Was sent the following question this morning, thought it was worth sharing for all to read –

So – everything I’m reading in the realm of “photography 101” seems to suggest that at high ISO levels, there’s a lot of “noise.”

If that’s the case, what is the reason to shoot with such high ISO’s?

This is a great question-

First – the “noise” we are talking about shows up as grain in the images

SONY a65 ISO 400 vs ISO 6400
SONY a65 ISO 400 vs ISO 6400
As a photographer the goal most of the time you press the shutter is to capture a clear and crisp image that is properly exposed- for the image to be crisp or sharp you have to shoot at certain shutter speeds depending on the length of the lens you are using (focal length) and the speed of your subject. In daylight this is rarely an issue but as the light drops(indoors or at night) having a fast enough shutter speed to avoid blur from handshake becomes challenging – so you increase the ISO on your camera which increases the sensitivity of the sensor to light.  This allows you to keep a high enough shutter speed to avoid blur but the trade off is more noise in the image.  This is one reason some cameras cost thousands of dollars more than others, the sensor is able to shoot at higher ISOs with less noise.The rule about shutter speeds and focal length: The minimum shutter speed you can use is one over the focal length you are currently shooting at.  If you are shooting at 50mm your shutter speed should be at least 1/50 of a second.  Shooting at 270mm your shutter speed should be 1/300 or higher (there is no 1/270sec)  There are several catches to rule – 1) if you are using a crop sensor camera like the Canon T4i or Nikon D3200 you need to multiply your focal length x 1.5 or 1.6 – so when you have a 50mm lens on your camera you are actually shooting at 75 or 80 depending on the camera brand.  So your shutter speed should reflect that and the minimum needs to be 1/80 or higher. 2) If your lens or the camera has Image Stabilization (IS) or Vibration Reduction (VR) you can usually shoot at slower shutter speeds than your focal length, note that this will only help with non-moving subjects. 3) and if you are using a tripod you can go much slower – but then we should talk about mirror lockup and remote releases – that will be another discussion another time. 

And a quick plug here for Lightroom  – Lightroom has an excellent noise reduction feature – After tweaking the ISO 6400 shot above it becomes much harder to tell, especially at this size.

SONY a65 ISO 400 vs ISO 6400 - cups
SONY a65 ISO 400 vs ISO 6400



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