cover those two things another time, but basically the aperature controls how much light your lense lets into the camera body, and the shutter speed is how long the film (or digital sensor) needs to be exposed to that light to render an image of the proper brightness.  Each film speed (ASA) would have a different sensitivity to light.  The lower the speed rating, the longer it needed to be exposed to light from the same scene.  For example, suppose you put two cameras with the same aperature setting side by side, one with ASA 100 film and one with ASA 400 film. The ASA 400 film is 4 times more sensitive to light, so the shutter of the camera would be open 1/4 as long to get the same brightness image.  If you were taking these pictures outside with plenty of light, this faster shutter speed wouldn’t really matter.  If you were inside, it is a really big deal.  If you can shoot inside using ASA 400 with a shutter speed of 1/100th of a second or faster, it will likely not be blurry.  However, if you only have ASA 100, you are stuck with 1/25th of a second shutter speed with those same lighting conditions.  That is probably going to be blurry unless you have a tripod and nothing is moving.

So, why wouldn’t you always get the highest ASA speed film?  The trade off to speed is qualilty.  The increased sensitivity leads to film grain, or ‘fuzzy’ looking prints, especially in dark areas of low light images.

Fast forward to today’s cameras, even your camera phone.  ASA has been replaced with ISO, which is still a sensitivity (speed) rating.  It represents the exact same principle as film, except it is how much amplification gets added to the light signal hitting each pixel of your camera’s sensor.  The major benefit here is that it is adjustable on the fly, so you have the equivalent of all film speeds at the same time!  Now you can effect your exposure by using aperature, shutter speed, AND ISO and change it on each picture if you so choose.  Even better, most camera phones will go up to ISO 800 or more, and many SLR cameras can now push sensitivities to crazy numbers like ISO 128000.  The same trade-offs apply, such as noice and grain, and less sharpness, but if you don’t have very much light to work with or have a fast moving subject, you NEED a faster shutter speed.  Increasing your ISO may be the only way available to get you there.

More than likely, your camera will adjust your ISO automatically, especially if you shoot in ‘Auto’ mode.  On some camera phones, you can go into the settings while your camera app is open and find an option for ISO.  I recommend leaving it on Auto except in situations where the pictures are too dark.  You can then try to change from ‘Auto’ to whatever the highest number is available.  My phone allows me to shoot from ISO 50 to ISO 800, or ISO Auto.  In Auto mode, most cameras will never go to the highest available ISO in order to preserve image quality.  You have to change it manually.  If you have a SLR or nice point and shoot camera, you may need to change the shooting mode from Auto to Av (Aperature priority), P (Program mode), or Tv (Shutter Priority).  You can then usually adjust the ISO settings manually in the settings menu.

So remember, if you are in low light conditions and you are having trouble with blurry pictures, try to find your ISO settings.  Increasing this will allow for a faster shutter speed and help reduce the blurry pictures.  However, be prepared for a more ‘fuzzy’ and grainy looking image as the trade-off.

Hope this helps!

Josh